The document summarizes the structure and dynamics of the Earth. It describes how the Earth is composed of layers with different densities, including the crust, mantle, and core. It explains that the lithosphere is divided into tectonic plates that move over the asthenosphere due to convection currents in the mantle. There are three main types of plate boundaries - divergent where new crust forms, convergent where plates collide and one is subducted, and transform where plates slide past each other. Plate tectonics involves the creation of oceanic crust at mid-ocean ridges and recycling of crust through subduction.
The document discusses ophiolites, which are sections of the Earth's oceanic crust and upper mantle that have been uplifted and exposed above sea level. It describes the typical sequence of rocks found in an ophiolite, including sediments, pillow lavas, sheeted dykes, gabbros, and ultramafic rocks. It notes that ophiolites provide insights into ancient subduction zones and mantle processes. The document also discusses occurrences of ophiolites around the world and examples from India, as well as the economic resources sometimes associated with ophiolites, such as chromite, asbestos, and massive sulfides.
This document summarizes sedimentary ore deposits, specifically banded iron formations (BIF). It discusses the processes that form different types of BIF, including Algoma and Superior types, as well as their geologic time distribution. The document also explains the role of microbial communities in the deposition of iron minerals and formation of BIF layers through anoxic iron redox cycling, including phototrophic Fe(II) oxidation and nitrate-dependent Fe(II) oxidation mediated by bacteria. Overall, the document provides an overview of the genesis and microbial influences on the formation of important economic BIF deposits in sedimentary environments.
Supergene enrichment occurs when oxidizing acids dissolve metal ions from near-surface parts of ore deposits and re-deposit them at depth, resulting in higher metal concentrations. This process forms distinct zones - an oxidized cap, a leached zone, and an enriched zone below the water table where metals precipitate under reducing conditions. Common effects include rendering shallow parts of deposits barren while concentrating metals into narrow, rich zones at depth through mineral alterations and redeposition. Examples of deposits formed or enriched by this process include many copper, lead, zinc, silver, and iron deposits globally.
Contact metasomatism forms new minerals through reactions between intrusive rocks and escaping gases from magma chambers. Important requirements include a magma source of ore ingredients and intrusion into reactive host rocks. Metals like Fe, Cu, Zn, and W can be deposited through this process. Hydrothermal deposits are formed when hot, mineral-laden waters circulate through fractures, leaching and redepositing metals. Sedimentary deposits can form through evaporation, biochemical processes, or mechanical concentration of minerals in placer deposits.
The document summarizes a seminar on carbonatites. Carbonatites are igneous rocks composed of more than 50% carbonate minerals such as calcite or dolomite. They can be intrusive or extrusive. Carbonatites form from low degrees of partial melting in the mantle and have unusual geochemistry dominated by incompatible elements. They are often associated with alkaline complexes and may contain economic concentrations of rare earth elements, niobium, and fluorite. The document outlines the mineralogy, texture, classification, geochemistry, theories of origin, world occurrences, and economic importance of carbonatites.
1. The document discusses ore textures and paragenetic sequences, beginning with definitions and requirements for studying ore textures.
2. It describes various ore textures including single grain textures, magmatic ore textures, open space filling textures, and replacement textures.
3. The document concludes with a discussion on developing paragenetic sequences by analyzing features like cross-cutting relationships and exsolution textures.
The document describes the different metamorphic facies defined by their mineral assemblages under varying pressure and temperature conditions within the Earth's crust and upper mantle. It outlines the key facies including zeolite, prehnite-pumpellyite, greenschist, amphibolite, granulite, blueschist, eclogite, albite-epidote hornfels, hornblende hornfels, pyroxene hornfels, and sanidinite facies. Each facies is characterized by index minerals and typical mineral assemblages that reflect the prevailing metamorphic conditions.
Role of Trace Elements In Petrogenesis Gokul Anand
Trace elements occur in very low concentrations in rocks and provide important information about magmatic processes. They can be classified as compatible or incompatible based on whether they fit easily into mantle mineral crystal structures. Geochemical analysis of trace elements using techniques like XRF and ICP-MS allows determination of magma source and depth, identification of fractionating phases, and testing of models of magmatic differentiation. Trace elements are especially useful for rare earth elements, which indicate the type of basalt and can identify fractionating phases from REE patterns.
The document discusses ophiolites, which are sections of the Earth's oceanic crust and upper mantle that have been uplifted and exposed above sea level. It describes the typical sequence of rocks found in an ophiolite, including sediments, pillow lavas, sheeted dykes, gabbros, and ultramafic rocks. It notes that ophiolites provide insights into ancient subduction zones and mantle processes. The document also discusses occurrences of ophiolites around the world and examples from India, as well as the economic resources sometimes associated with ophiolites, such as chromite, asbestos, and massive sulfides.
This document summarizes sedimentary ore deposits, specifically banded iron formations (BIF). It discusses the processes that form different types of BIF, including Algoma and Superior types, as well as their geologic time distribution. The document also explains the role of microbial communities in the deposition of iron minerals and formation of BIF layers through anoxic iron redox cycling, including phototrophic Fe(II) oxidation and nitrate-dependent Fe(II) oxidation mediated by bacteria. Overall, the document provides an overview of the genesis and microbial influences on the formation of important economic BIF deposits in sedimentary environments.
Supergene enrichment occurs when oxidizing acids dissolve metal ions from near-surface parts of ore deposits and re-deposit them at depth, resulting in higher metal concentrations. This process forms distinct zones - an oxidized cap, a leached zone, and an enriched zone below the water table where metals precipitate under reducing conditions. Common effects include rendering shallow parts of deposits barren while concentrating metals into narrow, rich zones at depth through mineral alterations and redeposition. Examples of deposits formed or enriched by this process include many copper, lead, zinc, silver, and iron deposits globally.
Contact metasomatism forms new minerals through reactions between intrusive rocks and escaping gases from magma chambers. Important requirements include a magma source of ore ingredients and intrusion into reactive host rocks. Metals like Fe, Cu, Zn, and W can be deposited through this process. Hydrothermal deposits are formed when hot, mineral-laden waters circulate through fractures, leaching and redepositing metals. Sedimentary deposits can form through evaporation, biochemical processes, or mechanical concentration of minerals in placer deposits.
The document summarizes a seminar on carbonatites. Carbonatites are igneous rocks composed of more than 50% carbonate minerals such as calcite or dolomite. They can be intrusive or extrusive. Carbonatites form from low degrees of partial melting in the mantle and have unusual geochemistry dominated by incompatible elements. They are often associated with alkaline complexes and may contain economic concentrations of rare earth elements, niobium, and fluorite. The document outlines the mineralogy, texture, classification, geochemistry, theories of origin, world occurrences, and economic importance of carbonatites.
1. The document discusses ore textures and paragenetic sequences, beginning with definitions and requirements for studying ore textures.
2. It describes various ore textures including single grain textures, magmatic ore textures, open space filling textures, and replacement textures.
3. The document concludes with a discussion on developing paragenetic sequences by analyzing features like cross-cutting relationships and exsolution textures.
The document describes the different metamorphic facies defined by their mineral assemblages under varying pressure and temperature conditions within the Earth's crust and upper mantle. It outlines the key facies including zeolite, prehnite-pumpellyite, greenschist, amphibolite, granulite, blueschist, eclogite, albite-epidote hornfels, hornblende hornfels, pyroxene hornfels, and sanidinite facies. Each facies is characterized by index minerals and typical mineral assemblages that reflect the prevailing metamorphic conditions.
Role of Trace Elements In Petrogenesis Gokul Anand
Trace elements occur in very low concentrations in rocks and provide important information about magmatic processes. They can be classified as compatible or incompatible based on whether they fit easily into mantle mineral crystal structures. Geochemical analysis of trace elements using techniques like XRF and ICP-MS allows determination of magma source and depth, identification of fractionating phases, and testing of models of magmatic differentiation. Trace elements are especially useful for rare earth elements, which indicate the type of basalt and can identify fractionating phases from REE patterns.
Komattite
Named after the Komati River in South Africa.
first described by Morris and Richard (twins) for ultramafic units in the Barberton Greenstone belt of South Africa.
Mostly of komatiite are Archean age
distributed in the Archaean shield areas.
Also a few are Proterozoic and Phanerozoic.
In all ages komatiites are highly magnesium.
Mostly a volcanic rock; occasionally intrusive.
Mafic rocks were identified as extrusive because of their volcanic textures and structures, and they seem to have been accepted as a normal component of Archean volcanic successions, Abitibi in Canada.
The ultramafic rocks were interpreted as intrusive which are founded as sills and dykes, Barberton in South Africa.
Spinifex texture-typical of Komatiites:
This document discusses the importance of studying textures of ore deposits to understand their genesis. It describes various textures including: 1) magmatic ores with cumulus, intergranular, and exsolution textures; 2) hydrothermal ore deposits and skarns with replacement and open space filling textures identified by criteria like pseudomorphs and matching fracture walls; and 3) near-surface deposits with colloform textures like botryoidal aggregates and Liesegang rings formed from colloidal solutions. Understanding these textures provides insight into the formation processes, conditions, and evolution of different ore deposit types.
Alkaline magmatic rocks are igneous rocks that contain more alkalis (Na2O + K2O) than feldspars alone can accommodate. They commonly contain feldspathoids like nepheline, sodalite, or leucite. Examples include phonolites, nepheline syenites, and basanites. Alkaline rocks can be classified based on their silica and alumina content relative to alkalis. The most silica-undersaturated alkaline rocks are carbonatites. Debate occurred over whether carbonatites had an igneous or replacement origin, but experimental evidence and observations of carbonate lavas support a magmatic origin.
Tectonites are deformed rocks whose fabric is due to systematic movement under external forces. Their fabric reflects the deformation history. Fabric includes the geometric arrangement of mineral grains, layers, and other features at a scale that includes many samples. Tectonites can have planar (S-tectonite), linear (L-tectonite), or both (L-S tectonite) fabrics indicating different strain types. Foliations like cleavage, schistosity, and gneissosity are planar fabrics that cause rocks to break along parallel surfaces. Lineations indicate preferred linear fabrics, such as fold axes, boudins, and quartz rods. The orientation and interaction of foliations and lineations provide information about tect
The document discusses anorthosite, an intrusive igneous rock composed of 90-100% plagioclase feldspar. It describes the mineralogy, texture, and classification of anorthosite. Proteroic anorthosite formed during the Proterozoic era while Archean anorthosite formed during the Archean and are characterized by calcic plagioclase. Anorthosite is also found on the moon and classified as lunar anorthosite. Some anorthosite deposits are mined for titanium, iron, gemstones, and aluminum.
Kimberlite is a potassic, ultrabasic igneous rock that forms vertical pipes and intrusions. It has a porphyritic texture with large crystals in a fine-grained matrix. Kimberlites originate deep in the Earth's mantle and erupt explosively to the surface due to their high gas content. They are classified into Groups I and II based on mineral assemblages and textures. Kimberlites occur in crater, diatreme, and hypabyssal facies and are economically important sources of diamonds. The Wajrakarur field in India contains diamondiferous kimberlite pipes.
Metallogenic Epoch and Province
Metallogenetic Epochs
Metallogenetic epochs, as defined above, are specific periods characterised by formation of large number of mineral deposits. It does not mean that all the mineral deposits formed during a definite metallogenetic epochs. In India the chief metallogenetic epochs were:
1. Precambrian
2. Late Palaeozoic
3. Late Mesozoic to Early Tertiary
Mantle melting occurs when heat and pressure cause partial melting of the mantle, producing basaltic magma. Basalt is the most common volcanic rock on Earth and can be further differentiated to form other igneous rock types. Evidence for the composition and processes of the mantle comes from ophiolites, dredged samples from ocean floors, nodules contained in basalts, and xenoliths brought up from deep in the mantle via kimberlite eruptions. Together this evidence indicates that the upper mantle is composed predominantly of the minerals olivine, orthopyroxene, and clinopyroxene which make up the rocks dunite, harzburgite, and lherzol
Carbonatite is an igneous rock consisting primarily of carbonate minerals crystallized from a carbonate magma. There are three main hypotheses for the origin of carbonatite melts: 1) immiscible separation of parental carbonated silicate magmas, 2) crystal fractionation of carbonated silicate magmas, and 3) low-degree partial melting of carbonated mantle peridotite. Carbonatites can be classified based on their main carbonate mineral component, such as dolomite-carbonatite or ferroan-carbonatite. They commonly occur as shallow intrusive bodies like volcanic necks, dykes, and cone-sheets associated with alkali-rich silicate ig
COAL MICROLITHOTYPES AND THEIR USAGE IN INTERPRETING DEPOSITION ENVIRONMENTOlusegun Ayobami Olatinpo
This document discusses coal microlithotypes and how their analysis can be used to interpret depositional environments. It defines microlithotypes as natural rock associations found within coal that are differentiated based on maceral percentages. Specific microlithotypes form from different plant communities and depositional conditions. Analyzing the microlithotype composition of coal samples can provide insights into the swamp environment where peat formed, such as forested, reed, or open water settings. This information is valuable for geological research and coal quality evaluation.
This document discusses heavy minerals found in placer deposits. Placer deposits form from weathering and erosion of heavy minerals that are then transported and concentrated by gravity and deposited in areas like beaches. Common heavy minerals include ilmenite, magnetite, rutile, zircon and monazite. These minerals can be separated and extracted using physical processes that exploit differences in their magnetic, electrostatic and density properties, such as magnetic separation, electrostatic separation and gravity separation using spiral concentrators. Heavy minerals are economically important and indicators of sediment sources.
The Bastar Craton in central India covers an area of 130,000 square km and contains several important lithotectonic units from over 3 billion years ago. It is bounded by graben structures and mobile belts. The oldest unit is the Sukma Group dating to 3000 million years ago consisting of gneisses and iron formations. Younger granulite belts and sedimentary sequences include the Amgaon Group, Bengpal Group, and Sakoli Group indicating deposition between 2500-2600 million years ago. The Kotri-Dongargarh orogen contains the Bailadila iron formations and associated volcanic sequences like the Nandgaon Group dating to 2300 million years ago.
This document provides an overview of kimberlites, including their mineralogy, morphology, petrology, classification, origin, and economic importance. Kimberlites occur as vertical carrot-shaped intrusions called pipes and have an inequigranular texture consisting of large crystals in a fine-grained matrix. They are classified into Group I and Group II based on isotopic affinities. Kimberlites originate at depths of 100-200 km in the mantle and are emplaced explosively due to their high volatile content, forming diatremes with features like angular fragments. Kimberlites are economically important as the primary source of diamonds, though only 1 in 200 pipes contain gem-quality diamonds.
The document discusses ore formation systems and processes. It describes how ores were originally thought to form mainly from the cooling and crystallization of magmatic bodies. It then explains that four main ore formation processes are recognized: 1) orthomagmatic processes related to magma evolution and crystallization, 2) hydrothermal processes involving mineralization from magmatic fluids, 3) sedimentary processes concentrating metals through weathering, erosion and sedimentation, and 4) metamorphic processes transforming existing ore deposits. The document provides details on each of these processes and how they concentrate metals to form economic mineral deposits.
This document provides an overview of economic geology and the classification of ore deposits. It discusses how ore deposits are formed and classified based on their origin as magmatic, hydrothermal, or surficial deposits. A simple classification scheme is presented that categorizes ore deposits as igneous, sedimentary/surficial, or hydrothermal based on their forming processes. Key terms related to the study and classification of ore deposits are also defined.
This document summarizes the stratigraphy of the Cretaceous sediments in the Trichinopoly district of Tamil Nadu, India. It divides the sediments into four groups from oldest to youngest: Uttatur Group, Trichinopoly Group, Ariyalur Group, and Niniyur Formation. Each group contains multiple formations characterized by their lithology, thickness, fossil content, and age. The sediments were deposited in marine environments from the Aptian to early Paleocene stages and include limestones, sandstones, shales, and shell beds. Fossils found include ammonites, bivalves, wood, and dinosaur remains, providing insights into the paleoenvironment and basin evolution.
"Granites" Classification, Petrogenesis and Tectonic DescriminationSamir Kumar Barik
This document discusses the classification, petrogenesis, and tectonic discrimination of granites. It begins with definitions of granite and descriptions of its typical mineralogical and textural characteristics. It then outlines several common classification schemes for granites based on mineralogy, chemistry, and tectonic setting. These include QAPF, alumina saturation, S-I-A-M, and discriminations based on plate tectonic setting. The document also discusses models for the petrogenesis of granites involving magmatic differentiation and metasomatic processes. Geochemical discrimination diagrams are presented and the multiple possible origins of granites are noted. Future work on the geochemistry and uranium mineralization of granites in specific
Origin and Abundance of elements in the Solar system and in the Earth and its...AkshayRaut51
Definition of Elements and atom
Origin of Universe
Theories of origin of Solar system and Earth
Chemical Composition of Planets
Chemical Composition of Earth
Chemical composition of Meteorites
Abundance of Elements
This document discusses mineral and energy resources. It begins by describing how early humans began using minerals like flint and metals over 20,000 years ago. It then covers the formation of different types of mineral deposits including hydrothermal deposits formed from hot aqueous solutions, magmatic deposits within igneous rocks, and sedimentary deposits from precipitation or weathering. Specific examples of important mineral deposits are provided for different minerals. The document concludes by discussing classifications of useful mineral substances and various energy resources.
Remote sensing techniques can be used to identify mineral deposits. Landsat satellites have collected imagery since the 1970s that is useful for mineral exploration. Spectral bands can recognize hydrothermally altered rocks associated with ore deposits due to their distinct reflectance properties compared to unaltered rocks. At the Goldfield, Nevada mining district, Landsat imagery has been used to map hydrothermal alteration minerals like alunite and clays using ratio images of spectral bands 5 and 7, and 3 and 1, that highlight altered rock areas correlating with known deposits. Classification algorithms can further analyze imagery to automatically categorize altered and unaltered rock types to aid exploration.
This document discusses diagenetic ore deposits that form from fluids expelled during sediment compaction and lithification. It provides examples of deposit types formed this way, including the European Copper Shale and Mississippi Valley Type lead-zinc deposits. The core concept is that sediments contain large volumes of connate/formation waters that are expelled during diagenesis, becoming enriched in metals. When these hot, high-pressure fluids pass through permeability traps in the basinal sediments, they can precipitate ore minerals and form economic deposits. Microbes and geochemical conditions also influence metal mobility and deposition during this process.
This document discusses supergene ore formation systems resulting from chemical weathering of rocks. Supergene deposits form through two main processes - enrichment of valuable components in a residual left after dissolution/transport of other materials, or dissolution/transport/reprecipitation of valuable components. Key points: Bauxite, lateritic nickel/iron/gold/manganese deposits form through residual enrichment. Conditions like climate, vegetation influence weathering rates and supergene processes. Laterite profiles can be over 100m thick with vertical chemical zonation. Residual/eluvial placers concentrate weathering-resistant minerals.
Komattite
Named after the Komati River in South Africa.
first described by Morris and Richard (twins) for ultramafic units in the Barberton Greenstone belt of South Africa.
Mostly of komatiite are Archean age
distributed in the Archaean shield areas.
Also a few are Proterozoic and Phanerozoic.
In all ages komatiites are highly magnesium.
Mostly a volcanic rock; occasionally intrusive.
Mafic rocks were identified as extrusive because of their volcanic textures and structures, and they seem to have been accepted as a normal component of Archean volcanic successions, Abitibi in Canada.
The ultramafic rocks were interpreted as intrusive which are founded as sills and dykes, Barberton in South Africa.
Spinifex texture-typical of Komatiites:
This document discusses the importance of studying textures of ore deposits to understand their genesis. It describes various textures including: 1) magmatic ores with cumulus, intergranular, and exsolution textures; 2) hydrothermal ore deposits and skarns with replacement and open space filling textures identified by criteria like pseudomorphs and matching fracture walls; and 3) near-surface deposits with colloform textures like botryoidal aggregates and Liesegang rings formed from colloidal solutions. Understanding these textures provides insight into the formation processes, conditions, and evolution of different ore deposit types.
Alkaline magmatic rocks are igneous rocks that contain more alkalis (Na2O + K2O) than feldspars alone can accommodate. They commonly contain feldspathoids like nepheline, sodalite, or leucite. Examples include phonolites, nepheline syenites, and basanites. Alkaline rocks can be classified based on their silica and alumina content relative to alkalis. The most silica-undersaturated alkaline rocks are carbonatites. Debate occurred over whether carbonatites had an igneous or replacement origin, but experimental evidence and observations of carbonate lavas support a magmatic origin.
Tectonites are deformed rocks whose fabric is due to systematic movement under external forces. Their fabric reflects the deformation history. Fabric includes the geometric arrangement of mineral grains, layers, and other features at a scale that includes many samples. Tectonites can have planar (S-tectonite), linear (L-tectonite), or both (L-S tectonite) fabrics indicating different strain types. Foliations like cleavage, schistosity, and gneissosity are planar fabrics that cause rocks to break along parallel surfaces. Lineations indicate preferred linear fabrics, such as fold axes, boudins, and quartz rods. The orientation and interaction of foliations and lineations provide information about tect
The document discusses anorthosite, an intrusive igneous rock composed of 90-100% plagioclase feldspar. It describes the mineralogy, texture, and classification of anorthosite. Proteroic anorthosite formed during the Proterozoic era while Archean anorthosite formed during the Archean and are characterized by calcic plagioclase. Anorthosite is also found on the moon and classified as lunar anorthosite. Some anorthosite deposits are mined for titanium, iron, gemstones, and aluminum.
Kimberlite is a potassic, ultrabasic igneous rock that forms vertical pipes and intrusions. It has a porphyritic texture with large crystals in a fine-grained matrix. Kimberlites originate deep in the Earth's mantle and erupt explosively to the surface due to their high gas content. They are classified into Groups I and II based on mineral assemblages and textures. Kimberlites occur in crater, diatreme, and hypabyssal facies and are economically important sources of diamonds. The Wajrakarur field in India contains diamondiferous kimberlite pipes.
Metallogenic Epoch and Province
Metallogenetic Epochs
Metallogenetic epochs, as defined above, are specific periods characterised by formation of large number of mineral deposits. It does not mean that all the mineral deposits formed during a definite metallogenetic epochs. In India the chief metallogenetic epochs were:
1. Precambrian
2. Late Palaeozoic
3. Late Mesozoic to Early Tertiary
Mantle melting occurs when heat and pressure cause partial melting of the mantle, producing basaltic magma. Basalt is the most common volcanic rock on Earth and can be further differentiated to form other igneous rock types. Evidence for the composition and processes of the mantle comes from ophiolites, dredged samples from ocean floors, nodules contained in basalts, and xenoliths brought up from deep in the mantle via kimberlite eruptions. Together this evidence indicates that the upper mantle is composed predominantly of the minerals olivine, orthopyroxene, and clinopyroxene which make up the rocks dunite, harzburgite, and lherzol
Carbonatite is an igneous rock consisting primarily of carbonate minerals crystallized from a carbonate magma. There are three main hypotheses for the origin of carbonatite melts: 1) immiscible separation of parental carbonated silicate magmas, 2) crystal fractionation of carbonated silicate magmas, and 3) low-degree partial melting of carbonated mantle peridotite. Carbonatites can be classified based on their main carbonate mineral component, such as dolomite-carbonatite or ferroan-carbonatite. They commonly occur as shallow intrusive bodies like volcanic necks, dykes, and cone-sheets associated with alkali-rich silicate ig
COAL MICROLITHOTYPES AND THEIR USAGE IN INTERPRETING DEPOSITION ENVIRONMENTOlusegun Ayobami Olatinpo
This document discusses coal microlithotypes and how their analysis can be used to interpret depositional environments. It defines microlithotypes as natural rock associations found within coal that are differentiated based on maceral percentages. Specific microlithotypes form from different plant communities and depositional conditions. Analyzing the microlithotype composition of coal samples can provide insights into the swamp environment where peat formed, such as forested, reed, or open water settings. This information is valuable for geological research and coal quality evaluation.
This document discusses heavy minerals found in placer deposits. Placer deposits form from weathering and erosion of heavy minerals that are then transported and concentrated by gravity and deposited in areas like beaches. Common heavy minerals include ilmenite, magnetite, rutile, zircon and monazite. These minerals can be separated and extracted using physical processes that exploit differences in their magnetic, electrostatic and density properties, such as magnetic separation, electrostatic separation and gravity separation using spiral concentrators. Heavy minerals are economically important and indicators of sediment sources.
The Bastar Craton in central India covers an area of 130,000 square km and contains several important lithotectonic units from over 3 billion years ago. It is bounded by graben structures and mobile belts. The oldest unit is the Sukma Group dating to 3000 million years ago consisting of gneisses and iron formations. Younger granulite belts and sedimentary sequences include the Amgaon Group, Bengpal Group, and Sakoli Group indicating deposition between 2500-2600 million years ago. The Kotri-Dongargarh orogen contains the Bailadila iron formations and associated volcanic sequences like the Nandgaon Group dating to 2300 million years ago.
This document provides an overview of kimberlites, including their mineralogy, morphology, petrology, classification, origin, and economic importance. Kimberlites occur as vertical carrot-shaped intrusions called pipes and have an inequigranular texture consisting of large crystals in a fine-grained matrix. They are classified into Group I and Group II based on isotopic affinities. Kimberlites originate at depths of 100-200 km in the mantle and are emplaced explosively due to their high volatile content, forming diatremes with features like angular fragments. Kimberlites are economically important as the primary source of diamonds, though only 1 in 200 pipes contain gem-quality diamonds.
The document discusses ore formation systems and processes. It describes how ores were originally thought to form mainly from the cooling and crystallization of magmatic bodies. It then explains that four main ore formation processes are recognized: 1) orthomagmatic processes related to magma evolution and crystallization, 2) hydrothermal processes involving mineralization from magmatic fluids, 3) sedimentary processes concentrating metals through weathering, erosion and sedimentation, and 4) metamorphic processes transforming existing ore deposits. The document provides details on each of these processes and how they concentrate metals to form economic mineral deposits.
This document provides an overview of economic geology and the classification of ore deposits. It discusses how ore deposits are formed and classified based on their origin as magmatic, hydrothermal, or surficial deposits. A simple classification scheme is presented that categorizes ore deposits as igneous, sedimentary/surficial, or hydrothermal based on their forming processes. Key terms related to the study and classification of ore deposits are also defined.
This document summarizes the stratigraphy of the Cretaceous sediments in the Trichinopoly district of Tamil Nadu, India. It divides the sediments into four groups from oldest to youngest: Uttatur Group, Trichinopoly Group, Ariyalur Group, and Niniyur Formation. Each group contains multiple formations characterized by their lithology, thickness, fossil content, and age. The sediments were deposited in marine environments from the Aptian to early Paleocene stages and include limestones, sandstones, shales, and shell beds. Fossils found include ammonites, bivalves, wood, and dinosaur remains, providing insights into the paleoenvironment and basin evolution.
"Granites" Classification, Petrogenesis and Tectonic DescriminationSamir Kumar Barik
This document discusses the classification, petrogenesis, and tectonic discrimination of granites. It begins with definitions of granite and descriptions of its typical mineralogical and textural characteristics. It then outlines several common classification schemes for granites based on mineralogy, chemistry, and tectonic setting. These include QAPF, alumina saturation, S-I-A-M, and discriminations based on plate tectonic setting. The document also discusses models for the petrogenesis of granites involving magmatic differentiation and metasomatic processes. Geochemical discrimination diagrams are presented and the multiple possible origins of granites are noted. Future work on the geochemistry and uranium mineralization of granites in specific
Origin and Abundance of elements in the Solar system and in the Earth and its...AkshayRaut51
Definition of Elements and atom
Origin of Universe
Theories of origin of Solar system and Earth
Chemical Composition of Planets
Chemical Composition of Earth
Chemical composition of Meteorites
Abundance of Elements
This document discusses mineral and energy resources. It begins by describing how early humans began using minerals like flint and metals over 20,000 years ago. It then covers the formation of different types of mineral deposits including hydrothermal deposits formed from hot aqueous solutions, magmatic deposits within igneous rocks, and sedimentary deposits from precipitation or weathering. Specific examples of important mineral deposits are provided for different minerals. The document concludes by discussing classifications of useful mineral substances and various energy resources.
Remote sensing techniques can be used to identify mineral deposits. Landsat satellites have collected imagery since the 1970s that is useful for mineral exploration. Spectral bands can recognize hydrothermally altered rocks associated with ore deposits due to their distinct reflectance properties compared to unaltered rocks. At the Goldfield, Nevada mining district, Landsat imagery has been used to map hydrothermal alteration minerals like alunite and clays using ratio images of spectral bands 5 and 7, and 3 and 1, that highlight altered rock areas correlating with known deposits. Classification algorithms can further analyze imagery to automatically categorize altered and unaltered rock types to aid exploration.
This document discusses diagenetic ore deposits that form from fluids expelled during sediment compaction and lithification. It provides examples of deposit types formed this way, including the European Copper Shale and Mississippi Valley Type lead-zinc deposits. The core concept is that sediments contain large volumes of connate/formation waters that are expelled during diagenesis, becoming enriched in metals. When these hot, high-pressure fluids pass through permeability traps in the basinal sediments, they can precipitate ore minerals and form economic deposits. Microbes and geochemical conditions also influence metal mobility and deposition during this process.
This document discusses supergene ore formation systems resulting from chemical weathering of rocks. Supergene deposits form through two main processes - enrichment of valuable components in a residual left after dissolution/transport of other materials, or dissolution/transport/reprecipitation of valuable components. Key points: Bauxite, lateritic nickel/iron/gold/manganese deposits form through residual enrichment. Conditions like climate, vegetation influence weathering rates and supergene processes. Laterite profiles can be over 100m thick with vertical chemical zonation. Residual/eluvial placers concentrate weathering-resistant minerals.
This document discusses genetic classification of ore deposits. It notes that while various geological aspects like metals, orebody form, environment, and tectonic setting are used to classify deposits, a stringent genetic classification is difficult for two reasons. First, many deposits represent complex combinations of well-defined end members like volcanic, intrusive, sedimentary and diagenetic processes. Second, the origin of deposits like Kuroko and high-grade BIF-haematite seems to involve multiple geological processes interacting, like marine life proliferation and saline brine passage. The document recommends reading a specific review article for further detailed classification information.
This document discusses metamorphic and metamorphosed ore deposits. It explains that metamorphic ore deposits form through the isochemical metamorphic re-equilibration and recrystallization of pre-existing materials. Contact metamorphism near magmatic bodies causes changes to fabric, mineralogy, and chemistry through processes like dewatering. Regional metamorphism can reach temperatures of 1100°C and pressures of 30 kbar, driving off volatiles and causing grain coarsening and foliation. Metamorphic fluids liberate economically valuable metals and elements and can form ore deposits as they circulate through metamorphosing rock.
Porphyry copper deposits form from magmatic-hydrothermal activity associated with porphyritic intrusions. They contain low to moderate grades of copper, molybdenum, gold and other metals within stockwork vein systems and disseminated in the intrusion. Distinct hydrothermal alteration zones form around the intrusion, including potassic, phyllic, argillic and propylitic assemblages. Porphyry deposits provide the majority of the world's copper and molybdenum and are important sources for other metals like gold. They form due to crystallization and interaction of fertile magmas with hydrothermal fluids.
Economic geology is the study of economically valuable resources from the Earth, such as fuels and metals. It has several branches including geochemistry, mineralogy, geophysics, petrology, structural geology. Economic geology is important not only to geologists but also to investment bankers, engineers and others due to the significant impact extractive industries have on society, the economy and the environment.
Residual mineral deposits; Laterites; Laterite Profile; Laterisation system; Laterite/Bauxite Conditions; Laterite-type Bauxite, Constitution of Bauxite, Types of deposits; Origin and Mode of formation; Clay (Kaolinite) Deposits; Nickel Laterite Deposits; Mineralogy and Types of lateritic nickel ore deposits; World Nickel Laterite Deposits; Processing of Ni Laterites; Example: Ni-laterites, Ni in soils in east Albania
This document provides an overview of a lecture series on clastic depositional systems and their response to changes in base level. It describes the three main types of depositional systems - terrestrial, transitional, and marine. For marine systems, it focuses on coastal systems like wave-dominated coasts, tide-dominated coasts, and river-dominated deltas. It discusses the characteristics and facies of these coastal systems, and how they respond to changes in sea level. Diagrams and photos are provided as examples.
1. The document discusses the relationship between plate tectonics and metal deposits. It describes various tectonic settings associated with divergent and convergent plate boundaries that are favorable for forming different types of metal deposits.
2. Key settings discussed include continental rifts, failed rift arms, passive continental margins during seafloor spreading, mid-ocean ridges, and subduction zones. Metallogeny in these settings includes deposits forming from hydrothermal vents, volcanic-hosted massive sulfides, and porphyry copper deposits.
3. The formation of different deposit types is tied to the specific geological processes associated with different stages of plate interactions, such as crustal extension during rifting and compression during
Bauxite is the main ore of aluminum. It was first discovered in 1821 in southern France and is typically found near the surface in tropical and subtropical regions. Bauxite consists primarily of aluminum hydroxides and oxides with impurities like silica. It is refined via the Bayer process to produce alumina, which is then smelted using the Hall-Héroult process to produce aluminum. Aluminum has many uses including in transportation, packaging, and construction due to its light weight and corrosion resistance.
1.1 introduction of geology,Branches and Scope of GeologyRam Kumawat
This document discusses the branches and scope of geology. It outlines 15 branches of geology including physical geology, crystallography, mineralogy, petrology, structural geology, stratigraphy, paleontology, historical geology, economic geology, mining geology, civil engineering geology, hydrology, Indian geology, resources engineering, and photo geology. It then discusses the importance and scope of geology for civil engineering, including providing construction materials knowledge, helping with erosion and deposition projects, tunneling and foundations, and reducing engineering costs.
Geology is the study of the Earth, including its composition, structure, physical properties, history and the processes that shape it. The document outlines several key branches of geology, including economic geology, mining geology, petroleum geology, engineering geology, environmental geology, geochemistry, geomorphology, geophysics, historical geology, hydrogeology, mineralogy, paleontology, petrology, structural geology, sedimentology, stratigraphy and volcanology. Each branch deals with different aspects of the Earth and geological processes. Engineering geology specifically applies geological knowledge to civil engineering projects regarding construction materials, site selection, and safe design and construction.
This document summarizes various depositional environments including aeolian, fluvial, shallow marine/shoreline, deltaic, deep marine, and carbonates. For each environment, it describes the typical facies/depositional areas, geometries, trends, and potential reservoir and seal facies. The environments represent both clastic and carbonate depositional systems across continental, transitional, and marine settings.
The document provides an overview of a course on carbonates and sedimentary basins. It discusses how carbonate sediments form in different depositional environments and the factors controlling carbonate accumulation and distribution. It also summarizes the key components and textures of carbonate rocks and the processes of diagenesis.
Classification of Marine Depositional Environment Saad Raja
The document classifies and describes four major marine depositional environments:
1) The continental shelf is a gently sloping edge where sediments ranging from coarse sand to clays wash off the continent. Coral reefs or carbonate muds may also dominate.
2) The continental slope is a more steeply sloping edge below the shelf, with fine silts and clays.
3) The continental rise is a fan-shaped deposit at the base of the slope containing turbidites from turbidity currents, with sands, silts and clays.
4) The abyssal plain is the deep ocean floor, flat and covered by fine-grained sediments like clay and shells of microorganisms
This presentation reviews the complete water cycle, including some of the constructed water cycle. Used as an environmental overview for life science and environmental. Geared for Secondary students, but also could be used as an intro for up to College level classes.
MANGANESE ORE DEPOSITS, Sedimentary Manganese Deposits, Types of Sedimentary Manganese, Classification, Manganese Nodules, EGYPTIAN MANGANESE ORE DEPOSITS , IRON ORE DEPOSITS, Cycle of Iron , Ironstone (Sedimentary iron) Ore Deposits, Bog Iron Ore Deposits, Principal iron-bearing minerals, Geochemical stability of iron-rich minerals, World Resources Iron Deposit, EGYPTIAN IRON ORE DEPOSITS, Iron ore deposit of sedimentary nature, Sinai: Gabal Halal iron ore deposit, Aswan iron Ore Deposits, Bahariya iron Ore Deposits
Basic introduction to clinical trials and the placebo effect. Definitions, examples and cartoons illustrating the subject. Ends with short info on informed consent.
What is an ore?, Ore deposit environments, Formation of Mineral Deposits, Endogenous (Internal) processes, Exogenous (Surficial) processes, Types of Sedimentary Rocks, Mineral Deposits Associated with Sedimentary Process, physical processes of ore deposit formation in the surficial realm, Erosion, weathering , transportation, sorting, Precipitation, Depositional Environments, Deposits formed by Weathering, Deposits formed by Sediment, Resources from the Sedimentary Environments
The document discusses the four main layers that make up the Earth - the crust, mantle, outer core, and inner core. It describes each layer in detail, including their composition and physical properties. The mantle is divided into sections including the asthenosphere, which is a soft, plastic-like layer that causes plate tectonics by pushing the plates across its surface through convection currents within the Earth.
The document discusses the structure and layers of the Earth. It is composed of four main layers from outermost to innermost:
1) The crust, which is the thin solid outer layer people live on made of rocks and minerals. It is divided into thicker continental crust and thinner oceanic crust.
2) The hot, dense mantle that behaves like a solid but can flow very slowly over geologic timescales. Its convection currents influence plate tectonics at the surface.
3) The liquid outer core that is composed of melted nickel and iron due to extreme heat and pressure.
4) The inner solid core formed from compressed metals vibrating in place like a solid.
The document summarizes key concepts of plate tectonic theory. It explains that the lithosphere is made up of rigid tectonic plates that float on the asthenosphere and move at rates of 1-16 cm/year. There are three main types of plate boundaries - divergent where plates move apart, convergent where they move together, and transform where they slide past each other. Plate tectonics generates phenomena like earthquakes, volcanoes, mountain building and affects climate by moving continents and oceans over geologic time.
This document provides an overview of continental margins. It begins with introducing the objectives of understanding the importance and characteristics of continental margins in the context of earth and oceanographic studies. It then discusses various topics relevant to continental margins, including the earth's crust, plate tectonics, sea floor spreading, types of plate boundaries and movement, and features of convergent and divergent plate boundaries. The key aspects of continental margins are that they are the submerged zones separating thick continental crust from thin oceanic crust, and form the outer edges of continents.
The document discusses the possible causes of plate movement, including convection currents in the mantle, ridge push, and slab pull. Convection currents cause the mantle to circulate, ridge push is the force that causes plates to move away from mid-ocean ridges as new crust is formed, and slab pull occurs as dense oceanic plates are pulled into the mantle at subduction zones. The document also summarizes seafloor spreading theory, which proposes that new crust is formed at mid-ocean ridges due to upwelling magma.
CSEC Geography- Internal Forces - Plate Tectonics and EarthquakesOral Johnson
This document looks at the Earth's internal forces. The main layers of the earth are described. The history surrounding plate tectonics is discussed. The different types of plate boundaries is also explained.
GEOGRAPHY IGCSE: PLATE TECTONICS. Earth's layers. Inner core, outer core, mantle, crust, the structure of Earth, plate boundaries and interactions, magma and igneous rocks, forming a volcano, compressional boundaries, folding.
The document discusses the possible causes of plate tectonic movement, including convection currents, ridge push, and slab pull. Convection currents in the Earth's mantle are thought to be responsible for plate movements. Ridge push refers to the pushing force plates experience as they slide down the raised asthenosphere under mid-ocean ridges. Slab pull is the pulling force exerted as subducting plates sink into the mantle.
The document summarizes key aspects of seismology and plate tectonics. It describes how seismology studies earthquakes and seismic wave propagation to understand Earth's internal structure. It then outlines Earth's major layers - crust, mantle, and core. It introduces the theories of continental drift and plate tectonics to explain the movement of tectonic plates across Earth's surface, driven by convection currents in the mantle. It categorizes the three main types of plate boundaries - divergent boundaries where plates spread apart, convergent boundaries where they collide subduct or collide, and provides examples of each.
1. The document discusses seismology, the internal structure of the Earth, plate tectonics theory, and earthquake waves.
2. The Earth's interior is composed of a crust, mantle, and core. The mantle acts as a viscous fluid that causes convection currents, which in turn exert shear stresses on tectonic plates.
3. Plate tectonics theory proposes that the lithosphere is broken into plates that move relative to each other at plate boundaries. This movement generates earthquakes and other geological activity.
This document provides information about plate tectonics and is designed to meet South Carolina science standards. It discusses the layers of the Earth, tectonic plates and their movement, and the three types of plate boundaries - convergent where plates collide, divergent where they separate, and transform where they slide past each other. Specific examples are given for each boundary type, including discussions of sea floor spreading at mid-ocean ridges, subduction zones creating volcanoes and trenches, and the San Andreas Fault as a transform boundary.
WHAT IS A PLATE? MAJOR PLATES. Types of Earth’s Crust. Plate BoundaryUday Kumar Shil
The document discusses plate tectonics and the key concepts of plate tectonic theory. It describes how the lithosphere is broken into large plates that move over Earth's surface, driven by convection currents in the underlying mantle. It outlines the three main types of plate boundaries - divergent boundaries where new crust forms, transform boundaries where plates slide past each other, and convergent boundaries where plates collide and one slides under the other. It also discusses the evidence that supported the development of plate tectonic theory, such as seafloor spreading and magnetic reversals recorded in oceanic crust.
This is the entire CSEC geography syllabus (some things might be missing). The information was collected from various websites and textbooks. The topics are:
- Internal forces
-External forces
-Rivers
-Limestone
-Coasts
-Coral reefs and Mangroves
-Weather and Climate
- Ecosystems (vegetation and soils)
-Natural hazards
- Urbanization
-Economic activity
-Environmental degradation
The structure of the earth and plate tectonicsccbthirdgrade
The Earth is composed of four main layers - the inner core, outer core, mantle, and crust. The crust is divided into tectonic plates that slowly move due to convection currents in the mantle. There are three types of plate boundaries - divergent where plates move apart, convergent where they move together, and transform where they slide past each other. Plate interactions at boundaries cause volcanic and seismic activity, with volcanoes and earthquakes concentrated near plate margins.
The document discusses Earth's structure and plate tectonics. It describes how Earth formed layers with different densities, including the inner and outer core, mantle, crust, and lithosphere. The lithosphere is made up of tectonic plates that move over time. There are three types of plate boundaries - divergent where plates move apart, convergent where they push together, and transform where they scrape past each other. Plate tectonics explains how continents have changed positions over billions of years and continue to move today.
The document discusses the causes and types of earthquakes. It begins by noting that records of earthquakes date back thousands of years in some areas. It then explains that earthquakes are caused by the sudden movement of tectonic plates deep below the earth's surface. The major types of plate boundaries are divergent boundaries where new crust forms, convergent boundaries where plates collide and crust is destroyed, and transform boundaries where plates slide past each other. Specific examples like the Mariana Trench and San Andreas Fault are also described.
The document discusses plate tectonics and the structure of the Earth. It explains that the Earth's crust is broken into plates that slowly move due to convection currents in the mantle. There are seven major tectonic plates and three types of plate boundaries: divergent where plates move apart, convergent where they move together, and transform where they slide past each other. These plate movements shape the Earth's surface over millions of years through earthquakes, volcanoes, and mountain building.
The document discusses plate tectonics and how it shapes Earth. Plate tectonics involves large plates in Earth's lithosphere that slowly move over time. When plates meet, they form boundaries which can result in volcanoes and earthquakes. Convection currents in the mantle drive the plate movements. Plates diverge at mid-ocean ridges, where new crust is formed, and converge in some places, causing volcanoes or mountains to form.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
2. Structure of the Earth
The Earth is an irregular sphere,
with a radius that varies between
6,356 and 6,378 km. This solid
sphere is chemically divided into
layers that become less dense
from the centre towards the
surface.
The three main layers are:
(i)the core (which comprises an
Inner Core and an Outer Core);
(ii)the mantle, and
(iii) the crust.
Each layer has a distinctive
chemical composition, and a
different density (Figure 1).
3. The outer layer of the Earth is termed the
crust, which is divided into oceanic
crust and continental crust.
Overall, continental crust is richer in the
element silica, and is less dense, than
oceanic crust.
Oceanic crust (about 10 km thick) is
composed of iron-, magnesium-,
calcium-, and aluminium-rich silicate
minerals that typically form a dark
colored, heavy rock called basalt.
Continental crust (about 20 - 60 km thick)
is composed of potassium-, sodium-,
and aluminium-rich silicate minerals that
form a diverse range of rock types such
as granite.
The core is primarily composed of the
heavy elements iron and nickel.
The outer core is made of molten iron,
which produces the Earth's magnetic field.
The mantle is less-dense than the core. The
mantle extends to a depth of about 2,900
km. The mantle is rich in iron- and
magnesium-bearing silicate minerals.
The layers of the Earth.
4.
5.
6. The Earth consists of
series of concentric
layers which differ in
chemical and physical
properties.
The crust and upper part
of the mantle of the
Earth is further
subdivided into
the lithosphere and the
asthenosphere.
Dynamic Structure of the Earth
7.
8. The lithosphere is a strong layer, extending to a depth of 100 to 150 km, that
comprises the crust and part of the upper mantle (the upper rigid part). The
lithosphere is separated into seven large plates, and several smaller plates.
These plates, which terminate at different types of plate boundary, move over the
underlying asthenosphere.
9.
10. The asthenosphere (the middle part of the mantle - plastic, i.e., semi-liquid and
ductile) is a weaker layer, upon which the lithospheric plates move, and from
which magmas that form the oceanic crust are derived.
11. Heat from the Earth's core creates circulation patterns (i.e., convection currents)
in the mantle drive the motions of the overlying plates. The slow movement of the
lithospheric plates over the mobile asthenosphere is known as plate tectonics, a
process that maintains the surface of the Earth in a dynamic and active state.
Convection: is the process in which energy is transferred through a material with
any bulk motion of its particles. Convection is common in fluids.
12. Convection currents in the aesthenosphere
transfer heat to the surface, where plumes
of less dense magma break apart the plates
at the spreading centers, creating divergent
plate boundaries.
As the plates move away from the
spreading centers, they cool, and the
higher density basalt rocks that make up
ocean crust get consumed at the ocean
trenches/subduction zones. The crust is
recycled back into the aesthenosphere.
13. Because ocean plates are denser than continental plates, when these two types of
plates converge, the ocean plates are subducted beneath the continental plates.
Subduction zones and trenches are convergent margins. The collision of plates is
often accompanied by earthquakes and volcanoes.
14. Plate tectonics (previously known as continental drift) originated from the
geographical observation that the coastal profiles of South America and Africa
seem to fit one another.
First proposed by Alfred Wegener in the 1920s, the crust was imagined to be
made up of continent-sized slabs that "float" on a liquid layer and thus "drift"
around.
Plate tectonics
15. Plate tectonics, appeared in the 1960s when the mid-Atlantic ridge was
discovered, along with compelling evidence for injection rock caused "spreading“
leaving parallel north-south trending stripes of injected rock, the youngest of
which was adjacent to the injection ridge and the oldest farthest from it. The plate
tectonics solution to the seafloor spreading dilemma was the proposition that
new crustal mass created by injection must be compensated by "subduction", the
diving of ocean crust (more dense) under opposing continental plates (less
dense). Subduction zones and trenches are convergent margins. The collision of
plates is often accompanied by earthquakes and volcanoes.
16. This diagram shows the interaction between continental and oceanic plates, the
processes illustrated generally apply for the interaction between two oceanic
plates.
What happens in Plate Tectonics??!!
17. 1. There are two basic types of
LITHOSPHERE: CONTINENTAL
lithosphere has a low density because
it is made of relatively light-weight
minerals. OCEANIC lithosphere is
denser because it is composed of
heavier minerals. A plate may be made
up entirely of oceanic or continental
lithosphere, but most are partly oceanic
and partly continental.
What happens in Plate Tectonics??!!
18. 2. Beneath the lithospheric
plates lies the
ASTHENOSPHERE, a layer of the
mantle composed of denser
semi-solid rock. Because the
plates are less dense than the
asthenosphere beneath them,
they are floating on top of the
asthenosphere.
What happens in Plate Tectonics??!!
19. 3. Deep within the asthenosphere the
pressure and temperature are so high that
the rock can soften and partly melt. The
softened dense rock can flow very slowly.
Where temperature instabilities exist near
the core/mantle boundary, slowly moving
convection currents may form within the
semi-solid asthenosphere.
4. Once formed, convection currents bring
hot material from deeper within the mantle
up toward the surface.
What happens in Plate Tectonics??!!
20. What happens in Plate Tectonics??!!
5. As they rise and approach the surface,
convection currents diverge at the base of the
lithosphere. The diverging currents exert a weak
tension or “pull” on the solid plate above it.
Tension and high heat flow weakens the floating,
solid plate, causing it to break apart. The two
sides of the now-split plate then move away from
each other, forming a DIVERGENT PLATE
BOUNDARY.
21.
22.
23. What happens in Plate Tectonics??!!
6. The space between these
diverging plates is filled with molten
rocks (magma) from below. Contact
with seawater cools the magma,
which quickly solidifies, forming
new oceanic lithosphere. This
continuous process, operating over
millions of years, builds a chain of
submarine volcanoes and rift valleys
called a MID-OCEAN RIDGE or an
OCEANIC SPREADING RIDGE.
24. What happens in Plate Tectonics??!!
7. As new molten rock continues to be extruded at the mid-ocean ridge and added
to the oceanic plate (6), the older (earlier formed) part of the plate moves away
from the ridge.
8. As the oceanic plate moves farther and farther away from the active, hot
spreading ridge, it gradually cools down. The colder the plate gets, the denser
(“heavier”) it becomes. Eventually, the edge of the plate that is farthest from the
spreading ridges cools so much that it becomes denser than the asthenosphere
beneath it.
25. What happens in Plate Tectonics??!!
9. As it is known, denser materials
sink, and that’s exactly what
happens to the oceanic plate—it
starts to sink into the
asthenosphere! Where one plate
sinks beneath another a subduction
zone forms.
26.
27. What happens in Plate Tectonics??!!
10. The sinking lead edge of the oceanic plate actually
“pulls” the rest of the plate behind it—evidence
suggests this is the main driving force of subduction. It
is not sure how deep the oceanic plate sinks before it
begins to melt and lose its identity as a rigid slab, but it
remains solid far beyond depths of 100 km beneath the
Earth’s surface.
11. Subduction zones are one type of CONVERGENT
PLATE BOUNDARY, the type of plate boundary that
forms where two plates are moving toward one another.
Notice that although the cool oceanic plate is sinking,
the cool but less dense continental plate floats like a
cork on top of the denser asthenosphere.
28. What happens in Plate Tectonics??!!
12. When the subducting oceanic plate
sinks deep below the Earth’s surface,
the great temperature and pressure at
depth cause the fluids to “sweat” from
the sinking plate. The fluids sweated
out percolate upward, helping to
locally melt the overlying solid mantle
above the subducting plate to form
pockets of liquid rock (magma).
29. 13. The generated magma is less dense than
the surrounding rock, so it rises toward the
surface. Most of the magma cools and
solidifies as large bodies of plutonic
(intrusive) rocks far below the Earth’s
surface.
14. Some of the molten rock may reach the
Earth’s surface to erupt as the pent-up gas
pressure in the magma is suddenly released,
forming volcanic (extrusive) rocks.
What happens in Plate Tectonics??!!
30. There are three types of plate boundary: convergent, divergent, and transform plate
boundaries.
Divergent plate boundaries occur
where two lithospheric plates move
away from each other, driven by
magma rising from deep within the
mantle. Volcanic activity at a
divergent plate boundary creates
new lithosphere along what is
known as a spreading ridge.
Convergent plate boundaries occur
where two lithospheric plates move
towards each other, with one plate
overriding the other. The overridden
plate (sinking plate) is driven back into
the mantle, and is subsequently
destroyed along what is known as a
subduction zone. During this process,
earthquakes and volcanic activity are
generated in the overriding plate.
Types of Plate Boundary
31. Transform plate boundaries occur where two lithospheric plates slide laterally
past each other. Earthquakes are generated along this type of plate boundary.
Importantly, lithosphere is preserved along transform boundaries, it is not created
or destroyed as it is at divergent and convergent plate boundaries.
37. Plate tectonics is the
fundamental mechanism that
drives geological processes
in the geosphere. Plate
tectonic theory is based on an
understanding of the Earth's
internal structure, the
different types of tectonic
plates and plate boundaries,
and the driving forces of plate
movements.
The occurrence of
earthquakes and volcanoes,
the distribution of different
rock types, and the Rock
Cycle, as well as the
processes of mountain
building, continental rifting
and seafloor spreading, can
be concisely explained by
plate tectonic processes.
Plate Tectonics vs. Geological Processes
38. It is most often formed by
decompression-melting of
asthenosphere associated with
divergent plate boundaries or
mantle plumes, or by partial-
melting of water-rich crust
and/or asthenospheric material
in association with subduction
at convergent plate boundaries.
Magma is hot molten rock
within the earth. It can well-up
from deep to extrude from
fractures as lava flows and/or
pyroclastic ejecta.
The source for magma is not the
earth’s liquid outer core, a
common misconception;
instead, magma is generated at
the relatively shallow depths of
100 to 300 km, through the
partial melting of the earth’s
crust and mantle.
Magma
39. The ingredients necessary for the
production of magma involve the
interplay between heat, pressure,
intra-granular fluids (present as
gases within very hot rock or
magma) and the composition of the
material subject to melting.
1- Heating obviously brings
solids closer to their melting
points, the more heat, the more
likely a solid will melt.
2- In general, higher pressures
prevent melting because the
constituent atoms of minerals in
rocks are squeezed together and
remain solids under high
pressure. Consequently,
lowering pressure on hot rock
induces melting.
40.
41.
42.
43. 3- Intra-granular fluids (gases
within very hot rock or
magma) lower the melting
point of solids, so the
presence of fluids (gases),
generally water, allows solid
rock to melt at a lower
temperature (or heat content)
than it otherwise would.
Bubbles are common in
magmas erupted at the
Earth's surface
44. Factors that control the composition and viscosity of a magma; which in turn play a
determining role in the style of volcanic eruption, eruptive products, and the nature of the
volcano formed.
4- Finally, there are two general trends to explore in relation to rock
composition: rock that contains a relative abundance of silica (SiO2) and
aluminum (aluminum oxide) will melt at a lower temperature (heat content);
while a rock containing a relative abundance of ferromagnesian (Fe, Mg, and
Ca) ions will melt at higher temperatures (heat content).
45. Summary Table
Magma
Type
Solidified
Rock
Chemical Composition Temperature Viscosity Gas Content
Basaltic Basalt
45-55 SiO2 %, high in Fe, Mg, Ca,
low in K, Na
1000 - 1200 o
C 10 - 103
PaS Low
Andesitic Andesite
55-65 SiO2 %, intermediate in Fe,
Mg, Ca, Na, K
800 - 1000 o
C 103
- 105
PaS Intermediate
Rhyolitic Rhyolite
65-75 SiO2 %, low in Fe, Mg, Ca,
high in K, Na.
650 - 800 o
C 105
- 109
PaS High
46. Magma can also be generated by
melting due to the lowering of the
mantle melting temperature because
water and other volatile components
have been introduced into the mantle.
The occurs chiefly in subduction zones
where oceanic lithosphere is
descending back into the mantle. The
oceanic lithosphere carries with it water
in sediments and altered rocks.
The majority of magma erupted at the
Earth's surface is produced by melting
of mantle rock at depths of less than 50
km. Some magmas are produced by
melting of crustal rocks at shallower
levels (less than 30 km). The Earth's
interior is very hot, but it is solid
because of the high pressures. The
melting occurs when mantle rock rises
toward the surface, such as at mid-
ocean ridges, and undergoes
depressurization melting.
47. The melting of continental crust generates felsic magma enriched in silica and
aluminum, while melting of mantle rock (asthenosphere) and oceanic crust forms
ferromagnesian-rich, mafic magma. The earth’s crust naturally contains a higher
water content (because of its proximity to the hydrosphere) than the mantle,
accounting for higher water (and thus gas) content in felsic to intermediate
magmas. The relatively high content of silica and water in continental crust also
correlates with the lower melting temperatures of felsic to intermediate magmas.
Mantle material melts at greater depth and higher temperatures and pressures,
not requiring as much “assistance” from silica and water in the melting process.
48. Magma composition
The composition of magma (and
extruded lava) depends on three main
factors:
1)the degree of partial melting of the
crust or mantle;
2) the degree of magma mixing;
3) magmatic differentiation by fractional
crystallization.
49. Several types of basaltic lavas result from partial melting of mantle and oceanic
crust at subduction zones and mantle plumes.
Emplacement of basaltic magma chambers within continental crust often raises
the temperature of the surrounding silica- and water-rich country rock enough to
cause the country rock significant melting. The country rock becomes
assimilated into the basaltic magma to greater or lesser degree, contaminating it
with felsic material.
If substantial mixing of the magmas occurs, usually requiring significant plate
movement and/or magmatic convection, intermediate magma is born (ranging
from andesitic to dacitic or rhyodacitic).
50.
51.
52. Mafic magmas are generated
by decompression-melting
of highly mafic
asthenosphere and
assimilation-melting of mafic
oceanic lithosphere and
crust in association with
divergent plate boundaries
and some mantle plumes.
The magma source is
naturally low in water
content, however, these
magmas have a much easier
time of it; greater heat and
less silica allows it to readily
reach the surface as
volcanic eruptions (despite
its lack of gases). Mafic
magmas have lower
viscosities because of their
greater heat content and lack
of silica (they have a greater
abundance of iron and
magnesium ions).
53. Felsic magmas have higher viscosities because of their lower heat content and
enrichment with respect to silica. Felsic magmas are generated by the partial
melting of the more siliceous upper portion of water-saturated oceanic crust
(more siliceous because of the thick sedimentary cover it carries) where it is
subducted at convergent plate boundaries and by assimilation-melting of
siliceous, water-rich, continental crust into the magma derived from partial
melting of mafic oceanic crust and asthenosphere as it rises toward the surface.
54. Intermediate magma:
During oceanic-oceanic plate
collisions, a basic magma rises
through the overlying oceanic plate
and is little changed by assimilation-
melting (the original mafic magma
simply assimilates more mafic material
on its way upward); volcanic eruptions
on the sea floor form island chains
called island arcs. Volcanism is
initially mafic in composition, but as
time progresses and the volcanic arc
ages and is subject to erosion
(producing sediment that accumulates
in the subduction zone), newer
magmas become increasingly silicic
and become intermediate. During
oceanic-continental collisions, the
generally mafic magma rises through
felsic continental lithosphere to build a
volcanic arc on the continental
margin. Assimilation-melting of the
overlying felsic continental plate
produces intermediate magma. oceanic-continental collisions
55.
56.
57.
58.
59.
60.
61.
62.
63. Types of Granites
Mineralogically:
Essential minerals - Quartz , Feldspar
Accessory minerals – Biotite, muscovite,
amphibole.
Other accessories are zircon, apatite,
ilmenite, magnetite, sphene, pyrite etc.
Texturally:
Medium to coarse grained crystalline rock
generally exhibiting Hypidiomorphic
texture and Intergrowth textures (perthite,
Antiperthite, Myrmekite, Graphic, Granophyric,
rapakivi).
The granites could be classified based on
mineralogy, geochemistry and tectonic
emplacement:
Mineralogical classifications (IUGS
classification)
Chemical classification (alumina saturation,
S-I-A-M classification etc.)
Tectonic classification (Based on plate
tectonic setting)
65. Classification based on Chemical composition
Alumina saturation classes based on the molar proportions of Al2
O3
/(CaO+Na2
O+K2
O)
(“A/CNK”) after Shand (1927).
66. S-type Granitoid
Derived due to partial melting of
sedimentary and metasedimentary rock.
more common in collision zones.
Peraluminous granites [i.e., Al2O3 > (Na2O
+ K2O+CaO)] and have Fe2O3/FeO ratio <
0.3.
characterised by muscovite, biotite and
marginally higher SiO2 contents
I-type Granitoid
Derived due to partial melting of igneous
proloith.
Derived from igneous or metaigneous rocks
of lower continental crust subjected to
partial melting due upwelling of mantle
material to higher levels.
Generally metaluminous granites,
expressed mineralogically by the absence of
peraluminous minerals like muscovite (with
exceptions) and have Fe2O3/FeO ratio > 0.3.
charecterised by presence of
hornblende/alkali amphiboles ± biotite.
Alphabetical Classification of Granites (SIAM classification)
67. M-type Granitoid
Derived due to fractional
crystallisation of basaltic
magma.
Relatively Plagioclase rich
(plagiogranite of ophiolite).
Associated with Gabbros
and Tonalites in the field.
Formed in subduction
zone.
A-type Granitoid
(anorogenic type)
emplaced in either within
plate anorogenic settings or
in the final stages of an
orogenic event.
High SiO2 (~73.81%)
High F contents (6000 to
8000 ppm)
Presence of fluorite is an
important characteristic of
A-type granites.
Ophiolite Sequence
68.
69. (S-Type)(M-Type)
Mountain building resulting
from compressive stresses
associated with subduction.
Magmatism
takes place
after the
main
orogenic
event.
(I-Type)
Magmatism within
plate or at a spreading
plate margin.
(A-Type)
Classification based on Tectonic emplacement
Granitoids occur in areas where the continental crust has been thickened by
orogeny, either continental arc subduction or collision.The majority of granitoids
are derived by crustal anatexis, however, mantle may also be involved. The mantle
contribution may range from that of a source of heat for crustal anatexis, or it may
be the source of material as well.
70. Ophiolite sequence
Ophilites are fragments of oceanic crust and upper mantle that have been uplifted
and emplaced on continental margins.
71.
72. Ophiolites consist of five distinct layers.
The first layer is the youngest and is primarily sediment
that was accumulated on the seafloor.
The second layer is pillow basalt. Pillow basalt is
characterized by large pillow. When erupting lava
encounters the cold sea water, the outside of the lava
immediately crystallizes, forming a thick crust. The
extremely hot lava still inside the blob, oozes out of the
crust and instantly crystallizes again.
The next layer consists of sheeted dikes. Sheeted dikes
form by rising magma within the earth's crust. As the
sheeted dikes cool fractures and cracks occur in the rock.
Gabbro underlains sheeted dikes and compositionally
similar to basalt. Isotropic (massive) gabbro, indicates
fractionation of magma chamber. Layered gabbro,
resulting from settling out of minerals from a magma
chamber.
The bottommost layer is peridotite, which is believed to
be mantle rock composition.
73. Dunite: more than 90% olivine, typically
with Mg/Fe ratio of about 9:1.
Wehrlite: olivine + clinopyroxene (Augite;
diopside).
Harzburgite: olivine + orthopyroxene
(enstatite),
Lherzolite: olivine + enstatite + diopside
74.
75. It is a process leading to
changes in mineralogy
and/or texture in a rock.
Metamorphism
The boundary between
diagenesis and
metamorphism defines by
noting the first occurrence of
a mineral that does not occur
as a detrital or diagenetic
mineral in surface sediments,
(e.g. chlorite, epidote,
lawsonite, laumontite, albite,
zeolite,…).
Formation of some of these
minerals requires a
temperature of at least 150-
200 °C or 1500 bars or depth
of about 5 km under normal
geothermal conditions. The
upper limit of metamorphism
is defined as the beginning of
appreciable melting.
76. Chemically Active Fluids (ion
transport): In some metamorphic
settings, new materials are
introduced by the action of
hydrothermal solutions (hot water
with dissolved ions). Many metallic
ore deposits form in this way.
Pressure (measured in bars - 1 kb
is approximately each 3 km depth).
Pressure changes both a rock's
mineralogy and its texture.
Pressure comes in different
varieties; confining pressure,
directed pressure (or stress), burial
pressure and fluid pressure.
Heat is the most important source
of energy allowing the formation of
new and more stable mineral and
textural reconstruction and
recrystallization during
metamorphism.
Agents of Metamorphism
77.
78. Type of metamorphism
1- Contact metamorphism occurs
when magma invades cooler rock.
Here, a zone of alteration called an
aureole (or halo) forms around the
emplaced magma. These large
aureoles often consist of distinct
zones of metamorphism. Near the
magma body, high temperature
minerals such as garnet may form,
whereas farther away such low-
grade minerals as chlorite are
produced. Contact metamorphism
produces a zone of alteration called
an aureole around an intrusive
igneous body. Shales baked by
igneous contact form very hard fine-
grained rocks called HORNFELS.
Calcareous rocks (dirty limestones)
when subject to contact
metamorphism an alteration by hot
fluids produce rocks called SKARNS.
Pyrometamorphism: Very high
temperatures at very low pressures,
generated by a volcanic or
subvolcanic body.
79. 2- Metamorphism along Fault
Zones is known as dynamic
metamorphism. In some cases, rock
may even be milled into very fine
components. The result is a loosely
coherent rock called fault breccia
that is composed of broken and
crushed rock fragments. This type
of localized metamorphism, which
involves purely mechanical forces
that pulverize individual mineral
grains, is called cataclastic
metamorphism.
Much of the intense deformation
associated with fault zones occurs
at great depth. In this environment
the rocks deform by ductile flow,
which generates elongated grains
that often give the rock a foliated or
lineated appearance. Rocks formed
in this manner are termed
mylonites.
80. 3- Regional Metamorphism. The
metamorphic rock produced
during regional metamorphism
are associated with mountain
building (orogenic metamorphism
– convergent plate boundaries).
During these dynamic events,
large segments of Earth's crust
are intensely squeezed and
become highly deformed. As the
rocks are folded and faulted, the
crust is shortened and thickened,
like a rumpled carpet. This general
thickening of the crust results in
terrains that are lifted high above
sea level.
In regional metamorphism, there
usually exists a gradation in
intensity. As we shift from areas
of low-grade metamorphism to
areas of high grade
metamorphism, changes in
mineralogy and rock texture can
be observed.
81.
82.
83.
84.
85.
86. 4- Burial metamorphism
Metamorphic effects attributed
to increased pressure and
temperature due to burial.
Range from diagenesis to the
formation of zeolites, prehnite,
pumpellyite, laumontite, etc.
Diagenesis and lithification
start when rocks reach several
kilometers depth. Continued
burial leads to low grade burial
metamorphism. It is common
for sedimentary structures in
the unaltered rocks to remain
in the metamorphosed rocks,
indicating relatively little
recrystallization. This style of
metamorphism grades into
regional metamorphism with
increasing pressure and
temperature. We find it in deep
sedimentary basins.
87. 5- High-pressure low- temperature
metamorphism: This metamorphism
is associated with subduction zones.
It is called high pressure/low
temperature metamorphism where the
subducting plates has been cooled by
interaction with seawater.
6- Hydrothermal metamorphism:
(caused by hot H2O-rich fluids and
usually involving metasomatism). This
style of metamorphism is
distinguished by high fluid content
and changes in rock composition. It
occurs when hot water percolates (or
convects) through rock. This happens
around plutons and in association
with underwater volcanism. Pressures
are usually low and temperatures
moderate. By dissolving components
that are least compatible within the
rocks, hydrothermal metamorphism
can produce very exotic deposits.
Sulfides and massive ore bodies are
associated with it.
88. 7- Ocean-Floor
Metamorphism: affects
the oceanic crust at
ocean ridge spreading
centers. May be
considered another
example of
hydrothermal
metamorphism. Highly
altered chlorite-quartz
rocks- distinctive high-
Mg, low-Ca
composition.
Metamorphic rocks
exhibit considerable
metasomatic
alteration, notably loss
of Ca and Si and gain
of Mg and Na. These
changes can be
correlated with
exchange between
basalt and hot
seawater
89.
90.
91. Metamorphic Facies
A metamorphic facies includes rocks of any chemical composition and hence of
widely varying mineralogical composition, which have reached chemical
equilibrium during metamorphism under a particular set of physical conditions.
92.
93. Facies of Low Pressure
1) Albite-epidote hornfels
facies,
2) Hornblende hornfels
facies,
3) Pyroxene hornfels
facies, and
4) Sanidinite facies.
Facies of Medium to
High Pressure
1) Zeolite facies,
2) Prehnite-pumpellyite
metagreywacke facies,
3) Greenschist facies,
4) Amphibolite facies, and
5) Granulite facies.
Facies of Very High
Pressure
1) Glaucophane-lawsonite
schist facies.
2) Eclogite facies.
94.
95.
96.
97. Convergent Plate Margin
At all three types of convergent boundary
(ocean-ocean, ocean-continent, continent-
continent), high stresses, high deposition
rates and volcanism can be found.
Amphibolite to granulite facies are found
within the cores of mountain belts.
Greenschists occur at shallower depths
within the belts. Blueschists are produced
by the rapid subduction of sediments and
oceanic crust where high pressures can
be reached before temperatures within the
subducted crust can be rised.
Eclogite facies are reached within the
subducting crust when it reaches depths
of 20 to 25 km. Hornfels are found in
contact aureoles around shallow
intrusions where hot magma heats the
surrounding rocks.
Plate Tectonic Settings of Metamorphism
98. The uplift of mountains results in regional metamorphism. Baking of "country"
rock by igneous intrusions produces Contact metamorphism. Faulting of highly
stressed crustal rocks results in Cataclastic metamorphism. Rapid sedimentation
and subsidence offshore produces Burial metamorphism. Lastly, Zeolite facies
metamorphism occurs within the accretionary prism located arc ward of the
trench.
105. Divergent Plate Margin
A unique form of metamorphism occurs at divergent plate boundaries. New plate
is created by the upwelling of hot mantle. Partial melting produces new oceanic
crust through which water percolates, or convects, and is heated. Where it exits
the rock, water temperatures can be as high 450 °C, and are commonly as high as
350 °C (high water pressure at the sea floor prevents boiling). As the heated water
passes through the fresh basalt, it leaches out silica, iron, sulfur, manganese,
copper and zinc. The basalt incorporates magnesium and sodium from the water,
altering its composition and mineralogy.