1) Ore deposits can form from the crystallization of magma in magma chambers (magmatic segregation deposits). Some major examples include deposits associated with layered igneous intrusions like the Bushveld Complex in South Africa, the Great Dyke of Zimbabwe, and the Sudbury Igneous Complex in Canada.
2) Skarn deposits form at the contact between intrusive igneous rocks and carbonate country rocks, where the carbonates are metamorphosed into marble, hornfels, and skarn minerals. Skarn deposits are a source for metals like copper, iron, tungsten, lead, and zinc.
3) Porphyry deposits are associated with porphy
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
Minerals are formed by changes in chemical energy in systems which contain one fluid or vapor phase. In nature, minerals are formed by crystallisation or precipitation from concentrated solutions. These solutions are called as ore-bearing fluids. Ore-bearing fluids are characterised by high concentration of certain metallic or other elements.
Fluids are the most effective agents for the transport of material in the mantle and the Earth's crust.
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
Minerals are formed by changes in chemical energy in systems which contain one fluid or vapor phase. In nature, minerals are formed by crystallisation or precipitation from concentrated solutions. These solutions are called as ore-bearing fluids. Ore-bearing fluids are characterised by high concentration of certain metallic or other elements.
Fluids are the most effective agents for the transport of material in the mantle and the Earth's crust.
Information about these fluids is an invaluable aid in mineral exploration.
Conventional academic methods of analysing fluid inclusions are too slow and tedious to be of practical application in typical mineral exploration activities.
However, the academic data from numerous studies does show that CO2 is an exceptionally important indicator when exploring for most types of gold deposit.
Because the baro-acoustic decrepitation method is a rapid and reliable method to measure CO2 contents in fluids, it can be used to study a spatial array of data and it is an invaluable and practical exploration method.
Measurements of temperatures of fluid inclusions does not usually help in mineral exploration as hydrothermal minerals deposit over a wide temperature range and there is no specific temperature which is indicative of mineralisation. However, if temperatures are available on a large spatial array of samples, then temperature trends may be a useful exploration method to find the hottest part of the system, which is presumably the location of the best economic mineralisation. Baro-acoustic decrepitation is the most practical method to determine temperatures of the large numbers of samples required.
Salinities of fluid inclusions are of limited use in exploration and are difficult to measure. However, they can be used to recognise intrusion related hydrothermal systems.
CLASSIFICATION OF ORE DEPOSITS
The Mixture of ore minerals are gangue minerals form an Ore deposit. The ore
deposits are generally found enclosed within the country rocks. The ore deposits
are formed in many different ways. Depending upon the process that may
operate to produce them, the ore deposits may be classified as follow:
Magmatic ore deposits.
Sublimation ore deposits.
Pegmatitic ore deposits.
Contact metasomatic ore deposits.
Hydrothermal ore deposits
Cavity filling deposits.
Replacement deposits.
Sedimentation ore deposits.
Evaporation ore deposits.
Residual and mechanical concentration deposits
Metamorphic ore deposits.
MAGMATIC ORE DEPOSITS:
The magmatic ore deposits are the magmatic products which crystallize from
magmas. The magmatic ore deposits are classified as follows:
o Early magmatic deposits
o Late magmatic deposits
Early magmatic deposits:
Early magmatic deposits are formed during the
early stage of the magmatic period. In this case the
ore minerals crystallize earlier than the rock
silicates. The Minerals of Nickel, Chromium, and
Platinum are usually found as early magmatic
deposits. The early magmatic deposits can be sub
divided into two groups:
o Dissemination deposits
o Segregation deposits
Dissemination deposits:
When magma crystallizes
conditions, a granular igneous rock is formed. In
such a rock early formed crystals of
may occur in dissemination.
Segregation deposits:
Magmatic segregation deposits are
formed as a result of gravitative
crystallization differentiation. In
case, the ore mineral which crystallize
early, get ocean-trated on a particular
part of igneous part. The ore deposits
thus formed are known as “Segregation
deposits”.
rly under seated
ore minerals
such
Late Magmatic Deposits:
The ore deposits which are formed to
called late magmatic deposits. The late magmatic deposits contain those ore
minerals which have crystallized at rather low temperature from the residual
magma. The magma which is left after crystallization of early for
is called residual magma. This magma frequently contains many ore minerals. The
late magmatic deposits include most of the magmatic deposits of iron and
titanium ores, these deposits are almost always associated with mafic igneous
rocks.
SUBLIMATION DEPOSITS:
Sublimation is a very minor process of formation of ore deposits. Sublimation
deposits contain only those minerals which have been volatilized by hear and
subsequently redeposit in the same form at low temperature and pressure. The
sublimation deposits are found associated with Volcanoes and Fumaroles. Sulfur
of this origin has been mined in Japan, Italy, and Mexico.
SUPERGENE ENRICHMENT; Definition; Zones; Morphology of Zoning; Oxidized zone ; Supergene zone ; Gossans and Cappings; Chemical Changes Involved; Electrowinning; Formation of Copper Oxides
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:
The name Spinifex refer to a spiky grass in Australian.
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:
Information about these fluids is an invaluable aid in mineral exploration.
Conventional academic methods of analysing fluid inclusions are too slow and tedious to be of practical application in typical mineral exploration activities.
However, the academic data from numerous studies does show that CO2 is an exceptionally important indicator when exploring for most types of gold deposit.
Because the baro-acoustic decrepitation method is a rapid and reliable method to measure CO2 contents in fluids, it can be used to study a spatial array of data and it is an invaluable and practical exploration method.
Measurements of temperatures of fluid inclusions does not usually help in mineral exploration as hydrothermal minerals deposit over a wide temperature range and there is no specific temperature which is indicative of mineralisation. However, if temperatures are available on a large spatial array of samples, then temperature trends may be a useful exploration method to find the hottest part of the system, which is presumably the location of the best economic mineralisation. Baro-acoustic decrepitation is the most practical method to determine temperatures of the large numbers of samples required.
Salinities of fluid inclusions are of limited use in exploration and are difficult to measure. However, they can be used to recognise intrusion related hydrothermal systems.
CLASSIFICATION OF ORE DEPOSITS
The Mixture of ore minerals are gangue minerals form an Ore deposit. The ore
deposits are generally found enclosed within the country rocks. The ore deposits
are formed in many different ways. Depending upon the process that may
operate to produce them, the ore deposits may be classified as follow:
Magmatic ore deposits.
Sublimation ore deposits.
Pegmatitic ore deposits.
Contact metasomatic ore deposits.
Hydrothermal ore deposits
Cavity filling deposits.
Replacement deposits.
Sedimentation ore deposits.
Evaporation ore deposits.
Residual and mechanical concentration deposits
Metamorphic ore deposits.
MAGMATIC ORE DEPOSITS:
The magmatic ore deposits are the magmatic products which crystallize from
magmas. The magmatic ore deposits are classified as follows:
o Early magmatic deposits
o Late magmatic deposits
Early magmatic deposits:
Early magmatic deposits are formed during the
early stage of the magmatic period. In this case the
ore minerals crystallize earlier than the rock
silicates. The Minerals of Nickel, Chromium, and
Platinum are usually found as early magmatic
deposits. The early magmatic deposits can be sub
divided into two groups:
o Dissemination deposits
o Segregation deposits
Dissemination deposits:
When magma crystallizes
conditions, a granular igneous rock is formed. In
such a rock early formed crystals of
may occur in dissemination.
Segregation deposits:
Magmatic segregation deposits are
formed as a result of gravitative
crystallization differentiation. In
case, the ore mineral which crystallize
early, get ocean-trated on a particular
part of igneous part. The ore deposits
thus formed are known as “Segregation
deposits”.
rly under seated
ore minerals
such
Late Magmatic Deposits:
The ore deposits which are formed to
called late magmatic deposits. The late magmatic deposits contain those ore
minerals which have crystallized at rather low temperature from the residual
magma. The magma which is left after crystallization of early for
is called residual magma. This magma frequently contains many ore minerals. The
late magmatic deposits include most of the magmatic deposits of iron and
titanium ores, these deposits are almost always associated with mafic igneous
rocks.
SUBLIMATION DEPOSITS:
Sublimation is a very minor process of formation of ore deposits. Sublimation
deposits contain only those minerals which have been volatilized by hear and
subsequently redeposit in the same form at low temperature and pressure. The
sublimation deposits are found associated with Volcanoes and Fumaroles. Sulfur
of this origin has been mined in Japan, Italy, and Mexico.
SUPERGENE ENRICHMENT; Definition; Zones; Morphology of Zoning; Oxidized zone ; Supergene zone ; Gossans and Cappings; Chemical Changes Involved; Electrowinning; Formation of Copper Oxides
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:
The name Spinifex refer to a spiky grass in Australian.
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:
In this presentation we discuss cobalt crusts, its classification, Occurrence and Distribution, Formation, Texture, Mineralogy, Scope for future mining and exploration.
Manganese ore deposits are widely scattered in various districts in Egypt.
They occur at some localities in Sinai Peninsula and at a few localities in the Eastern Desert.
Manganese deposits are known:
in the Um Bogma district in west central Sinai; and
in the Halaib "Elba" district in the southern portion of Eastern Desert.
In addition, minor occurrences are known in Wadi Mialik near Abu Ghosun and Ras Banas in the Southern Eastern Desert, and Wadi Abu Shaar El Qibli (Black Hill), to the north of Hurghada
Plate tectonics, like crustal evolution, provides a basis for understanding the distribution and origin of mineral and energy deposits. Different types of ores are characterized by distinct geological environment and tectonic settings.
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
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
1. ORE DEPOSITS
ORE DEPOSITS RELATED TO MAFIC, ULTRAMAFIC, INTERMEDIATE TO
FELSIC IGNEOUS ROCKS:
Kunwar Shruten Chauhan
Department of Geology
University of Rajasthan
Jaipur
2. PAGE 1
ORE DEPOSITS RELATED TO MAFIC AND ULTRAMAFIC ROCKS
.
Ore deposits formed during fractional crystallization of magmas are designated as magmatic
segregation deposits (also known as orthomagmatic deposits). These deposits are the direct
crystallization products of magma, usually form in the magma chamber and thus constitute deep-
seated intrusive bodies. However differentiated or immiscible melts and crystal mushes can be
driven into the walls or roofs of the magma chamber to form ore bodies in the form of dikes, sills,
and even extrusive flows. A magmatic segregation deposit may constitute an entire intrusive
body, form a single compositional layer within the igneous rock body, or occur as disseminated
minerals.
Mode of occurrence:A magmatic segregation deposit may occur in any of the following forms:
(i) constitute an entire intrusive body
(ii) form a single compositional layer within the igneous rock body
(iii) may be defined by the presence of disseminated minerals.
Orthomagmatic deposits of Cr-Pt-Ti-Fe and Cu-Ni-Fe (-Pt) associated with basic and ultrabasic
rocks emplaced in cratonic and active orogenic settings. The worlds major Orthomagmatic
deposits are associated with
(1) Layered igneous intrusive (Bushveld, Great Dyke and Sudbury)
a) Bushveld layered complex contains about 75% of the world’s chromium reserves.
The Bushveld complex is large reserves of platinoid ores (composed of
Pt+Pd+Rh+Ru+Ir+Os) and the average ore grade is 8.27ppm. Another significant
resource of the Bushveld complex is the layered magnetite – rich units associated
with titanium and vanadium.
b) The Great Dyke of Zimbabwe is a layered igneous intrusion, 532 km long, 5 to 9.5
km wide and consists of chromite layers that occur along the entire length and the
individual layers extend across the entire width.
c) The Sudbury basin is Shock metamorphic features favours a meteorite impact
hypothesis for the eruption of magma. Sudbury Igneous complex (1849 Ma) consists
of a lower zone of augite - norite, a thin middle zone of quartz–gabbro and an upper
zone of granophyres and these three rock units are reported to be comagamatic. In
steep to vertical, radial and concentric dykes that appear to penetrate downward into
the foot wall from the base of the complex and referred to as offsets,the inclusion–
rich sulphide bearing rock is quartz diorite. Most of the ore bodies occur in the
sublayer (inclusion- and sulphide- rich norite and gabbro) whose magma was rich in
sulfides with inclusions and peridotite, pyroxenite and gabbro. The sublayer and
offsets are at present the world’s richest source of nickel as well as an important
source of copper, cobalt, iron, platinum and 11 other elements.
(2) Intrusions related to flood basalts of cratonic areas (Norilsk–Talnakh)
3. PAGE 2
Noril’sk deposit , Russia, occurs in the differentiated layered, dominantly gabbroic
intrusion. The copper-nickel sulfides form breccia and disseminated and massive ores at
the base of the intrusion and vein ore bodies developed in the footwall rocks and the basal
portion of the intrusion.
(3) Bodies emplaced in active orogenic areas (Eastern Gold Field Province)
Eastern Goldfields province, Yilgran craton, Western Australia, is bestowed with several
occurrences of orthomagmatic copper-nickel sulfide deposits associated with komatiitic
suite of lava flows and related shallow dyke-like or sill-like dunitic intrusions.
Assosiated rocks;
1) KIMBERLITES AND LAMPROITES
About 20% of the world production of diamonds is derived from kimberlites and
lamproites and the rest is extracted from beach and alluvial placers deposits
containing diamonds.
Kimberlites and lamproites are carrot shaped and are generally regarded as having
been intruded upwards into cratonic areas through a series of deep–seated tension
fractures,often in terrains of regional doming and rifting.
2) CARBONATITES
Carbonatites are generally found in:
(1) stable cratonic regions along major faults and fault intersections and
(2) rift valleys.
Carbonatites are exploited for phosphorus (from apatite), magnetite, niobium (from
pyrochlore), zirconia, Rare earth elements (from monazite and bastanasite), barite,
strontianite and vermiculite. Only one carbonatite body (Palabora complex, South Africa)
is known for large reserves of copper ore.
3) ANORTHOSITES
Anorthosite massifs are essentially Proterozoic in age and confined to terrains of
anorogenic intercontinental rifting or incipient rifting tectonic setting in a broad belt
across North America, Britain and Scandinavia.
Anorthosite massifs are divisible into two groups (Herz 1976) based on their
plagioclase and oxide compositions; they are:
(1) Labradorite anorthosite massifs (e.g., Michigamau anorthosite, Labrador; Duluth
Gabbro complex, Minnesota), and
(2) Andesine anorthosite massifs (e.g., anorthosite massifs of Adirondack Mountains in
New York; Allard Lake region in Quebec,Canada and Rosland in Virginia, USA).
Anorthosite massifs are the major source of titanium minerals (ilmenite and rutile).
ORE DEPOSITS ASSOCIATED WITH INTERMEDIATE TO FELSIC IGNEOUS
ROCKS:
4. PAGE 3
Orthomagmatic deposits associated with felsic volcanism
Felsic magmatic melts are rarely in a position to generate significant Orthomagmatic deposits.
But iron ore deposits, consisting magnetite ± apatite encountered at severalplaces are considered
as of magmatic segregation origin. These deposits occur both as lava flows and dyke-like bodies
Pegmatites and their mineral deposits
Pegmatites are coarse-grained igneous or metamorphic rocks, generally of granitic composition.
Pegmatite developed at higher structural levels and spatially related to intrusive late tectonic
granitic plutons, are marked by minerals with volatile components (OH,F, B) and a whole range
of accessory minerals containing rare lithophile elements, including Be, Li, Sn, W, Rb, Cs, Nb,
Ta, REE and U.
Pegmatites are mined for:
(a) Sn, Nb-Ta,REE, Y, Zr, Be and U ores,
(b) Gem quality beryl, Chrysoberyl, topaz and tourmaline; optical grade fluorite crystals;
piezoelectric quartz crystals,
(c) feldspar required for ceramic industry
(d) Li-minerals (spodumene, petalite, lepidolite) for the glass industry and manufacture of
Licompounds, (e) book-mica (muscovite) for the electrical industry and electronic tubes.
Greisen deposits
Greisens are granoblastic aggregates of quartz and muscovite (or lepidolite) with accessory
amounts of topaz, tourmaline and fluorite formed by post-magmatic metasomatic alteration of
granite.
Greisens are usually developed at the upper contacts of granitic intrusions and mineralization
occurs as large irregular or sheet-like bodies immediately beneath the upper contact of late stage
Greisen deposits are mined for tin, tungsten and beryllium. In future, greisens may constitute
important sources of Be, Nb-Ta, REE, Y and other elements.
Skarn deposits
Skarn deposits have been referred to variously in literature as (a) hydrothermal metamorphic, (b)
igneous metamorphic, (c) contact metamorphic and (d) pyrometasomatic deposits. They are
developed at the contact of intrusive plutons and carbonate country rocks. The latter are
converted to marble, calc-silicate hornfelses and/or skarns by contact metamorphic effects. The
majority of the world’s economic skarn deposits occur in calcic exoskarns.
Skarn deposits are mined for Cu, Fe, W, Pb-Zn, Mo, tin etc; these deposits are generally smaller.
Most copper skarn deposits are associated with calc-alkaline granodiorite to monzogranite stocks
emplaced in continental margin arcs. A small number of copper skarns occur in oceanic island
arcs associated with quartz diorite to monzonite plutons.
Giant skarn type iron deposits at Sarbai in Turgai iron ore province, Kazakhstan are associated
with diorite and contain 715 Mt of iron ore with 46% Fe. Iron skarn deposit at Iron Springs, Utah
(USA) is an ideal example of Skarn development at the boundary between intrusive and
limestone.
5. PAGE 4
Bulk of the skarn tungsten (scheelite) comes form a few relatively large deposits,
Dolomite hosted skarn deposits of talc are encountered in France (Trimouns Mine) and
Austria. Minor amount of graphite production comes from skarns from Skaland Mine,
Norway. ‡ Sn- and Mo- skarns are typically associated with high-silica (~75% SiO2) well
differentiated plutons, while Au- and Fe- skarns relate with relatively less-evolved, low
silica (62% SiO2), high – iron plutons. Cu-Zn-and W- skarns are associated with plutons
having silica content ranging from 63-69%.
Skarn deposits are associated with magmatic rocks emplaced under diversified tectonic settings;
Oceanic back arc basin, subduction zone beneath continents and post-subduction or continental
rifting environment.
Porphyry deposit
The term “Porphyry system” relates to a composite (occasionally single), mediumto silicic
igneous intrusive complex wherein at least one member displays porphyritic texture, with
~25vol% of phenocrysts of alkali feldspar and/or quartz.
Three main types of “Porphyry” ores are recognised:
1) Porphyry copper with two sub-type Cu-Mo and Cu-Au (these two types of deposits
represent the Lowell-Guilbert model and Diorite model respectively)
2) Porphyry molybdenum which is subdivided into the “Climax-type” with Sn and W
and “Quartz-Monzonite type” (Endoco-type) which grades into Cu(Mo) porphyry
with decreasing Mo/Cu ratio.
Porphyry-tin, which contains minor/trace amounts of W, Mo, and Bi. Major
concentrations of porphyry Cu and Mo deposits are confined to Phanerozoic island arc
settings and Andean type continental margins,Porphyry Cu and Moores are also known
from Palaeozoic fold belts. Porphyry Mo deposits are mostly of Mesozoic and Tertiary
ages. Porphyry Sn deposits are mostly of Tertiary age ; Sn – granites of Asian countries are
of Mesozoic age.