A presentation on Hydrothermal wall rock alteration with case studies on geophysical applications.
References : https://drive.google.com/drive/folders/16VSZMPMASMNVB47JdBUa_7udBk1qvK2U?usp=sharing
Structural geology is the study of the three-dimensional of the rock units with respect to their deformational histories, Structure is spatial and geometrical configuration of rock components.
Structures are classified into two types:
Primary structures.
Secondary structures
Primary structures
Structures that form during deposition or crystallization of the rock, are the result of two processes:
Settling of solid particles from fluid medium in which they have been suspended, in most of the sedimentary rocks.
Crystallization of mineral grains from a liquid in which they have been dissolved as in igneous rocks.
metamorphic rocks and their distinguishing features-megascopic and microscopic study of gneiss, schist, quartzite, marble and slate
Properties and characteristics and uses of metamorphic rocks
Geology and Petrography of Sandstone of Murree formation, Kuldana formation and Abbottabad formation Nakial and Dandli section sub Himalayas district Kotli, Azad Jammu Kashmir, Pakistan.
This is a topic of Sequence stratigraphy in which I briefly describe about basin , formation of basin , Types , different basin of Pakistan and worldwide distribution of these basins.
A presentation on Hydrothermal wall rock alteration with case studies on geophysical applications.
References : https://drive.google.com/drive/folders/16VSZMPMASMNVB47JdBUa_7udBk1qvK2U?usp=sharing
Structural geology is the study of the three-dimensional of the rock units with respect to their deformational histories, Structure is spatial and geometrical configuration of rock components.
Structures are classified into two types:
Primary structures.
Secondary structures
Primary structures
Structures that form during deposition or crystallization of the rock, are the result of two processes:
Settling of solid particles from fluid medium in which they have been suspended, in most of the sedimentary rocks.
Crystallization of mineral grains from a liquid in which they have been dissolved as in igneous rocks.
metamorphic rocks and their distinguishing features-megascopic and microscopic study of gneiss, schist, quartzite, marble and slate
Properties and characteristics and uses of metamorphic rocks
Geology and Petrography of Sandstone of Murree formation, Kuldana formation and Abbottabad formation Nakial and Dandli section sub Himalayas district Kotli, Azad Jammu Kashmir, Pakistan.
This is a topic of Sequence stratigraphy in which I briefly describe about basin , formation of basin , Types , different basin of Pakistan and worldwide distribution of these basins.
S6E5. Students will investigate the scientific view of how the earth’s surface is formed.
g. Describe how fossils show evidence of the changing surface and climate of the Earth.
c. Classify rocks by their process of formation.
Classification of sedimentary Rocks
************************************
Sedimentary rocks are formed by the accumulation of sediments. There are three basic types of sedimentary rocks.
1.Clastic
2.Chemical
3.Organic
for more notes/ppt please visit vinoychakmalibrary.blogspot.in
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.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
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.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
DERIVATION OF MODIFIED BERNOULLI EQUATION WITH VISCOUS EFFECTS AND TERMINAL V...Wasswaderrick3
In this book, we use conservation of energy techniques on a fluid element to derive the Modified Bernoulli equation of flow with viscous or friction effects. We derive the general equation of flow/ velocity and then from this we derive the Pouiselle flow equation, the transition flow equation and the turbulent flow equation. In the situations where there are no viscous effects , the equation reduces to the Bernoulli equation. From experimental results, we are able to include other terms in the Bernoulli equation. We also look at cases where pressure gradients exist. We use the Modified Bernoulli equation to derive equations of flow rate for pipes of different cross sectional areas connected together. We also extend our techniques of energy conservation to a sphere falling in a viscous medium under the effect of gravity. We demonstrate Stokes equation of terminal velocity and turbulent flow equation. We look at a way of calculating the time taken for a body to fall in a viscous medium. We also look at the general equation of terminal velocity.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
1. Classification of sedimentary rocks-
Autochthonous sediments: Carbonate
sedimentary rocks
SUBMITTED BY: SUSHANT ADHIKARI
ROLL NO-19
MSC GEOLOGY, 1ST SEMESTER
2. CONTENT OVERVIEW:
• Introduction to sedimentary rock
• Types of sedimentary rocks
• Autochthonous sediments
• Carbonate sedimentary rocks
• Components
• Classification
• Limestone diagenesis and porosity evaluation
• Dolomite diagenesis
• Importance of carbonates rocks
3. INTRODUCTION
•Sedimentary rocks are formed when sediment is
deposited out of air, ice, wind, gravity, or water flows
carrying the particles in suspension.
•The most important geological process that leads to
the creation of sedimentary rocks are erosion
,weathering, dissolution , precipitation and
lithification.
•Figure.1- Showing process of formation of
sedimentary rocks.
4. TYPES OF SEDIMENTARY ROCKS
•Sedimentary rocks can be organized into two categories.
5.
6. Autochthonous sediments
•Autochthonous is a term that refers to sediments that are
found in the same place where they were formed or in a
location very close to its site of deposition.
•In simple word the deposited rock have no any
displacement from the deposited area.
•Autochthonous sediments are produced locally and
include biogenic sediment such as carbonate (e.g. shell,
foraminifer and coral fragments) and silica (e.g. sponge
spicules and diatoms).
Figure.2- A conceptual model for the
allochthonous and autochthonous sources for
the high altitude lacustrine sediments.
7. Carbonate sedimentary rocks
•Chemical/biochemical sedimentary rocks originate by precipitation of minerals from
water through various chemical or biochemical processes.
•Carbonate rocks are intrabasinal in origin
•Biochemical process includes the accumulation of fossils, the activity of organisms, and
other inorganic processes – all involving dissolved carbonates and water.
•They are distinguished from siliciclastic sedimentary rocks by their chemistry, mineralogy,
and texture.
8. CON’T
•The carbonate rocks make up 10 to 15% of sedimentary rocks. They largely consist of two types
of rocks and these two are most abundant Carbonate rocks.
a) Limestones which are composed mostly of calcite (CaCO3) or high Mg calcite [(Ca,Mg)CO3],
and
b) Dolostones which are composed mostly of dolomite [CaMg(CO3)2]
•They are present in many Precambrian assemblages and in all geologic systems from the
Cambrian to the Quaternary.
a. Precambrian-Paleozoic - Dolomite
b. Mesozoic and Cenozoic Carbonates –Limestone
•Another common carbonate rock, containing a mixture of fine-grained calcite and terrigenous
mud, is marl.
9. Minerology of carbonate Sediment
•The elemental chemistry of carbonate rocks is dominated by
calcium ( Ca 2+), magnesium ( Mg2+), and carbonate (C032 -)
ions.
•Calcium and magnesium are present in both limestones and
dolomites; however, magnesium is a particularly important
constituent of dolomites
•Calcium carbonates occurs in two mineral i.e.
•i)Aragonite and ii) Calcite
•Aragonite crystallizes in the orthorhombic crystal system, while
Calcite is rhombohedral. Calcite forms an isomorphous series
with magnesite (MgCO3).
10. • The principal carbonate minerals are the calcium
carbonates, calcite and its unstable polymorph
aragonite; and dolomite, calcium magnesium
carbonate. Modern carbonate sediments are
composed of both aragonite and calcite.
• Only calcite, the more stable variety, occurs in
lithified limestones. Dolomite does not occur as a
biogenic skeletal mineral.
11.
12. Components
There are two components of carbonate rocks
1. Allochemicals-
An allochems is a carbonate particle that was formed outside of the depositional area and
transported in, hence a carbonate "clast.“
2. Orthochemicals
Carbonate sediments that form within the depositional area represent the rock cement or
matrix
Orthochems binds allochems together and lithify the sediments
13. Allochems
Allochems are subdivided into two kinds.
1. Skeleton (Biogenic Grains)
2. Non Skeleton
1. Skeleton
The skeleton components includes all the bioclast of a carbonate –secreting invertebrates .These
invertebrates includes Foraminifera's, Mollusca, Gastropods .
15. 2. Non skeleton
Four major types on Non skeleton grains are
recognized
a) Various coated grains (ooids, Piiods, Oncoids)
b) Peloids
c) Clumped or aggregated grains(lumps, grape
stones) and
d) Limestone clasts(limeclasts)
Figure.4- Showing principal non skeletal components
16. a) Various coated grains
Ooids (Oolith)
Size range- 1-5mm(diameter)
Ooid are coated carbonate grains that contain a
nucleus of some kind-a shell fragment, pellet, or
quartz grain-surrounded by one or more thin
layers or coatings (the cortex) consisting of fine
calcite or aragonite crystals.
Ooids form where strong bottom currents and
agitated-water including tidal sand bars or tidal
deltas between barrier islands conditions exist
and where saturation levels of calcium
bicarbonate are high.
modern ooids -aragonite
ancient ooids -calcite.
Ooids with asymmetric coatings and
superficial oolites form in quiet water.
Figure.5- Oolith in thin section.
17. Pisolites, oncoids, and oncolites are enveloped
by irregular layers. All these grains are
frequently larger than ooids and commonly
are over a centimeter in diameter.
Pisolites form by the precipitation of calcium
Carbonate around nuclei trapped in sediment
within the vadose zone of soils or marine tidal
flats
Oncoids form on the surface of intertidal and
supratidal flats where Carbonate precipitates
from salt water spray and marine flood
waters.
A rock composed of oncoids is termed an
"oncolite."
19. b)Peloids
Fine grained (0.1-0.5mm) sand to silt sized
clast of microcrystalline carbonate which
lacks coherent internal structure
Peloids are formed in shallow marine low-
energy platform carbonate settings
Most common peloids (pellets) are fecal
pellets of waste matter generated by such
organisms as fish and shrimps
Others are produced by the micritization of
other kinds of allochems: ooids, oncoids,
interclass
Figure.7- Showing Fecal pellets
20. c)Clumped or aggregated grains(lumps, grape stones)
Grains aggregates are formed when carbonate particles such
as ooids and peloids attached to one another.
Figure.8- showing grape stone in thin section
d)Limestone clasts(limeclasts)
fragments of earlier-formed limestone, mostly
intraclasts from a local source.
Figure.9- showing limeclasts in thin section
d)Limestone clasts(limeclasts)
fragments of earlier-formed limestone, mostly
intraclasts from a local source.
22. 1. Micrite
Size-0.03-0.04 mm in diameter
Folk (1 959) proposed the contraction micrite for microcrystalline calcite, a term that has been
universally adopted to signify very fine grained carbonate sediments
Orthochemicals
• Calcium carbonate mud occurring as
a matric
• Translucent under microscope, dull
brown
• produced form biochemical ooze or
attrition of shells
23. 2. Spary calcite or spar
•Size- 0.02-0.1mm
•Spar is carbonate cement
•Crystals of spar are generally coarser than micrite
•Under the microscope, spar is crystal clear without the hazy brownish cast of micrite
Neomorphism- the various diagenetic processes of recrystallization and replacement ,including
changes in minerology- is very common in carbonate rocks.
Yesterday’s micrite can become today’s spar and vice versa
25. Classification
Three classification schemes are in common use by those who work on carbonate rocks
a) A very simple but often useful scheme divides limestones on the basis of grain size into
calcirudite (most grains >2mm), calcarenite (most grains between 2mm and 62mm) and
calcilutite (most grains less than 62mm
b) The classification scheme of R.L. Folk( Folk’s Classification)
Based mainly on composition, distinguishes three components:
I. the grains (allochems),
II. matrix, chiefly micrite and
III. cement, usually drusy sparite.
26. •An abbreviation for the grains (bio —skeletal
grains, oo —ooids, pel —peloids, intra —
intraclasts) is used as a prefix to micrite or
sparite, whichever is dominant. Terms can be
combined if two types of grain dominate, as
in biopelsparite or bio-oosparite.
•Another term introduced by Folk’s is
biolithite, referring to a limestone formed in
situ, such as a stromatolite or reef-rock; and
dismicrite, referring to a micrite with cavities
(usually sparfilled).
•Folk also indicated that the textual structure
of limestone had matured.
•Folks Classification is used only in lab.
Figure.12- showing Classification of limestones based on composition
28. C). The classification of R.J. Dunham ( Dunhams Classification)
Classification based on depositional texture
The three criteria used to define the original Dunham classes were:
•the supporting fabric of the original sediment
•the presence or absence of mud (the fraction <20 μm in size
•Evidence that the sediments were organically-bound at the time of deposition.
29. Based on these criteria defined four classes.
Mudstone- a mud-supported carbonate rock containing <10% grains. Generally
indicates calm water and apparent inhibition of grain-producing organisms (low-energy
depositional setting).
Wackestone- a mud-supported carbonate rock containing >10% grains. Generally
indicates calm water and restriction of grain-producing organisms (low-energy
depositional setting). In cases where grains are exceptionally large, Embry and Klovan
(1971) designated these carbonates “floatstones.”
Packstone- a grain supported fabric containing 1% or more mud-grade fraction. Embry
and Klovan (1971) designated these carbonates “rudstones.”
Grainstone- a grain-supported carbonate rock with <1% mud. hey generally are
deposited in moderate- to high-energy environments, but their hydraulic significance can
vary
30. Later two additional classes were added within this scheme:
Boundstone- Carbonate rocks showing signs of being bound during deposition (Dunham,
1962). Embry and Klovan (1972) further expanded the boundstone classification on the basis
of the fabric of the boundstone.
i)Framestone – Organism builds a rigid framework
ii)Bindstone- organism encrust and bind loose sediments together
iii)Bafflestone- the organisms do not form a framework or bind the sediments together
but provide protected areas for the sediment to accumulate by baffling the currents.
Boundstones generally are deposited in higher energy environments, where currents can
provide nutrients to the organisms that form the boundstone, as well as carry away waste
products.
Crystalline carbonates: Carbonate rocks that lack enough evidence of depositional texture to
be classified. Extensive dolomitization commonly obliterates the original depositional texture.
32. Limestone diagenesis and porosity evaluation
Diagenesis is the hardening of loose sediment into sedimentary rock, so in the case of
carbonate sediments – skeletons that make up carbonate sediments
The diagenesis of carbonates involves many different processes and takes place in near-surface
marine and meteoric environments, down into the deep-burial environment.
Six major processes can be distinguished:
a. Cementation,
b. Microbial micritization,
c. Neomorphism,
d. Dissolution,
e. Compaction and
f. Dolomitization
33. a . Cementation
Major diagenetic process
Infilling of primary voids in or between particles, or
of solution cavities by chemically precipitated
cements.
Sediments compact together in this way and result
in the formation of Carbonate rocks.
i) Early diagenetic cement formation ("cement A")
At the expense of metastable carbonate minerals
(e.g., aragonite in skeletal grains)
By evaporation of pore water rich in carbonates, in
the supratidal zone
On the ocean floor
ii) Late diagenetic cement formation ("cement B")
Cement formed after sediment consolidation or
after compaction
Figure.15-Showing Principal kinds of cements that
form in carbonate rocks during diagenesis
34. b. Microbial micritization
The formation of micrite by the boring into skeletal carbonate particles by
cyanobacteria(blue-green algae), and the subsequent precipitation of micrite within the
borings.
c. Neomorphism
This term was introduced by Folk (1965: 21) as a "comprehensive term of ignorance" for all
mineral transformations in which the mineral either remains intact or is converted into a
polymorphous mineral.
◦ i) Coalescive neomorphism
◦ Larger crystals grow at the expense of smaller crystals ("aggrading" neomorphism, or small crystals grow
within a large crystal ("degrading" neomorphism)
◦ ii) Transformation (inversion) of aragonite to calcite by solution and in-situ precipitation in an aqueous
environment.
◦ Homoaxial transformation
◦ Heteroaxial transformation:
35. iii)Recrystallization (Folk's terminology, 1965!)
Growth of unstrained crystals at the expense of strained
crystals of the same mineral, and increasing pressure and
temperature conditions (metamorphism)
d) Dissolution
Processes in which carbonate is selectively dissolved, e.g.,
in clay seams and secondary porosity occurs.
e) Compaction
Compaction takes place during burial, resulting in a closer
packing of grains, their fracture and eventual dissolution
where in contact. Compaction are of two types.
Compaction
Mechanical Chemical
Figure.16-Showing recrystallization that
destroyed fossil fragments
36. •Mechanical compaction in grainy sediments
leads to a closer packing of the grains and a
rotation of elongate bioclasts towards the
plane of the bedding
•Chemical compaction is the result of
increased solubility at grain contacts and
along sediment interfaces under an applied
stress.
Due to chemical composition three
kind of textures are developed
fitted fabrics, stylolites and pressure-
dissolution seams
Figure.17- Showing Irregular boundary (arrow)
between two echinoderm fragments formed as a
result of pressure solution (chemical compaction)
37. f) Dolomitization
Dolomitization is a major alteration process for many limestones and the dolomite, CaMg(CO3)2, may
be precipitated in near-surface and burial environments.
Dedolomitization
Dolomite may be replaced by calcite to produce limestone again. This calcification process is
referred to as dedolomitization and predominantly takes place through contact with
meteoric waters.
Silification
Like dolomitization, can take place during early or late diagenesis. It takes the form of
selective replacement of fossils or the development of chert nodules and layers.
38. Three major diagenetic environments are
distinguished
a) Marine
Diagenesis takes place on and just below
the sea-floor in both shallow and deep
water, and in the intertidal–supratidal zone
b) near-surface meteoric
Near surface diagenetic can affect a
sediment soon after it is deposited if there
is shoreline progradation or a slight sea-
level fall, or it may operate much later when
a limestone is uplifted after burial.
c) Burial
Begins at a depth below the sediment
surface of tens to hundreds of meters, that
is, below the zone affected by surface
processes
Figure.18- Showing Carbonate diagenetic environments
39. Porosity evaluation
•Porosity in carbonate rocks, most commonly limestones and dolostones, is of great importance
to study since around half of world’s hydrocarbon reserves are made up of dolomite and
limestone.
•The porosities of Holocene carbonate sediments are very high: *40–75% and these higher values
are common in micritic limestones.
•High porosities are associated in the deep water facies that are mainly oozes and these have
both inter-and intra-particle porosities (Schlanger and Douglas 1974).
•The porosity-permeability relation in carbonates may or may not be linear
•Archi’s scheme (based on qualitative evaluation of texture and porosity)
•The Choquette-Pray scheme (utilizes depositional and diagenetic changes in the rock),
•the Lucia scheme (works on inter-relationship between porosity, permeability and the particle
size) etc
40. Carbonates possess both primary and secondary
porosities, which reduces with progressive burial
leading to increasing rigidity of the rock.
Primary Porosity includes
1. framework porosity, formed by rigid carbonate
skeletons such as corals, stromatoporoids and algae,
especially in reef environments;
2. interparticle porosity in carbonate sands,
dependent on grain-size distribution and shape;
3. porosity in carbonate muds provided by fenestrae
(birdseyes) and stromatactis
Figure.19 –Showing Porosity in Carbonates.
41. Secondary porosity includes:
1. Moulds, vugs and caverns formed by dissolution of grains and rock, commonly through
leaching by meteoric ground watersr, but also by basinal (connate) water
2. Intercrystalline porosity produced through dolomitization
3. fracture porosity, formed through tectonic pressures, and through collapse and brecciation
of limestone as a result of dissolution
Primary porosity, and also secondary, is commonly facies controlled.
42. Table –Showing Summary of the Main Diagenetic Processes in Carbonate Rocks and Their
Effects on the Amount and Type of Porosity
43. Dolomite diagenesis
Dolomite is a rhombohedral mineral, CaMg(CO3 ) 2
Dolostone is the appropriate term for a rock composed of that mineral.
Carbonate rocks are divided on the basis of dolomite content into:
limestone 0–10% dolomite
dolomitic limestone 10–50% dolomite
Calcitic dolomite 50–90% dolomite
dolomite (dolostone) 90–100% dolomite
44. Dolomitization process by which limestone is altered into dolomite when limestone comes into
contact with magnesium-rich water, the mineral dolomite, calcium and magnesium carbonate,
Dolomite forms in super saline environment where Mg : Ca ratios exceed this value. It is
noteworthy, however, that dolomite may form at the expense of calcite for Mg: Ca ratios less
than 1:1 if the salinity is very low (Folk and Land, 1974).
Two main types of dolomite Primary and Secondary .
Primary Dolomites
Those which are formed at the time of deposition.
Secondary Dolomites
Secondary dolomites are defined as those that are obviously of post depositional origin. This is
clearly shown by the way in which such dolomites have an irregular distribution, discordant to
bedding and cross-cutting sedimentary structures
45. The origin of dolomites and dolomitization models
There is still much debate and argument over the origin of dolomite, particularly concerning the
pervasive dolomitization of extensive limestone platforms.
Ancient dolomite five wide-ranging classes of dolomitization models are presently existing which
are given below:
a. Evaporative Dolomitization
b. Seepage-reflux Dolomitization
c. Mixing-Zone Dolomitization
d. Burial Dolomitization
e. Seawater Dolomitization
46. a. Evaporation dolomite
Dolomite is in fact formed in high intertidal supratidal and sabkhas environment.
Dolomitic that formed in the supratidal environment are precipitated from evaporated sea
water.
Early formation of gypsum and aragonite resulting to a sophisticated Mg/Ca proportion of pore
water to enhance the formation of dolomite.
b. Seepage-reflux dolomitization
This process comprises the formation of dolomitizing solutions over vaporization of lagoon
water or tidal flat pore water besides then the succession of these solutions into nearby
carbonate rocks.
47. c. Mixing zone dolomitization
This type of dolomite formed by the mixing of seawater with
the fresh water. The source of water may be rainwater .
d. Burial dolomitization
Burial dolomitization involves prime mechanism which is the
dewatering of basinal mud rocks due to compaction and
removal of Mg-rich fluids into neighboring shelf edge.
e. Seawater dolomitization
Seawater itself can also be a source of dolomite because it
contains the sufficient amount of Mg ions with little
modification if a good pumping process exists.
Figure.20- Models for seawater dolomitization of
limestones, all basically different ways of pumping
seawater through a carbonate platform
The widely accepted hypothesis of dolomitization is that limestone is transformed into dolomite by
the dissolution of calcite followed by dolomite precipitation.
48. Figure.21 –Showing Models of dolomitization, illustrating the variety of
mechanisms for moving dolomitizing fluids through the sediments
49. Importance of Carbonates rocks
1. Marine environments,
2. Palaeoecological conditions and the evolution of life form.
3. Agriculture,
4. Industrial purposes ,
5. Act as a reservoir rocks for more than 1/3 of the world’s petroleum reserves