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:
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.
This document provides an introduction to ore microscopy. It defines ores and discusses sample preparation techniques and properties that can be observed through microscopic analysis, including:
- Classification of ore deposits as primary, secondary, syngenetic, or epigenetic
- Properties of ore minerals like color, reflectance, hardness, cleavage, and twinning
- Techniques like polishing, etching, and use of an ore microscope
- Advanced techniques like electron microprobe analysis, Raman spectroscopy, and stable isotope studies
The document aims to outline the key aspects of microscopic ore analysis.
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.
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 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.
Paired metamorphic belts occur where zones of high-pressure low-temperature metamorphism are parallel to zones of low-pressure high-temperature metamorphism. They were first recognized in Japan and form due to subduction of oceanic crust beneath continental crust. Paired metamorphic belts support the theory of plate tectonics, as the contrasting pressure-temperature conditions in the two parallel belts can be explained by ocean-continent convergence. Examples of paired metamorphic belts are found throughout the basement rocks of the former Gondwanaland supercontinent.
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.
This document provides an introduction to ore microscopy. It defines ores and discusses sample preparation techniques and properties that can be observed through microscopic analysis, including:
- Classification of ore deposits as primary, secondary, syngenetic, or epigenetic
- Properties of ore minerals like color, reflectance, hardness, cleavage, and twinning
- Techniques like polishing, etching, and use of an ore microscope
- Advanced techniques like electron microprobe analysis, Raman spectroscopy, and stable isotope studies
The document aims to outline the key aspects of microscopic ore analysis.
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.
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 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.
Paired metamorphic belts occur where zones of high-pressure low-temperature metamorphism are parallel to zones of low-pressure high-temperature metamorphism. They were first recognized in Japan and form due to subduction of oceanic crust beneath continental crust. Paired metamorphic belts support the theory of plate tectonics, as the contrasting pressure-temperature conditions in the two parallel belts can be explained by ocean-continent convergence. Examples of paired metamorphic belts are found throughout the basement rocks of the former Gondwanaland supercontinent.
The document discusses lamprophyres, which are ultramafic, mafic, or intermediate intrusive rocks that form dikes or sills at shallow crustal levels. It covers the mineralogy, petrology, classification, occurrence in India, and economic importance of lamprophyres. Lamprophyres are classified into three main types - calc-alkaline, alkaline, and melilitic. Common lamprophyre types discussed include vogesites, minettes, spessartites, and kersantites. Lamprophyres in India are mostly found in Gondwana basins and some alkaline complexes. They can potentially contain diamonds or host gold mineralization.
Role of trace elements in rare earth elementsPramoda Raj
Trace elements play an important role in igneous petrogenesis and can be used to understand magmatic processes. Trace elements are classified based on their behavior into incompatible and compatible elements. Rare earth elements (REE) are especially useful as their near-parallel patterns can indicate crystal fractionation. REE and other trace element analyses help determine the source depth of primary magmas and identify fractionating phases. Trace element discrimination diagrams also allow determination of paleotectonic settings. Overall, trace element studies provide insights into magma differentiation, source characterization, and petrogenetic modeling.
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.
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
The document discusses the Precambrian-Cambrian boundary, which saw major biotic changes like the emergence and extinction of soft-bodied Ediacaran fauna and the emergence of organisms with hard parts. Trace fossils from this period provide important stratigraphic information. In India, sections in Kashmir and Spiti Valley contain microbiota and trace fossils that help delineate the boundary. The Precambrian-Cambrian transition witnessed an evolutionary explosion of life and the emergence of many new animal phyla. Detailed study of sections in the Himalayas continues to provide insights into this important period in Earth's history.
Geochemical cycle and mobility of elementsPramoda Raj
The document discusses geochemical concepts relevant to mineral exploration, including the geochemical environment, cycle, dispersion, and mobility of elements. It describes the deep-seated and surfacial environments and how materials move between them in the geochemical cycle. Mobility depends on factors like viscosity and particle size. Hypogene mobility occurs under high pressure-temperature conditions, while supergene mobility is influenced by siliceous or sulfide environments at the surface. Indicator and pathfinder elements are discussed for detecting targeted ore deposits.
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.
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
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.
Metamorphism limits temperature and pressure limits Sajith Sadanandan
Metamorphism is the process by which the mineralogical and chemical composition and structure of rocks change due to elevated temperatures and pressures within the Earth's crust and mantle. It is caused by heat, pressure, chemically active fluids, and results in changes like recrystallization and mineral transformations. The main types of metamorphism include contact, regional, hydrothermal, and impact metamorphism.
India is the 4th largest producer of manganese ore in the world, with Karnataka and Orissa having some of the largest deposits. Manganese ore occurs in various forms like massive, columnar, fibrous, botryoidal, and granular deposits. It is an important raw material used in steel production and also has various other industrial applications. The key manganese ore producing states in India are Karnataka, Orissa, Maharashtra, and Madhya Pradesh, which have deposits of different types including residual, sedimentary, hydrothermal, and metamorphosed ores.
The document discusses the Western Dharwar Craton located in peninsular India. It is bounded by mobile belts and contains various rock groups like the Sargur, Bababudan, and Chitradurga groups. The oldest rocks are the Gorur gneisses dated to 3500-3600 million years ago. Younger granites and schist belts containing ultramafic and mafic rocks cut across the craton. The economic deposits in the area include magnesite, iron, chromium, vanadium, and copper-nickel ores. The craton shows increasing metamorphic grade from greenschist in the north to amphibolite and granulite facies in the south.
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.
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.
The document discusses lead and zinc minerals found in India. It describes the world class lead-zinc ore body discovered in Zawar, Rajasthan in 1977. The important lead mineral is galena and the important zinc mineral is sphalerite. It details the properties, origins, occurrences and uses of galena and sphalerite. The Zawar deposit is a cavity filling deposit formed in dolomite rock through the solution of minerals in rock openings. Lead and zinc have many industrial uses such as in batteries, alloys, coatings and more. India is a major producer of zinc, led by the deposits in the Zawar area.
The document summarizes the Cudappah Supergroup, an important Proterozoic sedimentary basin in India. It describes the basin's lithostratigraphy, which includes groups like the Papaghni, Chitravati, Nallamalai, and Srisailam quartzites. The basin provides economic resources like barytes, chrysotile, asbestos, steatite, diamonds, uranium, and building/ornamental stones. Radiometric dating indicates the basin formed between 1500-1800 million years ago. The Cudappah Supergroup is a significant paleo-Mesoproterozoic basin that records much of India's early geological history.
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.
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.
Geochemical anomalies in drainage sedimentsPramoda Raj
The document discusses geochemical anomalies found in various types of drainage sediments that can be used for mineral exploration, including spring/seepage sediments, active stream sediments, flood plain sediments, lake sediments, and marine sediments. It explains that drainage sediments provide a sampling medium and anomalies may form from elements precipitating or being eroded, transported, and deposited. The document also notes that lake and marine sediments can indicate mineral deposits based on elements incorporated in sediments or precipitates.
This document discusses mantle melting and magmatic processes. It begins by describing the composition and petrology of the mantle, obtained from samples such as ophiolites, dredged rocks, and mantle xenoliths. Mantle melting can occur through heat-induced melting, adiabatic decompression melting, or flux melting through the addition of volatiles. Magmatic processes include partial melting, magma accumulation and separation, mixing, emplacement, and differentiation during solidification. Magmas are classified based on their composition into mafic, intermediate, and felsic types. Trace elements are enriched or depleted during partial melting depending on their bulk distribution coefficients. Models of magma evolution include batch and fractional melting.
The Rare Earth Elements (REE) are a group of elements in the periodic table that are generally incompatible and have a characteristic abundance pattern in igneous rocks. REE have unique geochemical properties due to their similar ionic radii and oxidation states. Fractional crystallization causes the heavier REE to be more incompatible, resulting in depletion of heavy REE in the upper mantle and enrichment in evolved rocks. Individual REE can also have anomalous compatibilities, such as Europium's affinity for plagioclase feldspar that provides insights into processes like the formation of the Moon's crust. Dating techniques using REE isotopes like Sm-Nd and Rb-Sr have also proven useful for determining the age of
This document provides information on igneous petrology and the classification of igneous rocks. It discusses different classification systems including genetic, textural, chemical, and mineralogical classifications. It also describes techniques for chemical analysis of rocks and key concepts in igneous petrology such as saturation, variation diagrams, and the use of major and trace elements to understand rock origins.
The document discusses lamprophyres, which are ultramafic, mafic, or intermediate intrusive rocks that form dikes or sills at shallow crustal levels. It covers the mineralogy, petrology, classification, occurrence in India, and economic importance of lamprophyres. Lamprophyres are classified into three main types - calc-alkaline, alkaline, and melilitic. Common lamprophyre types discussed include vogesites, minettes, spessartites, and kersantites. Lamprophyres in India are mostly found in Gondwana basins and some alkaline complexes. They can potentially contain diamonds or host gold mineralization.
Role of trace elements in rare earth elementsPramoda Raj
Trace elements play an important role in igneous petrogenesis and can be used to understand magmatic processes. Trace elements are classified based on their behavior into incompatible and compatible elements. Rare earth elements (REE) are especially useful as their near-parallel patterns can indicate crystal fractionation. REE and other trace element analyses help determine the source depth of primary magmas and identify fractionating phases. Trace element discrimination diagrams also allow determination of paleotectonic settings. Overall, trace element studies provide insights into magma differentiation, source characterization, and petrogenetic modeling.
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.
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
The document discusses the Precambrian-Cambrian boundary, which saw major biotic changes like the emergence and extinction of soft-bodied Ediacaran fauna and the emergence of organisms with hard parts. Trace fossils from this period provide important stratigraphic information. In India, sections in Kashmir and Spiti Valley contain microbiota and trace fossils that help delineate the boundary. The Precambrian-Cambrian transition witnessed an evolutionary explosion of life and the emergence of many new animal phyla. Detailed study of sections in the Himalayas continues to provide insights into this important period in Earth's history.
Geochemical cycle and mobility of elementsPramoda Raj
The document discusses geochemical concepts relevant to mineral exploration, including the geochemical environment, cycle, dispersion, and mobility of elements. It describes the deep-seated and surfacial environments and how materials move between them in the geochemical cycle. Mobility depends on factors like viscosity and particle size. Hypogene mobility occurs under high pressure-temperature conditions, while supergene mobility is influenced by siliceous or sulfide environments at the surface. Indicator and pathfinder elements are discussed for detecting targeted ore deposits.
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.
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
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.
Metamorphism limits temperature and pressure limits Sajith Sadanandan
Metamorphism is the process by which the mineralogical and chemical composition and structure of rocks change due to elevated temperatures and pressures within the Earth's crust and mantle. It is caused by heat, pressure, chemically active fluids, and results in changes like recrystallization and mineral transformations. The main types of metamorphism include contact, regional, hydrothermal, and impact metamorphism.
India is the 4th largest producer of manganese ore in the world, with Karnataka and Orissa having some of the largest deposits. Manganese ore occurs in various forms like massive, columnar, fibrous, botryoidal, and granular deposits. It is an important raw material used in steel production and also has various other industrial applications. The key manganese ore producing states in India are Karnataka, Orissa, Maharashtra, and Madhya Pradesh, which have deposits of different types including residual, sedimentary, hydrothermal, and metamorphosed ores.
The document discusses the Western Dharwar Craton located in peninsular India. It is bounded by mobile belts and contains various rock groups like the Sargur, Bababudan, and Chitradurga groups. The oldest rocks are the Gorur gneisses dated to 3500-3600 million years ago. Younger granites and schist belts containing ultramafic and mafic rocks cut across the craton. The economic deposits in the area include magnesite, iron, chromium, vanadium, and copper-nickel ores. The craton shows increasing metamorphic grade from greenschist in the north to amphibolite and granulite facies in the south.
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.
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.
The document discusses lead and zinc minerals found in India. It describes the world class lead-zinc ore body discovered in Zawar, Rajasthan in 1977. The important lead mineral is galena and the important zinc mineral is sphalerite. It details the properties, origins, occurrences and uses of galena and sphalerite. The Zawar deposit is a cavity filling deposit formed in dolomite rock through the solution of minerals in rock openings. Lead and zinc have many industrial uses such as in batteries, alloys, coatings and more. India is a major producer of zinc, led by the deposits in the Zawar area.
The document summarizes the Cudappah Supergroup, an important Proterozoic sedimentary basin in India. It describes the basin's lithostratigraphy, which includes groups like the Papaghni, Chitravati, Nallamalai, and Srisailam quartzites. The basin provides economic resources like barytes, chrysotile, asbestos, steatite, diamonds, uranium, and building/ornamental stones. Radiometric dating indicates the basin formed between 1500-1800 million years ago. The Cudappah Supergroup is a significant paleo-Mesoproterozoic basin that records much of India's early geological history.
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.
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.
Geochemical anomalies in drainage sedimentsPramoda Raj
The document discusses geochemical anomalies found in various types of drainage sediments that can be used for mineral exploration, including spring/seepage sediments, active stream sediments, flood plain sediments, lake sediments, and marine sediments. It explains that drainage sediments provide a sampling medium and anomalies may form from elements precipitating or being eroded, transported, and deposited. The document also notes that lake and marine sediments can indicate mineral deposits based on elements incorporated in sediments or precipitates.
This document discusses mantle melting and magmatic processes. It begins by describing the composition and petrology of the mantle, obtained from samples such as ophiolites, dredged rocks, and mantle xenoliths. Mantle melting can occur through heat-induced melting, adiabatic decompression melting, or flux melting through the addition of volatiles. Magmatic processes include partial melting, magma accumulation and separation, mixing, emplacement, and differentiation during solidification. Magmas are classified based on their composition into mafic, intermediate, and felsic types. Trace elements are enriched or depleted during partial melting depending on their bulk distribution coefficients. Models of magma evolution include batch and fractional melting.
The Rare Earth Elements (REE) are a group of elements in the periodic table that are generally incompatible and have a characteristic abundance pattern in igneous rocks. REE have unique geochemical properties due to their similar ionic radii and oxidation states. Fractional crystallization causes the heavier REE to be more incompatible, resulting in depletion of heavy REE in the upper mantle and enrichment in evolved rocks. Individual REE can also have anomalous compatibilities, such as Europium's affinity for plagioclase feldspar that provides insights into processes like the formation of the Moon's crust. Dating techniques using REE isotopes like Sm-Nd and Rb-Sr have also proven useful for determining the age of
This document provides information on igneous petrology and the classification of igneous rocks. It discusses different classification systems including genetic, textural, chemical, and mineralogical classifications. It also describes techniques for chemical analysis of rocks and key concepts in igneous petrology such as saturation, variation diagrams, and the use of major and trace elements to understand rock origins.
This document provides background information on the Kalahari Craton in southern Africa, which consists of the Archaean Zimbabwe and Kaapvaal Cratons separated by the Limpopo Mobile Belt. It discusses the geological history and tectonic setting of the craton and its constituent terranes. The focus is on peridotite xenoliths from the Letlhakane kimberlite mine in northern Botswana, which will be studied to characterize the sub-cratonic lithospheric mantle beneath this region and better understand its origin and modification over time. A variety of analytical techniques will be used, including petrography, geochemistry, and Sm-Nd and Lu-Hf isotope analyses
This document discusses ore deposits and the fluids involved in their formation. It covers five main types of ore-bearing fluids: 1) magmas and magmatic fluids, 2) meteoric waters, 3) connate waters, 4) fluids associated with metamorphic processes. It then discusses the migration of ore-bearing fluids through rocks, noting that permeability and porosity allow fluids to circulate over long periods of time. Metals can also migrate in the colloidal state within fluids. The document provides an overview of the key fluids and processes involved in forming various ore deposit types.
This study analyzed trace elements within augite samples from komatiitic basalts in the Barberton Greenstone Belt in South Africa using LA-ICP-MS. Results showed that rare earth elements in the freshest augites closely matched predicted values from bulk rock analyses when accounting for distribution coefficients and fractionation. Zirconium and titanium also exhibited anomalies that corresponded to bulk rock data, indicating these elements remained in a closed system. However, sodium, strontium, and barium were mobilized during alteration in the bulk rocks. Analyzing trace elements in augites provides a better representation of these mobile elements and confirms fractionation and assimilation processes during komatiite petrogenesis.
Austman - Departmental Seminar - Fraser Lakes Zone B MineralizationChristine McKechnie
Granitic pegmatites in the Fraser Lakes area contain uranium, thorium, and rare earth element mineralization. The pegmatites formed from partial melting of metasedimentary rocks in the lower crust, and were transported upwards along structural discontinuities. They intrude the contact between Archean orthogneisses and Paleoproterozoic metasedimentary rocks. Regional metamorphism reached lower granulite facies. The mineralization shows similarities to unconformity-related uranium deposits in Athabasca Basin.
The document provides information on igneous petrology including definitions of key terms like petrography, petrology, and petrogenesis. It describes techniques for classifying igneous rocks based on their texture, mineralogy, chemistry and other properties. Bowen's reaction series is explained as the process by which magma cools and crystallizes into rocks of different compositions. Diagrams like Harker variation diagrams and triangular variation diagrams are used to visualize chemical variations in rock compositions.
The copper isotope ratios were measured in 42 mineral separates from the Cañariaco Norte porphyry copper deposit in northern Peru. Isotopic ratios ranged from -8.42‰ to 0.61‰, with near-surface iron oxides having the most depleted values and deeper chalcocite, covellite, and chalcopyrite having more typical hypogene ratios. The data indicate that most of the chalcocite and covellite formed from high-temperature hypogene processes, with only a minor portion resulting from supergene enrichment. The lack of an enriched isotopic signature suggests little potential for an extensive supergene enrichment blanket at depth due to the weathering history.
This document provides an overview of the classification of igneous rocks. It discusses several key criteria used for classification, including texture, mode of occurrence (intrusive vs extrusive), and chemical composition based on silica and alumina content. Texture types include phaneritic, aphanitic, porphyritic, glassy, and pyroclastic. Mode of occurrence divides rocks into plutonic (intrusive) and volcanic (extrusive) types. Chemical classification schemes analyze silica content to categorize rocks as felsic, intermediate, or mafic, and also consider silica and alumina saturation states. Diagrams are provided illustrating these classification approaches. Examples of different rock types are also briefly described,
This document summarizes a study examining variations in carbonate mineralogy and chemistry in banded iron formations (BIFs) of the Transvaal Supergroup in South Africa. The study aims to determine if carbonate minerals ankerite and siderite formed primarily or through diagenesis by analyzing their distribution, textures, and chemistry across stratigraphy. Results show manganese increases upwards while iron decreases in carbonates, inconsistent with diagenetic models but supporting primary precipitation from stratified waters. The author concludes carbonates likely formed primarily in the water column rather than through diagenesis, recording the unique chemistry of the paleoenvironment.
This document discusses radiometric dating techniques used by geologists to determine the age of rocks. It introduces radiometric dating, the concept of half-life, and commonly dated minerals like zircon and monazite. Methods like uranium-lead dating are explained in detail. Instruments used for dating like laser ablation-ICPMS and electron microprobe are also mentioned. The document concludes that radiometric dating, especially uranium-lead dating of zircon, is a reliable method for determining the age of rocks and major geological events.
This document discusses geochemical exploration techniques, including the principles of dispersion and mobility of elements. It explains that elements disperse from their source through clastic, hydromorphic, and biogenic dispersion. The mobility of an element depends on factors like its ionic potential and stability in different environmental conditions. Certain elements act as pathfinders that correlate to and help locate elements of economic interest. The document provides examples of element associations that can help interpret geochemical data from different rock and sediment types.
Geological criteria for ore prospecting.pptxMasroor4
This document discusses various geological criteria that can be used for mineral prospecting, including stratigraphic, lithological, structural, magmatogenic, and geomorphological criteria. Stratigraphic criteria involve examining rock formations and horizons where desired mineral resources are known to occur. Lithological criteria consider the composition of wall rocks and surrounding sediments. Structural criteria analyze rock structures and faults that may have channeled mineral-bearing fluids. Magmatogenic criteria focus on the lithology of rocks intruded by mineral-bearing magma. Geomorphological criteria examine landforms like river beds that can concentrate minerals. Understanding these criteria can help delimit areas for more efficient mineral exploration.
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.
1. The document discusses skarn zoning patterns and controlling factors based on a webinar presented by Zhaoshan Chang from Colorado School of Mines.
2. Skarns typically show zoning based on the transfer of heat and mass away from intrusions, with endoskarns nearest intrusions containing garnet and pyroxene that change in ratio and composition farther out.
3. Important controlling factors on skarn formation and metal zoning include the redox state, composition, and degree of fractionation of the causative magma as well as the composition, permeability and depth of the wall rocks.
Metamorphic ore deposits form as a result of metamorphic processes within metamorphic rocks. They can form under various metamorphic conditions from low to high temperatures and pressures. Examples include the transformation of claystones to kyanite/sillimanite deposits or the formation of graphite flakes between magmatic bodies. There are three main types - copper-rich deposits associated with mafic rocks and organic sediments, archean iron formation-related gold deposits in quartz veins hosted in iron formations, and lead-zinc-silver rich deposits containing galena, sphalerite, and other minerals in quartz-carbonate veins.
This document provides information on igneous rocks, including their classification, textures, and mineralogy. It discusses:
1. The classification of igneous rocks based on texture (phaneritic, aphanitic, porphyritic, etc.) and composition (felsic, mafic, ultramafic).
2. The main igneous minerals like quartz, feldspars, olivines, and pyroxenes.
3. How mineral assemblages in igneous rocks are determined by melt composition and cooling rate. Texture is influenced by the rate of nucleation and crystal growth.
4. Different types of igneous textures including glassy, vesicular
The document discusses crustal architecture and how it relates to mineral wealth and ore deposits. It describes how the oceanic crust is typically less than 10km thick and divided into layers, including an upper sedimentary layer and lower basaltic layers. Continental crust is thicker at around 35-40km and has a more complex architecture reflecting a long tectonic history. Most exploitable ore deposits are found in the upper parts of the continental crust in rocks like granite, diorite, and sediments. The composition of magmas influences the types and concentrations of metals they carry, with more fractionated felsic magmas associated with lithophile elements and certain ore deposits.
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
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for investigating, for example, Earth’s gravity1
, the gravitational constant2
, deviations
from Newtonian gravity3–6
and general relativity7
. However, using atoms in free fall
limits measurement time to a few seconds8
, and much less when measuring
interactions with a small source mass2,5,6,9
. Recently, interferometers with atoms
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demonstrated10–14. However, the optical lattice must balance Earth’s gravity by
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sensitivity of a lattice interferometer and use a system of signal inversions to suppress
and quantify systematic efects. We measure the attraction of a miniature source mass
to be amass = 33.3 ± 5.6stat ± 2.7syst nm s−2, consistent with Newtonian gravity, ruling out
‘screened ffth force’ theories3,15,16 over their natural parameter space. The overall
accuracy of 6.2 nm s−2 surpasses by more than a factor of four the best similar
measurements with atoms in free fall5,6
. Improved atom cooling and tilt-noise
suppression may further increase sensitivity for investigating forces at sub-millimetre
ranges17,18, compact gravimetry19–22, measuring the gravitational Aharonov–Bohm
efect9,23 and the gravitational constant2
, and testing whether the gravitational feld
has quantum properties24.
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The Limited Role of the Streaming Instability during Moon and Exomoon Formation
Role of Trace Elements In Petrogenesis
1. ROLE OF TRACE ELEMENTS IN
PETROGENESIS
GUIDED BY:
Prof. K.N. Prakash Narsimha
PRESENTED BY:
GOKUL ANAND
Mysore University
2. MAGMA
Hot or semi-fluid material below or within the earth crust
from which lava and other igneous rock is formed on
cooling.
Magma often collects in magma chambers that may
feed a volcano or turn into a pluton.
Besides molten rock, magma may also contain
suspended crystals, dissolved gas & sometimes gas
bubbles
Temperatures of most magmas are in the range
700ºC to 1300ºC
3. CLASSIFICATION OF MAGMA
Magma = liquid (molten rock) + crystals + dissolved gasses
(volatiles)
As result of melting of crust yield’s most Si rich magmas
that also contain considerable Al, Ca, Na, Fe, Mg, K and
several other elements in lesser quantity.
Melting of Earth’s upper mantle, which is composed of
rocks that contain mostly ferromagnesian silicates thus
magma from this sources contain comparatively less amount
of silica and more iron and magnesium contain.
5. GEOCHEMISTRY OF MAGMA
Major elements:
Comprise most of the rock
Expressed as weight (wt.) % oxides,
each >0.1% SiO2, Al2O3, FeO, MgO, CaO , Na2O, K2O, H2O.
Analysed by XRF, ICP-MS
Minor elements:
usually 0.1 - 1% ,
TiO2,MnO, P2O5 ,CO2.
Trace elements:
Present in concentrations <0.1 %
Expressed in ppm or ppb
Analysed by XRF, ICP-MS, INAA
Volatile elements:
H2O, CO2, SO4
Rare gases: He, Ar, Ne, etc.
Analysed by spectroscopy or mass spectrometry
7. Trace elements are those which occur in very low
concentrations in common rocks (usually < 0.1 % by
weight).
0
50
100
Trace Elements
8. Geochemical Analysis Of Trace Elements Can Be Done By
These
Techniques
X-ray Fluoresence Spectroscopy
(XRF)
Atomic Absorbtion Spectrometry
(AAS)
ICP-OCP-Optimus 5300
Spectrometer
9. Concentrations are commonly expressed in parts per
million(ppm)
For eg: chromium = 150ppm
Trace elements tend to concentrate in fewer
minerals, and are therefore more useful in
formulating models for magmatic differentiation, and
in some cases to predict the source of a particular
magma.
10. The concentration of trace elements will vary with
the rock type; whereas Ni and Cr show higher
concentrations in mafic and ultramafic rocks, Zr
and Rb are more concentrated in acidic rocks.
Eg. Potassium never forms its own phase in mid-ocean ridge
basalts (MORB), its concentration rarely exceeding 1500 ppm;
but K is certainly not a trace element in granites
Trace elements can be classified as compatible and
incompatible
11. TYPES OF TRACE ELEMENTS
Incompatible elements :
K, Rb, Cs, Ta, Nb, U, Th, Y, Hf, Zr, Most have a large
ionic radius.
Do not easily fit into the crystal structure of minerals in
the mantle.
Mantle minerals like olivine, pyroxene, spinel, & garnet
do not have crystallographic sites for large ions.
Compatible elements :
Ni, Cr, Co, V, and Sc, which have smaller ionic radii
Fit easily into the crystal structure of minerals in the
mantle.
Crystallographic sites that normally accommodate Mg,
13. Large Ion Lithophile Elements
The ionic radius is large These are incompatible.
They are more concentrated in liquid phase of the magma,
These are found in olivine Opx, Cpx and garnet largely
"incompatible“ particularly with respect to mantle phases
(Ol, Opx, Cpx, Gt, .. etc)
Examples: K, Rb, Sr and Ba.
14. Higher Field Strength Elements
These are also concentrated in liquid phase but are
compatible
They are seen in sphene, zircon and apatite (SZA)
They are basically Titanium, Th, U, Nb and Hf.
15. Transitional Elements
Small ionic radii, and are either bi- or tri-valent .
strongly partitioned in the solid phases that crystallize
during the early stages of magmatic evolution
"compatible" with mantle phases
Eg: Ni, Co, Cr, and Sc.
16. Rare Earth Elements
A group of elements comprising the 15 elements from
Lanthanum (At. no. 57) to Lutetium (At. No. 71)
- Yttrium (At. No. 39) and Scandium (At. no. 21) are also
sometimes included in this group.
17. Behaviour Of Trace Elements In Magmatic
Processes
When a mantle rock begins to melt, the incompatible elements will be
ejected preferentially from the solid and enter the liquid.
A low degree melting of a mantle rock will have high concentrations of
incompatible elements.
As melting proceeds the concentration of these incompatible elements
will decrease because
(1) there will be less of them to enter the melt, and
(2) their concentrations will become more and more diluted as other
elements enter the melt. Thus incompatible element concentrations will
decrease with increasing % melting.
18. Applications of trace elements and Rare Earth Elements to
Igneous Petro genesis
1- Testing models of magmatic differentiation using trace elements:
On calculating the concentrations of trace elements remaining in the
liquid determine how much partial melting is needed to produce a specific
magma from a given rock type
2- Determination of the depth of generation of a primary magma:
magmas produced by small degrees of partial melting
-at shallow depths will be depleted in Sr
-from intermediate depths will be depleted in V and Cr,
-from depths > 80 km will be depleted in HREE.
19. 3 - Prediction of the phases fractionating from a magma:
Identification of the phases which have fractionated from a magma
undergoing fractional crystallization.
Separation of:
(a)Plag depletes the remaining melt in Sr and Eu,
(b) Ol depletes it in Ni and Co,
(c) spinels deplete it in V, Cr and possibly Zn,
(d) K-spar in Ba and Rb, ... etc.
4- REE and REE diagrams:
REE are very useful for petrogenetic interpretations.
REE diagrams are also useful in identifying which phase or phases fractionate
from a magma,
In order to identify such phases, it is necessary to know which REE are
preferentially incorporated in which phases.
REE diagrams are also used to determine the type of basalt.
20. 5- Discriminant diagrams:
Trace elements can also be used to identify the paleotectonic setting of
some volcanic rocks (i.e. to determine where they were erupted).
In this case rather than use the absolute concentrations of trace elements
(which may have been affected by such post-magmatic processes as
weathering, alteration or metamorphism),ratios of relatively immobile trace
elements (as these are least affected by post magamatic processes.)
21. Trace elements are useful in formulating models for magmatic
differentiation, in predicting the source of a particular magma.
Trace elements occur in very low concentrations in common rocks.
Large ion lithophile elements (LILE) have large ionic radii, and low
charges.
High field strength elements (HFSE) excluded from mantle phases and
more concentrated in residual liquids.
Trace elements are useful for determination of the depth of generation of
a primary magma.
During crystal fractionation the ratios of incompatible elements show
little change, and that we can use this factor to distinguish between
crystal fractionation and partial melting.
Geochemical analysis of trace elements can be done by XRF,AAS & ICP
techniques.
Conclusion
22. Brian Mason and Carleton Moore B.,(1982) Principales Of Geochemistry. pp.75-
150
Gilbert Hanson N.,1980,Rare Earth Elements in Petrogenessis of igneous
systems:Ann.Rev.Eatrh Planet.Sci.v.8, pp.371-406
James Moneroe S.,and Reed Wicander, 2006, Changing Earth. pp.88-102
Joseph Arth G., 1976, Behavior of trace elements during magmatic processes: U.S.
Geol. Survey. v.4,no.1,pp.41-47
White W.M., 2009, Geochemistry. pp 258-312
en.wikipedia.org/transition_elements
REFERENCES
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