Assignment Code; BGYET-141/TMA/2023

Course Code: BGYET-141

Assignment Name: Ore Geology and Industrial Minerals

Year: 2023

Verification Status: Verified by Professor

Part A

1. Write short notes on the following:

a) Explain the ore deposition at constructive plate boundaries. (5)

Ans) Ore deposits can form at constructive plate boundaries, where two tectonic plates are moving away from each other. These boundaries are characterized by volcanic activity, earthquakes, and the formation of new oceanic crust. The geological processes that occur at these boundaries can lead to the formation of several types of ore deposits, including volcanic-hosted massive sulfide deposits and rift-related gold deposits.

Volcanic-hosted massive sulfide deposits are typically formed in submarine volcanic environments at mid-ocean ridges. At these locations, hot, metal-rich hydrothermal fluids are expelled from the Earth's mantle through fissures in the seafloor. The fluids mix with cold seawater, causing rapid cooling and deposition of sulfide minerals, such as pyrite, chalcopyrite, and sphalerite. These deposits can be rich in copper, zinc, lead, and other metals and are often associated with black smoker chimneys, which are vent structures that emit hot, mineral-rich fluids.

Rift-related gold deposits, on the other hand, are formed in continental rift zones, where tectonic forces are pulling the Earth's crust apart. These deposits are often associated with faults and fractures that allow hydrothermal fluids to migrate through the rock. The fluids are heated by magma deep within the Earth's crust and can dissolve gold and other metals. As the fluids cool and react with the surrounding rocks, the metals are precipitated out of solution and deposited in fractures and other void spaces.

In addition to these types of deposits, constructive plate boundaries can also host porphyry copper deposits, which are formed in the shallow crust near volcanic centers. These deposits are characterized by disseminated copper minerals, such as chalcopyrite and bornite, in altered volcanic and sedimentary rocks. The copper is often associated with other metals, such as gold and molybdenum. Overall, the formation of ore deposits at constructive plate boundaries is a complex process that involves a combination of geological and hydrothermal processes. These deposits can be valuable sources of metals and minerals and are often found in regions of high tectonic activity, such as mid-ocean ridges and continental rift zones.

b) List the characteristic features of any two metallogenic epochs. (5)

Ans) The characteristic features of the Precambrian epoch and the Late Paleozoic epoch in terms of metallogenesis:

Precambrian epoch (4.6 billion - 541 million years ago)

1. The Precambrian period is distinguished by the accumulation of many different kinds of mineral deposits, the most notable of which are those composed of iron, gold, copper, nickel, and platinum group elements.

2. During this epoch, the crust of the Earth was still in the process of evolving, and the development of various types of mineral deposits was connected to the chemical and physical processes that were involved in the formation and evolution of the crust.

3. Archean and Proterozoic terranes are home to a wide variety of mineral deposits, including orogenic gold, volcanogenic massive sulphide (VMS) deposits, iron formations, layered intrusions with nickel-copper-platinum group element (PGE) deposits, and unconformity-related uranium deposits. Some of these deposits are found in orogenic gold veins, while others are found in iron formations.

4. In addition to rare earth element (REE) deposits, chromite deposits, and diamond deposits can be found in Precambrian terranes.

Late Palaeozoic epoch (298.9 - 251.902 million years ago)

1. The production of various types of mineral deposits occurred throughout the Late Paleozoic epoch. These deposits include coal, gold, copper, lead-zinc-silver, tin, tungsten, and uranium deposits, among others.

2. During this time period, the supercontinent Pangaea began to take shape, which resulted in the collision of several different tectonic plates and the birth of numerous mountain ranges, including the Andes, the Appalachians, and the Ural Mountains.

3. As a result of the construction of these mountain ranges, large-scale hydrothermal mineralizing systems were able to evolve, which resulted in the production of porphyry copper deposits and epithermal gold-silver deposits.

4. Significant coal deposits began to form during the Late Paleozoic epoch as a result of the accumulation of organic material that took place in swamps and low-lying places throughout the Carboniferous and Permian periods. This process occurred during the Late Paleozoic epoch.

2. Discuss major components of ore microscope with suitable diagrams. (10)

Ans) The major components of an ore microscope include the following:

1. Illumination System: The illumination system of an ore microscope is responsible for providing adequate light to the sample being observed. It typically consists of a light source, a condenser lens, and a diaphragm. The light source is usually diaphragm controls the amount of light that passes through the sample, which is important for adjusting the contrast and brightness of the image.

2. Stage and Objectives: The stage is the flat platform where the sample is placed and secured for observation. The objectives are lenses that are located below the stage and are responsible for magnifying the sample. Typically, an ore microscope has several objective lenses of different magnifications, ranging from 2.5x to 100x. The objectives are selected based on the level of detail required in the observation.

3. Polarizing Filters: The polarizing filters are located above and below the stage and can be rotated to adjust the polarization of the light passing through the sample. The polarizing filters are essential for studying the optical properties of minerals, such as birefringence, which is the property of double refraction that some minerals exhibit.

4. Compensators: Compensators are thin plates of material, usually made of quartz or gypsum, that are placed in the optical path of the microscope to modify the polarization of light passing through the sample. They are used to measure the birefringence of minerals and to identify the orientation of mineral crystals.

5. Eyepieces: The eyepieces are lenses that are located at the top of the microscope and are used to view the magnified image of the sample. Typically, an ore microscope has two eyepieces, which can be adjusted to accommodate the user's individual eyesight. The eyepieces also provide a means for focusing the image.

6. Camera and Imaging Software: Many modern ore microscopes are equipped with a camera that can capture digital images of the sample. The images can be saved, analyzed, and shared with other researchers. The imaging software provides tools for adjusting the brightness, contrast, and colour balance of the images.

3. Discuss in detail the Modern classification of ore deposits. (10)

Ans) The modern classification of ore deposits:

4. Give a brief account of igneous host rocks associated with the ore bodies. (10)

Ans) Rocks can be divided into three major categories: igneous rocks, metamorphic rocks, and sedimentary rocks. Igneous rocks are the oldest type of rock on Earth. These rocks serve as a host for the myriad mineral deposits that may be discovered in the crust of the earth, which they are responsible for protecting. Rocks are formed when magma either on or below the surface of the earth undergoes the processes of crystallisation and consolidation, which results in the formation of rocks. The igneous rocks that fall within these categories are categorised as either volcanic or plutonic. There is a certain sort of genetic link that occurs between a specific kind of igneous rocks and a specific kind of mineral deposits. This link exists between the rocks and the minerals. Let us go on to the next step, which is to conduct an investigation into the mineral deposits that are associated with volcanic and plutonic rocks.

Volcanic Rocks: Ore deposits associated to volcanic rock are those that are created as a result of a volcanic eruption in an environment that is either oceanic, undersea, or continental in nature. Both vesicular filling deposits and volcanic associated massive sulphide deposits (often abbreviated as VMS deposits) are types of mineral deposits that can be discovered in volcanic rocks. The VMS deposits, on the other hand, are far more typical than the vesicular filling deposits. The VMS deposits mostly produce base metals, with only trace amounts of gold and silver being extracted. Minerals, such as native copper, can be found within the vesicular infill deposits as well. The copper deposits that are found housed in basalts that date back to the Precambrian era can be found on the Keweenaw Peninsula in the United States.

Plutonic Rocks: Ore deposits are typically located within plutonic rocks, which are igneous rocks that were formed beneath the surface of the Earth and are known as plutonic rocks. These rocks contain a significant amount of ore deposits. The mafic and felsic minerals are arranged in alternating bands inside the stratified plutonic rocks that are mafic in composition. Ore deposits rich in chromite, magnetite, ilmenite, and platinum group elements can be found within these mafic and felsic mineral belts in significant amounts. Stratiform geology and a substantial degree of lateral extension are characteristic features of the ore deposits that belong to this category. Consider, for instance, the chromite riches that can be discovered in the Bushveld region of South Africa.

5. What is wall rock alteration? Describe the types of wall rock alteration and their mineral assemblages. (10)

Ans) All hydrothermal deposits are usually linked to changes in the wall rock. Wall rock alteration is the chemical change of minerals that happens when hydrothermal solutions react with the rocks around them or the rocks that they are in. Close to the vein, these changes are more obvious. As you move away from the vein, they become less obvious. Changes in the minerals, textures, and chemical makeup of the rocks around the wall are caused by this process. The amount of change depends on the temperature and pressure of the fluid, as well as the type and make-up of the rocks that are in contact with it. Other things that affect how host rock changes are its permeability, grain size and shape, and how easily it breaks. Studies in the field and in the lab can give you a deep understanding of how wall rocks change. Changes to the wall rock create the high temperature minerals. Some of these minerals are topaz, tourmaline, and amphibole.

Types of Wall Rock Alteration and their Mineral Assemblages

1. Greisenisation: Greisen-altered granitic rocks have mineralized quartz veins. Dark, hard rocks have transformed. They contain muscovite, quartz, fluorite, topaz, tourmaline, altered feldspars, wolframite, cassiterite, and others. Feldspar minerals release Na and Ca when hydrothermal fluids meet granitic rocks.

2. Silicification: One of the most common and well-known types of hydrothermal change is silicification. This change is marked by the appearance of quartz and cryptocrystalline silica in the country rock, such as in chert and opal. This happens when the silicate minerals break down.

3. Carbonatisation: Calcite, dolomite, magnesite, and siderite form in country rock through carbonatisation. A high-carbon dioxide, neutral-to-alkaline fluid reacts with country rock to cause this rock alteration. South India's greenstone belt gold resources are the best example of carbonatisation.

4. Feldspathisation: Hydrothermal fluid alkalinity creates soda-feldspars. This alteration produces microcline, perthite, albitic plagioclase, sericite, chlorite, and quartz. Na and K added to country rocks modify this.

5. Prophylitic Alteration: Most changes are propylitic. This alteration is largely chlorite and epidote, with little calcite, zoisite, albite, or clinozoisite. This shift normally occurs between 200 and 350°C with a low fluid-to-rock ratio.

6. Phyllic/Sericitic Alteration: Hydrothermal ore deposits undergo this transformation over a wide temperature range. Most important minerals are muscovite, hydromica, and phengite. Silicate minerals include feldspars, micas, and mafic minerals. Feldspars, micas, and mafic minerals become sericite (white mica) and quartz. Phyllic alteration is common around porphyry Cu deposits.

7. Argillic Alteration: Plagioclase changed into kaolinite and montmorillonite during argillic alteration, while amphiboles changed into montmorillonite. This change happens when the temperature is low, the ratios of K+/H+ and Na+/H+ are low, the activity of the alkalis is low, the acid is strong, and the H+ fluids are high. A drawing of the different effects of alteration on the edge of a mineralized ore body.

Part B

6. Discuss the mode of occurrence of chromium ores. (10)

Ans) Based on the structures, Indian chromite comes in the following forms:

1. Banded, Massive.

2. Banded, Crystalline.

3. Disseminated.

Ores in the Kondapalli District in Andhra Pradesh and the Chaibasa District in Jharkhand are massive and banded, whereas ore deposits in the Sukinda and Nausahi Districts in Odisha are enormous and banded and comprised of crystals. Both of these districts are located in Odisha. The areas of Kondapalli and Nausahi are both good places to look for dispersed chromite ores. The chromite deposits are typically formed when magma undergoes an early stage of crystallisation, and they are typically located in close proximity to a deep-seated ultrabasic intrusive. Additionally, data from the ground and under a microscope demonstrates that the chromite ores were concentrated during the early process of magmatic segregation. This may be shown to be the case. In addition to this, chromite deposits can also be formed as a result of late magmatic and hydrothermal processes. The deposits of chromite in India can be found in a wide variety of rock types. These include:

1. Eastern Ghat Mobile Belt Rocks: As a result of the orogeny that occurred in the Eastern Ghats, these rocks contain chromite. They are typically discovered as lens-shaped ore deposits that have the appearance of layered rock. They are typically found in association with minerals such as bronzitite, hypersthene, pyroxenite, and charnockites. Ore bodies with an en-echelon lensoidal structure can be seen running from north to south in both Andhra Pradesh and Tamil Nadu.

2. Iron-Ore Group: There is a connection between the chromite ores in these rocks and the iron-ore orogeny. They have been folded so that they resemble lenses and bands. They are typically located next to peridotite and pyroxenite. These ores can be found in the states of Odisha and Jharkhand.

3. Dharwarian Rocks: These kinds of rocks included chromite ores that were deposited there during the Dharwar orogeny. The deposits are connected to ultramafic rocks such as peridotite, pyroxenite, and dunite, which are encircled by Dharwar schists and are within their immediate vicinity. The chromite ores found in Karnataka and Maharashtra are two excellent instances of this.

4. Tertiary Rocks: These are the chromite deposits that may be found in Kargil, which is located in the Union Territory of Ladakh, and Ukhrul, which is located in Manipur East (Manipur). The Tertiary rocks that make up Manipur contain trace levels of chromite deposits, which can be found in conjunction with peridotite and serpentinite in some cases. In the volcanic rocks of Dras that date back to the Cretaceous period and may be found in Ladakh, chromite deposits can be discovered alongside dunite and serpentinite.

7. Write short notes on:

a) Mineralogical guides. (5)

Ans) A mineral that is located close to or inside an ore body and is connected to the processes that led to the deposition of the ore might act as a highly useful guide when searching for ore. These mineralogical guides have the potential to serve as search targets for ores. The existence of these minerals may serve as an indicator of the presence of a certain mineral deposit, alteration, or rock lithology; they are also known as indicator minerals. Because of their physical and chemical properties, they can be easily extracted from the geological samples (e.g., rock, stream, alluvial, glacial or aeolian sediments or soils).

The presence of minerals that have been oxidised on the surface provides a hint about what is located beneath it. For instance, when sulphide minerals come into contact with water, they quickly become oxidised, and their metal content is either carried away in solution or else fixed as stable compounds elsewhere in the form of oxides, carbonates, and silicates. This leaves iron-rich rock on the surface of the earth. Limonite is the name given to rocks or ores that contain multiple hydrous iron oxide minerals and often dominate the weathered outcrop of an ore deposit. This type of rock or ore is known as limonite. In favourable conditions, the colour, texture, and structure of the limonite can provide vital hints regarding the nature of unweathered mineralization lying beneath it. These indications can be found by looking at the limonite.

b) Distribution of coal bed methane. (5)

Ans) An uncommon kind of natural gas known as coal bed methane, or CBM, can be discovered in coal deposits and coal seams. This is a reference to the process through which methane becomes incorporated into the solid matrix of the coal. The methane is in a form that is almost liquid, and it lines the pores that are present in the coal (called the matrix). Free gas can also be found within the open fissures in the coal, which are known as cleats, and these fractures can get saturated with water. In the process of coalification comes about the formation of CBM. CBM is a reliable source of energy since it can be extracted using a variety of methods. It is possible to extract it from underground coal either before, while, or after mining operations have taken place. It is also possible to obtain it from coal seams that are inaccessible to mining. For extraction, wells need to be drilled into the coal seams, and the water that is contained inside the seam needs to be extracted. This lowers the hydrostatic pressure and allows both absorbed and free gas to escape from the coal. Because it does not contain any hydrogen sulphide, it is sometimes referred to as "sweet gas."

The majority of India's coal reserves as well as all of the present CBM producing blocks may be found in the Gondwana sediments that are found in eastern India. Damodar Koel valley and Son valley in eastern India are home to the vast majority of the most promising sites for the development of coal bed methane (CBM) resources. CBM projects can be found in the areas of Raniganj South, Raniganj East, and Raniganj North in the Raniganj coalfield, as well as in the Parbatpur block in the Jharia coalfield, the East and West of the Bokaro coalfields, and the Raniganj South, East, and North areas of the Raniganj coalfield. The Son valley encompasses the Sohagpur East and West blocks in addition to the Sonhat North block.

8. Discuss the physical properties of chief ores of zinc. (10)

Ans) The physical properties of chief ores of zinc are:

9. Discuss the salient features of National Mineral Policy of India. (10)

Ans) The National Mineral Policy (NMP) of India was first formulated in 1993 and has been revised several times since then to reflect changing needs and priorities. The latest version of the NMP was announced in 2019, with the goal of creating a more sustainable, equitable, and transparent mineral sector that contributes to economic growth and social development. Some of the salient features of the NMP are:

1. Mineral Exploration: The NMP seeks to promote increased exploration for minerals and to accelerate the process of mineral development. This will be achieved by simplifying regulatory processes, encouraging private sector participation, and leveraging new technologies for exploration.

2. Mineral Conservation: The NMP emphasizes the need for sustainable use and conservation of minerals, recognizing that these resources are finite and must be managed carefully. The policy promotes the adoption of best practices for environmental protection and rehabilitation and encourages the use of recycled minerals and waste materials wherever possible.

3. Mineral Development: The NMP aims to promote sustainable development of mineral resources, with a focus on maximizing economic benefits while minimizing social and environmental costs. The policy encourages the adoption of best practices for mine safety, health, and welfare, and seeks to promote the development of local communities through job creation, infrastructure development, and other measures.

4. Mineral Governance: The NMP emphasizes the need for transparent and efficient governance of the mineral sector, with a focus on promoting accountability, equity, and social justice. The policy promotes the use of technology and e-governance to improve transparency and reduce corruption and seeks to ensure that the benefits of mineral development are shared equitably among all stakeholders.

5. Mineral Value Addition: The NMP encourages the development of downstream industries for value addition to minerals, with the goal of creating new jobs and enhancing economic growth. The policy promotes the use of advanced technologies for mineral processing and beneficiation and seeks to promote investment in the mineral sector through incentives and other measures.

6. Research and Development: The NMP emphasizes the need for research and development in the mineral sector, with a focus on promoting innovation and sustainability. The policy encourages the use of advanced technologies for mineral exploration, extraction, and processing, and seeks to promote collaboration between industry, academia, and government in research and development.

Overall, the National Mineral Policy of India represents a comprehensive and forward-looking framework for the sustainable development of the country's mineral resources. The policy reflects the government's commitment to promoting economic growth and social development while minimizing the social and environmental costs of mineral development. Through its emphasis on exploration, conservation, development, governance, value addition, and research and development, the NMP seeks to create a more transparent, efficient, and equitable mineral sector that benefits all stakeholders

10. a) Describe in detail the rare metals and metalloids. (5)

Ans) Because of the one-of-a-kind qualities they possess, rare metals and metalloids make up a group of elements that are put to use in a wide range of different industrial applications. Because of the low concentrations at which these elements are typically found in the crust of the earth, it can be challenging to extract and refine them.

The following are some examples of rare metals as well as metalloids:

1. Lithium: This soft, silver-white metal is used in rechargeable batteries, ceramics, and glass. It is also used in the production of aluminum and steel.

2. Beryllium: This lightweight metal is used in the aerospace industry, as well as in nuclear reactors, X-ray machines, and other medical equipment. It is also used in the production of electronic components, such as computer chips.

3. Tungsten: This hard, dense metal is used in the production of cutting tools, electrical contacts, and heating elements. It is also used in the aerospace and defense industries.

4. Rare Earth Elements: This group of elements includes lanthanum, cerium, neodymium, and others. They are used in a variety of industrial applications, including magnets, catalytic converters, and electronics.

5. Antimony: This metalloid is used in the production of flame retardants, batteries, and other electronics. It is also used as a catalyst in the production of polyethylene terephthalate (PET) plastics.

6. Tellurium: This metalloid is used in the production of solar cells, as well as in the production of alloys for steel and copper.

Many rare metals and metalloids are considered crucial materials by both governments and industry due to the fact that they are extremely uncommon and possess distinctive features. The process of extracting and refining these elements can be time-consuming, costly, and harmful to the surrounding ecosystem; as a result, there is frequently concern regarding the availability of these elements in the future. As a direct consequence of this, there is a growing interest in the development of innovative techniques and methods for the environmentally responsible extraction and recycling of these important resources.

b) Write about the methods of geological exploration. (5)

Ans) Geological exploration is the process of searching for minerals, oil, gas, and other natural resources hidden beneath the Earth's surface. There are several methods of geological exploration that are used to find and identify these resources. Some of the most common methods are:

1. Geological Mapping: This involves studying the surface geology of an area to identify the types of rocks, minerals, and other features that may indicate the presence of natural resources. Geological mapping may involve fieldwork, remote sensing, or aerial photography.

2. Geophysical Surveys: Geophysical surveys involve measuring the physical properties of rocks and sediments beneath the Earth's surface using various techniques, including seismic surveys, magnetic surveys, and electrical surveys. These surveys can help to identify the location, size, and composition of mineral deposits, as well as the structure of the Earth's subsurface.

3. Geochemical Surveys: Geochemical surveys involve collecting and analyzing samples of rocks, soils, and water to identify the presence of minerals and other substances that may indicate the presence of natural resources. This may involve drilling or excavation, as well as laboratory analysis of samples.

4. Remote Sensing: Remote sensing involves using satellite imagery, aerial photography, or other high-resolution imaging technologies to study the surface geology of an area. This can help to identify potential areas for exploration, as well as the location and distribution of mineral deposits.

5. Drilling and Excavation: Once potential resource deposits have been identified, drilling and excavation can be used to collect additional data and samples. This can involve drilling core samples from deep beneath the Earth's surface or excavating trenches or pits to study the subsurface geology.

6. Computer Modeling: Computer modeling involves using advanced software and data analysis techniques to simulate and visualize the subsurface geology of an area. This can help to identify potential resource deposits and guide the exploration process.

Overall, the methods of geological exploration are diverse and complex, requiring a combination of fieldwork, laboratory analysis, and advanced technologies. Successful exploration often depends on the integration of multiple methods and a deep understanding of the geology and physical properties of an area.