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Geology Civil Services Paper 2 Section- B, Questions 7,8_ Solutions



7. (a)


Answer : To calculate the tonnage and average grade of bauxite using the extended area method, we first need to determine the volume of the ore body by calculating the volume of each block defined by the boreholes. We can assume that the ore body is approximately rectangular in shape and that the thickness and assay values of the bauxite are relatively consistent throughout the deposit. Using the given data, we can calculate the volume of each block as follows: Block 1: Volume = 4.2 m x 100 m x 100 m = 42,000 m3 Assay = 43.2% Block 2: Volume = 5.6 m x 100 m x 100 m = 56,000 m3 Assay = 40.4% Block 3: Volume = 6.4 m x 100 m x 100 m = 64,000 m3 Assay = 36.2% Block 4: Volume = 6.0 m x 100 m x 100 m = 60,000 m3 Assay = 38.5% Block 5: Volume = 3.5 m x 100 m x 100 m = 35,000 m3 Assay = 44.8% Block 6: Volume = 5.0 m x 100 m x 100 m = 50,000 m3 Assay = 35.6% Block 7: Volume = 5.6 m x 100 m x 100 m = 56,000 m3 Assay = 32.4% Block 8: Volume = 6.8 m x 100 m x 100 m = 68,000 m3 Assay = 30.6% Block 9: Volume = 3.2 m x 100 m x 100 m = 32,000 m3 Assay = 46.3% Block 10: Volume = 4.0 m x 100 m x 100 m = 40,000 m3 Assay = 41.2% Block 11: Volume = 3.8 m x 100 m x 100 m = 38,000 m3 Assay = 36.5% Block 12: Volume = 4.4 m x 100 m x 100 m = 44,000 m3 Assay = 33.7% Total Volume: 560,000 m3 Total Tonnage: 560,000 m3 x 2.6 g/cm3 / 1,000,000 g/ton = 1,456 tons To calculate the average grade of the deposit, we can use the following formula: Average Grade = (Assay 1 x Volume 1 + Assay 2 x Volume 2 + ... + Assay n x Volume n) / Total Volume Plugging in the values from the table, we get: Average Grade = (43.2% x 42,000 m3 + 40.4% x 56,000 m3 + ... + 33.7% x 44,000 m3) / 560,000 m3 Average Grade = 38.9% Therefore, the estimated tonnage of bauxite in the ore body by the extended area method is 1,456 tons and the average grade is 38.9%.

7. (b) What are the drilling techniques adopted in mineral exploration ? What is exploratory mining and its application? Answer : There are several drilling techniques adopted in mineral exploration, including: Diamond Drilling: This is the most commonly used technique in mineral exploration. It involves drilling a hole into the ground with a diamond-impregnated drill bit to extract a cylindrical core of rock. This core is then analyzed for mineral content and other geological information. Reverse Circulation Drilling: In this technique, a high-pressure air compressor is used to drive a bit down into the ground. The cuttings are blown up the drill pipe and collected at the surface for analysis. Air Core Drilling: This technique uses a pneumatic drill bit to pulverize the rock and create a cuttings column. The cuttings are then brought to the surface for analysis. Rotary Drilling: This is a simple technique where a drill bit is attached to the end of a long drill pipe and rotated to drill through the rock. Exploratory mining refers to the process of extracting mineral resources from an area for the purpose of evaluating their commercial potential. The main application of exploratory mining is to assess the quality and quantity of a mineral deposit before deciding whether to undertake full-scale mining operations. The goal is to determine whether the deposit is economically viable and whether the mining operation can be carried out in a safe and environmentally responsible manner. Exploratory mining can involve the use of drilling, trenching, and other methods to extract samples of the mineral deposit for analysis.

7. (c) How is geochemical anomaly recognised from frequency distribution plot of concentration of indicator elements in samples collected during a bedrock geochemical survey? Answer : Geochemical anomalies can be recognized from frequency distribution plots of concentration of indicator elements in samples collected during a bedrock geochemical survey by looking for a departure from the normal or background distribution of the elements in the area being surveyed. An anomaly can be defined as an area that has a significantly higher or lower concentration of an element compared to the background concentration. To identify a geochemical anomaly, the following steps can be taken: Determine the background distribution of the indicator element(s) in the survey area. This can be done by collecting a large number of samples across the area and plotting the frequency distribution of the element(s) of interest. Look for departures from the normal or background distribution of the element(s) in the area. These departures can take the form of high or low concentrations of the element(s). Establish a threshold or cutoff value that defines what constitutes an anomaly. This can be done based on statistical analysis of the data or by using expert knowledge of the geological and geochemical processes in the area. Once the threshold value is established, identify areas that have concentrations of the element(s) above or below the threshold as potential anomalies. Confirm the anomalies by collecting additional samples in the area and analyzing them for the indicator element(s) to establish the extent and magnitude of the anomaly. Overall, the recognition of geochemical anomalies from frequency distribution plots requires a combination of statistical analysis and expert knowledge of the geological and geochemical processes in the survey area. 8. (a) Give the classification of landslides and discuss the causes of landslide. 20 Answer : Landslides can be classified based on several factors, such as their type of movement, type of material involved, and the triggering mechanism. The following are some of the common types of landslides: Rockfall: Rockfalls are the most common type of landslide and involve the rapid fall of individual rocks or boulders. Rockslide: A rockslide is a type of landslide where a mass of rock slides down a slope. Debris flow: A debris flow is a type of landslide that involves a mixture of soil, rock, and water flowing down a slope. Mudflow: A mudflow is a type of landslide that involves the flow of mud or fine-grained soil down a slope. Earthflow: An earthflow is a type of landslide where the soil or rock material moves slowly and spreads out as it moves. The causes of landslides can be natural or human-made. The natural causes of landslides include: Geological factors: Geological factors such as the type of soil, slope angle, and slope stability can contribute to landslides. Weather and climate: Heavy rainfall or snowmelt can saturate the soil and trigger a landslide. Earthquakes: Earthquakes can cause landslides by destabilizing the soil or rock on a slope. Volcanic activity: Volcanic activity can cause landslides by destabilizing the soil or rock on a slope. The human-made causes of landslides include: Deforestation: Deforestation can lead to landslides by reducing the stability of the soil and increasing the risk of erosion. Construction: Construction activities such as excavation, filling, and grading can destabilize a slope and trigger a landslide. Mining: Mining activities can destabilize a slope and trigger a landslide. Land use change: Land use change such as urbanization can increase the risk of landslides by altering the natural drainage patterns and reducing the stability of the soil. Overall, landslides can be devastating events that cause significant damage to property and loss of life. Understanding the causes and types of landslides is crucial for mitigating the risk of landslides and reducing their impact.


8(b) What is the structure of the Earth? Is the Earth compositionally homogeneous or composition of the Earth varies with depth? Write a note on distribution of elements in the Earth. Answer : The Earth's structure can be divided into several layers based on their physical properties and chemical composition. From the center outwards, the Earth can be divided into the following layers: the inner core, outer core, mantle, and crust. The inner core is a solid sphere of iron and nickel with a radius of approximately 1,220 km. The outer core surrounds the inner core and is a liquid layer of molten iron and nickel. The mantle is the thickest layer and extends from the bottom of the crust to the outer core. It is composed of silicate minerals and is divided into the upper mantle and the lower mantle. The crust is the outermost layer and is the thinnest layer, ranging from 5 to 70 km thick. It is composed of a variety of rocks, including granite, basalt, and sedimentary rocks. The composition of the Earth is not homogeneous, and it varies with depth. The inner and outer core are primarily composed of iron and nickel, while the mantle and crust are composed of silicate minerals, such as olivine and pyroxene. The distribution of elements in the Earth can be divided into three layers: the core, mantle, and crust. The core is primarily composed of iron and nickel, with smaller amounts of other elements such as sulfur, oxygen, and silicon. The mantle is primarily composed of oxygen, silicon, magnesium, and iron, with smaller amounts of other elements such as aluminum, calcium, and sodium. The crust is primarily composed of oxygen, silicon, aluminum, iron, calcium, sodium, and potassium, with smaller amounts of other elements such as magnesium and titanium. The distribution of elements in the Earth is thought to have been largely influenced by the process of differentiation during the Earth's formation. As the Earth was forming, heavier elements sank to the core, while lighter elements rose to the surface, resulting in the layered structure we observe today. 8(c)Write the classification of meteorites. Discuss importance of study of meteorites in Earth Science. Answer : Meteorites are classified into three main types: Stony meteorites: These are the most common type of meteorites and are composed primarily of silicate minerals. They are further classified into two subtypes: chondrites and achondrites. Chondrites are primitive meteorites that have not undergone significant differentiation or melting, while achondrites are meteorites that have undergone partial melting or differentiation. Iron meteorites: These are composed mostly of iron and nickel, with minor amounts of other elements. They are believed to be the remnants of the cores of small planets or planetesimals. Stony-iron meteorites: These meteorites are composed of roughly equal amounts of silicate minerals and iron-nickel metal. They are believed to be the result of mixing of the core and mantle materials of a differentiated planetesimal. The study of meteorites is important in Earth science for several reasons. First, meteorites provide us with direct samples of material from other celestial bodies in our solar system, allowing us to study their composition and history. This can provide insights into the formation and evolution of our solar system. Second, meteorites can also provide important information about the early history of the Earth. For example, the presence of certain isotopes in meteorites suggests that the Earth underwent a period of intense bombardment by meteorites early in its history, a phenomenon known as the Late Heavy Bombardment. Finally, the study of meteorites can also help us understand the potential hazards posed by near-Earth objects, such as asteroids and comets, and how we might mitigate those hazards. By studying the composition and properties of meteorites, we can gain a better understanding of the nature of these objects and how they might interact with the Earth.




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