Geology 2022 Paper II 50 marks Calculate

Q7

(a) In a bauxite exploration, 12 vertical boreholes were drilled in square grid pattern along 3 E-W traverses, at an interval of 100 m. Thickness of bauxite and assay value determined from borehole samples are given in the above table. Density of bauxite is 2·6 g/cm³. Calculate the tonnage and average grade of bauxite in the ore body by extended area method. (20 marks) (b) What are the drilling techniques adopted in mineral exploration ? What is exploratory mining and its application ? (15 marks) (c) How is geochemical anomaly recognised from frequency distribution plot of concentration of indicator elements in samples collected during a bedrock geochemical survey ? (15 marks)

हिंदी में प्रश्न पढ़ें

(a) एक बॉक्साइट गवेषण में, 100 मीटर के अंतराल पर 3 पूर्व-पश्चिम मालरेखा में वर्ग ग्रिड पैटर्न में 12 उद्वार्धर वेधछिद्र प्रवेशन किये जाते हैं। वेधछिद्र से प्राप्त बॉक्साइट की मोटाई एवं आमापन मूल्य नीचे सारणी में दर्शाई गई है। बॉक्साइट का घनत्व 2·6 ग्राम/घन सेमी है। विस्तारित क्षेत्र विधि द्वारा अयस्क पिंड में टन भार और बॉक्साइट की औसत कोटि की गणना कीजिये। (20 अंक) (b) खनिज गवेषण में प्रवेशन की कौन सी विधियों का उपयोग किया जाता है ? खोजपूर्ण खनन क्या होता है और उसकी उपयोगिता क्या है ? (15 अंक) (c) एक संस्तर शैल के भू-रासायनिक सर्वेक्षण के समय एकत्र किये गये नमूनों में संकेतक तत्त्वों की सांद्रता के आवृत्ति वितरण आलेख से भू-रासायनिक विसंगति को कैसे पहचाना जाता है ? (15 अंक)

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Directive word: Calculate

This question asks you to calculate. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'calculate' for part (a) demands precise numerical computation using the extended area method, while parts (b) and (c) require descriptive-explanatory responses. Allocate approximately 40% time/words to part (a) given its 20 marks weightage, with 30% each to parts (b) and (c). Structure: begin with the quantitative solution for (a) showing all steps clearly, followed by systematic enumeration of drilling techniques and exploratory mining applications for (b), and conclude with statistical interpretation of geochemical anomalies for (c).

Key points expected

  • Part (a): Correct application of extended area method using 100 m grid spacing, calculation of influence areas for corner, edge and interior boreholes, tonnage computation using T = V × density where V = Σ(area × thickness), and weighted average grade calculation
  • Part (a): Proper handling of borehole configuration—3 E-W traverses with 4 boreholes each, identification of boundary conditions and edge effects in the square grid pattern
  • Part (b): Classification of drilling techniques—percussion drilling (cable tool, rotary-percussion), rotary drilling (direct/indirect circulation, diamond core drilling), and their specific applications in different geological terrains
  • Part (b): Definition of exploratory mining as bulk sampling method including pitting, trenching, aditing, shaft sinking and winzing; applications in verifying drill data, metallurgical testing, and geotechnical studies
  • Part (c): Explanation of frequency distribution plots—histograms and probability plots, recognition of anomaly through deviation from log-normal or normal distribution, threshold determination using mean + 2σ or cumulative frequency curves
  • Part (c): Concepts of contrast (anomaly/background ratio), clarity of anomaly, and use of cumulative probability plots to separate geochemical populations in bedrock surveys

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Demonstrates flawless understanding of extended area method principles for (a), correctly distinguishes between core drilling and non-core methods for (b), and accurately explains statistical anomaly recognition including log-normal distribution characteristics for (c); cites appropriate formulae and geological principles throughoutShows basic grasp of calculation method but may confuse influence area assignments; lists drilling techniques with minor errors; describes anomaly recognition superficially without clear statistical basisFundamental misunderstanding of extended area method, confuses drilling techniques, or fails to explain how anomalies are statistically distinguished from background in geochemical surveys
Diagram / cross-section15%7.5Includes clear grid diagram for (a) showing borehole locations with influence polygons, schematic cross-sections of drilling methods for (b) illustrating diamond core vs. RC drilling, and well-drawn frequency distribution/probability plots for (c) with labeled threshold and anomaly populationsProvides rough sketches or incomplete diagrams; grid pattern shown but influence areas not marked; drilling methods described without visual support; basic histogram drawn for (c) without proper labelingOmits essential diagrams entirely or provides irrelevant sketches; no visualization of grid geometry, drilling mechanics, or statistical distributions despite their importance for full marks
Field evidence15%7.5Cites specific Indian examples—bauxite deposits of Odisha (Panchpatmali), Gujarat (Jamnagar) or Maharashtra for (a); Zawar zinc-lead or Kolar gold for exploratory mining in (b); references to GSI or NGRI geochemical survey protocols for (c)Mentions generic field contexts without specific Indian examples; refers to 'bauxite belts' or 'base metal deposits' without naming locations; acknowledges GSI surveys without methodological detailNo field examples provided; entirely theoretical treatment ignoring Indian geological context and actual exploration practices in the country
Quantitative reasoning25%12.5Part (a): Correctly calculates influence areas (corner: 2500 m², edge: 5000 m², interior: 10000 m² for 100 m grid), computes volume and tonnage with proper unit conversions (g/cm³ to tonnes/m³), and determines weighted average grade using thickness-weighted assay values; shows all steps with proper significant figuresAttempts calculation with partially correct method but errors in influence area determination, unit conversion mistakes, or incorrect weighting for grade calculation; final answer numerically wrong but method partially soundMajor computational errors, incorrect formula application, or complete absence of quantitative work for the 20-mark numerical component; fails to demonstrate any systematic calculation approach
Indian / economic relevance20%10Emphasizes India's critical dependence on bauxite for aluminum industry (NALCO, Vedanta operations), strategic importance of indigenous exploration reducing import dependence; discusses Make in India and critical minerals policy relevance; connects geochemical surveys to national mineral security and UNFC classification for resource estimationBrief mention of economic importance without policy context; notes India as bauxite producer but lacks depth on industrial linkages or exploration economics; superficial connection to national mineral resourcesIgnores economic significance entirely; no reference to India's mineral industry, import-export scenario, or how exploration methods directly impact national resource security and industrial development

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