Geology 2025 Paper II 50 marks Discuss

Q7

(a) Discuss the direct and indirect geochemical methods used for prospecting of hydrocarbon deposits. (20 marks) (b) What are the physiological and morphological changes of the plants helpful in geobotanical prospecting of copper, manganese and uranium deposits? Add a note on commonly found plant indicators for zinc. (15 marks) (c) What do you understand by 'tonnage factor'? Discuss the geometric and graphic methods used in reserve calculation. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) हाइड्रोकार्बन निक्षेपों के अन्वेषण में प्रयुक्त प्रत्यक्ष और अप्रत्यक्ष भूरसायनिक विधियों की विवेचना कीजिए। (20 अंक) (b) तांबा, मैंगनीज व युरेनियम निक्षेपों के भूवनस्पतिकीय अन्वेषण में पादपों के कौन-से कार्यिकीय एवं आकारिकीय बदलाव मददगार होते हैं? जस्ते के आमतौर पर मिलने वाले सूचक पादपों पर एक टिप्पणी लिखिए। (15 अंक) (c) 'टनेज फैक्टर' से आप क्या समझते हैं? भंडारों के संगणन में प्रयुक्त होने वाली ज्यामितिक व लेखाचित्रीय विधियों की विवेचना कीजिए। (15 अंक)

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Directive word: Discuss

This question asks you to discuss. 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 'discuss' demands a comprehensive, analytical treatment with balanced coverage across all three sub-parts. Allocate approximately 40% of time/words to part (a) given its 20 marks, and 30% each to parts (b) and (c). Structure as: brief introduction on exploration methodologies → systematic treatment of (a) direct/indirect hydrocarbon methods with Indian examples like Bombay High or KG Basin → (b) geobotanical indicators with specific plant species and physiological mechanisms → (c) tonnage factor definition followed by geometric/graphic reserve estimation methods → concluding synthesis on integrated exploration approaches.

Key points expected

  • Part (a): Direct methods (soil gas analysis, microbial prospecting, adsorbed soil hydrocarbons) versus indirect methods (trace element halos, radiometric surveys, geomagnetic/electrical anomalies associated with hydrocarbon seepage)
  • Part (a): Specific techniques like headspace gas analysis, acid extraction of soil hydrocarbons, and iodine/uranium halo methods; Indian case studies from Cambay Basin or Assam-Arakan fold belt
  • Part (b): Physiological changes (chlorosis, stunted growth, altered flowering patterns) and morphological changes (leaf size reduction, root system modification, stem deformation) in copper, manganese and uranium indicator plants
  • Part (b): Specific plant indicators—Copper: Aeolanthus biformifolius (copper flower); Manganese: Macadamia neurophylla; Uranium: certain lichens and aquatic plants; Zinc note: Viola calaminaria (zinc violet) or Thlaspi species
  • Part (c): Definition of tonnage factor (volume to tonnage conversion using specific gravity) and its importance in reserve estimation
  • Part (c): Geometric methods (triangular, trapezoidal, polygonal, cross-sectional, isopach methods) and graphic methods (planimeter, graticule, statistical grid methods) with appropriate formulae
  • Integration: How geochemical, geobotanical and reserve estimation methods complement each other in integrated exploration programs

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise definitions of direct vs indirect geochemical methods with correct distinction; accurate physiological/morphological terminology for plant responses; correct mathematical formulation of tonnage factor and geometric methods; no conceptual confusion between exploration techniquesGenerally correct definitions but some blurring between direct/indirect methods; basic plant changes mentioned without specificity; tonnage factor understood but geometric methods described vaguely; minor errors in technical terminologyFundamental confusion between method categories; incorrect or missing definitions; tonnage factor misunderstood; significant factual errors in exploration concepts or reserve estimation principles
Diagram / cross-section15%7.5Clear schematic of hydrocarbon microseepage model showing vertical migration and halo patterns; labeled diagrams of plant morphological changes; geometric method illustrations (triangular/prism diagrams, cross-sections showing ore body geometry); tonnage factor calculation flowchartBasic diagrams present but lacking detail or proper labeling; one or two relevant sketches without integration with text; geometric methods described textually without visual representationNo diagrams or irrelevant sketches; failure to illustrate key concepts that demand visual representation; poorly drawn diagrams that misrepresent geological relationships
Field evidence20%10Specific Indian field examples: Bombay High/Kerala-Konkan basin for hydrocarbon geochemistry; Malanjkhand copper belt geobotanical studies; Jaduguda uranium deposits; Singhbhum manganese belt; documented case studies with quantitative results where availableGeneric mention of Indian localities without specific details; broad references to 'Rajasthan' or 'Eastern Ghats' without precision; field evidence mentioned but not integrated with method descriptionNo Indian examples; purely theoretical treatment; incorrect attribution of deposits to wrong geological settings; confusion between different mineral belts
Quantitative reasoning20%10Numerical treatment of tonnage factor (TF = SG × volume conversion); worked example or clear formula for geometric methods (triangular: V = A × (t1+t2+t3)/3; trapezoidal: V = A/2 × (t1+t2)); threshold values for geochemical anomalies; statistical treatment of reserve categoriesFormulae mentioned without application; basic understanding that tonnage factor involves specific gravity; geometric methods named without mathematical elaboration; qualitative appreciation of quantitative aspectsNo quantitative content; incorrect formulae; failure to understand that reserve estimation requires mathematical treatment; confusion between volume and tonnage calculations
Indian / economic relevance20%10Economic significance of hydrocarbon exploration for energy security (ONGC, OIL operations); strategic importance of Cu, Mn, U for Indian industry; mention of NMP 2019 or atomic mineral policies; cost-effectiveness of geobotanical methods for grassroots exploration in India; employment generation in mineral sectorBrief mention of economic importance without elaboration; standard references to 'self-reliance' without specific policy linkage; generic statements about mineral importanceNo economic or policy context; failure to connect technical methods to national resource needs; purely academic treatment without applied relevance

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