Geology 2025 Paper II 50 marks Discuss

Q8

(a) What do you understand by isomorphism and polymorphism? Discuss monotropy by citing example of diamond and graphite. (20 marks) (b) What are the most important conditions necessary for safe disposal of radioactive waste in geological repositories? Add a note on the concept of multiple barriers to protect biosphere and hydrosphere. (Give suitable diagrams wherever necessary.) (15 marks) (c) What are the major environmental considerations while treating with the disseminated precious metal mine waste? (15 marks)

हिंदी में प्रश्न पढ़ें

(a) समरूपता व बहुरूपता से आप क्या समझते हैं? हीरा एवं ग्रेफाइट का उदाहरण देते हुए मोनोट्रॉपी की विवेचना कीजिए। (20 अंक) (b) रेडियोधर्मी कचरे के भूवैज्ञानिकीय निक्षेपागारों में सुरक्षित निस्तारण हेतु कौन-सी अति महत्वपूर्ण परिस्थितियाँ जरूरी होती हैं? बायोस्फीयर व हाइड्रोस्फीयर को बचाने के लिए बहुरोधकों के सिद्धांत पर एक टिप्पणी लिखिए। (जहाँ आवश्यक हो उपयुक्त चित्र दीजिए।) (15 अंक) (c) प्रकीर्ण कीमती धातु की खान के निस्तारित कचरे के उपचार के समय पर्यावरण-संबंधी कौन-से मुख्य विचारणीय विषय होते हैं? (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 weightage, and roughly 30% each to parts (b) and (c). Structure with a brief integrated introduction, then dedicated sections for each sub-part with clear sub-headings, and a concluding synthesis on mineralogy-environment interlinkages. For part (a), define terms first then analyse monotropy through diamond-graphite thermodynamics; for (b), explain repository conditions then illustrate multi-barrier systems with diagrams; for (c), enumerate environmental considerations specific to disseminated deposits like those in Hutti or Kolar gold fields.

Key points expected

  • Part (a): Clear definitions of isomorphism (same structure, different composition e.g., calcite-rhodochrosite) and polymorphism (same composition, different structure); explanation of monotropy as irreversible polymorphic transformation with ΔG-T diagrams showing graphite as stable phase at ambient conditions
  • Part (a): Diamond-graphite example with crystal structure details (sp³ vs sp² hybridization), density contrast (3.51 vs 2.26 g/cm³), and kinetic barrier preventing spontaneous diamond conversion
  • Part (b): Critical repository conditions—low permeability host rock (granite, salt, clay), tectonic stability, absence of exploitable resources, oxidizing front control, and long-term groundwater chemistry
  • Part (b): Multi-barrier concept illustrated with engineered barriers (waste matrix, canisters, bentonite buffers) and natural barriers (host rock, geosphere); diagram showing KBS-3 concept or Indian repository design
  • Part (c): Environmental considerations for disseminated precious metal waste—acid mine drainage potential, cyanide/amalgamation residues, tailings dam stability, heavy metal mobilization, and revegetation challenges; Indian examples from Hutti gold mines or Kolar gold fields

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise definitions distinguishing isomorphism from polymorphism; accurate thermodynamic treatment of monotropy with correct identification of metastable diamond; scientifically sound repository criteria including redox front control; correct identification of disseminated deposit characteristics and their specific environmental risksBasic definitions present but conflates isomorphism with solid solution series; describes diamond-graphite without thermodynamic rigor; lists repository conditions without prioritization; generic mine waste discussion without disseminated deposit specificityConfuses isomorphism with polymorphism; misidentifies diamond as thermodynamically stable; omits critical repository conditions like hydraulic conductivity; fails to distinguish disseminated from vein deposits
Diagram / cross-section20%10Clear Gibbs free energy vs temperature diagram for carbon system showing metastable diamond domain; detailed multi-barrier repository cross-section with engineered and natural barrier layers labeled; process flow diagram for disseminated waste treatment with environmental controlsSimple diamond-graphite structure diagrams without thermodynamic context; basic repository sketch missing engineered barrier details; generic mine waste diagram without process specificityNo diagrams despite explicit instruction; poorly labeled or incorrect diagrams; diagrams copied without integration into explanation
Field evidence15%7.5Cites specific Indian examples: Kolar gold fields for disseminated deposits; mentions actual repository investigations in granitic terrains of Rajasthan or proposed sites; references AMD incidents from Indian gold mining; uses specific mineral examples like aragonite-calcite for polymorphismMentions generic gold mining regions without specificity; vague reference to international repositories (Yucca Mountain, WIPP) without Indian context; standard textbook mineral examplesNo field evidence or case studies; hypothetical or invented examples; irrelevant international examples without application
Quantitative reasoning15%7.5Provides numerical values: diamond-graphite density contrast, transformation activation energy, repository depth requirements (typically 300-1000m), half-life considerations for waste classification, permeability thresholds (<10⁻¹² m/s for host rock), and tailings volume estimates for disseminated depositsMentions 'deep burial' or 'low permeability' without numbers; qualitative discussion of stability without timeframes; generic 'large volume' for disseminated wasteNo quantitative data; incorrect orders of magnitude; confuses units (e.g., permeability vs porosity)
Indian / economic relevance25%12.5Integrates India's nuclear program (PHWR spent fuel, reprocessing at Trombay/Tarapur) with repository needs; discusses Hutti-Maski and Kolar gold belt environmental legacy; connects polymorphism to industrial diamond synthesis (India's diamond cutting industry); evaluates economic viability of disseminated deposit exploitation versus environmental costsBrief mention of Indian mining or nuclear program without integration; standard international examples with superficial Indian add-on; acknowledges economic importance without analysisCompletely ignores Indian context; no economic dimension; treats question as purely academic exercise

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