Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Yamuna Singh ¹, K. D. P. Singh ¹, S. Srinivasan ¹, Jyotsna Chhabra ², R. K. Gupta ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad- 500 016, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, West Block, R.K. Puram, New Delhi - 110 066, IN

Abstract

No Abstract.

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Jyotsna Chhabra ¹, Dhirendra Kumar ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, New Delhi - 110066, IN

Abstract

Textural, mineralogical and chemical features of radioactive biotites from the melanosomes and leucosomes of migmatites in Chhotanagpur Gneiss at Kudri Hills are described. Biotite from melanosome is usually large and contains profuse inclusions of zircon, allanite, uranothorite and uraninite, as compared to thc biotite from leucosome. The melanosome biotite also shows contrasting microtextures, viz., presence of Fe-Ti oxide granules along cleavages and as rims around the flakes, as well as sieve texture as compared to leucosome biotite. The FeO(t)/MgO value in melanosome biotite varies from 5.0 to 5.3, whereas it is 5.9 to 6.5 in leucosome biotite. Structural formulae of biotite, calculated on the basis of 24 (0, OH, CI, F), show that the 12-coordinated cations of X-group do not reach the ideal figure of 2 in either case. The octahedral sites occupied by Y-group cations have a wide range in leucosome biotite in contrast to the very narrow range in melanosome biotite.

Anomalous concentration of rare and radioactive elements, viz., U (up to 1200 ppm), Th (up to 656 ppm), Zr (up to 31076 ppm), Ce (up to 1576 ppm), Nb (up to 193 ppm) and Y (up to 2053 ppm) in melanosome biotite seems to result from its favourable crystal structure, conducive physico-chemical attributes and stability at high temperature of amphibolite facies. The most important feature of melanosome biotite is the presence of inclusions of radioactive minerals like uraninite, uranothorite, allanite and zircon.

Keywords

Mineralogy, Radioactive biotite, Migmatite, Leucosome, Melanosome, Sonbhadra District, Uttar Pradesh.

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Yamuna Singh ¹, K. D. P. Singh ¹, Jyotsna Chhabra ², S. Srinivasan ¹, Y. C. Sharma ², R. K. Gupta ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 016, IN
2 R.K. Puram, West Block VII, New Delhi - 110 066, IN

Abstract

Koutekite and two polymorphs (i.e., alpha and beta) of domeykite (rare copper arsenide minerals) are reported for the first time from the uraniferous Lower Siwalik sandstones of the Romehra area, Hamirpur district, Himachal Pradesh. The calculated cell size of . alpha-domeykite (Cubic) is a₀ = 9.646 Å and that of betadomeykite (Hexagonal) is a₀ = 7.151 Å and c₀ = 7.304 Å. Koutekite (Hexagonal) has measured cell parameters of a₀ = 11.58 Å and c₀ = 14.55 Å. However, in koutekite of Romehra area an important interplanar spacing (d) at 2.081Å is merging with 'd' of beta dorneykite at 2.061Å and another interplanar spacing at 2.47Å exhibits comparatively higher intensity than the one published in JCPDS Data Card No.13-581. Association of domeykite with uraniferous sandstones points out that uranium mineralisation in Lower Siwaliks of the Romehra took place possibly below 90°C temperature.

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