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

D. C. Ghosh ¹, A. B. Mukherjee ¹

Affiliations
1 Department or Geology and Geophysics, Indian Institute of Technology, Kharagpur 721 302 (West Bengal), IN

Abstract

Hydrothermal synthesis of 1:1 type and 2:1 type trioctahedral hydrous layer lattice minerals covering the entire Mg-Ni compositional range is reported. Electronprobe microanalyses and X-ray diffraction data conform to the serpentine-type and talc-type chemistry and structure of these phases. Infra-red absorption spectra for the frequency range 4000-600 cm^-1 have been presented to characterize, their OH stretching vibrations, OH libration and the general lattice vibration modes. Optical absorption spectra between 2500 nm and 300 nm supplement the infra-red absorption data and clearly establish the d-d transition bands at about 1099 nm, 658 nm and 380 nm as caused by octahedrally coordinated Ni²⁺. Uniformity of the conditions- of synthesis between 250°C and 300°C and 350 bar P_H20 and the X-ray, infra-red and optical absorption spectra confirm the stability of the entire Mg-Ni compositional range under low pressure-temperature epizonal/hydrothermal conditions.

Keywords

Mineralogy, Hydrothermal Synthesis, Mg-Ni Layer Lattice Minerals.

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S. Soni ¹, A. B. Mukherjee ¹, D. K. Sengupta ¹

Affiliations
1 Department of Geo]ogy and Geophysics, Indian Institute of Technology, Kharagpur-721302, (West Bengal), IN

Abstract

Fluorite ore has been located at the Gore and Nawadih magnetite mines, about 20 km SW of Daltonganj. Palamau district, Bihar. The fluorite-bearing parageneses include amphibole-magnetite-quartz schists. mica schists and magnetite-quartz rocks-all occurring as discontinuous bands within the Chotanagpur granite gneiss. The amphiboles include hornblende, cummingtonite and anthophyllite. Scheelite occurs as an accessory mineral with fluorite', Pegmatitic granite and tonalitic gneiss occur as tongue-like intrusives within the schists. A calcite-clinohumite-periciase (brucite)-spinel-magnetite-sphalerite paragenesis is also reported from an adjoining area at Teliaband, 14 km east from the Gore-Nawadih mines. Thermal metamorphism of the hornblende hornfels facies accompanying a high temperature Fe-F-W pneumatolysis has apparently produced the fluorite-magnetite ore.

Keywords

Fluorite, Iron-Fluorine-Tungsten Skarn, Palamau, Bihar.

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