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Abhijeet Mukherjee ¹, Amitabh Tripathi ¹, Prakash K. Singh ¹, E. V. S. S. K. Babu ²

Affiliations
1 National Mineral Development Corporation Limited, Khanij Bhawan, Masab Tank, Hyderabad - 500 028, IN
2 Atomic Minerals Division, Begumpet, Hyderabad - 500 016, IN

Abstract

Garnet concentrates from the Bahradih kimberlite pipe were analysed by electron microprobe and found to be mostly of the pyrope-almandine variety with significant amount of Na₂O and a pyrope content in the range of 48.76-61.45%, almandine 30.82-41.97% and grossular 2.313-9.983%, indicating eclogitic paragenesis. Their Mg# ranges from 53.92 to 66.59. The presence of traces of Na and Ti in these garnets indicates that substitution of these elements into the garnet structure is feasible at high pressure. Five out of 50 garnets analysed from Bahmdih show Na₂O = 0.07 wt.% which indicates that they are from the diamond stability field, as confirmed further by the recovery of diamonds from the pipe.

Keywords

Kimberlite, Garnet, Pyrope, Almandine, Diamond, Raipur District, Madhya Pradesh.

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Abhijeet Mukherjee , Amitabh Tripathi , Prakash K. Singh , E. V. S. S. K. Babu

Abstract

No Abstract.

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Abhijeet Mukherjee ¹, Gautam Roy ², Amitabh Tripathi ¹

Affiliations
1 National Mineral Development Corporation Ltd., Khanij Bhawan, Masab Tank, Hyderabad - 500028, IN
2 Department of Applied Geochemistry, Osmania University, Hyderabad - 500007, IN

Abstract

Three types of fluid inclusions i.e., Type I (C0₂-H₂O) primary inclusions, trail- bound Type II biphase (H₂O, L+V) inclusions and Type III monophase C0₂ inclusions associated within intra-granular fluid inclusion trails, have been observed in quartz veins associated with BIFs of Kunchiganahalu. For constraining the mobilization-deposition conditions in the high PT region, the isochore for Type I inclusions is drawn for the density of 0.86 gm/cm³ for a C0₂-H₂O mixture with XCO₂ of about 0.6. Type II inclusions are of low salinity (<2wt % NaCl equivalent) H₂O variety with a density of 0.73 gm/cm³ Type III inclusions are of pure CO₂ variety with a density of 0.81 gm/cm³. Conditions of the mobilizing fluid are approximated by the intersection of the upper temperature for the assemblage pyrite-arsenopyrite which is fixed at 491°C and may be considered as a minimum estimate, as this assemblage and the CO₂-H₂O isochore correspond to the Type I fluid inclusions. The main depositional condition is constrained through the intersection of the isochores for the low salinity H₂O (Type II) and CO₂ (Type III). The identified conditions are 1900±150 bars at 425±150°C.The modification of a parental CO₂-H₂O+-NaCl fluid during boiling resulted in the decrcase in the activity of reduced sulphur in the hydrothermal solution which ultimately led to gold precipitation.

Keywords

Fluid Inclusions, Gold Mineralization, BIF, Kunchiganahalu, Chitradurga Belt, Karnataka, Dharwnr Craton.

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Amitabh Tripathi ¹

Affiliations
1 Department of Pharmacology, United College of Engineering and Research, IN

Abstract

No Abstract.

Keywords

No keywords

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