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The occurrence of breithauptite and nisbite-like Sb-Ni phases at Sindesar-Khurd, Rajasthan, India; implications for melt-assisted sulfide remobilization

B. Govinda Rao, Rachit Parihar, Kamal Lochan Pruseth and Biswajit Mishra
The occurrence of breithauptite and nisbite-like Sb-Ni phases at Sindesar-Khurd, Rajasthan, India; implications for melt-assisted sulfide remobilization
The Canadian Mineralogist (January 2017) 55 (1): 75-87

Abstract

Breithauptite (NiSb) generally occurs in magmatic Ni-Cu-PGE ores and in hydrothermal veins associated with Ni and Co arsenide minerals. Its presence in the Rajpura-Dariba-Sindesar-Khurd-Bethumni metallogenic belt, Rajasthan, India, may be ascribed to metamorphic remobilization as observed elsewhere, e.g., Sulitjelma, Norway. From the coexistence of breithauptite with probable Sb-Ni melt phases at Sindesar-Khurd, a temperature of approximately 930-970 degrees C is indicated from the phase relations in the Ni-Sb binary phase diagram. However, this temperature is substantially above the peak metamorphic temperature of 580-600 degrees C estimated from equilibrium silicate phase assemblages in the rocks around the Rajpura-Dariba ore body, which is situated six kilometers to the south of Sindesar-Khurd. We have conducted experiments at 600 degrees C in the Ni-Sb system in the presence of Ag to understand if Ag is responsible for such a drastic decrease of the temperature of melting. The presence of other phases including freibergite [(Ag,Cu,Fe,Zn) (sub 12) Sb (sub 4) S (sub 13) ], Ag-rich tetrahedrite [(Cu,Ag,Fe,Zn) (sub 12) Sb (sub 4) S (sub 13) ], approximately 2FeS.Ag (sub 2) S, and approximately CuPbSbS (sub 3) Ag (sub 2) S along with breithauptite at Sindesar-Khurd indicates the selective incorporation of Ag. In a second assemblage nisbite (NiSb (sub 2) ) instead of breithauptite was observed along with 3PbS.Ag (sub 2) S, 2Ag (sub 2) S.FeS, (Fe,Ag)S, a Sb-Ni-Ag-Fe-S phase, and a Ag-Sb-Ni-Cu-Fe-S phase. Nisbite is stable only below 628 degrees C, suggesting that these assemblages formed below this temperature, and the presence of several additional phases of variable compositions further indicates disequilibrium and probable rapid crystallization from a melt. Our results suggest that Ag significantly depresses melting temperatures in the Ni-Sb system, making possible the existence of an Ag-Sb-Ni melt at 600 degrees C. In the presence of S and other elements such as Fe, Pb, Cu, etc. the melting temperature would be further depressed. Thus the removal of Ag from the melt through formation of Ag-bearing phases, e.g., 2FeS.Ag (sub 2) S, 3PbS.Ag (sub 2) S, 2Ag (sub 2) S.FeS, or CuPbSbS (sub 3) Ag (sub 2) S, may result in a residual metastable melt at the ambient temperature. Such a melt may quench to a fine-grained assemblage containing breithauptite and nisbite-like Sb-Ni solid phases, such as encountered at Sindesar-Khurd. The second assemblage, which is nisbite-bearing, could result from a relatively Ag-rich Ni-poor melt fraction that becomes extremely Sb-rich due to the removal of Ag.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 55
Serial Issue: 1
Title: The occurrence of breithauptite and nisbite-like Sb-Ni phases at Sindesar-Khurd, Rajasthan, India; implications for melt-assisted sulfide remobilization
Affiliation: Indian Institute of Technology, Department of Geology and Geophysics, Kharagpur, India
Pages: 75-87
Published: 201701
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 56
Accession Number: 2017-058804
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
N23°00'00" - N30°10'00", E69°30'00" - E77°49'60"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201731
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