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Title: Amphibole - A key indicator mineral for petrogenesis of the Purulia carbonatite, West Bengal, India
Authors: Chakrabarty A.
Sen A.K.
Ghosh T.K.
Published in: Mineralogy and Petrology
Abstract: The Purulia carbonatite of West Bengal, India is a dyke occurring within the 100 km long South Purulia Shear Zone (SPSZ), which marks the boundary between the Singhbhum Group of Rocks and the Chhotanagpur Granite Gneissic Complex (CGGC). It is composed essentially of calcite with apatite, amphibole, phlogopite, biotite, magnetite and ilmenite as common accessories. Based on optical properties and mineral chemistry two varieties of the amphibole are recognized: magnesiokatophorite and richterite. The latter is characterized by a relatively high content of Si and Na, while the former is enriched in Al and Ca. Such a composition of the amphibole is characteristic for the intermediate to the late stage carbonatite development. These two co-existing amphiboles reflect a sudden variation in total pressure within the magma chamber during the intrusion of the carbonatite dyke. It is inferred that the magnesiokatophorite started crystallizing first along with calcite and apatite. Subsequently, the ascent of carbonatitic magma to a more shallow depth (hypabyssal) resulted in the formation of the richterite. The difference in amphibole composition reflects a variation in the total pressure within the magma chamber that took place during the formation of the Purulia carbonatite. However, an alternative explanation, such as wallrock contamination, or liquid immiscibility, followed by carbonate magma segregation or magma mixing, may also be possible. There is, however, no evidence corroborating such an interpretation. © pringer-Verlag 2008.
Citation: Mineralogy and Petrology (2009), 95(43832): 105-112
Issue Date: 2009
ISSN: 9300708
Author Scopus IDs: 25121521500
Author Affiliations: Chakrabarty, A., Department of Earth Sciences, IIT Roorkee, Roorkee 247667, India
Sen, A.K., Department of Earth Sciences, IIT Roorkee, Roorkee 247667, India
Ghosh, T.K., Institute Instrumentation Centre, IIT Roorkee, Roorkee 247667, India, R and D Division, Tata Steel Ltd., Jamshedpur, India
Corresponding Author: Sen, A.K.; Department of Earth Sciences, IIT Roorkee, Roorkee 247667, India; email:
Appears in Collections:Journal Publications [ES]

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