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Title: First report of eudialyte occurrence from the Sushina hill region, Purulia district, West Bengal
Authors: Chakrabarty A.
Pruseth K.L.
Sen A.K.
Published in: Journal of the Geological Society of India
Abstract: Eudialyte is a group of hydrated silicate minerals essentially consisting of Na and Zr with a very complex crystal structure, and generally associated with alkaline rocks. The complexity of the eudialyte structure can be understood from the fact that Na alone exist in five distinct sites and extensive solid solubility can occur in almost all cation sites, sometimes one element occupying multiple sites to the extent of exclusion of other elements. Structurally, eudialyte can be represented as Na15[M 1 ]6[M 2]3Zr3[M 3 ](Si25O 73)(O,OH,H2O)3X2 (Johnsen and Grice, 1999), where M 1 and M 2 sites are occupied by Ca, Mn and Fe, M 3 by Nb and X by OH, Cl and F. In addition, cations like Al, Hf, W, Ta, Sr, Ba and various REEs get incorporated into the eudialyte structure by substitution, and additional site vacancies even may develop in order to maintain electrical neutrality. Eudialyte, approximately of the composition Na9Ca8Mn3Nb(Zr,Ce)3Si 25O73(OH)2, has hydrothermally replaced albite in the nepheline syenite gneiss exposed south of the Sushina hill of Purulia district, West Bengal. The eudialyte contains ?2.25 atom% Zr and 0.75 atom% Nb. In addition to eudialyte in nepheline syenite, an unknown Na-Zr silicate (NZS) has also replaced the albite crystals. The NZS contains ? 7 atom% Zr with a possible empirical formula of Na12Zr11Si 36O95(OH)10. Surface exposures of these rocks are limited at Sushina hill, yet a detailed and systematic investigation on this enigmatic rock is warranted for they may turn out to be a resource for Zr. © 2011 Geological Society of India.
Citation: Journal of the Geological Society of India (2011), 77(1): 12-16
Issue Date: 2011
Keywords: Agpaitic nepheline syenite
Na-Zr silicate (NZS)
Sushina Hill
ISSN: 167622
Author Scopus IDs: 25121521500
Author Affiliations: Chakrabarty, A., Department of Earth Sciences, IIT Roorkee, Roorkee 247 667, India, Department of Geology, Durgapur Government College, Durgapur 713 214, India
Pruseth, K.L., Institute Instrumentation Centre, IIT Roorkee, Roorkee 247 667, India
Sen, A.K., Department of Earth Sciences, IIT Roorkee, Roorkee 247 667, India
Funding Details: thesis of AC which was financially supported by the Council for Scientific and Industrial Research (CSIR), New Delhi through a research project (no. 24(0286)/05/EMR-II). This support is gratefully acknowledged. The authors thank Director, Wadia Institute of Himalayan Geology, Dehradun for providing Raman Spectroscopy facility and Dr. Barun Mukherjee, Scientist for Raman Spectroscopic analysis. The authors sincerely thank Prof. A.K. Jain for his moral support and Dr. Vadlamani Ravikant for his stimulating discussions during the course of this work. AC acknowledges Prof. Roger. H. Mitchell (Lakehead University, Ontario, Canada) and Ms. Katharina Pfaff (Tübingen University, Germany) for their help during the early stages of this work.
Corresponding Author: Chakrabarty, A.; Department of Geology, Durgapur Government College, Durgapur 713 214, India
Appears in Collections:Journal Publications [ES]

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