Geochemistry of Khandadharpahar-Thakuranipahar metabasites from the western Singhbhum Craton, eastern India : implications for subduction-zone tectonics and mantle-wedge metasomatism
Rajanikanta Singh, Mutum (Wadia Institute of Himalayan Geology)

Fecha:	2022
Resumen:	The identification of new rock types in the volcano-sedimentary sequences of the Singhbhum Craton has attracted much attention in recent years. The present study deals on newly identified Nb-Enriched Basalts (NEB) from the Khandadharpahar-Kadakala-Thakuranipahar (KKT) section, western Singhbhum Craton, which is comparable in composition to basalts-basaltic andesites and calk-alkaline in character. These metabasites have a porphyritic texture with phenocrysts of pyroxene and plagioclase, as well as a groundmass that has metamorphosed to the greenschist facies. High Nb contents (7. 5-22. 8ppm) combined with high (Nb/Th)PM (0. 28-0. 59), (Nb/La)PM (0. 40-0. 69) and Nb/U (11. 7-34. 4) ratios, compared to arc basalts ((Nb/Th)PM= 0. 10-1. 19; (Nb/La)PMn 0. 17-0. 99, Nb/U<10), characterized them as NEB. Negative Nb, Zr, Hf and Ti anomalies, and Nb/Th vs La/Nb and Th/Nb vs. La/Sm relationships, collectively indicate typical arc volcanics. The available geochemical parameters suggest a genesis of KKT metabasites through i) slab melt migration from the downgoing oceanic crust, ii) low-degree melting of the garnet-bearing peridotite in the mantle wedge metasomatized by the slab melts, iii) slab melt - peridotite interaction triggering increasing Nb concentrations and iv) NEB generation in an arc-related environment. The discovery of KKT NEB sheds new information on Paleoproterozoic subduction-zone processes and crustal growth in the Singhbhum craton.
Nota:	Acknowledgement. The author is grateful to Dr. Kalachand Sain, Director, Wadia Institute of Himalayan Geology (WIHG) for his kind permission to publish this work. The motivation for this study comes from Dr. C Manikyamba (Ph.D. supervisor), Emeritus Scientist, CSIR-NGRI and Dr. Sohini Ganguly, Goa University. In addition, he would like to thank Prof. J. Ray for his assistance during the fieldwork. The constructive comments from the anonymous reviewers are greatly appreciated. This is WIHG's contribution no. 0180.
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria de l'obra original.
Lengua:	Català
Documento:	Article ; recerca ; Versió publicada
Materia:	Singhbhum Craton ; Porphyritic texture ; Slab Melting ; Mantle Wedge Metasomatism ; Nb-Enriched Basalts
Publicado en:	Geologica acta, Vol. 20 (2022) , p. 1-17 (Articles) , ISSN 1696-5728

Adreça original: https://raco.cat/index.php/GeologicaActa/article/view/404244
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/37348
DOI: 10.1344/GeologicaActa2022.20.11

17 p, 1.9 MB

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