Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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Tremolite-Olivine-Phlogopite-Bearing Ultramafic Enclaves in The Archaean Migmatite Gneiss near Naregal, Gadag District, Karnataka


Affiliations
1 Department of Applied Geology, Kuvempu University, Jnanasahyadri Shankaraghatta, Shimoga- 577 45 1, India
2 Institute of Geosciences, University of Oulu, PO Box 3000, Oulu, Finland
 

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The polyphase migmatite gneiss exposed in the vicinity of Naregal contains unusual ultramafic enclaves with the modal composition of 50% tremolite, 21% olivine, 16% phlogopite, 10% Cr-magnetite(with 5 6 wt% Cr2O3) and 2% anthophyllite. Geochemically the enclaves resemble 'Barberton komatite' in respect of high MgO, Ni, Cr and Low Al2O3, and TiO2, and one of 'Wajrakarur kimberlite' plug rocks with reference to'high K2O, Rb Zr and Ba. The finding suggests the possible existence of pristine crust in the northern part of the Western Dharwar Craton.

Keywords

Ultramafic Enclaves, Polyphase Gneiss, Fresh Olivine, Phlogopite, Pristine Crust, Naregal Karnataka.
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  • Tremolite-Olivine-Phlogopite-Bearing Ultramafic Enclaves in The Archaean Migmatite Gneiss near Naregal, Gadag District, Karnataka

Abstract Views: 200  |  PDF Views: 141

Authors

T. C. Devaraju
Department of Applied Geology, Kuvempu University, Jnanasahyadri Shankaraghatta, Shimoga- 577 45 1, India
R. J. Kaukonen
Institute of Geosciences, University of Oulu, PO Box 3000, Oulu, Finland
T. L. Sudhakara
Department of Applied Geology, Kuvempu University, Jnanasahyadri Shankaraghatta, Shimoga- 577 45 1, India
T. T. Alapieti
Institute of Geosciences, University of Oulu, PO Box 3000, Oulu, Finland

Abstract


The polyphase migmatite gneiss exposed in the vicinity of Naregal contains unusual ultramafic enclaves with the modal composition of 50% tremolite, 21% olivine, 16% phlogopite, 10% Cr-magnetite(with 5 6 wt% Cr2O3) and 2% anthophyllite. Geochemically the enclaves resemble 'Barberton komatite' in respect of high MgO, Ni, Cr and Low Al2O3, and TiO2, and one of 'Wajrakarur kimberlite' plug rocks with reference to'high K2O, Rb Zr and Ba. The finding suggests the possible existence of pristine crust in the northern part of the Western Dharwar Craton.

Keywords


Ultramafic Enclaves, Polyphase Gneiss, Fresh Olivine, Phlogopite, Pristine Crust, Naregal Karnataka.