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

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Geochemistry of the Precambrian Magmatic Rocks of Mayurbhanj District, Orissa


Affiliations
1 Geological Survey of India, Calcutta, India
2 Mineralogisk-Geologisk Museum, Sarsgate, Oslo, Norway
3 Mineralogical Museum Oslo, Norway
     

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In the Mayurbhanj area, Orissa, Badampahar group of rocks formed the cratonic block for younger Dhanjori Group. From the composition of the chilled facies of the gabbro-anorthosite, the parent magma is believed to be low in potash and alumina. The chondrite normalised REE pattern of the ultrabasic rock of Badampahar Group is unfractionated. In contrast, the gabbro-anorthosites have fractionated REE pattern with Eu anomaly. The degree of fractionation increases in the granite-granophyres. Th/U ratios systematically increase with the total REE content. It is suggested that the source region of the magmatic rocks is anomalous in respect of the large ion lithophile elements.
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  • Geochemistry of the Precambrian Magmatic Rocks of Mayurbhanj District, Orissa

Abstract Views: 185  |  PDF Views: 2

Authors

S. V. P. Iyengar
Geological Survey of India, Calcutta, India
P. Kresten
Mineralogisk-Geologisk Museum, Sarsgate, Oslo, Norway
D. K. Paul
Geological Survey of India, Calcutta, India
A. O. Brunfelt
Mineralogical Museum Oslo, Norway

Abstract


In the Mayurbhanj area, Orissa, Badampahar group of rocks formed the cratonic block for younger Dhanjori Group. From the composition of the chilled facies of the gabbro-anorthosite, the parent magma is believed to be low in potash and alumina. The chondrite normalised REE pattern of the ultrabasic rock of Badampahar Group is unfractionated. In contrast, the gabbro-anorthosites have fractionated REE pattern with Eu anomaly. The degree of fractionation increases in the granite-granophyres. Th/U ratios systematically increase with the total REE content. It is suggested that the source region of the magmatic rocks is anomalous in respect of the large ion lithophile elements.