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

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A Petrochemical Study of the Proterozoic Alkaline Complex of Uppalapadu, Prakasam Province, Andhra Pradesh, India


Affiliations
1 Geological Survey of India, Bandlaguda, Hyderabad-500 660, India
2 Department of Geology, Post-Graduate College of Science, Osmania University, Hyderabad-500 004, India
3 Department of Geology, Osmania University, Hyderabad-500 007, India
     

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The Proterozoic Uppalapadu alkaIine complex (1348±41 Ma) in the Prakasam province of Andhra Pradesh is predominantly composed of nepheline syenite, hornblende syenite and quartz syenite, all of which represent an alkaline series. The pluton is closely associated with tholeiitic gabbro and ferrosyenite representing a sub-alkaline series. Geochemical characters suggest that the rocks of the alkaline series were formed by the differentiation of the hydrous alkaline basaltic magma under high PH2O, whereas those of the sub-alkaline series were formed by differentiation of an anhydrous olivine tholeiitic magma under low fO2 (reducing) conditions. Quartz syenite (an offshoot in the alkaline series) is formed either by fractionation of K-feldspar, ferrohastingsite and/or biotite under high PH2O conditions or by crustal contamination of critically saturated syenitic liquids.

Keywords

Petrochemistry, Proterozoic, Alkaline Complex, Andhra Pradesh.
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  • A Petrochemical Study of the Proterozoic Alkaline Complex of Uppalapadu, Prakasam Province, Andhra Pradesh, India

Abstract Views: 250  |  PDF Views: 3

Authors

K. Krishna Reddy
Geological Survey of India, Bandlaguda, Hyderabad-500 660, India
J. Ratnakar
Department of Geology, Post-Graduate College of Science, Osmania University, Hyderabad-500 004, India
C. Leelanandam
Department of Geology, Osmania University, Hyderabad-500 007, India

Abstract


The Proterozoic Uppalapadu alkaIine complex (1348±41 Ma) in the Prakasam province of Andhra Pradesh is predominantly composed of nepheline syenite, hornblende syenite and quartz syenite, all of which represent an alkaline series. The pluton is closely associated with tholeiitic gabbro and ferrosyenite representing a sub-alkaline series. Geochemical characters suggest that the rocks of the alkaline series were formed by the differentiation of the hydrous alkaline basaltic magma under high PH2O, whereas those of the sub-alkaline series were formed by differentiation of an anhydrous olivine tholeiitic magma under low fO2 (reducing) conditions. Quartz syenite (an offshoot in the alkaline series) is formed either by fractionation of K-feldspar, ferrohastingsite and/or biotite under high PH2O conditions or by crustal contamination of critically saturated syenitic liquids.

Keywords


Petrochemistry, Proterozoic, Alkaline Complex, Andhra Pradesh.