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Characterisation and Petrogenesis of Enclaves in Punugodu Granite Pluton, Prakasam District, Andhra Pradesh, India


Affiliations
1 Department of Applied Geochemistry, Osmania University, Hyderabad-500007, India
2 Geochemistry Division, CSIR-NGRI, Hyderabad-500007, India
 

Punugodu Granite Pluton (PGP) is one among the many granitic plutons hosted by Nellore Schist Belt (NSB) and considered as post collisional A-type Granite. It consists a variety of enclaves; they are seen as Xenoliths, Mafic magmatic enclaves (MME), Felsic magmatic enclaves (FME) and Basic Microgranular Enclaves (BME) which are having a distinct field, petrographic, and geochemical characteristics. They are subalkaline tholitic to alkaline and magnesian to ferroan in nature. Chondrite normalized REE patterns of MME, FME and xenoliths show fractionation, relative LREE enrichment and HREE depletion with negative-Eu anomalies. When compared among these enclaves, BME show slightly less fractionated REE patterns without Eu-anomalies, which is transitional between tholitic-alkaline basalts, and akin to oceanic-continental tectonic settings. BME of OIB signatures which are early formed and assimilated into granitic melts or late stage chemical exchange/equilibration of coeval melts at high temperatures. Enclaves could have derived from a single magma source more likely to be a high Ti-basaltic parentage with an involvement of magma chamber process in connection with mixing-mingling process at the coeval generation of magmas and assimilation process by the late stage granitic plutonism.

Keywords

Granitoid, Enclaves, Nellore Schist Belt, Petrogenesis.
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  • Characterisation and Petrogenesis of Enclaves in Punugodu Granite Pluton, Prakasam District, Andhra Pradesh, India

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Authors

Ch. Narshimha
Department of Applied Geochemistry, Osmania University, Hyderabad-500007, India
K. S. V. Subramanyam
Geochemistry Division, CSIR-NGRI, Hyderabad-500007, India
U. V. B. Reddy
Department of Applied Geochemistry, Osmania University, Hyderabad-500007, India

Abstract


Punugodu Granite Pluton (PGP) is one among the many granitic plutons hosted by Nellore Schist Belt (NSB) and considered as post collisional A-type Granite. It consists a variety of enclaves; they are seen as Xenoliths, Mafic magmatic enclaves (MME), Felsic magmatic enclaves (FME) and Basic Microgranular Enclaves (BME) which are having a distinct field, petrographic, and geochemical characteristics. They are subalkaline tholitic to alkaline and magnesian to ferroan in nature. Chondrite normalized REE patterns of MME, FME and xenoliths show fractionation, relative LREE enrichment and HREE depletion with negative-Eu anomalies. When compared among these enclaves, BME show slightly less fractionated REE patterns without Eu-anomalies, which is transitional between tholitic-alkaline basalts, and akin to oceanic-continental tectonic settings. BME of OIB signatures which are early formed and assimilated into granitic melts or late stage chemical exchange/equilibration of coeval melts at high temperatures. Enclaves could have derived from a single magma source more likely to be a high Ti-basaltic parentage with an involvement of magma chamber process in connection with mixing-mingling process at the coeval generation of magmas and assimilation process by the late stage granitic plutonism.

Keywords


Granitoid, Enclaves, Nellore Schist Belt, Petrogenesis.

References