Basement-Cover Relationship in the Khetri Copper Belt and the Emplacement Mechanism of the Granite Massifs, Rajasthan, India
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Geochronological data from several granite bodies suggest a plutonic event around 1500 ± 200 Ma which constrains the third phase of deformation in the basement rocks. TWo types of granites are recognised; one akin to the Hercynian-type peraluminuous, compositionally restricted ilmenite-bearing S-type granite and the other Caledonian-type, compositionally restricted I-type granite.
Both forceful ballooning and forceful permitted type processes were responsible for the plutonic activity. Significant amongst the first-type are the Udaipurwati Granite and the Chapoli Granite; the former shows stretching of the sodium-rich early consolidated intrusion as a result of inflation of the potassium-rich central part of the magma balloon.
A general readjustment of the isotopic systems within minerals occurred around 700 - 800 Ma or even later, possibly a Pan-African event, which has been correlated with widespread granitic activity in western Rajasthan.
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