A K Choudhary
Articles written in Journal of Earth System Science
Volume 93 Issue 3 August 1984 pp 337-342
Age determinations mostly by Rb/Sr whole rock isochrons of the Precambrian rocks of Rajasthan in northwest India are summarized and discussed. On present sampling and subject to its possible bias, the following conclusions can be made. The Untala Granite believed to be intrusive into the gneissic terrain (
Heron’s original Delhi Supergroup has recorded acid magmatism widely separate in space and time. The earliest activity between 1700 and 1500 m.y. is recorded mainly in the Alwar basin in northeastern Rajasthan while the younger activity between 850 and 750 m.y. is represented by the ‘Erinpura type’ granites in the central and southern Aravalli sector. This younger event not only has let its thermal overprinting on the older Alwar rocks but also marks the onset of emplacement of the Malani Igneous suite in the trans-Aravalli terrain. This raises the new possibility that the Delhi rocks of Heron represent atleast two chronologically independent sequences with varying geographical extent. The trans-Aravalli terrain is most probably floored by partly reworked, crystalline basement and developed along linear rift zones which acted as loci for high heat flow and igneous activity since about 800 m.y. ago.
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