An Ediacaran–Cambrian thermal imprint in Rajasthan, western India: Evidence from 40Ar-39Ar geochronology of the Sindreth volcanics

Journal of Earth system science

A M Dayal3¹  Harish Mistry2³  Archisman Sen1²  Kanchan Pande1²  Kamal Kant Sharma2³  Hetu C Sheth1²  Shraboni Sarkar1² 

[1] National Geophysical Research Institute, Hyderabad 500 007, India.$$;Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.$$;Government Postgraduate College, Sirohi 374 001, Rajasthan, India.$$

关键词: Gondwanaland;    India;    Rajasthan;    Sirohi;    Sindreth;    geochronology.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

The Sindreth Group exposed near Sirohi in southern Rajasthan, western India, is a volcanosedimentary sequence. Zircons from Sindreth rhyolite lavas and tuffs have yielded U–Pb crystallization ages of ∼768–761 Ma, suggesting that the Sindreth Group is a part of the Malani magmatic event. Earlier 40Ar-39Ar studies of other Malani volcanic and plutonic rocks yielded disturbed argon release spectra, ascribed to a ∼550 Ma thermal event possibly related to the Pan-African orogeny. To test and confirm this possibility, we dated two whole-rock and three feldspar separate samples of the Sindreth volcanics by the 40Ar-39Ar method. All samples yield disturbed argon release spectra suggesting radiogenic argon loss and with plateau segments at 550 Ma or 490 Ma. We interpret these as events of argon loss at 550–490 Ma related to an Ediacaran–Cambrian thermal event, possibly related to the Malagasy orogeny. The combined older and new 40Ar-39Ar results are significant in showing that whereas Ediacaran–Cambrian magmatic and metamorphic events are well known from many parts of India, they left thermal imprints in much of Trans-Aravalli Rajasthan as well. The overall evidence is consistent with a model of multiphase assembly of Gondwanaland from separate continental landmasses.

【 授权许可】

Unknown