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Coupled U-Pb and Rb-Sr laser ablation geochronology trace Archean to Proterozoic crustal evolution in the Dharwar Craton, India

Journal article
Authors Shan Shan Li
M. Santosh
Juraj Farkaš
Ahmad Redaa
Sohini Ganguly
Sung Won Kim
Cun Zhang
Sarah Gilbert
Thomas Zack
Published in Precambrian Research
Volume 343
ISSN 03019268
Publication year 2020
Published at Department of Earth Sciences
Language en
Links doi.org/10.1016/j.precamres.2020.10...
Keywords Crustal growth, In-situ Rb-Sr geochronology, Karwar Block, Metamorphism, Western Dharwar Craton, Zircon U-Pb-Hf isotopes
Subject categories Earth and Related Environmental Sciences

Abstract

© 2020 Elsevier B.V. The Western Dharwar Craton (WDC) and the Karwar Block (KB) in southern Peninsular India provide important windows to Earth's early crustal evolution and continental growth as these domains likely represent fragments of the first landmass or supercontinent on our planet. Here we employ, for the first time, a coupled laser ablation zircon U-Pb dating and in-situ Rb-Sr dating of micas (biotite, muscovite) and feldspars to evaluate the Meso- to Neoarchean crustal evolution and Proterozoic magmatism/metamorphism in the Karwar Block. This novel approach based on integrated geochronological results show that the WDC and KB experienced (i) a major Mesoarchean continental growth event (c. 3.2 to 2.9 Ga), (ii) younger Neoarchean and Paleoproterozoic magmatism/migmatization (syn- and post-tectonic granite formation events at c. 2.8–2.6 Ga and 2.2 Ga, respectively), and (iii) Mesoproterozoic metamorphism/thermal imprint (as young as 1.2 Ga). The zircon εHf(t) values exhibit a range from +0.4 to +9.8 in amphibolite, hornblende gneiss and trondhjemite (3.28–3.08 Ga), as well as the +6.1 to +9.7 range for 2.96 Ga old zircons in porphyritic granite, which suggests juvenile source for the magmatism that constructed this crustal block. Overall, this study illustrates the benefits of using coupled zircon U-Pb and in-situ Rb-Sr mica and feldspar dating approaches, as the former (U/Pb) provides robust constraints or a ‘baseline age’ for initial crystallization of crustal sequences whereas the latter (Rb/Sr) is sensitive to younger magmatic and metamorphic events. Thus, the integration of these two laser ablation ICP-MS based geochronometers applied to crustal evolution studies, has the potential to provide more comprehensive insights into continental growth in the early Earth, and later magmatic and metamorphic history of the region.

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