U–Pb zircon geochronology of a pyroclastic rock from the Parsoi Formation, Mahakoshal Group: Implications towards age and tectonics of the Basin in Central Indian Tectonic Zone. Issue 10 (30th June 2022)

• Record Type: Journal Article
• Authors: Sharma, Aditi; Das, Kaushik; Chakraborty, Partha Pratim; Shiraishi, Fumito; Kayama, Masahiro
• Is Part Of: Geological journal. Volume 57:Issue 10(2022)
• Page Start: 4122
• Page End: 4138
• Publication Date: 2022-06-30
• Subjects: Central Indian Tectonic Zone (CITZ) -- Mahakoshal Basin -- pyroclastic rocks -- U–Pb zircon Orosirian age; Geology -- Periodicals; 551
• DOI: 10.1002/gj.4533
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : The Mahakoshal Group of rocks in the Central Indian Tectonic Zone (CITZ) holds the key to documenting the early events in the CITZ evolution and initiation of collision/accretion between the North and South Indian cratons (NIC, SIC). Centimetre to decimetre‐thick conformable pyroclastic beds, sandwiched within the siltstone‐argillite metasedimentary succession of the Parsoi Formation allows us to generate (i) a robust depositional age, which otherwise is bracketed based on basement and intrusive age, and (ii) track the earliest record of accretion at the plate margin of NIC. A magmatic origin for the inferred pyroclastic unit is established from petrographic signatures and, in particular, the CL response of quartz grains. The dominance of the Dauphiné twin in fine‐grained (~100 μm and <20 μm) quartz fraction implies sub‐aquatic fast‐cooling across the phase transition temperature (573°C) of quartz within the pyroclastic rock. A volcanic arc to syn‐collisional granite affinity is suggested for the pyroclastic unit based on (i) dacitic to rhyolitic composition, (ii) LILE‐enrichment, (iii) HFSE depletion, and (iv) enrichment of Th, U, and Pb. The 207 Pb/ 206 Pb 1894.3 ± 9.4 Ma age of crystallization is estimated from the youngest and most prominent peak of near‐concordant oscillatory zoned zircon grain with a high Th/U ratio. The age data is important in documenting the earliest accretion event at the plate margin in the collisional history of NIC and SIC. Abstract : A pyroclastic unit (dacitic to rhyolitic composition) in Parsoi Formation, Mahakoshal Belt, central India yields 207 Pb/ 206 Pb age of 1894.3 ± 9.4 Ma as the crystallization age. This fixes the Orosirian age of BIF‐bearing Mahakoshal Basin Formation at the margin between NIC and SIC.