Subduction–accretion–collision history along the Gondwana suture in southern India: A laser ablation ICP-MS study of zircon chronology

Abstract

a b s t r a c tWe report the petrological characteristics and preliminary zircon geochronology based on laser ablation ICP mass spectrometry of the various units in an accretionary belt within the Palghat-Cauvery Shear/ Suture Zone in southern India, a trace of the Cambrian Gondwana suture. Zircons extracted from a plagiogranite in association with an ophiolite suite within this suture possess internal structure that suggests magmatic crystallization, and yield mid Neoproterozoic 206 Pb/ 238 U age of 817 ± 16 Ma (error: 1r) constraining the approximate timing of birth of the Mozambique Ocean floor. Compiled age data on zircons separated from a quartzite and metamorphosed banded iron formation within the accretionary belt yields a younger intercept age of 759 ± 41 Ma (error: 1r) which we relate to a mid Neoproteozoic magmatic arc. Detrital zircons extracted from the quartzite yield 207 Pb/ 206 Pb age peaks of about 1.9-2.6 Ga suggesting that they were sourced from multiple protolithis of Neoarchean and Paleoproterozoic. Metamorphic overgrowths on some zircon grains record ca. 500-550 Ma ages which are in good harmony with the known ages for the timing of high-grade metamorphism in this zone during the final stage of continent collision associated with the birth of the Gondwana supercontinent in the latest NeoproterozoicCambrian. The preliminary geochronological results documented in our study correlate with the subduction-accretion-collision history associated with the closure of the Mozambique Ocean and the final amalgamation of the Gondwana supercontinent.

The Cauvery Suture Zone: Map of Structural Architecture and Recent Advances

“…The interpretation of magnetotelluric and revised gravity model confirm the PCSZ to be the trace of a major suture zone, and correlate well with a plate tectonic model of subduction-collision-accretion tectonics along this zone related to the final amalgamation of the Gondwana supercontinent (Naganjaneyulu and Santosh, 2010). y New discoveries of ophiolitic complexes such as Manamedu (Yellappa et al, 2010;Sato et al, 2011), Devattur (Yellappa et a. 2012) Agali have come to light yielding the ages of ~ 0.8 Ga and ~ 2.5Ga.…”

The Manamedu Complex: Geochemical constraints on Neoproterozoic suprasubduction zone ophiolite formation within the Gondwana suture in southern India

“…The final closure of the Mozambique Ocean is thought to have occurred during the late Neoproterozoic at the end of Precambrian along with the formation of Gondwana. Magmatic cores of zircons from the plagiogranites in Manamedu yielded U-Pb age of 800 Ma (Sato et al, 2010), which correlate with the Wilson Cycle of the Mozambique Ocean following Rodinia breakup at around 800-750 Ma. Our results suggest that the development and evolution history of Manamedu ophiolite sequence can well be correlated with the life cycle of SSZ ophiolites such as those described by Shervais (2001).…”

Laser ablation ICP mass spectrometry for zircon U-Pb geochronology of metamorphosed granite from the Salem Block: Implication for Neoarchean crustal evolution in southern India

“…The PCSZ is considered to be a trace of the Gondwana suture in southern India, with its extensions in Madagascar to the west and in Sri Lanka and probably Antarctica to the east within the Gondwana supercontinent ensemble (e.g., Collins et al, 2007a;Santosh et al, 2009). A recent laser ablation ICP mass spectrometry (LA -ICP -MS) for zircon U -Pb study of plagio-granite in a dismembered ophiolite suite Yellappa et al, 2010) within the PCSZ system constrained the timing of magmatic history correlating with the opening of the Mozambique Ocean floor as ~ 800 Ma or older (Sato et al, 2011).…”