Crustal evolution and tectonomagmatic history of the Indian Shield at the periphery of supercontinents

River sand detrital zircons from several rivers flowing through the Peninsular Indian cratons were ana-lyzed for U-Pb, Lu-Hf, and O isotopes to characterize the Precambrian crustal evolution of the Indian Shield and to constrain its role in the early supercontinent cycles. Analyzed river sand zircon samples exhibit a prominent age grouping at 2.7-2.4 Ga and additional peaks at 1.8-1.7 Ga, 1.0-0.8 Ga, and 0.6-0.5 Ga. The time-related Hf and O isotope trends of the Indian zircons display a slight offset from the global trends. The age peaks and distinct Hf-O isotopic compositions of the Indian zircons also lack coherence with the global patterns associated with supercontinent cycles, implying a discrete crustal evolutionary history for the Indian Shield. Their contrasting eHf-age trajectories indicate that the Indian Shield was accreted to the Columbia/Nuna supercontinental framework through a collision event that postdated the 2.1-1.8 Ga global-scale orogeny, and was part of a long-lived subduction system along the margin of Rodinia. This implies that the Indian Shield occupied a peripheral paleo-position during the assembly of the two Precambrian supercontinents. The ca. 2.6-2.4 Ga Indian river sand zircons have remarkably low 818O values that are distinct from the global zircon O isotopic record. This period coin-cides with the fragmentation of the Archean supercraton and the flaring-up of a subaerial Large Igneous Province that facilitated the generation of 18O-depleted magmas. Depending on whether the 2.6-2.4 Ga zircons with low 818O values (<4.7 %.) are considered or not, approximately 2.77 %. or 1.78 %. rise in the zircon 818O values occurred between ca. 2.4 Ga and ca. 1.87 Ga (decoupled from zircon Lu-Hf isotopes), further suggesting that the fine-grained sediments were enriched in 18O after the Great Oxidation Event. These high 818O sediments were subsequently incorporated into the magmatic systems resulting in elevated 818O in the zircons crystallizing from such melts. Nevertheless, a ca. 0.9 Ga peak of >10 %. in 818O system was followed by a pronounced 818O drop at ca. 0.759 Ga, suggesting that 818O of recycled sedimentary reservoirs was not the only controlling factor for zircon 818O characteristics. Variations in the Hf-O data for Indian and global zircons could be attributed to the initiation of the super-continent cycle at ca. 2.0 Ga. A significant volume of the juvenile crust was added during the 3.0-2.7 Ga mafic magmatism in the Indian Shield, as underlined by the Hf model ages of all the zircon grains and those with mantle-like 818O signatures. A gradual addition of continental crust during ca. 3.6 Ga to 3.1 Ga can also be deduced, with the oldest crust being derived from the mantle at ca. 4.4 Ga.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

River sand detrital zircons from the Peninsular Indian cratons were analyzed for their U-Pb, Lu-Hf, and O isotopes to understand the crustal evolution of the Indian Shield and its role in supercontinent cycles. The zircon samples exhibit distinct age peaks and isotopic compositions, indicating a discrete evolutionary history for the Indian Shield. The study suggests that the Indian Shield occupied a peripheral paleo-position during the assembly of Precambrian supercontinents, and experienced collision events and subduction systems. The analysis also reveals variations in isotopic signatures and oxygenation levels, suggesting changes in sedimentary reservoirs and the role of continental crust addition during the supercontinent cycle.