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Strike-slip tectonics during the Neoproterozoic–Cambrian assembly of East Gondwana: evidence from a newly discovered microcontinent in the Indian Ocean (Batavia Knoll)

Citation

Halpin, JA and Daczko, NR and Kobler, ME and Whittaker, JM, Strike-slip tectonics during the Neoproterozoic-Cambrian assembly of East Gondwana: evidence from a newly discovered microcontinent in the Indian Ocean (Batavia Knoll), Gondwana Research, 51 pp. 137-148. ISSN 1342-937X (2017) [Refereed Article]

Copyright Statement

Copyright 2017 International Association for Gondwana Research

DOI: doi:10.1016/j.gr.2017.08.002

Abstract

The first dredge samples recovered from the Batavia Knoll in the eastern Indian Ocean demonstrate it is a rifted continental fragment that now lies submerged in 2 km of water between the Perth Abyssal Plain and Wharton Basin, ~ 1600 km offshore Western Australia. This knoll is the second microcontinent to have been discovered in this region, lying ~ 180 km to the NE of Gulden Draak Knoll; both knolls rifted from the Indian margin at c. 104–101 Ma during the breakup of East Gondwana. Dredged rocks include granite, granodiorite, charnockite and quartz-rich pegmatite, preserving igneous microstructure and biotite-schlieren. The composite nature of many samples suggests derivation from a felsic igneous complex. This basement is at least partly covered by Late Cretaceous sedimentary strata. Zircon grains from five representative granitoid samples primarily display modified oscillatory zoning and U-Pb data that spread along concordia over ~ 50–70 m.y., suggesting protracted magmatism and Pb-loss during the latest Neoproterozoic–early Cambrian (c. 580–530 Ma). Despite the span in U-Pb zircon ages, the primary igneous populations exhibit a relatively narrow range of initial Hf isotopic ratios (Hfi = 0.281290–0.281814; εHfi = − 41.40 to − 23.32). This evolved nature of the Hf signature suggests derivation of melts from ancient crust (TDM2 = 4.05–2.92 Ga) with very limited juvenile input. Plate models based on sparse paleomagnetic data imply significant relative motion between India and Australia during the late Neoproterozoic–Cambrian. We suggest the new isotopic data from the Batavia Knoll granitic rocks, coupled with other regional geological constraints, are consistent with magmatic intrusion and subsequent disturbance of U-Pb systems along a late Neoproterozoic–Cambrian sinistral strike-slip margin related to Gondwana assembly.

Item Details

Item Type:Refereed Article
Keywords:Batavia Knoll, Gondwana, Hf-isotopes, Kuunga Orogen/Suture, zircon age
Research Division:Earth Sciences
Research Group:Geology
Research Field:Tectonics
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Halpin, JA (Dr Jacqueline Halpin)
Author:Whittaker, JM (Dr Jo Whittaker)
ID Code:120309
Year Published:2017
Deposited By:Centre for Oceans and Cryosphere
Deposited On:2017-08-21
Last Modified:2017-09-07
Downloads:0

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