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The 132 Ma Comei-Bunbury large igneous province: Remnants identified in present-day southeastern Tibet and southwestern Australia

¹ State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
² Department of Geosciences, National Taiwan University, Taipei 106, Taiwan
³ Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
⁴ Beijing SHRIMP II Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
⁵ Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

Correspondence: *E-mail: dchengzhu{at}163.com; moxx38{at}yahoo.com.

We report 11 new U-Pb zircon ages obtained by sensitive high-resolution ion microprobe (SHRIMP) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP–MS) for a large province of Early Cretaceous Comei igneous rocks consisting of basaltic lavas, mafic sills and dikes, and gabbroic intrusions together with subordinate layered ultramafic intrusions and silicic volcanic rocks exposed in the Tethyan Himalaya, southeastern Tibet. Available zircon U-Pb ages obtained from various rocks in this province, which has an areal extent of ~40,000 km² (~270 km x 150 km), indicate that the magmatism occurred ca. 132 Ma ago, coeval with the Bunbury Basalt in southwestern Australia. Such a striking similarity in emplacement age, in combination with the tectonic reconstruction of eastern Gondwana ca. 132 Ma ago, allows us to propose that the extensive Comei igneous rocks in southeastern Tibet and the Bunbury Basalts in southwestern Australia may represent the erosional and/or deformational remnants of a large igneous province, which we call the Comei-Bunbury LIP. We argue that this newly identified LIP was likely caused by the Kerguelen mantle plume, which started in the Early Cretaceous and may have played a role in the breakup of eastern Gondwana and the development of the 132 Ma old Weissert oceanic anoxic event.