Short duration of Early Permian Qiangtang-Panjal large igneous province: Implications for origin of the Neo-Tethys Ocean

Abstract

Northward drift of the Cimmerian microcontinents and opening of the Neo-Tethys Ocean in Early Permian are prominent events in northern Gondwana's protracted breakup history. However, the geodynamic setting responsible for these events is controversial. The dispersal of the eastern Cimmerian microcontinents was accompanied by the emplacement of Qiangtang-Panjal large igneous province (QP-LIP). Previously published zircon U-Pb data imply the QP-LIP was emplaced over a long interval (320-280 Ma) but are inconsistent with the short eruption interval constrained by biostratigraphic studies. New secondary ion mass spectrometry (SIMS) zircon U-Pb ages from 15 mafic dikes and gabbroic intrusions from the Southern Qiangtang terrane as well as age data from other parts of the QP-LIP show a much shorter duration (∼290−285 Ma) for this LIP. The QP-LIP was characterized by an initial ∼290 Ma alkalic and tholeiitic phases and a subsequent ∼285 Ma tholeiitic phase, in agreement with regional biostratigraphic data constraining the timing of departure of the eastern Cimmerian microcontinents from Gondwana at ∼285 Ma and the opening of the Neo-Tethys Ocean. The QP-LIP was most likely the consequence of the arrival in the upper mantle of a mantle plume beneath the northern Gondwanan margin. This event, in combination with slab pull associated with subduction beneath Laurasia, may have caused extension and rifting of east Cimmerian continental fragments from the northern margin of Gondwana. This study may elucidate the mechanism responsible for repeated episodes of one-way northward drifting terranes from northern Gondwana that commenced in Paleozoic.