Cambrian−Ordovician magmatic flare-up in NE Gondwana: A silicic large igneous province?

Abstract

The origin of the Cambrian−Ordovician tectono-magmatic events affecting NE Gondwana and the adjacent peri-Gondwanan terranes (e.g., Himalaya, Lhasa, Southern Qiangtang, Baoshan, Tengchong, Sibumasu, Helmand, and Karakorum) is controversial. Although its volume is poorly constrained, we propose that an extensive belt of granitic rocks that formed in various pulses between ca. 510 Ma and 460 Ma may represent the remains of a potential silicic large igneous province (LIP), which is referred to here as the Pinghe silicic LIP, with an areal extent of ∼2.5 Mkm2. The putative Pinghe silicic LIP is composed predominantly of S-type granites with subordinate A-type granites and minor intraplate mafic rocks. The recognition of this belt of granitic rocks aids in the refinement of tectonic reconstructions of Gondwana and of models for the rifting of terranes from its northern margin. The Pinghe silicic LIP broadly coincides with the adjacent 511 Ma Kalkarindji LIP in northern Australia, and the plume or mantle upwelling that triggered the Kalkarindji LIP may have been responsible for driving crustal melting that generated the granitic rocks, in a manner analogous to the Karoo−Chon Aike association.