The Early Jurassic magmatism in northern Guangdong

Authors: XinQi Yu YongJun Di GanGuo Wu Da Zhang Yong Zheng YanPei Dai

Publish Date: 2009/04/09

Volume: 52, Issue: 4, Pages: 471-483

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Abstract

This paper reports SHRIMP zircon UPb ages of 196±2 Ma for granite and 195±1 Ma for gabbro from the Xialan complex in the Meizhou area northern Guangdong Province These results shed new light on the calm stage of magmatic activity in southeastern China during 200–180 Ma and revealed that the backarc extension induced by the subduction of the western Pacific plate may have begun at 195 Ma at least Field observation on the fresh outcrops allows us to recognize some features formed by magma mixing A part of the gabbro has a finegrained rim of 20–30 cm at the margin and thins gradually toward the granite numerous dark finegrained to microcrystalline dioritic enclaves developed in the granite These enclaves vary in shape and size dark minerals concentrated at the margin of enclaves and the contact between enclaves and host rock is either obvious or obscure or gradational In addition needleshaped apatites are included in the enclaves The REE patterns of gabbros as well as the trace element patterns are generally consistent with those of granitic rocks The above characters further suggest that in the Early Jurassic the injection of basic magma had melted deep continental crust and produced acidic magma and the Xialan complex was produced by the mixing of them

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