Late Jurassic to Early Cretaceous volcanism of Hong Kong: Insights from the Ping Chau Formation

作     者：Lulin Wang Longlong Zhao Mingzhong Tian Fadong Wu Xujiao Zhang 

作者机构：School of Earth Science and ResourcesChina University of Geosciences (Beijing) Key Laboratory of Digital Earth ScienceInstitute of Remote Sensing and Digital EarthChinese Academy of Sciences School of Earth Science and ResourcesChina University of Geosciences Beijing 

出 版 物：《Geoscience Frontiers》 (地学前缘（英文版）)

年 卷 期：2019年第10卷第2期

页      面：553-568页

核心收录：

学科分类：07[理学] 0708[理学-地球物理学] 0704[理学-天文学] 

基　　金：funded by the Hong Kong Agriculture  Fisheries and Conservation Department Investigation Program (Grant No. AFCD/SQ/92/14) 

主　　题：Hong Kong Ping Chau Formation Zircon U-Pb dating Geochemistry Early Cretaceous Southeast China 

摘      要：The vast expanse of Mesozoic igneous rocks in Hong Kong contain important geological records of late Mesozoic magmatic events and tectonic processes from the coastal region of Southeast China. Of these,the Ping Chau Formation in the northwestern New Territories is the youngest known stratum. We perform a detailed study of the volcanic rocks of the Ping Chau Formation utilizing zircon U-Pb dating,with major and trace elements geochemistry. LA-ICP-MS zircon U-Pb data reveal Early Cretaceous age from two volcanic rock samples, with zircon crystallization from magmas at 140.3 ± 0.8 Ma and 139.3 ± 0.9 Ma,respectively. These rocks have high contents of total alkalis(Na_2O + K_2O = 5.58-9.45 wt.%), high-field-strength elements and light rare earth elements, conspicuous negative Eu anomalies, and depletions in Nb, Ta, Ti, Sr, Ba and P. Using this data, in combination with previous studies on the late Mesozoic volcanic belt in Southeast China, we propose that the volcanic rocks of the Ping Chau Formation probably originated from deep melting of the crust in a back-arc extensional setting induced by the subduction of the paleo-Pacific Plate. This formation represents the final stages of Early Cretaceous volcanic activity in Hong Kong, as associated with large-scale lithospheric extension, thinning and magmatism. Our results provide new information that can be used in evaluating the significance of Early Cretaceous volcanism and tectonics in Southeast China.