Geochemistry and zircon U-Pb geochronology of the rhyolitic tuff on Port Island, Hong Kong： Implications for early Cretaceous tectonic setting

作     者：Longlong Zhao Lulin Wang Mingzhong Tian Fadong Wu 

作者机构：School of Earth Science and ResourcesChina University of Geosciences 

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

年 卷 期：2017年第8卷第3期

页      面：565-581页

核心收录：

学科分类：070904[理学-构造地质学] 0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 

基　　金：supported by a geological survey program of Agriculture Fisheries and Conservation Department of Hong Kong Special Administrative Region(Grant No.AFCD/SQ/92/14) 

主　　题：Geochemistry Geochronology Rhyolitic tuff Petrogenesis Tectonic setting Hong Kong 

摘      要：Early Cretaceous rhyolitic tuffs, widely distributed on Port Island, provide insights into the volcanism and tectonic setting of Hong Kong. In this paper we present petrological, geochronological and geochemical data of the rhyolitic tuff to constrain the diagenesis age and petrogenesis of the rocks, tectonic setting and early Cretaceous volcanism of Hong Kong. The first geochronological data show that the zircons in the volcanic rocks have U-Pb age of 141.1-139.5 Ma, which reveals that the rhyolitic tuff on Port Island was formed in the early Cretaceous （K1）. Geochemically, these acid rocks, which are enriched in large ion lithophile elements （LILEs） and light rare earth elements （LREEs）, and depleted in high field strength elements （HFSEs）, belong to the high K calc-alkaline to shoshonite series with strongly-peraluminous characteristic. The geochemical analyses suggest that the volcanic rocks were derived from deep melting in the continental crust caused by basaltic magma underplating. Based on the geochemical analysis and previous studies, we concluded that the rhyolitic tufts on Port Island were formed in a back- arc extension setting in response to the subduction of the Paleo-Pacific Plate beneath the Eurasian Plate.