New insights into the origin of the bimodal volcanism in the middle Okinawa Trough： not a basalt-rhyolite differentiation process

作     者：Yuxiang ZHANG Zhigang ZENG Shuai CHEN Xiaoyuan WANG Xuebo YIN 

作者机构：Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences Qingdao 266071 China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266071 China University of Chinese Academy of Sciences Beijing 100049 China 

出 版 物：《Frontiers of Earth Science》 (地球科学前沿（英文版）)

年 卷 期：2018年第12卷第2期

页      面：325-338页

核心收录：

学科分类：07[理学] 

基　　金：the valuable comments and suggestions from the anonymous reviewers and editors. This work was supported by the National Basic Research Program of China 国家自然科学基金 Special Fund for the Global Change and Air-Sea Interaction Project Strategic Priority Research Program of the Chinese Academy of Sciences Special Fund for the Taishan Scholar Program of Shandong Province AoShan Talents Program Supported by Qingdao National Laboratory for Marine Science and Technology Innovative Talent Promotion Program Science and Technology Development Program of Shandong Province Scientific and Technological Innovation Project Financially Supported by Qingdao National Laboratory for Marine Science and Technology National High Level Talent Special Support Program, CAS/SAFEA International Partnership Program for Creative Research Teams, and Qingdao Collaborative Innovation Center of Marine Science and Technology 

主　　题：Okinawa Trough rhyolite andesite remelting fractional crystallization 

摘      要：In the middle Okinawa Trough （MOT）,rhyolites have been typically considered as products ofcrystallization differentiation of basaltic magma as afeature of bimodal volcanism. However, the evidence isinsufficient. This paper compared chemical trends ofvolcanic rocks from the MOT with fractional crystal-lization simulation models and experimental results andutilized trace element modeling combined with Rayleighfractionation calculations to re-examine fractional crystal-lization processes in generating rhyolites. Both qualitativeand quantitative studies indicate that andesites, rather thanrhyolites, originate by fractional crystallization frombasalts in the MOT. Furthermore, we established twobatch-melting models for the MOT rhyolites and proposedthat type 1 rhyolites are produced by remelting of andesiteswith amphiboles in the residue, while type 2 rhyolites arederived from remelting of andesites without residualamphiboles. It is difficult to produce melts with a SiO2content ranging from 62% to 68% either by magmaticdifferentiation from basalts or by remelting of andesites,and this difficulty might help account for the compositionalgap （Daly gap） for bimodal volcanism in the OkinawaTrough.