Hot subduction in the southern Paleo-Asian Ocean:Insights from clinopyroxene chemistry and Sr-Nd-Hf-Pb isotopes of Carboniferous volcanics in West Junggar

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外文摘要：The chemical evolution and pressure-temperature conditions of subduction zone magmatism along ancient suture zones in orogenic belts can provide important information regarding plate convergence processes in paleo-oceans.Carboniferous magmatism in West Junggar is key to understanding the tectonothermal and subduction history of the Junggar Ocean,which was a branch of the Paleo-Asian Ocean,as well as the accretionary processes in the southwestern Central Asian Orogenic Belt(CAOB).We undertook a geochronological,mineralogical,geochemical,and Sr-Nd-Hf-Pb isotopic study of vol-canic rocks from the Baikouquan area of West Junggar.We used these data to determine the petrogenesis,mantle source,and pressure-temperature conditions of these magmas,and further constrain the subduc-tion and tectonic history of the Junggar Ocean.The studied volcanic rocks yielded zircon U-Pb ages of 342-337 Ma and are characterized by enrichments of large-ion lithophile elements(LILEs),and deple-tions in high-field-strength elements(HFSEs),indicative of an island arc affinity.The volcanic rocks have positive εNd(t)(5.83-7.04)and εHf(t)(13.47-15.74)values,87Sr/86Sr(t)ratios of 0.704023-0.705658,and radiogenic 207Pb/204Pb(t)and 208Pb/204Pb(t)ratios at a given 206Pb/204Pb(t)ratio,indicative of a depleted mantle source contaminated by subduction-related materials.Geochemical modeling calculations indi-cate that ≤1％of a subduction component comprising fluid and sediment melt could have generated the source of the parental melts of the Baikouquan volcanic rocks.Clinopyroxene phenocrysts in the vol-canic rocks are classified as high-and low-Ti clinopyroxene,and pressure-temperature calculations sug-gest the host rocks formed at high temperatures(～1300 ℃)and shallow to moderate depths(＜2 GPa).The magma was probably generated by hot and hydrous melting in a mantle wedge in response to sub-duction of young,hot oceanic lithosphere.The present results,combined with published data,suggest that the Baikouquan volcanic rocks record a transition in tectonic setting from normal cold to anomalous hot subduction of young oceanic lithosphere close to a mid-ocean ridge.This indicates ridge subduction began shortly after 337 Ma.Our results provide new insights into the tectonomagmatic evolution during intra-oceanic subduction prior to ridge subduction.

外文关键词：

Hot subductionSr-Nd-Hf-Pb isotopesClinopyroxene chemistryWest JunggarCentral Asian Orogenic Belt

作者：

Yao Xiao、Xijun Liu、Wenjiao Xiao、Xiao-Han Gong、Hao Wu、Yujia Song、Zhiguo Zhang、Pengde Liu

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作者单位：

Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,College of Earth Sciences,Guilin University of Technology,Guilin 541004,China

Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resource Guilin University of Technology,Guilin 541004,China

National Key Laboratory of Ecological Security and Resource Utilization in Arid Areas,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,China

School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China

College of Civil Engineering,Hexi University,Zhangye 734000,China

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基金：

国家自然科学基金国家自然科学基金Guangxi Science Innovation Base Construction FoundationFifth Bagui Scholar Innovation Project of Guangxi Province(to XU Jifeng)Gansu Province Youth Science and Technology Fund ProjectGuangxi Young and Middleaged Teachers'Basic Competence Enhancement ProgramXinjiang Tianchi Distinguished ExpertGuangxi Key Mineral Resources Deep Exploration Talent Highland

项目编号：

9205520841888101GuikeZY2119503123JRRG00172023KY0270

出版年：

2024

DOI：

10.1016/j.gsf.2023.101716

地学前缘(英文版)

中国地质大学（北京）北京大学

地学前缘(英文版)

CSTPCD

影响因子：0.576

ISSN：1674-9871

年,卷(期)：2024.15(1)

参考文献量4