West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean.Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for unde...West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean.Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for understanding the tectonic framework and accretionary processes in West Junggar,Central Asian Orogenic Belt.A series of Early Carboniferous volcanic and intrusive rocks,namely,basaltic andesite,andesite,dacite,and diorite,occur in the Mayile area of southern West Junggar,northwestern China.Our new LA-ICPMS zircon U-Pb geochronological data reveal that diorite intruded at 334(±1)Ma,and that basaltic andesite was erupted at 334(±4)Ma.These intrusive and volcanic rocks are calc-alkaline,display moderate MgO(1.62%-4.18%)contents and Mg#values(40-59),and low Cr(14.5×10-6-47.2×10-6)and Ni(7.5×10-6-34.6×10-6)contents,and are characterized by enrichment in light rare-earth elements and large-ion lithophile elements and depletion in heavy rare-earth elements and high-field-strength elements,meaning that they belong to typical subduction-zone island-arc magma.The samples show low initial 87Sr/86Sr ratios(range of 0.703649-0.705008),positiveεNd(t)values(range of 4.8-6.2 and mean of 5.4),and young TDM Nd model ages ranging from 1016 to 616 Ma,indicating a magmatic origin from depleted mantle involving partial melting of 10%-25%garnet and spinel lherzolite.Combining our results with those of previous studies,we suggest that these rocks were formed as a result of northwestward subduction of the Junggar oceanic plate,which caused partial melting of sub-arc mantle.We conclude that intra-oceanic arc magmatism was extensive in West Junggar during the Early Carboniferous.展开更多
基金This study was jointly supported by the CAS"Light of West China"Program(2018-XBYJRC-003)the National Natural Science Foundation of China(41772059,92055208)+1 种基金the Guangxi Natural Science Foundation for Distinguished Young Scholars,China(2018GXNSFFA281009)the Fifth Bagui Scholar Innovation Project of Guangxi Zhuang Autonomous Region,China.We are grateful for editor's excellent editorial handling and constructive comments from two anonymous reviewers,which substantially improved the final presentation of the manuscript.This is a contribution to International Geoscience Programme(IGCP)662 and Guangxi Key Mineral Resources Deep Exploration Talent Highland.
文摘West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean.Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for understanding the tectonic framework and accretionary processes in West Junggar,Central Asian Orogenic Belt.A series of Early Carboniferous volcanic and intrusive rocks,namely,basaltic andesite,andesite,dacite,and diorite,occur in the Mayile area of southern West Junggar,northwestern China.Our new LA-ICPMS zircon U-Pb geochronological data reveal that diorite intruded at 334(±1)Ma,and that basaltic andesite was erupted at 334(±4)Ma.These intrusive and volcanic rocks are calc-alkaline,display moderate MgO(1.62%-4.18%)contents and Mg#values(40-59),and low Cr(14.5×10-6-47.2×10-6)and Ni(7.5×10-6-34.6×10-6)contents,and are characterized by enrichment in light rare-earth elements and large-ion lithophile elements and depletion in heavy rare-earth elements and high-field-strength elements,meaning that they belong to typical subduction-zone island-arc magma.The samples show low initial 87Sr/86Sr ratios(range of 0.703649-0.705008),positiveεNd(t)values(range of 4.8-6.2 and mean of 5.4),and young TDM Nd model ages ranging from 1016 to 616 Ma,indicating a magmatic origin from depleted mantle involving partial melting of 10%-25%garnet and spinel lherzolite.Combining our results with those of previous studies,we suggest that these rocks were formed as a result of northwestward subduction of the Junggar oceanic plate,which caused partial melting of sub-arc mantle.We conclude that intra-oceanic arc magmatism was extensive in West Junggar during the Early Carboniferous.
