Petrology,Zircon Chronology and Geochemistry of the Late Silurian Ophiolitic Mélanges and the Baiyunshan Forearc Complex in the Central Beishan Orogenic Belt,NE China  

作　　者：Hou-Tian Xin Jian Tian Xue-Jian Teng Li-Xin Sun Guo-Zhen Zhang Yong Zhang Bang-Fang Ren 

机构地区：[1]Shenyang Center,China Geological Survey,Shenyang 110086,China [2]Tianjin Center,China Geological Survey,Tianjin 300170,China

出　　处：《Journal of Earth Science》2023年第2期444-455,共12页地球科学学刊（英文版）

基　　金：supported by the Geological Survey of China(Nos.DD20160039,DD20190038)。

摘　　要：The WNW-ESE-trending Baiyunshan ophiolitic mélange is exposed in the central Beishan orogenic belt(BOB),between the Hongliuhe-Niujuanzi and Xichangjing ophiolitic mélanges in the west and east,respectively.Here we present new petrological,geochemical,and zircon U-Pb age data for the Baiyunshan ophiolitic mélange and metamorphosed lithic sandstones of“the Baiyunshan Formation”.The Baiyunshan ophiolitic mélange is characterized by a block-in-matrix structure,and the blocks of ultramafic-mafic rocks are mainly pyroxenites,dunites,gabbros,and minor hornblendites.Zircon U-Pb dating yielded an emplacement age of 424.2±3.7 Ma for the gabbros.The ultramaficmafic rocks have geochemical features of supra-subduction zone-type ophiolites,including low Ti contents(TiO2=0.01 wt.%–0.35 wt.%),negative Nb-Ta anomalies,and U-shaped rare earth element patterns with positive Eu anomalies(δEu=0.99–3.25).“The Baiyunshan Formation”is exposed to the north of the ophiolitic mélange,and comprises mainly meta-cherts in its lower part and metasandstones and marbles in its upper part.Blocks of basalt are locally dispersed in the sand-slate matrix.The ages of detrital zircons in the metamorphosed lithic sandstones range from 521 to 464 Ma,with an age peak of 500 Ma,which is similar to those of the Gongpoquan arc in the north.The central Beishan orogenic belt experienced continuous subduction of the Hongliuhe-Xichangjing oceanic lithosphere in the Late Silurian,which produced the Baiyunshan forearc complex and supra-subduction zone-type ophiolite.

关 键 词：Beishan orogenic belt the Hongliuhe-Xichangjing Ocean the ultramafic-mafic rocks Late Silurian SSZ-type ophiolite Subduction and accretion GEOCHEMISTRY 

分 类 号：P587[天文地球—岩石学] P597.3[天文地球—地质学]