论文部分内容阅读
The Paleo-Asian Ocean was a Neoproterozoic to Paleozoic ocean located between Tarim-North China and East Europe-Siberia,whose opening was related to the breakup of the Rodinia supercontinent and whose expansion and closure led to the formation of the Central Asian Orogenic Belt(CAOB)and collision of Tarim-North China and East Europe-Siberia.However,there is a hot debate on the issue of whether or not the Paleo-Asian Ocean had experienced southward subduction beneath the North China Craton before its closure and when the southward subduction initially started if such subduction did happen.To resolve this issue,we carried out an integrated petrological,geochemical and geochronological study on the Delinggou intrusion in the Siziwangqi area(central Inner Mongolia),which is situated at the northern margin of the North China Craton.The Delinggou intrusion consists predominantly of diorite and quartz diorite,with minor gabbroic diorite.LA-ICP-MS U-Pb zircon dating results indicate that these rocks were emplaced during early Carboniferous time from 330 to 343 Ma.Geochemically,the rocks from the Delinggou intrusion belong to the calc-alkaline and metaluminous type,and are enriched in large ion lithophile elements(LILE,e.g.,Rb,Sr and Ba),but depleted in high field strength elements(HFSE,e.g.,Zr,Nb,Hf,Ta and Ti),characterizing magmatic arc rocks.On the basis of these geochemical features,the Delinggou intrusion is interpreted to have resulted from the partial melting of an enriched subcontinental lithospheric mantle contaminated by ancient lower crustal material in a continental margin arc setting.Accordingly,the results of this study confirm that the Paleo-Asian Ocean did undergo southward subduction beneath the North China Craton,which started in the Carboniferous(343-330 Ma),not in the Devonian as previously considered.