Geochemistry And Tectonic Background Of The Volcanic Rocks Of Early Carboniferous Moergenhe Formation In Nenjiang Area, Heilongjiang Province

This paper gived a detailed descriptionof MoErGenHeformation in the NenJiangarea in HeiLongJiangprovince,includingvolcanic rocks of the stratigraphic sequence,rock association, the forming time, the geochemical characteristics, and discussed thecauses of volcanic rock formation of tectonic background.MoErGenHeformation volcanic rocks were controlledby NenJiang-HeiHetectonic melangebelt,which were obviously divided into two parts: the lowerpart was a medium acidic volcanics combination, including andesite, dacite, volcanicbreccia, etc.; The upper part was a set of acidic volcanic rock combination,includingrhyolite, rhyolitic mass volcanic breccia tuff, variable acid volcanic rocks,etc. Volcanic rocks of LA-ICPMS zircon U-Pb age gived353±2ma, which indicatedit was formed in the early Carboniferous. The geochemical characteristics showed thatMoErGenHeformation volcanic rocks belonged to calc-alkalic series, whichenrichedlithophile elements and light rare earth elements, and lostNb, Ta, Zr and Hf,which was similar to island arc calc-alkaline volcanic rocks. Above all,this papersuggested that the volcanic rock formation were formed in the island-arc tectonicenvironment, which represented a set of arc volcanic rock combination in the strongsubduction of ancientAsian ocean.