Metallogenesis and Metallogenic Differences of the Early Mesozoic Granites in the Yichun Area,Heilongjiang Province

The late Triassic to early Jurassic granites are widely distributed in the Yichun area,Heilongjiang Province,which are dominated by porphyaceous monzonitic granite,monzonitic granite porphyry,syenogranite,alkali-feldspar granite and alkali granite.And the discovered iron-plolymetallic deposits and gold deposits related to these rocks are mainly of porphyry,skarn,skarn-hydrothermal,magmatic hydrothermal and epithermal hydrothermal types.The major rock-forming and ore-forming ages are late Triassic to early Jurassic(U-Pb zircon LA-ICPMS age of 191~225Ma),and the ore-forming age is slightly later than the metallogenic epoch.This paper studies the major rock types,geologic ages,tectono-magmatic evolution,genetic types of the early Mesozoic granites and mineralization characteristics of different continental-collision stages.We divide the metallogenic series into two metallogenic subseries:the Mo-Pb-Zn-Fe-W-Au(Ag) metallogenic subseries of porphyaceous monzonitic granite-monzonitic granite porphyry of continental collisional-postcollisional structural transposition and the Fe-Mo-Pb-Zn-NbTa metallogenic subseries of syenogranite-alkali-feldspar granite-alkali granite of postcollisional collapse episode.These two metallogenic subseries differ in metallogenic features,i.e.,ore-forming elements,mineralization intensity and types.And these differences are related with granite source areas,the degree of crust-mantle mixture,mixture ratio,granite emplacement depth and metallogenic tectonic background.