Geochemical characteristics,tectonic environment and significance of Triassic magmatic rocks in the Erdaokan silver deposit,Heilongjiang Province
In order to further reveal the significance of Triassic magmatism to mineralization of the Erdaokan silver deposit in Heilongjiang Province,in this paper,we have selected diabase,basaltic andesite porphyrite,andesite porphyrite and quartz diorite porphyry dikes developed in the deposit as the research objects,and have carried out their LA-ICP-MS zircon U-Pb geochronological and petrogeochemical studies for constrining their diagenetic ages and tectonic environments.The dating results show that diagenetic ages of all kinds of dikes range from 235.4 Ma to 225.7 Ma.The petrogeochemical characteristics of rocks show that their LREE and HREE are obviouly fractionated and their LREE are relatively enriched.Especially,the diabase samples are depleted in Th and U,but enriched in Nb,Ta,Sr and Ti.The basaltic andesite porphyrite,andesite porphyrite and quartz diorite porphyrite samples are enriched in U,but depleted in Nb,Ta and Ti.Their zircon εHf(t)values range from 9.3 to 11.8,with tDM1 and tDM2 ages ranging from 408 Ma to 495 Ma and from 626 Ma to 841 Ma,respectively.It is believed that the magma of diabase was originated from the enriched mantle source and was contaminated by crustal materials.Basalt andesite porphyrite/andesite porphyrite and quartz diorite porphyrite were formed in the island arc environment of the active continental margin,which was related to the southeastward subduction of the Mongolia-Okhotsk Ocean,and the magma was originated from the partial melting of the juvenile lower crust due to the underplating of basaltic magma.
万方数据
维普
