Geochemical Characteristics Of Permian-Cretaceous Granites In The Heihe Area,Heilongjiang Province

The study area is located at the junction of Daxing'anling and Xiaoxing'anling,which is the eastern part of Xingmeng orogenic belt and is the north and south sides of Heihe collision zone.It is one of the key areas to study the tectonic evolution of the orogenic belt.In the past,the study of Permian-Cretaceous granites in the Heihe area was relatively low.This paper mainly studies the Permian-Cretaceous granite rock masses in Heihe region of Heilongjiang province,through the field geological survey,to identify its distribution and rock combination,based on the geochemical study of the main trace elements and rare earth elements,the authors discuss the rock genesis,magmatic source area and tectonic setting.According to its rock assemblage and chronological data,the Permian-Cretaceous granites in the study area can be divided into Early Permian(292±4Ma),Late Triassic-Middle Jurassic(167.0-180.1Ma)?Early Cretaceous(110.5±0.8-137.4Ma).Early Permian granite mainly composed of long granite rocks,belonging to sub-aluminum alkaline granite,for the orogenic A-type granite,formed in the Carboniferous Duobaoshan basin closed orogenic extension of the environment,indicating that the North China plate and the Siberian plate in the Carboniferous collision orogeny after the orogenic extension of the environment.The Late Triassic-Middle Jurassic granites have the widest distribution area,and the main rocks are granodiorite-monzonitic granite-muscovite monzogranite combination,which granite diorite,monzonitic granite for the high potassium calc-alkaline series of quasi-aluminum type I granite,the muscovite monzonite granite is a high-kalcium alkaline series,showing a certain S-type granite characteristics.Alkali-feldspar granite is a kind of A-type granite,which is related to island arc magma and land-land collision,which may be formed in the subduction of the closed plate of the Duobaoshan basin.It reflects that the northeastern part of the Xing'an block belongs to the continental margin environment associated with the oceanic crust.The early Cretaceous granite rocks are complex,and the granodiorite-monzonitic granite is the main rock assemblage of the Early Cretaceous granite,Granite diorite,monzonitic granite belongs to the sub-aluminum high potassium calc-alkaline type I granite,alkali-feldspar granite belongs to sub-aluminum alkaline A-type granite.The rock type consists of type I?type A,which constitutes a relatively complete collisional orogenic rock assemblage,which may be formed in the closure of the Mongolian-Okhotsk Sea,the Shehhot Sea and the closed orogeny of the Mesoproterozoic-Mohe rift in the Heilongjiang Basin and the Tarimagou River.