Geochemical Characteristics And Geological Significance Of The Oxidaban Complex Rock Mass,South Tianshan,Xinjiang

The study area is mainly located in the southern margin of the South Tianshan orogenic belt in Xinjiang.According to the latest 1:2.5 million tectonic map of intrusive rocks in China,the study area is located in the northern margin of Tarim and its north tectonomagmatic sub province.Based on the field geological survey,petrological analysis,geochemical analysis,zircon U-Pb geochronology,zircon trace element analysis and analysis of zircon Lu-Hf isotopes,this paper discusses the genesis of the oxidaban complex and the geotectonic environment during diagenesis,and draws the following conclusions:1?There are three types of rocks in the oxidaban complex rock mass:medium-coarse grained tonalite,granodiorite and gabbro diorite,Among them,the medium-coarse grained tonalite and granodiorite are generated by the same magmatism with the same source area,while the gabbro diorite is from different sources.The three types of rocks are mainly subalkaline series,the medium potassic calc alkaline series,and meta aluminous to peraluminous.Medium coarse grained tonalite and granodiorite belong to the magnesium diorite series,and the gabbro diorite belongs to the high magnesium diorite series.2?As a whole,the oxidaban complex rock mass shows that Cs?Rb?Th?U?K?Pb?Nd and Sm are enriched,Ba?Nb?Ta?Zr?Hf?P and Ti are depleted.Light rare earth elements are relatively enriched,with weak negative europium anomaly.The REE distribution curve is right dip.3?The weighted average age of LA-ICP-MS of the coarse-grained tonalite in the oxidaban complex rock mass is 422.33 ± 0.99 Ma and 425.4 ± 1.0Ma,which is an intrusion of the late Silurian.4?The magma of the medium-coarse grained tonalite and granodiorite in oxidaban is the product of the reaction between the magma formed by the partial melting of the South Tianshan ocean crust plate and the overlying mantle peridotite after it subducted to the South under the Tarim plate;the magma of the gabbro diorite(high magnesium)is the product of the partial melting of the mantle peridotite.Thetectonic environment of oxidaban is the oceanic subduction environment,which belongs to the active continental margin arc.Combined with the previous research results,it can be determined that there is southward subduction of South Tianshan ocean of Silurian,and two-way subduction of South Tianshan ocean crust plate in Devonian.