Metamorphic Plutonic Rocks And Metamorphic Supercrust Rock Of The Bayanwula Mountains And Their Tectonic Implications

The study area is located in the western part of the northern margin of the North China Craton,on the northeastern margin of the Alxa block,and distributed a set of high-grade metamorphic rocks of the Precambrian.The high-grade metamorphic complexes exposed in Bayanwula Mountain are systematically divided by rock field occurrence,rock combination and rock characteristics,geochemical analysis,etc.,and the metamorphic complex in the study area is divided into metamorphic supercrust rock with volcanic rocks.and protoliths are metamorphic plutonic rocks of intrusive rocks.The Metamorphic supercrust rocks in the study area are divided into three subgroups from bottom to top: dark gneiss(Pt₁pg),light gneiss(Pt₁q),and marble(Pt₁mb).Laser ablation plasma mass spectrometry(LA-ICP-MS)isotope determination was performed on selected zircons.The test results show that three groups of ages,the age of metamorphic supercrust rock formation is about 2250 Ma,and has undergone two phases of metamorphism,1.95Ga and 1.85Ga.effect.According to petrochemical analysis,it is determined that its protolith is a high-calcium-alkaline-calcalkaline series,formed in the ocean arc-active continental marginal environment.An-Ab-Or(potassium feldspar-albite-orthoclase)triangle diagram shows that metamorphic deep diagenesis is the original rock is tonalite-granodiorite,further combined with trace element spider diagram and rare earth element distribution curve Analysis shows that the large ion-philic elements Ba,K,Sr,La,Ce,and Hf are relatively enriched,the high field strength elements Nb,P,and Ti are relatively depleted,the light rare earths are relatively enriched,and the heavy rare earths are deficient.Eu shows no obvious The negative anomaly is consistent with the pre-Cambrian TTG rock geochemical characteristics,indicating that the metamorphic deep diagenesis in the study area is a lowaluminum TTG rock.Zircon LA-ICP-MS U-Pb isotope dating was performed on the Heilongjiang oblique long-angle gneiss,and the metamorphic deep diagenetic rock was formed at 1850Ma.According to the chronological analysis of metamorphic supercrust rocks and metamorphic deep diagenesis,metamorphic deep bodies represent large-scale magmatic activities,breaking the geotectonic stage of the stable environment represented by metamorphic supercrust raw rocks,and entering an abnormal tectonic and magmatic activity.And experienced a strong regional metamorphism.