Geochemical characteristics,zircon U-Pb dating and the geological significance of West Tashdaban granite pluton in the Azhong Block of Altyn Orogen
The Kumdaban pluton,distributed in an uplift belt of the Meso-Neoproterozoic strata on the northern margin of the Azhong block of the Altyn orogenic belt,is a large-scale composite pluton.In recent years,with the discovery of a number of large and medium-scaled lithium deposits represented by the Huanglongling super-large lithium deposit around this pluton,making the area a new hotspot for mineral exploration.The author identified a new intrusion during a 1∶50,000 regional geological survey,which was separated from the original Kumdaban pluton.It is located western of Tashdaban,with the main lithology being coarse-grained two-mica monzogranite.There has been relatively little research on this pluton.This paper explores the magmatism and geological significance of the pluton through petrology,geochemistry,and isotope geochronology research.The study shows that the granite in the western Tashdaban is characterized by high SiO2,K2O and relatively low Na2O,with aluminum saturation index values greater than 1.1,belonging to the peraluminous high-K calc-alkaline granite series.In addition,the total amount of rare earth elements is low,with a relative enrichment of light rare earth elements and a deficit of heavy rare earth elements,exhibiting a right-sloping type and a significant negative Eu anomaly.It is enriched in large ion lithophile elements such as Rb,Th,U,K,etc.,and depleted in Ba,Sr,Ti,etc.,showing typical characteristics of S-type granites.It is inferred that it was formed under conditions of～726℃ temperature and pressure<8kbar,from partial melting of crustal pelitic rock series.The zircon U-Pb age of the coarse-grained two-mica monzogranite is(466.5±3.0)Ma,indicating an emplacement era in the Middle Ordovician.The pluton was formed in a syn-collisional tectonic setting,and it is inferred to be the product of the continent-continent collision after the closure of the South Altyn Ocean.
geochemical characteristiczircon U-Pb datingAzhong blockwestern of Tashdabangranite
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