Zhongza Block Intrusive Rocks In Sanjiang Region Chronology And Cause

Previous studies show that Zhongza block cracked in the late Paleozoic from the western margin of the Yangtze block,it went along with the gradually development of Ganzi Litang oceanic basin;and Ganzi Litang oceanic basin began to close up in the middle Late Triassic(<227Ma)with subduction to Zhongzan block,which formed the Yidundao arc fold belt between Zhongza block and Ganzi Litang suture zone.Ganzi Litang oceanic basin westward subduction would inevitably lead to Zhongza block corresponding magmatic activity accordingly.This paper selects Huangcaoping biotite diorite,Zawala complex massif,Yarigong quartz monzonite,Na Jiao granite for detailed research in petrography,petrogeochemistry and LA-ICPMS U-Pb chronology.The results show that the rocks are high potassium calc alkaline of I type granitic rocks formed in the subduction arc environments,and mainly belonged to the ilmenite series prototype granitic rock;their diagenetic ages are : Huangcaoping biotite diorite 227.4 + 1.8 Ma,Zavala quartz monzonite 225.15 ±0.96 Ma,Zavalla moyite 218 + 1.1 Ma,Yarigong quartz monzonite 224.94 + 0.93 Ma,Na Jiao granite 222.6 + 2.5Ma.Four granitic rocks generally consistent diagenetic ages imply that Ganzi Litang oceanic basin possibly began the westward subduction before the early Late Triassic(>227Ma),which triggered the granitic magmatism in Zhongza block within 218 ~ 227 Ma.The research shows that formation ages and environments of magmatic rocks in Zhongza block and Yidun island arc are approximately consistent,it refers that the rocks all belong to indosinian granites.Research on Nezawala Copper-Gold-Polymetallic Deposits in Zhongza block furtherly shows that ore deposits related to magmatic activity were formed after the separation of Zhongza block with Yangtze platform.Therefore,prospecting in Zhongza block can use prospecting model in Yidun island arc for reference.