Geological And Geochemical Characteristics Of Granite And Metallogenic Significance Of Litang Area In Sichuan Province

The “SanjiangArea” has always been an important study area for geologists in China,and the Yidun island Arc belt is one of essential components of this area.The Yongjie and the Ersijiu plutons distributed in this belt are all in discontinuous and smaller-sized exposure,but they plays an irreplaceable role in the study of regional framework.This study mainly discussed the geochemical characteristics and petrogenesis of the two plutons from petrological and geochemical aspects.High precision in-situ LA-ICP-MS zircon U-Pb dating analysis was determined for the Yongjie and Ersijiu plutons to decipher their emplacement age and source.Two biotite monzogranite samples from the Yongjie pluton yield zircon U-Pb age of 221 ± 1.9Ma and 226.1 ± 1.7 Ma,respectively.Similarly,one fine grained biotite monzogranite from the Ersijiu pluton yields zircon U-Pb age of 226.7 ± 2.1 Ma,indicating that they were all formed during the Late Triassic.By comparing major,trace and rare earth elements of rocks from the two plutons,the highly consistent distribution patterns indicate that they are homologous granitoids,and the distribution patterns are in good agreement with the patterns from island arc magmatic rocks.Furthermore,according to the tectonic discrimination diagrams,samples from the two plutons are all typical island arc magmatic rocks.Therefore,the two plutons consist mainly of Late Triassic biotite monzogranite and belong to the Shaluli magmatic belt within the Yidun Island Arc Belt.The Yongjie and Ersijiu plutons were formed during the Indosinian large-scale subduction orogenesis.according to their emplacement ages(226-221Ma).This paper discussed the metallogenic significance of the granite in Litang area through complex the geochemical characteristics between the pluton of Pulang typical porphyry copper deposit.Combined with the highly consistent chronological characteristics,the emplacement ages are about 220 Ma.It is believed that the Ersijiu pluton and Yongjie pluton have the potential to form typical porphyry copper deposit in Litang area.