新疆西天山晚古生代花岗岩的岩石成因及构造意义OA

The Western Tianshan Orogen is located in the southwestern Central Asian Orogenic Belt(CAOB).The widespread magmatic rocks provide a critical window for investigating regional tectonic-metallogenic dy-namics.To address controversies regarding the petrogenesis,tectonic setting of granitoids,and the closure tim-ing of the North Tianshan Ocean in the Western Tianshan region,this study focuses on the Late Paleozoic grani-toids(Guozigou,Halegati,Jinghe,and Nalati plutons)located along the northern margin of the Yili Block,through integrating geochronological,whole-rock elemental,and Sr-Nd-Hf isotopic analyses.The studied plu-tons are predominantly composed of monzonitic granite and potash feldspar granite.Zircon LA-ICP-MS U-Pb dating reveals that these plutons were emplaced between(368.1±1.5)Ma(Late Devonian)and(301.9±2.8)Ma(Late Carboniferous).Combined with regional geochronological data,the magmatism in the northern Yili Block can be temporally subdivided into two stages,late Devonian to early Carboniferous and late Carboniferous.The studied granitoids exhibit high silica(SiO2=66.62%-76.08%)and total alkali(K2O+Na2O=6.72%-8.85%)con-tents.In terms of rare earth elements,the studied samples show LREE-rich patterns with variable negative Eu anomalies(δEu=0.30-0.97).The trace element patterns of the studied rocks are characterized by enrichment in Rb and Th and depletion in Nb,Ta,and Ti,comparable to those of continental arc granites.The late Devonian granitoid samples show slightly enriched radiogenic isotopic signatures,with negative εNd(t)from-3.79 to-1.3 and εHf(t)from+0.3 to+5.0,indicating magma sources dominated by ancient crustal materials with mantle-de-rived contributions.In contrast,the Late Carboniferous granitoids show more radiogenic εNd(t)(+0.8 to+5.9)and εHf(t)(+4.1 to+15.1)values,indicative of a juvenile lower crustal origin.Integrating previous studies,we pro-pose that the 368-307 Ma granitoids are of I-type granite and were formed associated with the northward sub-duction of the Northern Tianshan Ocean beneath the Yili Block,whereas later A2-type potash feldspar granites and I-type monzonitic granites in the context of post-collisional lithospheric delamination initiated at～305 Ma.Additionally,the Late Devonian-Early Carboniferous to Late Carboniferous granitoids in the Borohoro region exhibit significant potential for Cu-Mo mineralization.