关键词: 石英闪长岩, 地球化学, 晚石炭世, 库什库都克, 西准噶尔

Abstract: The Kushenkuduke quartz diorite is located in the Late Paleozoic intermediate-acidic magmatic rocks belt along Dalbute
area in Western Junggar, Xinjiang. LA-ICP-MS zircon U-Pb dating yields an age of 305.3±2.8 Ma （n=19, MSWD= 0.17） for the
quartz diorite, indicating that it was generated during late stage of the Late Carboniferous (C2). The quartz diorite has a hypidiomorphic
heterogranular texture and a massive structure, and consists mainly of plagioclase, quartz, amphibole, and biotite, etc. A small amount
of quartz gabbro diorite with columnar pyroxene has also been observed in this pluton. The geochemical analyses show that the pluton
is characterized by SiO2 of 59.38%~63.37%, total alkali (Na2O+K2O) of 6.55%~7.51%, and Rittman index σ of 2.62~2.88, aluminumHREE=3.86~4.38, (La/Yb)N=2.99~3.66 ), with negative Eu anomalies (δEu=0.64~0.79) . The trace elements are characterized by Ba,
Nd, Zr, K, LREE enrichment, and Rb, Nb, Th, Sr, P, Ti, HREE depletion. All the features suggest a high K calcic-alkaline I-type
granite. The quartz diorite was likely derived from metabasalt in the upper crust, and subsequently underwent the fractional
crystallization of plagioclase, pyroxene, rutile, and apatite without amphibole. Based on comprehensive analysis of the genetic type of
the quartz diorite and evolution of regional tectonic environment, we suggest that when the Junggar Ocean perpetually continued its
deep subduction toward north from the early Late Carboniferous to the Early Permian, and the Kushenkuduke quartz diorite of the
island-arc type was formed during this tectonic evolution.

Key words: quartz diorite, geochemistry, Late Carboniferous, Kushenkuduke；Western Junggar