新疆西准噶尔沙勒克腾地区花岗岩锆石U-Pb年龄、地球化学特征及其对后碰撞构造环境的约束

以西准噶尔白杨河上游沙勒克腾山及周缘花岗岩为研究对象，在地质调查的基础上，进行岩石学、锆石U-Pb年龄、岩石地球化学特征研究，探讨其形成时代及构造背景。西准噶尔白杨河上游沙勒克腾山及周缘花岗岩可划分为沙勒克腾、查干恩干、阿拉乔古、坦子不拉克4个序列，各序列岩石组合分别为花岗闪长斑岩、二长花岗斑岩，碱长花岗岩、正长花岗岩，闪长玢岩、闪长岩、石英闪长玢岩，二长花岗斑岩、花岗斑岩。沙勒克腾序列锆石U-Pb年龄为302.1±1.4 Ma(n=26，MSWD=1.5)，形成时代为晚石炭世；具有低硅(SiO2=68.07%~70.49%)、贫碱(K2O+Na2O=7.23%~8.18%)、富铝(Al2O3=14.12%~15.69%)、富钛(TiO2含量0.43%~0.48%)、富钙(CaO含量1.71%~3.31%)特征；相对亏损Nb、Ta、Sr、P、Ti，富集Zr、Hf。查干恩干序列锆石U-Pb年龄为296.7±2.1 Ma(n=26，MSWD=0.41)，形成时代为早二叠世早期；具有相对高硅(SiO2=74.21%~74.37%)，富碱(K2O+Na2O=8.84%~9.19%)、富铝(Al2O3=12.59%~12.85%)，低钛(TiO2=0.19%~0.22%)、低钙(CaO=0.64%~1.24%)特征；稀土元素含量低，亏损Sm、Tb、Y、Yb、Lu、Sr，富集Zr、Hf。沙勒克腾序列、查干恩干序列、阿拉乔古序列、坦子不拉克序列分别属于准铝质—弱过铝质高钾钙碱性I型花岗岩、准铝质碱性高分异I型花岗岩、弱过铝质碱性I型花岗岩、S型花岗岩。研究表明，白杨河上游库勒克腾山及周缘花岗岩形成于后碰撞环境挤压应力体制向伸展应力体制转换期，查干恩干序列的侵位标志着区域应力体制进入伸展阶段，进而限定研究区进入伸展应力体制的时限应不晚于296.7±2.1 Ma，为西准噶尔地区晚石炭世—早二叠世后碰撞构造研究提供了新的依据。

Zircon U-Pb age,geochemistry of granites in Shaleketeng area,West Junggar,Xinjiang and its constraints on the post-collision tectonic environment

Choosing the granites in Shaleketeng area in West Junggar as the research objects, this paper aims to discuss the regional tectonic environment by studying its petrological, geochronological and geochemical characteristics on basis of the fieldwork.The granites can be divided into four sequences: Shaleketeng, Chaganengan, Alaqiaogu and Tanzibulake.Shaleketeng sequence is composed by granodiorite-porphyry and monzonitic granite-porphyry, and formed in the Late Carboniferous, which zircon LA-ICP-MS U-Pb age is 302.1±1.4 Ma(n=26, MSWD=1.5).Shaleketeng sequence is belong to quasi-aluminous to weakly peraluminous I-type granite characterized by relatively low SiO2 (68.07%~70.49%) and K2O+Na2O(7.23%~8.18%), Al2O3(14.12%~15.69%), TiO2(0.43%~0.48%)and CaO(1.71%~3.31%)in Major element compositions, and relatively depleted Nb, Ta, Sr, P, Ti and enriched Zr, Hf in trace element compositions.Chaganengan sequence is composed by alkali-feldspar granite and orthogranite, and formed in the Early Permian, which zircon LA-ICP-MS U-Pb age is 296.7±2.1Ma(n=26, MSWD=0.41).Chaganengan sequence is belong to quasi-aluminous alkaline fractionated I-type granite characterized by relatively high SiO2(74.21%~74.37%), K2O+Na2O (8.84%~9.19%), Al2O3(12.59%~12.85%)and low TiO2(0.19%~0.22%), CaO(0.64%~1.24%) in major element compositions, and low REE and relatively depleted Sm, Th, Y, Yb, Lu, Sr, and enriched Zr, Hf in trace element compositions.Alaqiaogu sequence is composed by diorite, diorite-porphyry and quartz diorite-porphyry, and Tanzibulake sequence is orthogranite and monzonitic granite-porphyry, which are respectively belong to weakly peraluminous alkaline I-type granite and S-type granite.Considering the Regional geological data, the research reflects the granites in the studying area is formed in the transfer stage from compression to extension of post-collision tectonic environment, and Shaleketeng sequence indicates the time limit for the study area to enter the extensional stress system should be no later than 296.7±2.1 Ma.