Granites in the Sawuer region of the west Junggar, Xinjiang Province, China: Geochronological and geochemical characteristics and their geodynamic significance
Granites in the Sawuer region of the west Junggar, Xinjiang Province, China: Geochronological and geochemical characteristics and their geodynamic significance
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DOI：
10.1016/j.lithos.2008.06.014
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发表时间：
2008-12
期刊：
影响因子：
3.5
通讯作者：
Taofa Zhou;F. Yuan;Yu Fan;Dayu Zhang;D. Cooke;Guochun Zhao
中科院分区：
文献类型：
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作者：
Taofa Zhou;F. Yuan;Yu Fan;Dayu Zhang;D. Cooke;Guochun Zhao
索乌尔地区位于中国西北部新疆自治区阿勒泰地区吉木乃县和塔城地区鹤峰县的准噶尔西部。研究区内花岗岩侵入物分布广泛，可分为i型花岗岩（塔斯特岩体、森塔西岩体、沃肯萨拉岩体和卡尔家岩体）和a型（A2）花岗岩（郭伊塔斯岩体和恰其海岩体）。i型花岗岩主要由花岗岩、二长花岗岩、花岗闪长岩组成，a型花岗岩主要以碱性花岗岩为代表。SHRIMP U-Pb定年结果表明，索乌尔地区花岗岩形成于337 ~ 290.7 Ma（晚石炭世—早二叠世）之间，其中i型花岗岩形成于337 ~ 302.6 Ma之间，a型花岗岩形成于297.9 ~ 290.7 Ma之间。根据全岩微量元素和稀土元素地球化学特征，从老花岗岩到新花岗岩，其组成由钙碱性到高钾钙碱性，再到碱性系列，由i型到a型。这一成分范围是晚古生代地球动力体制由挤压向张拉转变的结果。锶、Nd、Pb、O同位素系统表明，索乌尔地区的i型和a型花岗岩均来源于地幔（DM），但郭伊塔斯岩体受到一定的地壳污染。ⅰ型花岗岩主要由平衡部分熔融形成，而a型花岗岩主要由分馏结晶形成。基于Eby的Rb-Y +Nb和Nb - y - ce判别标准[j] . Eby g.n., 1992。a型花岗岩类的化学细分：岩石成因和构造意义。[j] .地质学报，2004,(1):1 - 6。花岗质岩石的来源和背景。通过与北疆其他地区花岗岩对比发现，ⅰ型花岗岩发育于碰撞后挤压向伸展过渡时期，而a型花岗岩发育于伸展时期。研究认为，在晚石炭世至早二叠世期间，新疆北部的索乌尔及整个准噶尔地区都经历了由挤压向伸展逐渐转变的构造活动。这种晚古生代花岗质岩浆活动促进了该地区地壳的垂直生长。
The Sawuer region is located in the west Junggar, Jimunai County of Altay district and Hefeng County of Tacheng district, Xinjiang Autonomous Region, in northwest China. In the study area granitic intrusions are widespread and can be subdivided into I-type granites (Tasite pluton, Sentasi pluton, Wokensala pluton and Kaerjia pluton) and A-type (A2) granites (Kuoyitasi pluton and Qiaqihai pluton). The I-type granites consist of granite, adamelite, granodiorite, and the A-type granites are mainly represented by alkali granite. SHRIMP U–Pb dating results indicate that the granites in Sawuer region were formed between 337 Ma and 290.7 Ma (late Carboniferous and early Permian), with the I-type granites being formed between 337 Ma and 302.6 Ma, and the A-type between 297.9 and 290.7 Ma. From the older to the youngest granites, their composition changes from calc-alkalic to high-K calc-alkalic, to alkali series, and from I-type to A-type, based on the characteristics of whole rock trace element and rare earth elements geochemistry. This compositional range is the result of a change in the geodynamic regime from compressional to tensional during the late Paleozoic. Strontium, Nd, Pb, O isotope systematics suggest that both the I-type and A-type granites in Sawuer were sourced from the mantle (DM), but with some crustal contamination for the Kuoyitasi pluton. The I-type granites were formed by equilibrium partial melting, while the A-type granites were formed mainly by fractional crystallization. Based on the Rb–Y+Nb and Nb–Y–Ce discrimination criteria by Eby [Eby G.N., 1992. Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications. Geology 20, 641–644] and Pearce [Pearce J.A., 1996. Sources and settings of granitic rocks. Episodes 19, 120–125] and comparisons with granites in other regions of northern Xinjiang, the I-type granites were emplaced during a transition from compressional to extensional settings in a post-collision regime, whereas the A-type granites were emplaced in an extensional setting. We concluded that the Sawuer as well as the whole Junggar region in northern Xinjiang were involved in tectonism that gradually changed from compressional to extensional between the late Carboniferous and early Permian. This late Paleozoic granitic magmatism contributed to vertical crustal growth in the region.