乌兹别克斯坦中天山Kattasay地区A型花岗岩的岩石成因和构造意义  

Petrogenesis and tectonic implications of A-type granites in the Kattasay region,Middle Tianshan,Uzbekistan

作　　者：姜雨奇 程志国[1] 魏博雯 JIANG YuQi;CHENG ZhiGuo;WEI BoWen(State Key Laboratory of Geological Processes and Mineral Resource,China University of Geosciences,Beijing 100083,China;School of the Earth Sciences,Hebei GEO University,Shijiazhuang 050031,China)

机构地区：[1]地质过程与矿产资源国家重点实验室,中国地质大学(北京),北京100083 [2]河北地质大学地球科学学院,石家庄050031

出　　处：《岩石学报》2023年第11期3284-3306,共23页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2021YFE0190600)资助。

摘　　要：A型花岗岩对认识区域构造背景具有重要指示意义。Kattasay地区石英斑岩和碱长花岗斑岩位于乌兹别克斯坦中天山恰特卡尔-库拉玛火山-深成岩带内。LA-ICP-MS锆石U-Pb数据表明石英斑岩在~297.3Ma形成,而碱长花岗斑岩在~294.5Ma侵位。地球化学结果显示它们均具有高SiO_(2)(70.14%~75.78%)和K_(2)O+Na_(2)O (8.07%~10.48%)含量以及高FeO^(T)/(FeO^(T)+MgO)(0.88~0.94)比值。样品还具有高的10000Ga/Al (2.51~3.14)比值和Zr+Nb+Y+Ce (439.5×10^(-6)~1141×10^(-6))含量,这些特征说明Kattasay地区石英斑岩和碱长花岗斑岩为A型花岗岩。二者具有相似的微量元素特征,Rb、K、Th、U显著正异常而Ba、Sr、Ti、Nb、Ta呈现负异常,表明它们在演化过程中经历了显著的分离结晶作用。同位素结果显示,它们的ε_(Hf )(t)值在+0.06~+5.03之间,ε_(Nd)(t)值为-2.21~-3.24。Nb-Hf同位素解耦的现象,可能是岩浆混合作用的结果。相近的侵位时间以及相似的地球化学和同位素组成表明两种岩石具有相似的源区。Kattasay地区A型花岗岩的识别暗示着Turkestan洋在晚石炭世末期已经完全闭合,在早二叠世中天山地区已经进入后碰撞环境。Petrogenesis of A-type granites has played an important role in revealing their geological settings.Granite intrusions in the Kattasay region,mainly consisting of quartz porphyry and alkali-feldspar granite porphyry,are located within the Chatkal-Kurama volcano-plutonic zone in the Middle Tianshan of Uzbekistan.LA-ICP-MS zircon U-Pb dating yields ages of ca.297.3Ma for quartz porphyry and ca.294.5Ma for alkali-feldspar granite porphyry,respectively.The quartz porphyry and alkali-feldspar granite porphyry show high SiO_2(70.14%~75.78%) and K_2O+Na_2O(8.07%~10.48%) contents,and they also have high FeO~T/(FeO~T+MgO)(0.88~0.94) ratios.All of them have high 10000Ga/Al(2.51~3.14) ratios and Zr+Nb+Y+Ce(439.5×10^(-6)~1141×10^(-6)) values and show an affinity to A-type granites.These rocks display similar trace elemental patterns,showing pronounced positive Rb-K-Th-U anomalies and negative Ba-Sr-Ti-Nb-Ta anomalies,implying that they have experienced advanced fractional crystallization.Based on the analysis of isotopic compositions,these samples display variously positive ε_(Hf)(t) values of +0.06~+5.03 and negative ε_(Nd)(t) values of-2.21~-3.24.The decoupling between Nb and Hf isotopes indicates the presence of a magma mixing.The quartz porphyry has analogical ages,similar geochemical features and isotopic compositions with alkali-feldspar granite porphyry,which suggests they might be derived from the similar source.The recognition of Kattasy A-type granites suggest that the Turkestan Ocean was ultimately closed at the end of the Late Carboniferous,while the Middle Tianshan was in a post-collisional environment in the Early Permian.

关 键 词：A型花岗岩 SR-ND-HF同位素 板片断离 中天山 乌兹别克斯坦 

分 类 号：P588.121[天文地球—岩石学] P97.3[天文地球—地质学]