阿尔金清水泉斜长角闪岩同位素定年及其地球化学特征

发布时间：2019-04-20 09:32

【摘要】：阿尔金南缘清水泉地区与超基性岩及斜长花岗岩伴生的斜长角闪岩岩石地球化学组成显示:SiO_2和Al_2O_3含量较高,分别为47.63%~55.26%和16.42%~18.97%,Na_2O+K_2O含量低为4.91%~5.60%,MgO和Mg~#值较低为4.41%~5.72%和44.9~57.9,具有负Eu异常,其Mg#与Ti O2、Fe OT及Cr与Rb呈明显的相关性,表明岩石为地幔岩浆经分异演化形成。岩石富集大离子亲石元素Rb、Ba、Sr及Sm和Th,亏损高场强元素Nb、Ta、Zr、Hf、Yb、Y、Lu及Ti,且Th/Ta为2.61~18.121,Nb/La为0.21~0.661,指示岩石在演化过程中受到了陆壳的混染,推断岩石形成于裂谷环境。利用LA-ICP-MS微区原位定年获得斜长角闪岩中锆石206Pb/238U加权平均年龄为461±4 Ma,指示阿尔金南缘在中奥陶世早期处于伸展的构造动力学背景之下,为研究阿尔金构造带的形成及演化提供了新的证据。
[Abstract]:The petrogeochemical composition of amphibolite associated with ultrabasic rocks and plagioclase in Qingshuiquan area, southern margin of Altyn, shows that the contents of SiO_2 and Al_2O_3 are higher, which are 47.63% ~ 55.26% and 16.42% ~ 18.97%, respectively. The content of Na_2O K _ 2O was 4.91% ~ 5.60%, the values of MGO and Mg~# were 4.41% ~ 5.72% and 44.9 ~ 57.9, respectively. There were negative Eu anomalies, and there was a significant correlation between Mg# and Ti O _ 2, Fe OT and Cr and Rb, and there was a significant correlation between Mg# and Ti O _ 2, Fe OT and Cr. It is indicated that the rocks are formed by differentiation and evolution of mantle magma. The rocks are enriched in large ion lithophile elements Rb,Ba,Sr and Sm and Th, deficient in high field strength elements Nb,Ta,Zr,Hf,Yb,Y,Lu and Ti, and Th/Ta is 2.61 ~ 18.121 and NB / La is 0.21 ~ 0.661, respectively. It indicates that the rocks were contaminated by the continental crust in the process of evolution, and it is inferred that the rocks were formed in the rift valley environment. The 206Pb/238U weighted average age of zircon in amphibolite from LA-ICP-MS microarea is 461 卤4 Ma, indicating that the southern margin of Altun is under extensional tectonic dynamic background in the early Middle Ordovician. It provides new evidence for the study of the formation and evolution of the Altun tectonic belt.
【作者单位】：国土资源部岩浆作用成矿与找矿重点实验室中国地质调查局西安地质调查中心;新疆地质勘查基金项目管理中心;
【基金】：国家自然科学基金项目(41103021、41272089、41302051) 中国地质调查局项目(1212011220861)联合资助
【分类号】：P597.3;P588.1

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