新疆中天山巴伦台地区花岗质侵入体地球化学、年代学研究及其构造意义

发布时间：2018-06-16 02:21

本文选题：岩石地球化学 + 年代学　；参考：《地质学报》2017年01期

【摘要】：新疆中天山巴伦台地区广泛分布着花岗质侵入体,本研究对乌瓦门断裂北侧的花岗质侵入体进行了LA-ICP-MS锆石U-Pb定年,获得岩体侵位年龄为452.7±1.4Ma和455.5±1.7Ma,属晚奥陶世。岩石地球化学结果表明其主要为一套准铝质钙碱性系列岩石,稀土元素配分图呈明显的右倾模式,具有较高的LaN/YbN比值(6.01~23.74)、弱的Eu负异常(δEu=0.67~0.83)。微量元素蛛网图上岩石总体富集大离子亲石元素Rb、Cs、Ba等,亏损高场强元素Nb、Ta及Ti。锆石原位Hf同位素测定结果表明,εHf(t)值变化于-14.8~-9.4(平均-12.4),二阶段Hf模式年龄(tDM2)变化于1730~1997Ma(平均1871Ma)。上述岩石地球化学特征表明巴伦台地区晚奥陶世花岗质侵入体形成于火山弧环境,是幔源岩浆底侵带来的大量热能使得早元古代下地壳物质发生部分熔融的产物。综合分析认为,该期侵入体可能代表了巴伦台地区南天山洋盆向北俯冲最早的岩浆记录。
[Abstract]:Granitic intrusions are widely distributed in the Palentai area of central Tianshan, Xinjiang. The LA-ICP-MS zircon U-Pb dating of granitic intrusions on the northern side of the Wawamen fault has been carried out. The emplacement ages of the intrusions are 452.7 卤1.4 Ma and 455.5 卤1.7 Ma, which belong to the late Ordovician. The petrogeochemical results show that it is mainly a set of quasi-aluminite calc-alkaline series rocks, and the REE distribution pattern shows an obvious right-dip pattern, with a high LaN- / YbN ratio of 6.01 ~ 23.74 and a weak negative EU anomaly (未 EU _ (0.67) ~ (0.83). On the trace element cobweb diagram, the rocks are enriched in the large ion lithophile elements RbCsBa-Ba and so on, and the high field strength elements NB, Ta and Ti are depleted. The results of in situ HF isotopic determination of zircon show that the 蔚 Hft values vary from -14.8 to 9.4 (mean -12.4g), and the two-stage HF model age (TDM2) varies from 1730 to 1997 Maa (mean 1871 Ma). The above petrogeochemical characteristics indicate that the late Ordovician granitic intrusions were formed in the volcanic arc environment and were the result of partial melting of the lower crust material from the early Proterozoic due to a large amount of heat generated by the mantle magma submersion. It is considered that the intrusions in this period may represent the earliest magmatic records of the southern Tianshan ocean basin subducting northward in the Balentai area.
【作者单位】：新疆地质调查院;新疆大学地质与矿业工程学院;
【基金】：中国地调局大调查项目“新疆巴伦台1∶5万K45E006010、K45E007010、K45E007011、K45E008010、K45E008011五幅区域地质调查”(编号:1212011140058)资助的成果
【分类号】：P597.3;P588.12

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