| 新疆谢米斯台地区晚古生代俯冲作用: 来自塞勒肯特岩体的岩石学、年代学及地球化学证据 |
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| 引用本文： | 张望, 王居里, 胡洋. 2021. 新疆谢米斯台地区晚古生代俯冲作用: 来自塞勒肯特岩体的岩石学、年代学及地球化学证据. 岩石学报, 37(4): 1139-1158. doi: 10.18654/1000-0569/2021.04.11 |
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| 作者姓名： | 张望 王居里 胡洋 |
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| 作者单位： | 1. 大陆动力学国家重点实验室, 西北大学地质学系, 西安 710069; 2. 商洛西北有色七一三总队有限公司, 商洛 726000 |
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| 基金项目： | 本文受国家自然科学基金项目（41572057）资助. |
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| 摘 要： | 塞勒肯特岩体出露于谢米斯台中东部，岩性主要为二长花岗岩、石英闪长岩及花岗闪长岩。本文通过锆石U-Pb年代学、岩石地球化学和Sr-Nd-Hf同位素等研究，探讨其形成的构造环境及岩石成因。结果表明，二长花岗岩(400.9±4.3Ma)和石英闪长岩(398.1±4.5Ma)形成于早泥盆世，花岗闪长岩(381.7±2.9Ma)形成于晚泥盆世。岩体整体富碱，属于准铝质-弱过铝质高钾钙碱性花岗岩类。轻重稀土分馏较明显且富集轻稀土((La/Yb)N=5.09~9.22)，Eu异常不明显，相对富集Rb、Th、U、K等元素，亏损Nb、Ta、Ti等高场强元素；二长花岗岩和石英闪长岩具有低的(87Sr/86Sr)i值(0.7040~0.7043)，正εNd(t)值(+4.85~+6.18)，年轻的tDM1(Nd)年龄(663~732Ma)，二长花岗岩锆石εHf(t)值为+7.94~+12.12，tDM2(Hf)=648~889Ma；花岗闪长岩也具有低的(87Sr/86Sr)i值(0.7045~0.7046)，正εNd(t)值(+4.61~+4.80)，年轻的tDM1(Nd)年龄(731~749Ma)，花岗闪长岩锆石εHf(t)值为+4.26~+11.69，tDM2(Hf)=631~1103Ma。综合研究表明，塞勒肯特岩体形成于俯冲背景下的大陆边缘弧环境，可能是俯冲板片脱水交代地幔楔产生的玄武质岩浆上涌，导致新生下地壳发生部分熔融。二长花岗岩及石英闪长岩均来源于新生下地壳的部分熔融；花岗闪长岩主要来源于新生下地壳的部分熔融，并有少量幔源物质的加入，花岗闪长岩中的暗色微粒包体可能是幔源物质与新生下地壳部分熔融的岩浆未发生完全混合，最终冷凝结晶的产物。谢米斯台地区与俯冲相关的中酸性岩浆活动至少从晚奥陶世一直延续至晚泥盆世。
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| 关 键 词： | 年代学 地球化学 俯冲作用 陆缘弧 新疆谢米斯台 |
| 收稿时间： | 2019-10-20 |
| 修稿时间： | 2020-10-28 |
Late Paleozoic subduction in Xiemisitai: Evidence from the petrology, geochronology and geochemistry of Sailekente pluton, Xinjiang |
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| ZHANG Wang, WANG JuLi, HU Yang. 2021. Late Paleozoic subduction in Xiemisitai: Evidence from the petrology, geochronology and geochemistry of Sailekente pluton, Xinjiang. Acta Petrologica Sinica, 37(4): 1139-1158. doi: 10.18654/1000-0569/2021.04.11 |
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| Authors: | ZHANG Wang WANG JuLi HU Yang |
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| Affiliation: | 1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China; 2. Shangluo Northwest Nonferrous Metals 713 Corps Co., Ltd, ShangLuo 726000, China |
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| Abstract: | The Sailekente pluton occurs in the middle-east part of Xiemisitai area. It is mainly composed of the monzonitic granite, quartz diorite and granodiorite. We carried out integrated studies of geology, geochronology, geochemistry and whole rock Sr-Nd and zircon Hf isotopes of the Sailekente pluton, and discuss their petrogenesis and implications on the tectonic evolution. The results show that monzonitic granite (400.9±4.3Ma) and quartz diorite (398.1±4.5Ma) are formed in Early Devonian, and granodiorite (381.7±2.9Ma) is formed in Late Devonian. The whole pluton belongs to metaluminous-weakly peraluminous high-K calc-alkaline granite, and which is characterized by high silicon and enrich of alkali. The pluton has obvious fractionation of LREE and HREE, and is enriched in LREE ((La/Yb)N=5.09~9.22). The REE patterns show negative Eu anomaly. They are also enriched in LILE and depleted in Nb, Ta and Ti. The monzonitic granite and quartz diorite are characterized by positive εNd(t) (+4.85~+6.18), low (87Sr/86Sr)i (0.7040~0.7043) and relatively young model ages tDM1(Nd) ranging from 663Ma to 732Ma, the monzonitic granite has εHf(t) values ranging from +7.94~+12.12 and tDM2(Hf) model ages of zircon between 648Ma and 889Ma, respectively; granodiorite is characterized by positive εNd(t) (+4.61~+4.80), low (87Sr/86Sr)i(0.7045~0.7046) and relatively young model ages tDM1(Nd) ranging from 731Ma to 749Ma, and the εHf(t) values and tDM2(Hf) model ages of zircon are ranging from +4.26 to +11.69, and between 631Ma and 1103Ma, respectively. In conclusion, Sailekente pluton is formed in the environment of continental margin arc under the subductional background, which could be a product of emplacement and condensation crystallization of magma which is derived from partial melting of the juvenile crust. Both monzonitic granite and quartz diorite originate from the partial melting of the juvenile crust; the granodiorite mainly comes from the partial melting of the juvenile crust with the addition of a small amount of mantle-derived materials. The dark microgranular enclaves may be the product of the mantle-derived material and the partially molten magma of the juvenile crust not being completely mixed, and finally condensed and crystallized. The medium-acid magmatism is associated with subduction continuing at least from the Late Ordovician to the Late Devonian in the Xiemisitai area. |
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| Keywords: | Geochronology Geochemistry Subduction Continental margin arc Xiemisitai Xinjiang |
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