SHRIMP Zircon U-Pb Age and Geochemical Characteristics of Ordovician Gabbro from Altun, Xinjiang Province
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摘要: 通过对新疆阿尔金长沙沟一带详细的野外地质调查,笔者首次解体出了奥陶纪辉长岩.采用高精度SHRIMP锆石U-Pb测年法获得了其206Pb/238U年龄加权平均值为(444.9±3.4)Ma(n=9,MSWD=1.83),可能代表了南阿尔金洋盆封闭后的一次岩浆事件.对岩石地球化学研究,表明该区辉长岩分异指数DI=35.26～44.76,固结指数SI=20.24～31.43,反映岩浆结晶分异程度较低;里特曼指数σ=3.26～9.49,A/CNK=0.75～0.82,属准铝质钙碱-碱性系列;稀土总量较高,∑REE=237.39×10-6～329.26×10-6,(La/Yb)N=6.14～8.55,轻、重稀土分馏较明显,REE配分曲线向右缓倾,Eu负异常不明显;Ba、Hf、Rb、Th、U含量明显偏高;Rb/Sr=0.04～0.47,明显低于陆壳平均值.结合区域地质背景及R1-R2图解指示:该套辉长岩应形成于板块碰撞前-碰撞后的抬升阶段,主要受阿尔金南深大断裂控制,为伸展构造环境下形成的幔源型侵入岩,可能为南阿尔金洋盆封闭后最近的一次伸展事件的产物.
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关键词:
- SHRIMP锆石U-Pb年龄 /
- 辉长岩 /
- 奥陶纪 /
- 地球化学 /
- 新疆
Abstract: The Ordovician gabbro was firstly discovered in Changshangou, Xinjiang province. The authors got for the first time the zircon U-Pb age [444.9±3.4 Ma (n=9, MSWD=1.83)] of gabbro, whose occurence may represent a magmatic event after the closure of south Altun ocean basin. Geochemical analysis show that the differentiation index(DI) is 35.26 to 44.76 and the solidification index(SI) is 20.24 to 31.43, which reflects a lower differentiation degree of magmatic crystallization; the values of Rittmann index(3.26-9.49) and A/CNK(0.75-0.82) indicates that the gabbro is quasi-aluminous calc-alkaline to alkaline series; the content of REE is relatively high(∑REE =237.39×10-6-329.26×10-6), the fractionation of LREE and HREE is obvious((La/Yb)N=6.14-8.55), the REE patterns show right oblique feature and unobvious negative Eu anomaly. Trace elements show enrichment of Ba, Hf, Rb, Th, U; the value of Rb/Sr is from 0.04 to 0.47, clearly lower than the average of continental crust. Combined with regional geological background and R1-R2 diagram, the authors hold that the gabbro is mantle-derived intrusive rock resulted from the plate uplift stage from pre-collision to post-collision, controlled by deep and major faults on the south of Altun. It is considered that the gabbro was formed in an extensional tectonic environment, probably be a result of lately extensional event after the closure of south Altun ocean basin.-
Keywords:
- SHRIMP Zircon U-Pb age /
- ordovician /
- gabbro /
- geochemistry /
- Xinjiang
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广西壮族自治区地质调查院. 1:25万瓦石峡幅、古尔嘎幅区域地质调查报告[R]. 2002. Guangxi Geological Survey, Geological survey report and geological map at scale 1:250000 of Washixia Quadrangle [R]. Published by Guangxi Geological Survey, 2002.
何国琦, 李茂松. 中国新疆古生代地壳演化及成矿[M]. 新疆: 人民出版社, 1994. He Guoqi, Li Maosong. Paleozoic crustal evolution and mineralization in xinjiang of china[M]. People's Publishing House, Xinjiang, 1994.
简平, 刘敦一, 孙晓猛. 滇川西部金沙江石炭纪蛇绿岩SHRIMP测年: 古特地斯洋盆演化的同位素年代学制约[J]. 地质学报, 2003, 77(2): 217-228. Jian Ping, Liu Dunyi, Sun Xiaomeng. SHRIMP Dating of Carboniferous Jinshajiang Ophiolite in western Yunnan and Sichuan: Geochronological constraints on the Evolution of the Paleo-Tethys Oceanic Crust[J]. Acta Geologica Sinica, 2003, 77(2): 217-228.
罗照华, 邓晋福, 韩秀卿. 太行山造山带岩浆活动及其造山过程反演[M]. 北京: 地质出版社, 1999. Luo Zhaohua, Deng Jinfu, Han Xiuqing. On characteristics of magmatic activities and orogrnic process of taihangshan intraplate orogen[M]. Geo Logical Publishing House, Bdijing, 1999.
王行军, 王根厚. 新疆和硕县包尔图一带花岗岩LA-ICP-MS锆石U-Pb年龄及其地质意义[J]. 地质通报, 2002, 31(8): 1251-1266. Wang Xingjun, Wang Genhou. LA-ICP-MS zircon U-Pb isotope age of granitoids in baoertu area, Hoxud County, Xinjiang, and its geological significance[J]. Geological Bulletin of China, 2002, 31(8): 1251-1266.
吴元保, 郑永飞. 锆石成因矿物学研究及其对U-Pb年龄解释的制约[J]. 科学通报, 2004, 49(16): 1589-1604. Wu Yuanbao, Zheng Yongfei. Genesis of zircon and its constraints on interpretation of U-Pb age [J]. Chinese Sciences Bulletin, 2004, 49(16): 1589-1604.
校培喜等. 阿尔金中段清水泉—茫崖蛇绿构造混杂岩带地质特征[J]. 西北地质, 2003, 36(2): 20-29. Xiao Peixi. The geologicalfeatures of phiolite tectonic mixtite belt from Qingshuiquan to Mangai in the middle section of Altun[J]. Northwesthrn Geology, 2003, 36(2): 20-29.
李卫东, 张翼. 阿尔金山中奥陶世恰什坎萨依侵入岩确定及对阿尔金洋盆闭合时间限定[J]. 新疆地质, 2012, 30(2): 141-145. Li Weidong, Zhang Yi. The Age Determination of the Middle Ordovician Qiashikansayi Intrusions in Altyn Mountains and its Constraints on the Closure of Altyn Oceanic[J]. Xinjiang Geology, 2012, 30(2): 141-145.
西安地质矿产研究所. 1:25万苏吾什杰幅区域地质调查报告[R]. 2002. Xi'an Institute of Geology and Mineral Resources, Geological survey report and geological map at scale 1:250000 of Suwushijie Quadrangle [R]. 2002.
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