| 西南天山科桑溶洞新元古代-早奥陶世花岗岩锆石U-Pb年代学研究 |
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| 引用本文： | 朱永峰.西南天山科桑溶洞新元古代-早奥陶世花岗岩锆石U-Pb年代学研究[J].岩石学报,2012,28(7):2113-2120. |
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| 作者姓名： | 朱永峰 |
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| 作者单位： | 北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 |
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| 基金项目： | 本文受国家自然科学基金项目(41072041、41121062)和国家国际科技合作项目(2010DFB23390)联合资助. |
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| 摘 要： | 在新疆西南天山科桑溶洞地区,新厘定出一套斜长角闪岩-花岗岩地质单元:侵入斜长角闪岩中的新元古代白云母花岗岩(片麻状构造)、以及侵入上述古老岩石单元的早奥陶世花岗岩(块状构造)。片麻状白云母花岗岩中锆石具有热液锆石边、岩浆锆石幔和碎屑锆石核(边-幔-核结构),剔除被热液锆石和碎屑锆石混染的SHRIMP测点,获得岩浆锆石幔的加权平均年龄752.3±5.1Ma(MSWD=0.95),代表岩浆的结晶年龄。块状花岗岩的锆石具有边-核结构,热液锆石边的U-Pb年龄(419.5±5.7Ma)明显偏低。剔除热液锆石和碎屑锆石,获得岩浆锆石的平均U-Pb年龄481.1±4.4Ma(MSWD=0.88),代表花岗岩的结晶年龄。早奥陶世早期,岩浆侵入新元古代片麻状白云母花岗岩中。在晚志留世或者更晚时期,两类花岗岩共同经受了变质热液改造,变质流体交代岩浆锆石,导致锆石溶蚀再生长。
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| 关 键 词： | 新元古代 早奥陶世 花岗岩 热液锆石 科桑溶洞 新疆西天山 |
| 收稿时间： | 2011/12/8 0:00:00 |
| 修稿时间： | 2012/3/13 0:00:00 |
The zircon U-Pb age for the Neoproterozoic-Ordovician granites in the Kesang Rongdong region, southwestern Tianshan Mts., Xinjiang |
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| ZHU YongFeng.The zircon U-Pb age for the Neoproterozoic-Ordovician granites in the Kesang Rongdong region, southwestern Tianshan Mts., Xinjiang[J].Acta Petrologica Sinica,2012,28(7):2113-2120. |
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| Authors: | ZHU YongFeng |
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| Institution: | The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Science, Peking University, Beijing 100871, China |
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| Abstract: | Neoproterozoic and Early Ordovician granite intruded into amphibolite has been identified in the Kesang Rongdong region, southwestern Tianshan Mts. Zircons in the gneissic muscovite granite have hydrothermal rims, which replaced their igneous mantles with detrital cores. SHRIMP analysis on these igneous zircon mantles(without mixture of hydrothermal rim and detrital core)gives an average U-Pb age of 752.3±5.1Ma(MSWD=0.95). This age represents the magma intrusion episode. Hydrothermal zircon rim formed in the Early Ordovician granite in some cases though most zircons do not show continuous hydrothermal rim. One euhedral zircon crystal consists of detrital core and hydrothermal rim, the latter has much younger U-Pb age of 419.5±5.7Ma comparing with most other measurements. In many other cases, however, zircon is composed with igneous rim and detrital core. The average U-Pb age, corresponding to igneous zircon rims(481.1±4.4Ma, MSWD=0.88), represents a magma intrusion episode in the Kesang Rongdong region. Thus, the gneissic muscovite granite and amphibolite have been intruded by the Early Ordovician granite. Afterwards, these different granites have undergone metamorphism as recorded by the hydrothermal zircon, which replaced igneous zircons. |
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| Keywords: | Neoproterzoic Early Ordovician Granite Hydrothermal zircon Kesang Rongdong Western Tianshan Mts Xinjiang |
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