| 邓科,袁仁华,何林武,张泽国,董玉杰,陈守关,辛堂.西藏桑耶寺西松卡村古新世石英闪长岩锆石U-Pb定年和Lu-Hf同位素组成及其构造意义[J].地质找矿论丛,2021,36(3):318-327 |
| 西藏桑耶寺西松卡村古新世石英闪长岩锆石U-Pb定年和Lu-Hf同位素组成及其构造意义 |
| Zircon U-Pb dating and Lu-Hf isotopic composition of the Paleocene quartz diorite at the west Songkacun village, Sangyesi temple area, Tibet and their tectonic significance |
| 投稿时间：2020-12-18 |
| DOI：10.6053/j.issn.1001-1412.2021.03.009 |
| 中文关键词: 冈底斯南缘 新特提斯洋俯冲 Lu-Hf同位素 幔源岩浆 西藏 |
| 英文关键词:southern Gangdise margin new Tethy subduction Lu-Hf isotope mantle-derived magma Tibet |
| 基金项目:中国地质调查局项目"西藏自治区桑耶地区1∶5万区域地质调查"（编号：DD20160015-09）资助。 |
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| 中文摘要: |
| 为解释冈底斯南缘中酸性岩体构造环境及物质来源等信息，以西藏桑耶寺西松卡村的石英闪长岩为研究对象，通过开展锆石U-Pb定年、Hf同位素组成、全岩地球化学分析与研究，结果表明：①松卡村石英闪长岩体的锆石U-Pb年龄为65.0 Ma±1.2 Ma；②松卡村石英闪长岩体具有富铝（16.97%~18.33%）的准铝质钙碱性系列岩石特征，样品富集大离子亲石元素，亏损高场强元素，在构造判别图解中样品多落在挤压岛弧区域，表明其形成构造环境应为俯冲岛弧环境；③锆石Hf同位素显示εHf（t）值为9.3~13.3，即具有很高的正值，单阶段模式年龄集中在207.1 Ma-370.2 Ma，大于其侵位年龄，表明幔源岩浆在侵位过程中受到地壳物质的混染；④结合区域构造演化史，认为西松卡村石英闪长岩体形成于新特提斯洋向拉萨地块俯冲过程中的陆缘弧期。 |
| 英文摘要: |
| This paper studies diorite at the West Songkacun village, sangyesi temple area, Tibet, interprets information of tectonic environment and material sources and intermediate rock mass in the southern margin of Gangdise. In addition zircon U-Pb dating, Lu and Hf isotropic composition and geo chemical analysis data of whole rock of the diorite are also studied. Zircon U-Pb age is 65.0 Ma±1.2 Ma, and characterized by high Al (w(Al2O3=16.9%-18.33%) and calc alkaline rock series. Samples are riched in large ion element and depleted in high field strength element. Data points of the samples fall in the subducted island arc environment in the geotectonic position discrimination diagram. Hf isotropic value is positive and very high εHf(t)=9.3-13.3. The single stage Hf model age is 207.1 Ma to 370.2 Ma larger than the emplacement of the diorite indicating that the mantle-derived magma is contaminated by the crustal material during emplacement. Combined with the regional tectonic evolution history the diorite is considered to be formed in the continental arc during subduction of the new Tethys Oceanic Lhasa terrane. |
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