新疆西准噶尔玉什喀腊岩体的地球化学特征、锆石U-Pb年龄及Hf同位素：对古亚洲洋闭合的制约
Geochemical characteristics, zircon U-Pb age, and Hf isotopes of Yushenkala pluton in western Junggar, Xinjiang：Constraint on the closure of Paleo-Asian Ocean
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摘要: 提要：玉什喀腊岩体位于新疆西准噶尔北部，西伯利亚板块与准噶尔板块交界的板块缝合带中，岩石类型由辉长岩、角闪辉长岩、闪长岩和石英闪长岩组成，它们侵入于中泥盆统蕴都喀拉组中。根据LA-ICP-MS锆石U-Pb定年结果，角闪辉长岩的年龄为（364±1） Ma，代表了该岩体的形成年龄。锆石的εHf (t)值变化范围为4.3~11.5，加权平均值为(9.0±1.2)，显示其原岩来源于地幔物质，其一阶段Hf模式年龄TDM1为529~827 Ma (平均值为(629±95) Ma)，指示其原岩为寒武-早寒武基底。根据野外地质关系和地球化学特征推断玉什喀腊岩体形成于岛弧环境或活动陆缘环境，在西准噶尔西北部地区，于晚泥盆世发育岛弧岩浆作用，洋陆俯冲事件己基本结束，指示古亚洲洋闭合时间不早于364 Ma。
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关键词:
- 西准噶尔 /
- 玉什喀腊岩体 /
- LA-ICP-MS锆石U-Pb年龄 /
- 锆石Hf同位素
Abstract: Abstract: The Yushenkala pluton is located in the northern part of west Junggar Basin of Xinjiang and lies along the suture zone between Siberia plate and Junggar plate. Petrologically, the pluton consists of gabbro, hornblende gabbro, diorite and quartz diorite which intruded in the middle Devonian Yudoukala Group. LA-ICP-MS zircon U-Pb dating shows that the age of the hornblende gabbro is 364±1Ma, which represents the formation age of the pluon. The εHf (t) values of the zircon are in the range of 4.3-11.5, with a weighted average of 9.0±1.2, suggesting that its original rock was derived from mantle materials. The one-stage Hf model ages (TDM1) are 529-827 Ma (629±95 Ma on average), indicating an original rock of Cambrian - Precambrian basement. Based on field geological and geochemical characteristics, the authors infer that the pluton formed in an island-arc environment or active epicontinental environment. In the late Devonian, the arc magmatism was well developed, and the ocean-continent subduction event basically came to an end in the northwestern part of western Junggar. These data indicate that the closing time of Paleo Asian ocean was not earlier than 364 Ma.-
Keywords:
- West Juggar /
- Yushenkala pluton /
- LA-ICP-MS zircon U-Pb /
- zircon Hf istope
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