西藏拉萨地块南缘日喀则地区比马组火山岩的年代学、地球化学及地质意义

发布时间：2018-07-09 10:41

本文选题：比马组 + 岛弧火山岩　；参考：《地球化学》2017年03期

【摘要】：拉萨地块广泛分布中生代岩浆岩,研究它们对于认识特提斯洋的演化和理解整个青藏高原的形成过程有着重要意义。本文首次对拉萨地块南缘日喀则地区的比马组火山岩进行了系统的锆石SHRIMP U-Pb年代学、全岩主元素、微量元素及Sr-Nd同位素研究。结果表明,日喀则地区的比马组火山岩主要为中基性岩(玄武岩)及酸性岩(粗面安山岩,英安岩),精确的SHRIMP U-Pb定年获得了(177.9±2.5)Ma的年龄值,略晚于东部桑日县地区比马组火山岩。比马组火山岩整体属于低钾拉斑系列岩石,稀土元素分布模式表现为轻稀土元素富集右倾型,Eu显示弱的正异常,微量元素蛛网图显示岩石富集大离子亲石元素Th、U、Sr等,亏损高场强元素Nb、Ta、Ti等。岩石具有相对低的Sr同位素组成和高的eNd(t)值,(~(87)Sr/~(86)Sr)i值为0.703767~0.704886,eNd(t)值为5.28~6.37,显示典型的岛弧火山岩特征。认为日喀则比马组火山岩应为中生代时期新特提斯洋北向俯冲消减过程中导致亏损地幔楔部分熔融的产物,并受到了地壳的混染,形成时代上具有东早西晚的特点。
[Abstract]:Mesozoic magmatic rocks are widely distributed in Lhasa massif. It is of great significance to study the evolution of the Tethys ocean and to understand the formation of the whole Qinghai Tibet Plateau. In this paper, the systematic zircon SHRIMP U-Pb chronology, the main elements, trace elements and Sr-Nd of the whole rock of the volcanic rocks in the Shigatse region of the southern margin of the Lhasa massif have been carried out in this paper. The results show that the volcanic rocks in the Shigatse area are mainly middle base rock (Xuan Wuyan) and acid rock (Rough andesite, anganite). The accurate SHRIMP U-Pb years obtained the age value of (177.9 + 2.5) Ma, slightly later than the Pima group volcanic rocks in the eastern SANGRI county. The distribution pattern of stone and rare earth elements shows that the light rare earth elements are enriched right type, and Eu shows weak positive anomalies. The trace element cobweb map shows that the rocks are rich in large ion lithospheric elements Th, U, Sr, Nb, Ta, Ti and so on. The rock has relatively low Sr isotopic composition and high eNd (T) value, and (~ (87) Sr/~ (86) Sr) The Nd (T) value is 5.28~6.37, showing typical characteristics of island arc volcanic rocks. It is considered that the volcanic rocks in the Shigatse Bi Ma formation should be the product of partial melting of the depleted mantle wedge during the Mesozoic period of the North subduction subduction of the new Tethys ocean, and are contaminated by the crust, which has the characteristics of the late East early West.
【作者单位】：桂林理工大学地球科学学院;中国科学院地球化学研究所矿床地球化学国家重点实验室;中国科学院广州地球化学研究所同位素地球化学国家重点实验室;成都地质矿产研究所;
【基金】：国家自然科学基金(41003018,41463001) 中国地质调查局青藏高原地质研究中心开放课题(2014-02) 广西八桂学者项目(2013许继峰) 广西矿冶与环境科学实验中心资助项目(KH2011ZD002) 广西自然科学基金(2016GXNSFAA380012;2014GXNSFAA118304)
【分类号】：P588.14

【相似文献】