| 孔垂鹏,张志平,吴勇,焦世文,曹勇刚,段凯,芝世玉.西藏改则县物玛乡北多尼组火山岩地球化学特征、年代学特征及地质意义[J].矿产勘查,2019,(6):1304-1315 |
| 西藏改则县物玛乡北多尼组火山岩地球化学特征、年代学特征及地质意义 |
| Geochemical characteristics, chronology and geological significance of volcanic rocks in Duoni Formation in the north of Wuma Township, Gaize County, Tibet |
| 投稿时间：2019-01-10 |
| DOI： |
| 中文关键词: 物玛乡 地球化学特征 锆石U-Pb年龄 岛弧环境 多尼组 |
| 英文关键词: Wuma township, geochemistry, zircon U-Pb age, island arc environment, Duoni formation |
| 基金项目:中国地质调查局项目(编号:1212011221089)资助。 |
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| 中文摘要: |
| 冈底斯北缘出露的中生代火山岩,对于研究认识冈底斯北缘和班公湖-怒江结合带的构造演化和中生代岩浆活动的地球动力学环境有着重要的意义。对出露于冈底斯北缘物玛乡北部的多尼组火山岩进行了岩石学、岩石地球化学及年代学研究,物玛乡北地区的多尼组火山岩主体为中基性岩,火山岩的地球化学特征表明多尼组中基性岩具有高铝、富钠、富镁、低钾、偏铝质特征,属钙碱性系列火山岩,轻稀土富集,铕负异常不明显,岩浆分异作用不强,微量元素富集大离子亲石元素Ba、Sr,富集强不相容性元素Rb、Th、U,而亏损高场强元素Nb、Ta、Ti、P的特点,显示明显的弧火山岩成分特征。通过对火山岩样品中锆石U-Pb LA-ICP-MS定年,获得了113.4±1.2Ma的年龄值,显示多尼组火山岩形成于早白垩世晚期。研究显示,物玛乡北多尼组火山岩形成于增厚地壳背景下与板块俯冲有关的活动大陆边缘的岛弧环境,可能与来自消减沉积物或蚀变玄武质洋壳的含水流体引起上覆地慢楔物质的部分熔融有关,并在岩浆上升过程中经历了浅部地壳物质的同化混染。 |
| 英文摘要: |
| It is great significance for understanding the tectonic evolution of the northern margin of Gangdise and the Bangong Lake-Nujiang junction zone and the geodynamic environment of Mesozoic magmatic activity, which researching the Mesozoic volcanic rocks exposed in the northern margin of Gangdise. This paper discusses the petrology, geochemistry and chronology of the volcanic rocks in the Duoni Formation of Early Cretaceous in the northern part of Wuma Township, northern margin of Gangdise. Medium-basic rocks are the main lithology of volcanic rocks of the Doni Formation.The research show that the basic volcanic rocks of the Duoni Formation belongs to calc-alcaline series, has high Al2O3、Na2O、MgO,low K2O and metaaluminium,enrich in HREE,LILE(Ba、Sr),HFSE(Rb、Th、U),depleted HFSE(Nb、Ta、Ti、P),no significant negative Eu anomaly, weak magmatic differentiation and has obvious composition characteristics of arc volcanic rocks.The U-Pb dating of zircons shows that the volcanic rocks of the Duoni Formation were formed in the middle of Early Cretaceous(113.4±1.2Ma).The study shows that the volcanic rocks of the Douni Formation were formed in the island arc environment of the active continental margin related to plate subduction under the background of thickening crust, which may be related to the partial melting of slow wedge materials in the overlying ground caused by water-bearing fluids from sediments or altered basaltic oceanic crust, and experienced the assimilation and mixing of shallow crustal materials during magma ascension. |
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