西准噶尔谢米斯台山西北段中志留世火山岩地球化学与Sr-Nd-Os同位素特征及其地质意义

发布时间：2018-03-04 00:21

本文选题：中志留世　切入点：火山岩　出处：《岩矿测试》2017年03期 　论文类型：期刊论文

【摘要】：西准噶尔谢米斯台山火山岩近期报道形成于志留纪而非之前认为的中泥盆世,但有关中志留世火山岩特征及构造意义研究较弱。本文对西准噶尔谢米斯台山西北段乌兰浩特中志留世玄武岩、玄武安山岩样品进行了系统的地球化学主量、微量元素与Sr-Nd-Os同位素特征分析。火山岩样品表现出高MgO(5.15%~7.81%)、镁值(56.0~60.7)和低CaO(4.56%~5.09%)、FeOT/MgO(1.15~1.40)的特征,属于高镁火山岩类。玄武岩的εNd(t)值为+2.65,87Sr/86Sr和~(187)Os/~(188)Os初始比值分别为0.70439和0.4901。略显富集的同位素比值与高Th/Yb值(2.2~2.7)、低Ba/La值(17.4~33.4)表明其可能是受洋底沉积物熔体交代地幔部分熔融的产物,并遭受了一定程度地壳混染。火山岩样品为钙碱性,具有轻稀土和大离子亲石元素富集、Nb和Ta亏损等弧岩浆特征,推测乌兰浩特中志留世火山岩形成于与准噶尔洋板片由南向北俯冲有关的弧后环境。
[Abstract]:Recent reports of the shemis Taishan volcanic rocks in West Junggar were formed in Silurian rather than in the early Middle Devonian. However, the study on the characteristics and tectonic significance of the Middle Silurian volcanic rocks is relatively weak. In this paper, the samples of the Middle Silurian basalt and Black Tortoise andesite in the northwest section of the West Junggar Shermisi Mountains have been systematically studied. The characteristics of trace elements and Sr-Nd-Os isotopes. The volcanic rock samples show the characteristics of high MgO 5.15 and high MgO 5.15 ~ 7.81, mg = 56.0 ~ 60.7) and low Cao ~ (4.56) ~ 5.09% FeOT / MgO _ (1.15O ~ (1.40)), respectively. The initial ratios of the basalts are 2.65 ~ 87Sr ~ (86) Sr and ~ (18) O ~ (18) O ~ (18) O ~ (18) O ~ (88) O = 0.70439 and 0.4901, respectively. The isotopic ratios which are slightly enriched and the high Th/Yb values are 2.2 ~ 2.7and 17.433.4 respectively, indicating that the basalts may be the products of partial melting of mantle metasomatism by the melt metasomatism of the ocean floor sediments. The volcanic rock samples are calc-alkaline and characterized by the enrichment of NB and Ta depleted arc magma by light rare earth and large ion lithophile elements. It is inferred that the volcanic rocks of the Middle Silurian in Wulanhaote were formed in the back-arc environment related to the subduction of the Junggar Ocean plate from the south to the north.
【作者单位】：东北大学资源与土木工程学院;北京大学地球与空间科学学院;中国地质科学院Re-Os同位素重点实验室;
【基金】：国家自然科学基金资助项目(41202161,41672217) 中央高校基本科研业务费项目(N140104003,N140104004)
【分类号】：P597

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