新疆哈尔里克山地区晚石炭世火山作用:锆石U-Pb年代学、元素地球化学及Sr-Nd同位素研究

发布时间：2018-04-25 02:19

本文选题：火山岩 + 板内环境　；参考：《岩石学报》2017年02期

【摘要】：新疆哈尔里克地区出露大面积的石炭纪火山岩,岩石类型包括玄武岩、安山岩和流纹岩等。然而目前对该套火山岩的形成时间仍缺乏较精确的年代学约束,其成因和构造属性(岛弧/陆内环境)也存在较大分歧。本文选择哈尔里克地区的火山岩剖面进行研究,通过LA-ICP-MS锆石U-Pb定年获得该套火山岩形成于约302Ma,为晚石炭世火山喷发的产物。地球化学数据表明,基性火山岩为拉斑质玄武岩系列,低Ti/Y(343~406)和Ce/Y(1.5~1.7),具有正ε_(Nd)(t)值(+3.9)和低初始~(87)Sr/~(86)Sr_((i))值(0.7043),表明玄武岩起源于同位素适度亏损的岩石圈上地幔。相对而言,中酸性火山岩则表现出高场强元素(HFSE;Nb、Ta、Ti等)负异常和大离子亲石元素(LILE;LREE、Sr、Ba等)富集的特征,与典型的弧岩浆岩类似,ε_(Nd)(t)和~(87)Sr/~(86)Sr_((i))值分别为+3.3~+6.0和0.7032~0.7046,具有较年轻的Nd模式年龄(t_(DM)=543~797Ma),指示中酸性岩浆源自年轻岛弧基底的重熔。哈尔里克晚石炭世火山岩的形成标志着大洋向大陆环境的转变,是后碰撞伸展转换背景下软流圈物质上涌诱发岩石圈上地幔和年轻下地壳再次熔融的结果。
[Abstract]:A large area of Carboniferous volcanic rocks, including basalt, andesite and rhyolite, are exposed in Hallick area, Xinjiang. However, the formation time of this set of volcanic rocks is still lack of accurate chronological constraints, and the origin and tectonic attributes (island arc / intracontinental environment) of the volcanic rocks are still quite different. In this paper, the volcanic rock profile in Halrick area is studied. The volcanic rocks were formed at about 302 Ma by LA-ICP-MS zircon U-Pb dating, which is the product of late Carboniferous volcanic eruption. Geochemical data show that the basic volcanic rocks belong to tholeiite series with low Ti / Y ~ (343N) ~ (406) and ce / Y ~ (1.5) ~ (1.7), with a positive 蔚 -S ~ (+ +) (NdT) value (3.9) and a low initial value of 0.7043 ~ (th), indicating that the basalts originated from the upper mantle of the lithosphere with moderate isotopic depletion. The results show that the basaltic rocks are derived from the upper mantle of the lithosphere with moderate isotopic depletion. On the other hand, the intermediate-acid volcanic rocks exhibit negative anomalies of high field strength elements (HFSEE, NbSe, Ta-Ti, et al.) and the enrichment of large ion lithophile elements (LILEN LREEN Sr Ba, etc.). Similar to typical arc-magmatic rocks, the values of 蔚 _ S _ S _ D ~ (T) and ~ (87) S ~ (-P) ~ (86) S ~ (-1) are 3.3 ~ 6.0 and 0.7032 ~ (0.7046), respectively. They have a younger ND model age of 543797 Ma, indicating that the intermediate-acid magma originated from the remelting of the young island substrates. The formation of the late Carboniferous volcanic rocks in Harrik indicates the transition of the ocean to the continental environment and is the result of the remelting of the upper mantle of the lithosphere and the younger lower crust induced by the upwelling of the asthenospheric material under the background of the post-collision extensional transformation.
【作者单位】：北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室;中国地质调查局油气资源调查中心;中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;
【基金】：国家青年科学基金项目(41202033) 国家“305”项目(2011BAB06B04-2) 国家“973”项目(2012CB416603)联合资助
【分类号】：P588.14;P597

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