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εNd(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,εNd(t)和87Sr/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(ttM=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.%Voluminous Carboniferous volcanic rocks outcrop in the Harlik of Xinjiang.The rock types include basalt,andesite and rhyolite.However,accurate chronological data of these rocks are lacking,and the petrogenesis and tectonic implications are debated.LA-ICP-MS zircon U-Pb dating results indicate volcanic rocks formed at 302Ma (Late Carboniferous).Basahs are tholeiite series.The low Ti/Y (343 ～406) and Ce/Y (1.5 ～ 1.7),high εNd(t) (+3.9) and low 87Sr/86Sr(i) (0.7043) values,indicate basalts originated from a depleted lithospheric mantle.Intermediate-acid volcanic rocks,which are depleted in HFSE (e.g.,Nb,Ta and Ti),and enriched in LILE (e.g.,LREE,Sr and Ba),show an island arc affinity.High εNd(t) (+3.3 ～ +6.0),low 87Sr/86Sr(i) (0.7032 ～ 0.7046) values and young model ages (tDM =543 ～ 797Ma) suggest that intermediate-acid volcanic rocks originated from a young source which is composed of island arc materials formed in the processes of subduction and coalition of Paleo-Asian Oceanic.The formation of Late Carboniferous volcanic rocks in the Harlik indicates the transformation from oceanic environment to continental environment.In the post-orogenic setting,asthenosphere upwelling and lithosphere readjustment induced the re-melting of upper mantle and young crust,which resulted in the formation of Late Carboniferous volcanic rocks in the Harlik area.
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