| 大兴安岭北段扎兰屯地区斜长角闪岩年代学、地球化学和Hf同位素特征及其构造意义 |
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| 引用本文： | 钱程,汪岩,陆露,秦涛,李林川,崔天日,陈会军,杨柳.大兴安岭北段扎兰屯地区斜长角闪岩年代学、地球化学和Hf同位素特征及其构造意义[J].地球科学,2019,44(10):3193-3208. |
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| 作者姓名： | 钱程 汪岩 陆露 秦涛 李林川 崔天日 陈会军 杨柳 |
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| 作者单位： | 1.中国地质调查局沈阳地质调查中心, 辽宁沈阳 110034 |
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| 基金项目： | 中国地质调查局项目1212011220435中国地质调查局项目DD20190039中国地质调查局项目DD20160345-17中国地质调查局项目D20160048-01 |
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| 摘 要： | 扎兰屯地区位于贺根山-黑河构造带中段，发育叠加韧性变形的晚古生代岩浆岩，可较好地记录这一时期的构造演化历史，但其研究程度较低.在野外调查基础上，对扎兰屯头道沟花岗质糜棱岩中的斜长角闪岩构造透镜体进行年代学和地球化学研究，探讨其成岩、变质及构造意义.头道沟斜长角闪岩原岩为玄武安山岩，锆石LAICP-MS U-Pb年龄为373.0±2.6 Ma，相当于大民山组火山岩.该岩石属钠质岩石，富集大离子亲石元素和轻稀土元素，亏损高场强元素，锆石原位εHf（t）为+5.39~+10.06，类似兴安岛弧的Hf同位素特征.上述特征暗示其原岩可能起源于蚀变洋壳流体交代亏损地幔演化而来的年轻下地壳，形成于板块消减带之上的前弧盆地.晚泥盆世在额尔古纳-兴安地块东南缘发育弧后、弧间和弧前盆地.斜长角闪岩变质年龄为~241.5±9.6 Ma，该变质可能与天山-兴蒙造山带演化晚期的伸展作用有关.
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| 关 键 词： | 斜长角闪岩 锆石U-Pb年代学 Hf同位素 贺根山-黑河构造带 岩石学 |
| 收稿时间： | 2019-02-21 |
Geochronology,Geochemistry and Hf Isotopic Composition of Amphibolite from Zhalantun Region in Northern Great Xing'an Range and Its Tectonic Significance |
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| Abstract: | The Late Paleozoic magmatic rocks with ductile deformation occurred in the Zhalantun region located in the middle of the Hegenshan-Heihe tectonic belt, which well record the tectonic evolution history of the Late Paleozoic, but the research degree is low. Through the field investigation, the geochronology and geochemistry of amphibolite lenticles from granitic mylonite in the Toudaogou, southern Zhalantun, are systematically studied, and the petrogenesis and tectonic setting of the amphibolite are discussed. It is found that the protolith of amphibolite is basaltic andesite, yielding an average zircon U-Pb age of 373.0±2.6 Ma which is equivalent to the volcanic rocks of Daminshan Group. The rocks belong to sodium series, which are enriched in light rare earth elements, large ion lithophile elements, but are depleted in high field strength elements. The zircon εHf(t) values of the amphibolite range from +5.39 to +10.06, similar to the features of the Xing'an island arc, suggesting that the protolith of amphibolite may be derived from the melting of a juvenile lower crust originating from depleted mantle which were modified by fluids stemmed from altered ocean crust, and supposedly formed in an fore arc basin above the subduction zone. In the Late Devonian, back-arc basin, inter-arc basin and fore-arc basin ocurred in the southeast region of Erguan-Xing'an block. The amphibolite and its surrounding granitic mylonite experienced multistage metamorphic deformation. The amphibolite yielded a metamorphic age of about 241.5±9.6 Ma, which may be related to the extension of the late evolution of the Tianshan-Xingmeng orogenic belt. |
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