| 胶东海阳所超镁铁岩中强亲铁元素的地球化学特征及其构造环境探讨 |
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| 引用本文： | 马雪盈,刘庆,闫方超,何苗,张宏远.胶东海阳所超镁铁岩中强亲铁元素的地球化学特征及其构造环境探讨[J].岩石学报,2021,37(8):2562-2578. |
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| 作者姓名： | 马雪盈 刘庆 闫方超 何苗 张宏远 |
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| 作者单位： | 中国科学院地球动力学重点实验室, 中国科学院大学地球与行星科学学院, 北京 100049;中国地质大学(北京)地球科学与资源学院, 北京 100083 |
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| 基金项目： | 本文受国家重点研发计划"深地资源勘查开采"重点专项（2016YFC0600401）、国家自然科学基金项目（41273046）和中央高校基本科研业务费专项资金联合资助. |
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| 摘 要： | 强亲铁元素与亲石元素具有不同的地球化学行为，因此能够从不同的角度为造山带中超镁铁岩的成因及演化提供重要信息。位于苏鲁造山带东北端的胶东海阳所超镁铁岩主要由橄榄岩和辉石岩组成，它们常以团块状赋存于花岗质片麻岩中。虽然前人对这些超镁铁岩已经开展大量岩石学研究，但关于其成因及构造属性仍存在较大争议。本文开展了海阳所超镁铁岩的全岩主微量元素、强亲铁元素及Re-Os同位素的分析工作，结果显示蛇纹石化橄榄岩具有较高的MgO和Fe2O3T含量，较低的Al2O3、TiO2和CaO含量，明显富集流体迁移元素（U、Pb），亏损高场强元素（Zr、Hf），强亲铁元素没有发生明显分异，但Ru显示正异常，表明海阳所蛇纹石化橄榄岩是经历了低-中等程度部分熔融及熔/流体交代作用影响的残余地幔橄榄岩。海阳所辉石岩的主量元素表现出明显的结晶分异特征，稀土元素较原始地幔富集，铂族元素（PGEs）含量较低且发生了明显的分异，表明辉石岩的地幔源区经历过高程度的部分熔融和硫化物的分离。海阳所蛇纹石化橄榄岩的Os同位素地球化学特征表现出大洋亲和性，与辉石岩不具有熔体-残留体的关系。由于该地区发育较深层次的韧性剪切带，蛇纹石化橄榄岩中的橄榄石与辉石表现出韧性变形的特征，同时有辉石岩侵入到橄榄岩的现象，表明该地区的蛇纹石化地幔橄榄岩与辉石岩既不同时，也不同源，因此，暗示了该套岩石组合可能形成于大洋核杂岩（OCC）与洋脊型蛇绿岩（MOR）堆晶岩交互发育环境。
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| 关 键 词： | 海阳所 超镁铁岩 强亲铁元素 部分熔融 熔/流体交代 结晶分异 |
| 收稿时间： | 2021/1/22 0:00:00 |
| 修稿时间： | 2021/4/21 0:00:00 |
Highly siderophile element geochemistry and tectonic setting of ultramafic rocks from Haiyangsuo in eastern Shandong |
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| MA XueYing,LIU Qing,YAN FangChao,HE Miao,ZHANG HongYuan.Highly siderophile element geochemistry and tectonic setting of ultramafic rocks from Haiyangsuo in eastern Shandong[J].Acta Petrologica Sinica,2021,37(8):2562-2578. |
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| Authors: | MA XueYing LIU Qing YAN FangChao HE Miao ZHANG HongYuan |
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| Institution: | CAS Key Laboratory of Computational Geodynamics, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China |
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| Abstract: | Highly siderophile elements can provide important information for the genesis and evolution of the ultramafic rocks in orogenic belts. The Haiyangsuo ultramafic rock, located in the northeast part of the Sulu orogenic belt,is mainly composed of peridotite and pyroxenite, which often occur in granitic gneiss and metamorphic rocks in masses. Although a lot of petrological studies have been carried out on these ultramafic rocks, there are still great controversies about their genesis and tectonic setting. Our geochemical data show that the serpentine peridotite in Haiyangsuo has higher MgO and Fe2O3T contents, and lower Al2O3, TiO2 and CaO contents while depleted in high field strength elements (Zr, Hf) and unfractionated highly siderophile elements. The results implied that the Haiyangsuo serpentinized peridotite is a remnant mantle peridotite that has undergone low to moderate partial melting and melt/fluid metasomatism. The pyroxenite in Haiyangsuo underwent intensive fractional crystallization. The Haiyangsuo pyroxenite shows relatively higher rare elements and strong depletions in all platinum group elements (PGEs), indicating it experienced high degree of partial melting and sulfide separation in the mantle source region. The Os isotopic geochemistry of the serpentinized peridotite in Haiyangsuo shows oceanic affinity. Due to the development of deep level ductile shear zone in this area, olivine and pyroxene in the serpentine peridotite show ductile deformation characteristics, and pyroxenite intruded into peridotite, indicating that there is no genetic relationship between the peridotites and pyroxenites. Therefore, it is suggested that the serpentinized peridotites may belong to oceanic core complex (OCC), while the pyroxenites could represent cumulates formed by magma intruded into serpentinized mantle peridotite. |
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| Keywords: | Haiyangsuo Ultramafic rocks Highly siderophile elements Partial melting Melt-rock interaction Fractional crystallization |
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