• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Petrology >Heterogeneous Oceanic Arc Volcanic Rocks in the South Qilian Accretionary Belt (Qilian Orogen, NW China)
【24h】

Heterogeneous Oceanic Arc Volcanic Rocks in the South Qilian Accretionary Belt (Qilian Orogen, NW China)

机译：南祁连增生带中的非均质海弧火山岩（中国西北祁连造山带）

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Primitive arc magmas in oceanic island arcs are probes of sub-arc magmatic processes and are crucial for understanding oceanic subduction. We report data for an Early Paleozoic oceanic arc volcanic complex in the Lajishan-Yongjing terrane, South Qilian Accretionary Belt (SQAB), Qilian Orogen, including zircon U-Pb dating and Hf-O isotopes, mineral and whole-rock geochemistry, and Sr-Nd isotope compositions. New zircon ages of approximate to 455-440Ma constrain the timing of arc volcanism and the subduction of the Qilian Ocean. Based on petrography and bulk-rock composition, five lithological types have been identified: ankaramite; high-Mg basaltic andesite; high-Al andesite; boninite; sanukite. The volcanic sequence thus is one of the few island arcs where three types of near-primitive arc rocks including boninite, ankaramite and sanukite have been simultaneously produced. All these rocks have variably enriched Sr-Nd isotopic compositions, positive to slight negative zircon epsilon(Hf)(t) values and elevated zircon O-18 values. Boninites, ankaramites and sanukites are interpreted as contemporary near-primitive melts generated from different sources and conditions within an island arc setting. Boninites are characterized by low Ti and REE concentrations and high Cr# chrome spinel, and are interpreted as melts of refractory, Cpx-poor, spinel lherzolite or harzburgite at >25% partial melting. Anomalous zircon O-18 values of 657-761 parts per thousand and Sr-Nd mixing calculations suggest less than 2% incorporation of subducted oceanic sediments into the mantle source of the magmas. The ankaramites are characterized by low SiO2 and high MgO (Mg#), Cr, Ni and La/Yb ratios, and have similar isotopic ratios to tectonically adjacent ocean island basalt (OIB) lavas. The ankaramite lavas are likely to have derived from mantle sources similar to those of OIB; that is, pyroxenite-bearing garnet peridotite enriched in incompatible elements. High-Mg basaltic andesites and high-Al andesites may be derived from parental ankaramite magmas. Sr-Nd-Hf isotopic mixing modeling constrains the amount of silicic melt to approximate to 1-4% for ankaramite magma. Sanukites are of andesitic-dacitic composition with high Mg#, Cr and Ni, and enriched large ion lithophile elements and high La/Yb ratios. They are interpreted as having been generated by reaction of mantle peridotite with a silicic melt, itself derived from subducted sediments. Enriched Sr-Nd-Hf isotopic compositions constrain the amount of silicic melt to approximate to 10-15% for sanukite. Large compositional variations among the volcanic rocks from the same arc reflect heterogeneous mantle sources and variable degrees of mantle metasomatism by sediment-derived hydrous fluids or silicic melts, accompanied by secondary assimilation-fractional crystallization processes during magma ascent to the surface. The generation of the island arc volcanic sequence in the Lajishan-Yongjing Terrane is a response to the collision between the Lajishan-Yongjing Oceanic Plateau (recorded by the Lajishan-Yongjing Ophiolite) and the pre-existing trench-continental margin. Evolution from a continental margin in the North Qilian Accretionary Belt to an oceanic island arc in the SQAB records subduction advance and retreat in the history of the Qilian Ocean.
机译：海洋岛弧中的原始弧岩浆是亚弧岩浆作用过程的探索，对于理解海洋俯冲作用至关重要。我们报告了Lajishan-Yongjing地层，南祁连增生带（SQAB），祁连造山带的早期古生代大洋弧火山综合体的数据，包括锆石U-Pb测年和Hf-O同位素，矿物和全岩地球化学以及Sr -Nd同位素组成。大约455-440Ma的新锆石年龄限制了弧形火山活动的时间和祁连海的俯冲。根据岩相学和块岩组成，确定了五种岩性类型：安卡拉石；高镁玄武岩安山岩；高铝安山岩; in石紫水晶。因此，火山层序是为数不多的岛弧之一，在该岛弧中同时生成了三种类型的近原始弧岩，包括邦尼石，安卡拉石和红宝石。所有这些岩石均具有丰富的Sr-Nd同位素组成，锆石epsilon（Hf）（t）值正值或负值，以及锆石O-18值升高。 Boninite，ankaramites和sanukite被解释为现代的近原始熔体，是由岛弧环境中的不同来源和条件产生的。 in石的特征在于低的Ti和REE浓度和高的Cr＃铬尖晶石，并被解释为部分熔化率> 25％的难熔，Cpx贫，尖晶石锂铁矿或Harzburgite的熔体。锆石O-18的异常值为千分之657-761，Sr-Nd的混合计算表明，俯冲的海洋沉积物并入岩浆的幔源不到2％。安卡拉米特的特征是低SiO2和高MgO（Mg＃），Cr，Ni和La / Yb比，并且与构造相邻的大洋洲玄武岩（OIB）熔岩具有相似的同位素比。安卡拉母岩熔岩可能来自与OIB类似的地幔来源。就是说，富含辉石的石榴石橄榄岩富含不相容元素。高镁玄武质安山岩和高铝安山岩可能来自母体安卡拉母岩浆。 Sr-Nd-Hf同位素混合模型将硅镁矿岩浆的硅质熔体量限制在大约1-4％。檀香石具有高锰酸镁，铬和镍的安山岩-菊苣成分，并富含大离子亲石元素和高La / Yb比。它们被解释为是由地幔橄榄岩与硅质熔体反应生成的，而硅质熔体本身又来自俯冲沉积物。富集的Sr-Nd-Hf同位素组成将硅熔矿的硅质熔体含量限制在大约10-15％。来自同一弧线的火山岩之间的大成分变化反映了地幔来源的不均一性和沉积物衍生的含水流体或硅质熔体对地幔交代程度的变化，伴随着岩浆上升到地表时发生的二次同化-分形结晶过程。 Lajishan-Yongjing地形中岛弧火山序列的产生是对Lajishan-Yongjing海洋高原（由Lajishan-Yongjing蛇绿岩记录的）与预先存在的海沟大陆边缘之间的碰撞的响应。从北祁连增生带的大陆边缘到SQAB中的一个大洋岛弧的演变记录了祁连海洋历史上俯冲的进退。

著录项

  • 来源
    《Journal of Petrology》 |2019年第1期|85-116|共32页
  • 作者

    Yang Liming; Song Shuguang; Su Li; Allen Mark B.; Niu Yaoling; Zhang Guibin; Zhang Yuqi;

  • 作者单位

    Peking Univ, Sch Earth & Space Sci, MOE Key Lab Orogen Belt & Crustal Evolut, Beijing 100871, Peoples R China;

    Peking Univ, Sch Earth & Space Sci, MOE Key Lab Orogen Belt & Crustal Evolut, Beijing 100871, Peoples R China;

    China Univ Geosci, Inst Earth Sci, Beijing 100083, Peoples R China;

    Univ Durham, Dept Earth Sci, Durham DH1 3LE, England;

    China Univ Geosci, Inst Earth Sci, Beijing 100083, Peoples R China|Univ Durham, Dept Earth Sci, Durham DH1 3LE, England;

    Peking Univ, Sch Earth & Space Sci, MOE Key Lab Orogen Belt & Crustal Evolut, Beijing 100871, Peoples R China;

    Peking Univ, Sch Earth & Space Sci, MOE Key Lab Orogen Belt & Crustal Evolut, Beijing 100871, Peoples R China;

  • 收录信息
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    intra-oceanic arc; ankaramite; boninite; sanukite; mantle metasomatism by subducted sediments; zircon Hf-O isotope; Qilian Orogen;

    机译：大洋内弧;南卡拉母岩;次长短岩;蜡质岩;俯冲沉积物的地幔交代作用;锆石Hf-O同位素;祁连造山带;

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号