Petrogenesis of the ~500 Ma Fushui mafic intrusion and early paleozoic tectonic evolution if the Northern Qinling belt
Petrogenesis of the ~500 Ma Fushui mafic intrusion and early paleozoic tectonic evolution if the Northern Qinling belt
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北秦岭~500 Ma富水基性岩体的岩石成因及早古生代构造演化
DOI：
10.1016/j.jseaes.2016.09.003
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发表时间：
2017
影响因子：
3
通讯作者：
Zhichao Guo
中科院分区：
文献类型：
--
作者：
Yu Shi;Xiaoli Pei;Paterno R. Castillo;Xijun Liu;Haihong Ding;Zhichao Guo
秦岭富水镁铁质侵入体由变辉长岩、变辉长闪长岩、辉长闪长岩和正长岩组成。这些岩石大多在上绿片岩相-下角闪岩相变质作用下变质。8个样品中锆石的LA-ICP-MS U-Pb年龄为497-501 Ma，为富水岩体岩浆侵位的年龄。大部分锆石的eHf值为负值，对应于古元古代晚期-中元古代早期或新元古代的TDM 2模式年龄，表明镁铁质岩石很可能是由变质后的岩石圈地幔部分熔融而形成的镁铁质熔体。侵入体没有受到地壳物质的广泛污染，大多数化学成分在绿片岩到角闪岩相变质作用期间没有发生变化。of.rocks岩体岩石具有原始地幔标准化微量元素模式，轻稀土元素和大离子亲石元素（LILE）显著富集，高场强元素（HFSE）亏损。根据微量元素含量，富水岩体的母岩浆来源于金云母-二辉橄榄岩和石榴子石-二辉橄榄岩幔源的部分熔融，熔融程度均小于10%。这些震源最好解释为与俯冲有关的弧环境，并已被俯冲板片释放的流体所改变。富水岩体的形成与500 Ma古特提斯-商丹洋岩石圈俯冲有关。
The Fushui mafic intrusion in the Qinling orogenic belt (QOB) is composed of meta-gabbro, meta-gabbrodiorite,.diorite, and syenite. Most of these rocks are metamorphosed under the upper greenschist facies to.lower amphibolite facies metamorphism. Zircon separates from eight samples have LA-ICP-MS U-Pb ages.of 497–501 Ma which are taken to be the emplacement age of magmas that formed the Fushui intrusion..Most of the zircon grains exhibit negative eHf values, correspond to TDM2 model ages of late.Paleoproterozoic-early Mesoproterozoic or Neoproterozoic and suggest that the mafic rocks were most.probably derived from mafic melts produced by partial melting of a previously metasomatized lithospheric.mantle..The intrusion is not extensively contaminated by crustal materials and most chemical compositions of.rocks are not modified during the greenschist to amphibolite-facies metamorhism. Rocks from the intrusion.have primitive mantle-normalized trace element patterns with significant enrichment in light-REE.and large ion lithophile elements (LILE) and depletion in high field-strength elements (HFSE). On the basis.of the trace element contents, the Fushui intrusion was derived from parental magmas generated by <10%.partial melting of both phlogopite-lherzolite and garnet-lherzolite mantle sources. These sources are best.interpreted to be in a subduction-related arc environment and have been modified by fluids released.from a subducting slab. The formation of the Fushui intrusion was related to the subduction of the.Paleotethyan Shangdan oceanic lithosphere at 500 Ma.