Late Triassic E-MORB-likebasalts associated with porphyry Cu-deposits in the southern Yidun continentalarc, eastern Tibet: Evidence of slab-tear during subduction?
Late Triassic E-MORB-likebasalts associated with porphyry Cu-deposits in the southern Yidun continentalarc, eastern Tibet: Evidence of slab-tear during subduction?
复制标题
晚三叠世E-MORB类玄武岩与西藏东部义敦大陆弧南部斑岩铜矿床有关：俯冲过程中板片撕裂的证据？
DOI：
10.1016/j.oregeorev.2016.12.006
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发表时间：
2017
影响因子：
3.3
通讯作者：
XiaoXiao Huang
中科院分区：
文献类型：
--
作者：
JianLin Chen;JiFeng Xu;JiangBo Ren;XiaoXiao Huang
一般认为安山岩-英安岩-流纹岩套和当代斑岩型铜矿床与活动大陆边缘的俯冲作用有关。然而，究竟是哪些构造事件导致了斑岩型铜矿床的形成，软流圈地幔物质是否参与了这一过程，目前尚不清楚。然而，这些玄武岩的年代学和地球化学资料很少，从而阻碍了该岩浆事件地球动力学模型的发展和该地区相关斑岩型铜矿床的形成。本文首次报道了西亚带下小流玄武岩的地球化学和SIMS（次级离子质谱）锆石U-Pb数据。晚三叠世下小流玄武岩的年龄（216.1±2.8 Ma）与SYA内大量斑岩侵入岩体侵位时间和铜矿床形成时间（峰值在215 ~ 217 Ma）一致。下小流玄武岩具有e - morb样微量元素模式，无负Nb-Ta异常，143nd /144Nd(t)值较高，表明其来源于软流圈地幔，未受弧型影响。结合SYA内部分晚三叠世矿化斑岩侵入体具有同源性的事实，认为SYA内的玄武岩等火成岩及伴生斑岩型铜矿床是在甘泽—理塘洋壳俯冲过程中，由向西倾斜的板块撕裂引发软流圈地幔物质上涌而形成的。
It is generally believed that andesite–dacite–rhyolite suites and contemporary porphyry Cu deposits are related to subduction in active continental margin settings. However, it is still unclear which tectonic events result in the generation of porphyry Cu deposits and whether asthenospheric mantle material is involved in this process. Widespread andesitic–dacitic felsic intrusions associated with porphyry Cu deposits and rarer basalts have been identified in the Late Triassic southern Yidun arc (SYA) of eastern Tibet. However, few geochronological and geochemical data are available for these basalts, thereby hampering the development of geodynamic models for this magmatic event and the formation of related porphyry Cu deposits in the region. Here we present the first geochemical and SIMS (secondary ion mass spectrometry) zircon U–Pb data of Xiaxiaoliu basalts in the SYA. The age of the Late Triassic Xiaxiaoliu basalts (216.1 ± 2.8 Ma) is consistent with the timing of emplacement of voluminous porphyritic intrusions and the formation of Cu deposits within the SYA (peaking at 215–217 Ma). The Xiaxiaoliu basalts have E-MORB-like trace element patterns that are free of negative Nb–Ta anomalies, and have high143Nd/144Nd(t)values, suggesting they were sourced from asthenospheric mantle without any arc-type influence. These observations, combined with the fact that some Late Triassic mineralized porphyritic intrusions within the SYA have adakitic affinities, suggest that the basalts and other igneous rocks and associated porphyry Cu deposits within the SYA were produced by tearing of a westward-dipping slab, triggering the upwelling of asthenospheric mantle material during subduction of the Garze–Litang Ocean crust.