New U Pb zircon and geochemical constraints on Late Devonian Back-arc basin origin of eclogite protoliths from northeastern Hainan Island, South China
New U Pb zircon and geochemical constraints on Late Devonian Back-arc basin origin of eclogite protoliths from northeastern Hainan Island, South China
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DOI：
10.1016/j.lithos.2022.106677
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发表时间：
2022-03
期刊：
影响因子：
3.5
通讯作者：
Mengmeng Xia;Xiaochun Liu;Yi Chen;Juan Hu;Guang-Can Zheng;Longyao Chen;Jian'en Han;D. Hu
中科院分区：
文献类型：
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作者：
Mengmeng Xia;Xiaochun Liu;Yi Chen;Juan Hu;Guang-Can Zheng;Longyao Chen;Jian'en Han;D. Hu
本文利用年代学、地球化学和Sr、Nd单键同位素资料，对海南岛东北部潮滩壁新发现的榴辉岩的原岩年龄、成因和构造环境进行了研究。新的高灵敏高分辨离子探针（SHRIMP）U-单Pb锆石定年结果表明，潮滩壁榴辉岩的原岩形成于364 ± 2 Ma，变质作用发生于297 ± 1 Ma。所有采集自岛上潮间带和潮下带约1.8 km 2相干区域的样品均显示拉斑玄武岩成分，初始87 Sr/86 Sr和ε Nd值分别为0.705-0.707和− 1.1至+7.4。根据不相容的微量元素，样品可进一步分为三组。第1组样品具有正常的洋中脊玄武岩（N-MORB）亲和力，起源于贫化尖晶石二辉橄榄岩地幔源的相对高度的部分熔融，并被板状流体轻微修改。第2组样品具有富集的洋中脊玄武岩（E-MORB）的亲和力，并来自富集的尖晶石和尖晶石-石榴石二辉橄榄岩过渡地幔源，深度大于第1组。第3组样品有岛弧玄武岩（IAB）的亲和力，并产生了部分熔融的富集尖晶石石榴石二辉橄榄岩地幔源修改流体和沉积物相关的再循环成分。这些玄武岩类型的组合（MORB型样品约占90%）表明，海南岛东北部存在一个晚泥盆世成熟弧后盆地，是金沙江-哀牢山-宋马-海南弧后盆地系统的一部分。因此，潮滩壁榴辉岩是古特提斯洋东部开合的一个指纹。
Geochronological, geochemical, and Srsingle bondNd isotopic data are used to constrain the age, origin, and tectonic setting of the protoliths of newly discovered eclogites from Chaotanbi, northeastern Hainan Island, South China. New sensitive high-resolution ion microprobe (SHRIMP) Usingle bondPb zircon dating reveals that the protoliths of the Chaotanbi eclogites formed at 364 ± 2 Ma and were metamorphosed at 297 ± 1 Ma. All samples collected from a coherent area of ~1.8 km2in the intertidal and subtidal zones on the island exhibit tholeiitic compositions, with initial87Sr/86Sr and εNdvalues of 0.705–0.707 and − 1.1 to +7.4, respectively. The samples can be further categorized into three groups based on incompatible trace elements. Group #1 samples have a normal mid-ocean ridge basalt (N-MORB) affinity and were originated from relatively high-degree partial melting of a depleted spinel lherzolite mantle source slightly modified by slab-derived fluids. Group #2 samples have an enriched mid-ocean ridge basalt (E-MORB) affinity and were derived from an enriched spinel and spinel–garnet lherzolite transition mantle source at depths greater than that of Group #1. Group #3 samples have an island arc basalt (IAB) affinity and were generated by partial melting of an enriched spinel–garnet lherzolite mantle source modified by fluid- and sediment-related recycled components. The association of these diverse basalt types, with MORB-type samples accounting for ~90% of all samples, suggest a Late Devonian mature back-arc basin existed on northeastern Hainan Island, as a part of the Jinshajiang–Ailaoshan–Song Ma–Hainan back-arc basin system. Therefore, the Chaotanbi eclogites are a fingerprint of the opening and closure of the eastern Paleo-Tethyan Ocean.