Plume-ridge interaction in the South China Sea: Thermometric evidence from Hole U1431E of IODP Expedition 349
Plume-ridge interaction in the South China Sea: Thermometric evidence from Hole U1431E of IODP Expedition 349
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南海羽脊相互作用：来自 IODP 349 号探险队 U1431E 孔的测温证据
DOI：
10.1016/j.lithos.2018.11.031
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发表时间：
2019-01
期刊：
影响因子：
3.5
通讯作者：
He Peng Li
中科院分区：
文献类型：
--
作者：
Yang Fan;Huang Xiao Long;Xu Yi Gang;He Peng Li
验证海南地幔柱引发南海张开并与扩张脊相互作用的假说，对于理解南海演化动力学具有重要意义。本文对国际海洋探索计划（IODP）第349次科考队U1431E孔采集的玄武岩和玻璃样品中最原始的橄榄石（Fo = 83.1-87.1）和尖晶石（Cr = 28-60%）进行了研究，目的是估算结晶温度。尖晶石大多被橄榄石包裹，其Fe3+和Ti含量较低，与寄主橄榄石呈平衡状态。al -in- ololiine温度计的应用为研究样品提供了结晶温度，温度范围为1208 ± 29 °C至1287 ± 29 °C。外推Fo = 90原始橄榄石时，原始橄榄石的结晶温度约为1350 °C，远高于其他原始洋中脊玄武岩（MORB），但与冰岛洋岛玄武岩（OIB）相当。因此，在~16 Ma，南海灭脊处的地幔势温远高于正常洋中脊下的地幔势温，反映了南海最后一次扩张过程中地幔柱脊的相互作用。考虑到南海缺乏厚洋壳、海山链或地貌，我们认为影响南海的羽流可能富含榴辉岩且浮力较低。
Testing the hypothesis that the Hainan mantle plume triggered the opening of the South China Sea (SCS) and interacted with the spreading ridge is important for the purpose of understanding the dynamics of the evolution of the SCS. This study examined the most primitive olivine (Fo = 83.1–87.1) and spinel (Cr# = 28–60%) in the basalt and glassy samples collected from Hole U1431E of International Ocean Discovery Program (IODP) Expedition 349, with the goal of estimating the crystallization temperature. Spinels mostly enclosed by olivines have low Fe3+and Ti contents and show compositional equilibrium with the host olivines. The application of the Al-in-olivine thermometer provided crystallization temperatures for the studied samples, which varied from 1208 ± 29 °C to 1287 ± 29 °C. When extrapolating to primitive olivine of Fo = 90, the crystallization temperature of primitive olivine is approximately 1350 °C, which is much higher than that of other primitive mid-ocean ridge basalt (MORB) but comparable to that of Iceland oceanic island basalt (OIB). Therefore, the mantle potential temperature at the extinct ridge of the SCS at ~16 Ma is much higher than that beneath a normal mid-ocean ridge, manifesting the mantle plume-ridge interaction during the last spreading of the SCS. Given the lack of thick oceanic crust, seamount chains or lineaments in the SCS, we propose that this plume impacted on the SCS might be eclogite-rich and of low buoyancy.
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