Origins of lithium in submarine mud volcano fluid in the Nankai accretionary wedge
Origins of lithium in submarine mud volcano fluid in the Nankai accretionary wedge
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DOI：
10.1016/j.epsl.2015.01.018
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发表时间：
2015-03-15
影响因子：
5.3
通讯作者：
Inagaki, Fumio
中科院分区：
文献类型：
--
作者：
Nishio, Yoshiro;Ijiri, Akira;Inagaki, Fumio
为了研究南开增生楔的流体状态，我们利用南开弧前盆地熊野泥火山5号(KMV#5)回收的流体中的Li同位素比值(Li-7/Li-6)估算了锂(Li)藏的温度。KMV#5流体中Li-7/Li-6的比值是海底泥火山报告的最轻的。估算的锂储层温度(最高310摄氏度)明显高于蒙脱石向伊利石的转化温度(60-150摄氏度)，而南开更深的滑脱带流体的温度估计最高为150摄氏度。以往对海沟的电导率测量数据表明，南开俯冲带有两个与不同的脱水过程有关的流体储集层。根据这些结果，我们推测熊野弧前盆地不连续的泥底辟作用是通过逆冲断层向上运动的弧前蛇纹化地幔楔形角积累的深部流体周期性注入的结果。由于流体储集层上方低渗透屏障的周期性破裂，深部流体从南开增生楔体间歇性上涌，可能与孕震断裂活动有关。(C)2015爱思唯尔B.V.保留所有权利。
To investigate fluid regimes in the Nankai accretionary wedge, we estimated the temperatures of lithium (Li) reservoirs from the Li isotope ratio (Li-7/Li-6) in fluids recovered from Kumano mud volcano No. 5 (KMV#5) in the Nankai forearc basin. The Li-7/Li-6 ratios in the KMV#5 fluids are among the lightest reported from submarine mud volcanoes. The estimated Li reservoir temperatures (310 degrees C at maximum) were significantly higher than the smectite-to-illite conversion temperature (60-150 degrees C), whereas the temperature of fluid from the deeper Nankai decollement was estimated to be 150 degrees C at maximum. Data obtained from previous conductivity surveys across the trench suggest that there are two fluid reservoirs associated with distinct dehydration processes in the Nankai subduction zone. From these results, we inferred that the discontinuous mud diapirism in the Kumano forearc basin results from the periodic injection of deep-seated fluid accumulated in the corner of the serpentinized forearc mantle wedge that travels upward via a thrust fault. The intermittent upwelling of deep-seated fluid from the Nankai accretionary wedge due to periodic breaches of a low-permeability barrier above the fluid reservoir may be associated with seismogenic fault activity. (C) 2015 Elsevier B.V. All rights reserved.