Heat flow and fluid flow regime in the western Nankai accretionary prism
Heat flow and fluid flow regime in the western Nankai accretionary prism
复制标题
南开增生棱柱西部的热流和流体流态
DOI：
10.1016/0012-821x(92)90105-5
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发表时间：
1992
影响因子：
5.3
通讯作者：
R. Hyndman
中科院分区：
文献类型：
--
作者：
M. Yamano;J. Foucher;M. Kinoshita;A. Fisher;R. Hyndman
通过常规地热探头表面热流测量和天然气水合物底部模拟反射器深度热流估算，研究了南开俯冲带西部的热结构。 ODP Site 808（位于南开增生棱柱的趾部）的温度和热导率测量增加了有关热流随深度变化的重要信息，从而增加了有关棱柱中孔隙流体流动的热效应的重要信息。南海海槽地面的表面热流一般高于130 mW/m2。如此高的热流不能简单地用俯冲四国盆地岩石圈的传导冷却来解释。最近的紧密间距探针测量表明，槽底板上的热流显示出局部变化，在变形前沿附近的热流值特别高。热流分布表明，暖流体可能沿着滑脱向海流动，并沿着某些通道局部向海底上升，导致区域性和局地的高热流异常。与这一推论相反，在 808 站点没有检测到活跃的局部流体流。在正面推力下方的海底以下 347 m 的六个深度处测量的温度可以通过 125-130 mW/m2 的传导热流很好地解释。在从前冲断层或滑脱处回收的岩心中没有观察到与当今孔隙流体运动相关的地球化学异常。另一方面，站点 808 的高热流需要低于 350 mbsf 的热源。南开增生棱柱中的流体流动可能是局部的、瞬态的，因此在该单个钻探点没有检测到。
The thermal structure of the western Nankai subduction zone has been studied through surface heat flow measurements with conventional geothermal probes and estimation of heat flow from depths of gas hydrate bottom simulating reflectors. Temperature and thermal conductivity measurements at ODP Site 808, located at the toe of the Nankai accretionary prism, added important information on any variation in heat flow with depth and thus on thermal effects of pore fluid flow in the prism. Surface heat flow is generally higher than 130 mW/m2on the floor of the Nankai Trough. Such high heat flow cannot be explained simply by conductive cooling of the subducting Shikoku Basin lithosphere. Recent closely spaced probe measurements revealed that the heat flow on the trough floor shows local variation, with particularly high values near the deformation front. The heat flow distribution suggests that warm fluid flows seaward possibly along the décollement and locally rises toward the seafloor along some channels, resulting in both the regional and local high heat flow anomalies. Contrary to this inference, no active localized fluid flow was detected at Site 808. The temperatures measured at six depths down to 347 m below seafloor (mbsf) just below the frontal thrust can be well explained by conductive heat flow of 125–130 mW/m2. No geochemical anomaly associated with present-day pore fluid movement was observed in cores recovered from the frontal thrust or the décollement. On the other hand, the high heat flow at Site 808 requires some heat source below 350 mbsf. There is a possibility that the fluid flow in the Nankai accretionary prism is localized and transient, and thus was not detected at this single drill site.