IODP Expedition 322 Drills Two Sites to Document Inputs to The Nankai Trough Subduction Zone
IODP Expedition 322 Drills Two Sites to Document Inputs to The Nankai Trough Subduction Zone
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IODP 322 探险队钻探两个地点以记录南海海槽俯冲带的输入
DOI：
10.2204/iodp.sd.10.02.2010
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发表时间：
2010
影响因子：
1.2
通讯作者：
Y. Kubo
中科院分区：
文献类型：
--
作者：
M. Underwood;S. Saito;Y. Kubo
抽象的。在综合大洋钻探计划的第322次远征期间，主要目标是对南开海槽(日本西南部)向海的四国盆地进入的沉积地层和最上层的火成岩基底进行采样和记录。这些俯冲输入的表征是南开海槽孕震带实验总体科学计划的一部分。在我们评估各种材料性质如何沿着板块界面的倾角向下演化，并潜在地将断层的行为从稳定滑动改变为孕震滑动之前，我们必须确定初始的俯冲条件。向海沟方向钻探了两个地点，以展示相特征和沉积速率如何与水深结构相对应。C0011站点位于突出的地下室高压(Kashinosaki Knoll)的西北侧，而C0012站点位于海山顶部附近。尽管取心记录中仍然有很大的空白，而且在C0012站点恢复有线测井的尝试失败了，但可以在两个站点的地层单位之间进行对比。在整个基底隆起上方的浓缩部分，沉积速率都有所放缓，但在盆地演化过程中，海底起伏从未高到足以阻止沙质浊积物在海山顶部附近堆积。发现了以晚中新世火山碎屑浊积岩为代表的新地层单位--四国盆地中部相。沉积物-玄武岩接触面在C0012遗址被完整地恢复，其最小基底年龄为18.9 Ma。间隙水的样品在C0011处表现出相似的随深度变化的淡化趋势，但在C0012处的氯化度值高于海水的值，朝向基底接触。C0012点的地球化学趋势可能是火山碎屑沉积物中的水化反应和与上部火成岩基底中类海水流体的扩散交换的反应。这些数据很重要，因为它们最终为南开海槽建立了一个真实的地球化学参照点，不受脱水反应的影响，并为上火成岩地壳内活动的流体提供了证据。拥有两套地球化学剖面还表明，卡什诺萨克诺尔山脉的侧面和顶部之间缺乏水文地质连通性。DOI：10.2204/iop.sd.10.02.2010
Abstract. The primary goals during Expedition 322 of the Integrated Ocean Drilling Program were to sample and log the incoming sedimentary strata and uppermost igneous basement of the Shikoku Basin, seaward of the Nankai Trough (southwestern Japan). Characterization of these subduction inputs is one piece of the overall science plan for the Nankai Trough Seismogenic Zone Experiment. Before we can assess how various material properties evolve down the dip of the plate interface, and potentially change the fault’s behavior from stable sliding to seismogenic slip, we must determine the initial pre-subduction conditions. Two sites were drilled seaward of the trench to demonstrate how facies character and sedimentation rates responded to bathymetric architecture. Site C0011 is located on the northwest flank of a prominent basement high (Kashinosaki Knoll), and Site C0012 is located near the crest of the seamount. Even though significant gaps remain in the coring record, and attempts to recover wireline logs at Site C0012 failed, correlations can be made between stratigraphic units at the two sites. Sedimentation rates slowed down throughout the condensed section above the basement high, but the seafloor relief was never high enough during the basin’s evolution to prevent the accumulation of sandy turbidites near the crest of the seamount. We discovered a new stratigraphic unit, the middle Shikoku Basin facies, which is typified by late Miocene volcaniclastic turbidites. The sediment-basalt contact was recovered intact at Site C0012, giving a minimum basement age of 18.9 Ma. Samples of interstitial water show a familiar freshening trend with depth at Site C0011, but chlorinity values at Site C0012 increase above the values for seawater toward the basement contact. The geochemical trends at Site C0012 are probably a response to hydration reactions in the volcaniclastic sediment and diffusional exchange with seawater-like fluid in the upper igneous basement. These data are important because they finally establish an authentic geochemical reference site for Nankai Trough, unaffected by dehydration reactions, and they provide evidence for active fluid flow within the upper igneous crust. Having two sets of geochemical profiles also shows a lack of hydrogeological connectivity between the flank and the crest of the Kashinosaki Knoll. doi: 10.2204/iodp.sd.10.02.2010