Computed tomography scan analysis of site 941 cores, Western mass-transport deposit, Amazon fan
Computed tomography scan analysis of site 941 cores, Western mass-transport deposit, Amazon fan
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941 号站点核心的计算机断层扫描分析、西方大众运输沉积物、亚马逊风扇
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发表时间：
1997
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通讯作者：
W. Soh
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作者：
W. Soh
使用来自亚马逊扇上大洋钻探计划（ODP）第155航段941号站点的区域性广泛的西部质量运输存款（WMTD）的整个圆形岩心样品进行X射线计算机断层扫描（CT）和孔隙水化学分析。在这里，CT值与沉积物的容重和含水量有很好的相关性。CT图像显示，在海底以下-47米处，在2米厚的糊状和含气沉积物间隔的顶部，泥浆沉积物（样品155- 941 B-6 H-4，0 -20 cm）中有一个带有气泡的羽状流化结构。与周围未流化沉积物相比，流化沉积物中的含水量显着增加。含量符合淡水稀释估计从异常孔隙水化学。因此，流化是由气体水合物的解离引起的。定量CT值分析允许我们估计气体水合物含量的百分比达到流化沉积物的~ 10体积%（孔隙空间的17.5体积%）。这一含量似乎与其他水合物区报道的海底模拟反射层（BSR）上方天然气水合物的最高含量相当。从WMTD向上倾斜的大陆坡部分区域的海底反射带。2米厚的糊状和含气的沉积物被推断为来自一部分失踪的沉积物解释地震反射剖面的源区的WMTD是由高达200米的陡坎为界。此外，天然气水合物的分解应该是最重要的触发机制，导致区域广泛的边坡破坏，产生WMTD。
X-ray computed tomography (CT) and pore-water chemistry analyses were performed using whole round-core samples from the regionally extensive Western Mass-Transport Deposit (WMTD), Site 941 of Ocean Drilling Program (ODP) Leg 155, on the Amazon Fan. Here, the CT value has a good correlation with the bulk density and water content of the sediment. The CT image shows a plume-shaped, fluidized structure with gas bubbles in the mud sediment, Sample 155-941B-6H-4,0-20 cm, at -47 meters below seafloor, at the top of a 2-m-thick soupy and gassy sediment interval. Significant increase in the water content was recognized in the fluidized sediment when compared to those of the surrounding unfluidized sediments. The content coincided with the fresh-water dilution estimated from the anomalous pore-water chemistry. The fluidization was thus caused by the dissociation of gas hydrate. The quantitative CT value analysis allows us to estimate that the percentage of gas hydrate content reaches -10 vol% of the fluidized sediment (17,5 vol% of the pore space). This content seems to be equivalent to the highest contents of the gas hydrate above bottom-simulating reflectors (BSRs) reported from other hydrate regions. BSRs underlie parts of the continental slope updip from the WMTD. The 2-m-thick soupy and gassy sediment is inferred to be derived from a part of missing sediment interpreted from seismic-reflection profiles of the source area of the WMTD that is bounded by scarps up to 200 m high. Furthermore, the disassociation of gas hydrate should be the most important trigger mechanism for causing the regionally extensive slope failure that produced the WMTD.