The determination of resistivity and porosity of the sediment and fractured basalt layers near the Juan de Fuca Ridge
The determination of resistivity and porosity of the sediment and fractured basalt layers near the Juan de Fuca Ridge
复制标题
胡安德富卡海岭附近沉积物和裂隙玄武岩层电阻率和孔隙率的测定
DOI：
10.1111/j.1365-246x.1986.tb03830.x
复制
发表时间：
1986
影响因子：
2.8
通讯作者：
R. N. Edwards
中科院分区：
文献类型：
--
作者：
D. Nobes;L. Law;R. N. Edwards
摘要1984年夏天，在胡安·德富卡海脊复合体北方的一部分中谷的两个地点使用磁力离岸电测深（MOSES）进行了电测。MOSES的设计是为了尽量减少在导电的海洋层以下的地壳进行电测所固有的困难。地点1位于48° 32 N，128° 42 W，位于浊流充填盆地的中心部分。利用断裂玄武岩基底上的导电沉积物的两层模型，沉积物的电阻率和厚度分别为0.82 ± 0.06 Ωm和1800 ± 300 m。基底电阻率，虽然没有很好地约束的数据是一致的，在站点2获得的结果。
位于48° 10 N，128° 50 W的站点2具有较薄的沉积物层，这似乎随位置而变化。沉积物电导率-厚度乘积是由数据确定的参数。如果沉积物电阻率与站点1相同，则站点2东南方向的沉积物厚度为140 ± 30 m，西北方向的沉积物厚度为240 ± 55 m。断裂玄武岩基底的电阻率为8.5 ± 3.4 Ωm，厚度至少为1000 m。
使用温度校正的孔隙流体电阻率，计算出的孔隙度从沉积物顶部的62%到底部的21%不等，基底为8%。这些值与附近沉积物填充盆地中厚浊积岩序列的地震速度估计值以及DSDP孔504 B中2A/B层玄武岩的地震速度估计值吻合良好。
Summary. In the summer of 1984 an electrical survey using magnetometric off-shore electrical sounding (MOSES) was conducted at two sites in Middle Valley, part of the northern Juan de Fuca Ridge complex. MOSES has been designed to minimize the difficulties inherent in electrical surveys of the crust below the electrically conductive sea layer. Site 1, at 48°32N, 128°42W, is in the central part of the turbidite-filled basin. Using a two-layer model of conductive sediments overlying a fractured basalt basement, the sediment resistivity and thickness were found to be 0.82 ± 0.06 Ωm and 1800 ± 300 m, respectively. The basement resistivity, although not well constrained by the data is consistent with the results obtained at site 2.
Site 2, located at 48°10N, 128°50W, has a thinner sediment layer, which appears to vary with position. The sediment conductivity—thickness product is the parameter determined by the data. If the sediment resistivity were the same as at site 1, the sediment thickness would be 140 ± 30 m to the SE of site 2, and 240 ± 55 m to the NW. The fractured basalt basement has a resistivity of 8.5 ± 3.4 Ωm and is at least 1000 m thick.
Using temperature-corrected pore fluid resistivity, the calculated porosity is found to vary from 62 per cent at the top to 21 per cent at the base of the sediments and is 8 per cent in the basement. These values are in good agreement with estimates from seismic velocities for a thick turbidite sequence in a nearby sediment-filled basin and determined for layer 2A/B basalts in DSDP hole 504B, respectively.