论文部分内容阅读
为研究与喀斯喀特山脉(Cascade Range)火山有关的地壳结构,在华盛顿州布置了两条大地电磁(MT)剖面。一条从太平洋沿岸到华盛顿州东部,长约400Km。该剖面在莱尼尔(Rainier)山和阿丹姆斯(Adams)山之间,穿越喀斯喀特山脉中部。另一条较短的东西向剖面,从圣海伦斯(ST.Helens)山西南到阿丹姆斯山东南方向。从太平洋沿岸到莱尼尔山附近,即长剖面的西段,推断有厚达10Km的低阻第三系及第三系前期沉积岩和大山岩。MT测深和电测井结果表明,这些岩石的电阻率为2~10OM.解释结果说明,这些低阻岩石同莱尼尔山东南方羊石荒地(Goat Rock:Wilderss)的深成岩体相毗连.上述特征以及南部短剖面的一些特征被认为是在华盛顿州喀斯喀特山脉另一项研究中观测到的地磁差分异常产生的原因.长剖面西段巨厚低阻层以及在哥伦比亚河流域玄武岩下部发现的沉积层,在石油勘探中具有重要意义.穿过Cs.wover确定的圣海伦斯地震带(SHZ),上述巨厚低阻层出现位移.在普吉低地伊uoet Lowland)及其南部,地震活动的总模式可能同上述沉积层有关.与俄勒岗以及北加里佛尼亚的高喀斯喀特相比,华盛顿州火山喀斯喀特的地壳电性结构有明显差别.应用MT成果并结合海上地震和重力资料,可对胡安德富卡(Jan de Fuca)版块的古俯冲带特征有较好的认识。
To study the crustal structure associated with the Cascade Range volcano, two MT profiles are located in Washington State. One from the Pacific coast to the eastern state of Washington, about 400Km. The section crosses the middle of the Cascade Range between the Rainier and Adams mountains. Another relatively short east-west profile, from southwest of St Helens to southeast of Adams Mountains. From the Pacific Rim to the vicinity of the Nepalese Niier, ie, the western section of the long profile, there are inferred that there are low resistivity Tertiary and Tertiary sedimentary and dacitic rocks with a thickness of 10 km. MT sounding and electrical logging results show that the resistivity of these rocks is 2 ~ 10OM. Interpretation results show that these low resistivity rocks are adjacent to the deep diagenesis of the Goat Rock: Wilderss southeast of the Neilir Mountains. Features and some features of the southern short-section are believed to be responsible for the observed geomagnetic anomaly anomalies observed in another study in the Cascade Mountain, Washington State.The thick, low-resistivity layer of the western section of the long profile and the lower basalts found in the Columbia Basin Sedimentary layers are of great importance in oil exploration, with displacement through the thick, low-resistivity layer of the St. Helens Seismic Belt (SHZ) identified by C. wover, and seismic activity in the southern U.K. Lowland area of the Phuket lowlands Of the total pattern may be related to the above sedimentary layer.Compared with Oregon and North Cascades, the crustal electrical structure of the volcanic Cascades in Washington State is significantly different.Application of MT results and combined Marine earthquakes and gravity data provide a better understanding of the paleo-subduction zone features of the Jan de Fuca plate.