Distribution of Late Cenozoic volcanic vents in the Cascade range: Volcanic arc segmentation and regional tectonic considerations
Distribution of Late Cenozoic volcanic vents in the Cascade range: Volcanic arc segmentation and regional tectonic considerations
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喀斯喀特山脉晚新生代火山喷口的分布：火山弧分段和区域构造考虑
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
C. Weaver
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作者：
M. Guffanti;C. Weaver
空间，时间和成分分布的约4000火山口形成自16马在华盛顿，俄勒冈州，北方加州，和西北部内华达州说明火山活动的演变有关的胡安德富卡板块系统的俯冲和延伸的盆岭省。喷口数据是从出版的地图汇编中获得的，除了主要的复合中心外，还包括单成因火山和小型多成因火山。根据5 Ma以来形成的2821个火山口的分布，将喀斯喀特山脉划分为5个段，其中俄勒冈州盆岭省北方边缘高熔岩平原沿着的火山口为第6段。喀斯喀特山脉分割的某些方面可能与胡安·德富卡板块俯冲的总体结构特征有关。第一和第二段火山前缘的方位从北方华盛顿的NW向变为华盛顿南部的NE向，与俯冲的Juan de Fuca板块走向平行。第一段和第二段被雷尼尔山和冰川峰之间的90公里火山间隙隔开，该火山间隙位于俯冲板块向陆地的部分，平均倾角最小，深度为60公里。俄勒冈州主要由安山岩喷口组成的南北向狭窄带构成了第三个部分，它位于俯冲带地震平静部分的向陆方向。这一段的狭窄可能表明俄勒冈州喀斯喀特弧下俯冲板块的陡峭倾角。第四段（包含沙斯塔山和梅迪辛湖中心）和第五段（包含拉森峰）之间的通风孔稀疏，其中胡安·德富卡和戈尔达北部板块的特征是不同的年龄，地壳下地震活动量，以及可能的几何形状。从60公里深处的地震活动和自5 Ma以来形成的火山口前缘位置之间的关系，不同几何形状的俯冲板块段之间的过渡可能发生在俄勒冈州北方和北方加州独立定义的火山段之间的边界附近。在喀斯喀特弧以东的盆岭地区，火山活动在5-10 Ma期间迁移到喀斯喀特山脉附近地区。自5 Ma以来，这两个省的撞击特征是：俄勒冈州南部盆岭火山活动停止，加州东北部玄武岩火山活动持续，撞击过程可能尚未完成，以及沙斯塔山、梅迪辛湖和拉森峰周围的镁铁质火山活动区域收缩。在俄勒冈州中部，盆岭火山作用的北方边缘（高熔岩平原）与喀斯喀特弧相交，盆岭伸展火山作用的撞击在时间和空间上与三姐妹篇和杰斐逊山之间的高喀斯喀特地堑的发育大致一致。
Spatial, temporal, and compositional distributions of approximately 4000 volcanic vents formed since 16 Ma in Washington, Oregon, northern California, and northwestern Nevada illustrate the evolution of volcanism related to subduction of the Juan de Fuca plate system and extension of the Basin and Range province. Vent data were obtained from published map compilations and include monogenetic and small polygenetic volcanoes in addition to major composite centers. On the basis of the distribution of 2821 vents formed since 5 Ma, the Cascade Range is divided into five segments, with vents of the High Lava Plains along the northern margin of the Basin and Range province in Oregon forming a sixth segment. Some aspects of the Cascade Range segmentation can be related to gross structural features of the subducting Juan de Fuca plate. The orientation of the volcanic front of segments one and two changes from NW in northern Washington to NE in southern Washington, paralleling the strike of the subducting Juan de Fuca plate. Segments one and two are separated by a 90-km volcanic gap between Mount Rainier and Glacier Peak that is landward of the portion of the subducting plate having the least average dip to a depth of 60 km. A narrow, N-S trending belt of predominantly andesitic vents in Oregon constitutes a third segment, which is landward of the seismically quiet portion of the subduction zone. The narrowness of this segment may indicate steep dip of the subducting plate beneath the Cascade arc in Oregon. Vents are sparse between segment four (containing the Mount Shasta and Medicine Lake centers) and segment five (containing Lassen Peak), where the Juan de Fuca and Gorda North plates are characterized by differing age, amounts of subcrustal seismicity, and probably geometry. From the relation between seismicity at depth of 60 km and the position of the volcanic front of vents formed since 5 Ma, transitions between subducting-plate segments of varying geometry likely occur near boundaries between independently defined volcanic segments in northern Oregon and northern California. In the Basin and Range province east of the Cascade arc, volcanism migrated into the region adjacent to the Cascade Range during the interval 5–10 Ma. Since 5 Ma, the impingement of the two provinces is characterized by cessation of basin-range volcanism in southern Oregon, continuation of basaltic volcanism in northeastern California where the impingement process may not yet be complete, and contraction of the area of mafic volcanism around Mount Shasta, Medicine Lake, and Lassen Peak. In central Oregon where the northern margin of basin-range volcanism (the High Lava Plains) intersects the Cascade arc, impingement of basin-range extensional volcanism approximately coincides in time and space with the development of the High Cascade graben between Three Sisters and Mount Jefferson.