Alvin-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc
Alvin-SeaBeam studies of the Sumisu Rift, Izu-Bonin arc
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Alvin-SeaBeam 对伊豆-小笠原弧 Sumisu 裂谷的研究
DOI：
10.1016/0012-821x(90)90181-v
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发表时间：
1990
影响因子：
5.3
通讯作者：
T. Urabe
中科院分区：
文献类型：
--
作者：
B. Taylor;G. Brown;P. Fryer;J. Gill;A. Hochstaedter;H. Hotta;C. Langmuir;M. Leinen;A. Nishimura;T. Urabe
双峰式火山活动、正断层、快速沉积和热液循环是伊豆-小笠原弧在31°N的裂谷特征。从平面上分析了苏米什裂谷正断层的锯齿形构造，其伸展方向（080° ± 10°）与火山前缘的区域走向正交。正断层将裂谷分为弧侧的内部裂谷和更西边的外部裂谷，弧侧是最大沉降和沉积的场所。连接相对主断层和/或裂谷侧翼隆起的转换带进一步将裂谷沿走向沿着细分为三段。火山活动沿着ENE向的转换带集中，该转换带分隔了北方和中央裂谷段。该带的差异运动是由相互交错的北向正断层而不是由ENE向的错动-滑动断层调节的。外裂谷的火山活动建造了50-700 m高的大厦，没有山顶火山口，而在内裂谷，它形成了两个多喷口的雁列脊（最大的高600 m，长16 km）。火山作用以玄武质为主，成分反映地幔源区，受弧成分影响较小。在大脊的雁列台阶上发育一个细长的流纹岩穹隆和低温热液矿床，该台阶位于转换带与内裂谷的交汇处。烟囱、矿脉和结壳由二氧化硅、重晶石和氧化铁组成，其成分与覆盖黑矿矿床的含铁燧石相似。在30°48.5′N的一个1.2 km的断面上测量了7个阿尔温热流，结果表明，内部裂谷边界断层可能是水补给区，但它们不一定是集中的热液流出区，而是通过厚盆地沉积物发生的。裂谷盆地和弧缘沉积物可能主要是从海底弧破火山口（如Sumisu和South Sumisu火山）喷发的可渗透流纹质浮石和火山灰。
Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50–700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of sevenalvinheat flow measurements at 30°48.5′N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine arc calderas such as Sumisu and South Sumisu volcanoes.