Downward continued multichannel seismic refraction analysis of Atlantis Massif oceanic core complex, 30°N, Mid-Atlantic Ridge

被引：33

作者：

Henig, A. S. ^{[1
]}

Blackman, D. K. ^{[1
]}

Harding, A. J. ^{[1
]}

Canales, J. -P. ^{[2
]}

Kent, G. M. ^{[3
]}

机构：

[1] Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA

[2] Woods Hole Oceanog Inst, Dept Geol & Geophys, Woods Hole, MA 02543 USA

[3] Univ Nevada, Nevada Seismol Lab, Reno, NV 89557 USA

来源：

GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS | 2012年 / 13卷

基金：

美国国家科学基金会;

关键词：

Mid-Atlantic Ridge; detachment fault; gabbro; oceanic core complex; seismic structure; serpentinized peridotite; SOUTHWEST INDIAN RIDGE; SLOW-SPREADING RIDGES; EAST PACIFIC RISE; CRUSTAL THICKNESS; GRAVITY-ANOMALIES; EMPLACEMENT PROCESSES; HYDROTHERMAL FIELD; MAGMATIC ACCRETION; DETACHMENT FAULT; TRANSFORM-FAULT;

D O I：

10.1029/2012GC004059

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

Detailed seismic refraction results show striking lateral and vertical variability of velocity structure within the Atlantis Massif oceanic core complex (OCC), contrasting notably with its conjugate ridge flank. Multichannel seismic (MCS) data are downward continued using the Synthetic On Bottom Experiment (SOBE) method, providing unprecedented detail in tomographic models of the P-wave velocity structure to subseafloor depths of up to 1.5 km. Velocities can vary up to 3 km/s over several hundred meters and unusually high velocities (similar to 5 km/s) are found immediately beneath the seafloor in key regions. Correlation with in situ and dredged rock samples, video and records from submersible dives, and a 1.415 km drill core, allow us to infer dominant lithologies. A high velocity body(ies) found to shoal near to the seafloor in multiple locations is interpreted as gabbro and is displaced along isochrons within the OCC, indicating a propagating magmatic source as the origin for this pluton(s). The western two-thirds of the Southern Ridge is capped in serpentinite that may extend nearly to the base of our ray coverage. The distribution of inferred serpentinite indicates that the gabbroic pluton(s) was emplaced into a dominantly peridotitic host rock. Presumably the mantle host rock was later altered via seawater penetration along the detachment zone, which controlled development of the OCC. The asymmetric distribution of seismic velocities and morphology of Atlantis Massif are consistent with a detachment fault with a component of dip to the southeast. The lowest velocities observed atop the eastern Central Dome and conjugate crust are most likely volcanics. Here, an updated model of the magmatic and extensional faulting processes at Atlantis Massif is deduced from the seismic results, contributing more generally to understanding the processes controlling the formation of heterogeneous lithosphere at slow-rate spreading centers.

引用

页数：25

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