The Final Stages of Slip and Volcanism on an Oceanic Detachment Fault at 13°48′N, Mid-Atlantic Ridge
The Final Stages of Slip and Volcanism on an Oceanic Detachment Fault at 13°48′N, Mid-Atlantic Ridge
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大西洋中脊北纬 13°48° 处海洋滑脱断层上滑动和火山活动的最后阶段
DOI：
10.1029/2018gc007536
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Fornari, D. J.
中科院分区：
文献类型：
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作者：
Parnell-Turner, R. E.;Mittelstaedt, E.;Kurz, M. D.;Jones, M. R.;Soule, S. A.;Klein, F.;Wanless, V. D.;Fornari, D. J.
虽然与海洋拆离断层的形成和维持有关的过程越来越受到限制，但对导致断层废弃的构造和岩浆条件知之甚少。在这里，我们介绍了使用可潜水的Alvinand自主水下航行器Sentryat近海底调查的结果，该调查位于大西洋中脊13°48′N附近最近灭绝的拆离断层，可以记录断层活动和岩浆活动的最后阶段。海底成像、取样和近底磁性数据显示，拆离下盘被约850 m宽的火山露头（包括枕状熔岩）覆盖。在这些泡状玄武岩的饱和压力，溶解的H2O和CO2的基础上，小于其收集压力，这可以解释在一个较浅的水平比他们现在的深度喷发。浅海底剖面显示，火山地形顶部的沉积物厚度（海底年龄的一个松散代用指标）比邻近上盘截止线的下盘厚约2米。这种差异可以通过轴向山谷中的电流驱动侵蚀或火山就位后的持续滑动来解释，无论是新形成的还是预先存在的断层。由于目前的速度附近的下盘不太可能足以造成显着的侵蚀，我们赞成的假设，剥离滑继续后，岩浆活动的插曲，一致的越来越多的证据表明，海洋determinant可以继续滑动，尽管托管岩浆侵入。
While processes associated with initiation and maintenance of oceanic detachment faults are becoming better constrained, much less is known about the tectonic and magmatic conditions that lead to fault abandonment. Here we present results from near‐bottom investigations using the submersibleAlvinand autonomous underwater vehicleSentryat a recently extinct detachment fault near 13°48′N, Mid‐Atlantic Ridge, that allow documentation of the final stages of fault activity and magmatism. Seafloor imagery, sampling, and near‐bottom magnetic data show that the detachment footwall is intersected by an ~850 m‐wide volcanic outcrop including pillow lavas. Saturation pressures in these vesicular basalts, based on dissolved H2O and CO2, are less than their collection pressures, which could be explained by eruption at a shallower level than their present depth. Sub‐bottom profiles reveal that sediment thickness, a loose proxy for seafloor age, is ~2 m greater on top of the volcanic terrain than on the footwall adjacent to the hanging‐wall cutoff. This difference could be explained by current‐driven erosion in the axial valley or by continued slip after volcanic emplacement, on either a newly formed or pre‐existing fault. Since current speeds near the footwall are unlikely to be sufficient to cause significant erosion, we favor the hypothesis that detachment slip continued after the episode of magmatism, consistent with growing evidence that oceanic detachments can continue to slip despite hosting magmatic intrusions.