Patterns of event and chronic hydrothermal venting following a magmatic intrusion: new perspectives from the 1996 Gorda Ridge eruption
Patterns of event and chronic hydrothermal venting following a magmatic intrusion: new perspectives from the 1996 Gorda Ridge eruption
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DOI：
10.1016/s0967-0645(98)00085-x
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发表时间：
1998-01-01
影响因子：
3
通讯作者：
Baker, ET
中科院分区：
文献类型：
--
作者：
Baker, ET
1996 年 2 月 28 日，远程探测到戈尔达山脊北部的地震群，促使我们进行了三轮巡航响应工作，以调查与堤坝入侵相关的事件和长期热液排放。 GR1 游轮在地震活动开始后仅 10 天就到达了戈尔达北部，并发现了直径 15 公里的事件羽流 EP96A，其中心位于轴向谷轴最浅部分（类似于 3100 m）上方 1800 至 2800 m 的深度之间。一个月后，GR2 返回并在 EP96A 地点仅发现了微弱的、接近底部的慢性羽流。然而，在以南几公里处，GR2 在轴谷西壁上方绘制了一个明显不同的慢性羽流（类似于 2500-2900 米深度）以及第二个事件羽流 EP96B（类似于 1800-2400 米深度）的边缘。 EP96B 使用中性浮力漂浮物进行播种，该漂浮物向西北净移动 10 公里，然后于 6 月 10 日 GR3 开始时浮出水面。围绕漂浮物位置的测绘完全揭示了 EP96B，这是一种直径 10 公里的羽流，其热含量类似于 BP96A 的 25%。对轴谷内的广泛观察确定，慢性排气在三个月内有效耗尽。试图解释岩脉侵入和喷发对热液喷发的扰动的模型必须满足从这次事件和以前的事件中概括出来的几个标准：（1）喷发随着侵入/喷发而开始（或增加），然后呈指数下降； (2) 入侵后下降的时间尺度在站点内部和站点之间有所不同； (3) 多事件羽流排放普遍存在； (4) 现有的高温喷口场可能不是必要的，甚至有利于事件羽流的形成； (5) 总慢性放电与事件放电的比率因入侵事件而异。 (C) 1999 年由爱思唯尔科学有限公司出版。保留所有权利。
The remote detection of a seismic swarm on the northern Gorda Ridge on 28 February 1996 prompted a three-cruise response effort to investigate event and chronic hydrothermal discharge associated with a dike intrusion. The GR1 cruise reached the northern Gorda only 10 days after seismicity began and discovered a 15 km-diameter event plume, EP96A, centered between depths 1800 and 2800m above the shallowest portion of the axial valley axis (similar to 3100 m). One month later, GR2 returned and found only a weak, near-bottom chronic plume at the EP96A site. A few kilometers to the south, however, GR2 mapped a distinctly different chronic plume (similar to 2500-2900 m depth) as well as the edge of a second event plume, EP96B (similar to 1800-2400-m depth), above the western wall of the axial valley. EP96B was seeded with a neutrally buoyant float, which traveled 10 net km to the northwest before surfacing on 10 June at the start of GR3. Mapping around the float location fully revealed EP96B, a 10 km diameter plume with a heat content similar to 25% that of BP96A. Extensive observations within the axial valley determined that chronic venting was effectively exhausted within three months. Models seeking to explain the perturbation of hydrothermal venting by a dike intrusion and eruption must satisfy several criteria generalized from this and previous events: (1) venting begins (or increases) with the intrusion/eruption and declines exponentially afterwards; (2) the time scale of the post-intrusion decline varies within and among sites; (3) the discharge of multiple event plumes is common; (4) an existing high-temperature vent field may not be necessary or even conducive to event plume formation; and (5) the ratio of total chronic to event discharge varies among intrusion events. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.