Our knowledge of venting at intraplate seamounts is limited. Almost nothing is known about past hydrothermal activity at seamounts, because indicators are soon blanketed by sediment. This study provides evidence for temporary hydrothermal circulation at Henry Seamount, a re-activated Cretaceous volcano near El Hierro island, close to the current locus of the Canary Island hotspot. In the summit area at around 3000–3200 m water depth, we found areas with dense coverage by shell fragments from vesicomyid clams, a few living chemosymbiotic bivalves, and evidence for sites of weak fluid venting. Our observations suggest pulses of hydrothermal activity since some thousands or tens of thousands years, which is now waning. We also recovered glassy heterolithologic tephra and dispersed basaltic rock fragments from the summit area. Their freshness suggests eruption during the Pleistocene to Holocene, implying minor rejuvenated volcanism at Henry Seamount probably related to the nearby Canary hotspot. Heat flow values determined on the surrounding seafloor (49 ± 7 mW/m2) are close to the expected background for conductively cooled 155 Ma old crust; the proximity to the hotspot did not result in elevated basal heat flow. A weak increase in heat flow toward the southwestern seamount flank likely reflects recent local fluid circulation. We propose that hydrothermal circulation at Henry Seamount was, and still is, driven by heat pulses from weak rejuvenated volcanic activity. Our results suggest that even single eruptions at submarine intraplate volcanoes may give rise to ephemeral hydrothermal systems and generate potentially habitable environments.

中文翻译：

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白垩纪海山的热液活动，加那利群岛，由复兴的火山作用引起

我们对板内海山排气的了解是有限的。关于海山过去的热液活动几乎一无所知，因为指标很快就被沉积物覆盖了。这项研究为亨利海山的临时热液循环提供了证据，亨利海山是埃尔耶罗岛附近重新激活的白垩纪火山，靠近加那利岛热点的当前位置。在约 3000-3200 米水深的峰顶区域，我们发现了由 vesicomyid 蛤、一些活的化学共生双壳类动物的壳碎片密集覆盖的区域，以及流体排放较弱的地点的证据。我们的观察表明，自几千年或几万年以来，热液活动的脉冲正在减弱。我们还从峰顶地区回收了玻璃状的异岩性火山灰和散布的玄武岩碎片。它们的新鲜度表明在更新世至全新世期间喷发，这意味着亨利海山的轻微火山活动可能与附近的金丝雀热点有关。在周围海底确定的热流值 (49 ± 7 mW/m2) 接近传导冷却的 155 Ma 旧地壳的预期背景；靠近热点并没有导致基础热流升高。朝向西南海山侧翼的热流的微弱增加可能反映了最近的局部流体循环。我们认为，亨利海山的热液循环过去和现在仍然是由恢复活力的弱火山活动产生的热脉冲驱动的。我们的结果表明，即使是海底板块内火山的单次喷发也可能会产生短暂的热液系统并产生潜在的宜居环境。