Heat and Chemical Exchange During the Early Stages of Backarc Rifting in a Polar Region: Hydrothermal Activity in Bransfield Strait, Antarctica

NSF FORM 1358（1/94）该奖项由美国国家科学基金会极地项目办公室提供，支持调查南设得兰群岛和南极半岛之间的布兰斯菲尔德海峡热液喷口的研究。 以前在该海峡进行的勘探工作确定了几个从海底喷出热液的地点。 这些发现是使用一套专门设计的仪器来探测和绘制热液活动对上覆水柱造成的热异常和化学异常。 海峡内的热液地点水深200至1 300米，位于火山露头上，这些火山露头沿裂谷带走向沿着定期突出沉积物覆盖层。 这些地点与欺骗岛的破火山口相连，那里有活跃的温泉。 这些是在南极洲发现的第一批海底热液地点，因此代表了独特的研究机会。 该项目将返回海峡，进一步绘制这些地区的地图和取样。 有几个令人信服的理由相信，对布兰斯菲尔德喷口系统的进一步探索将产生令人兴奋的新信息：（1）布兰斯菲尔德海峡是一个弧后裂谷系统，在这种环境中与喷口有关的喷口流体和矿床很可能不同于迄今为止从海底喷口取样的任何东西。 (2)初步证据表明，布兰斯菲尔德的火山喷发发生在两种不同的火山基质中：安山岩和流纹岩。 这种情况提供了一个自然的实验室，研究基板上的喷口流体成分的化学作用。 (3)布兰斯菲尔德海峡与大洋中脊系统分离，裂谷作用历史相对较短（约4英里）。 因此，虽然该区域横跨大西洋和太平洋，但海峡中的喷口生物群很可能有一个独特的谱系。 关于布兰斯菲尔德喷口物种的生物化学信息将增加我们对深海生物扩散的了解。 在过去，这些发现导致了新物种的鉴定和以前未知的生化化合物的分离。(4)布兰斯菲尔德热液区的火和冰环境可能被证明是地球和外星天体原始环境的最接近的模拟。 布兰斯菲尔德海峡是世界海洋中最具生产力的地区之一，靠近南极大陆，远离大洋中脊系统。 富含有机物的沉积物和火山活动在弧后环境中产生的热量相结合，创造了一种有利于不寻常的流体、独特的喷口生物群和外来热液矿床的环境。 合作奖项：OPP 9725972和OPP 9813450

NSF FORM 1358 (1/94) This award, provided by the Office of Polar Programs of the National Science Foundation, supports research to investigate hydrothermal venting in Bransfield Strait, between the South Shetland Islands and the Antarctic Peninsula. Previous exploratory work in the Strait identified several sites where hot hydrothermal fluids emanate from the sea floor. These discoveries were made using an instrument package specially designed to detect and map the thermal and chemical anomalies that hydrothermal activity imparts on the overlying water column. Hydrothermal sites in the Strait range in water depth from 200 to 1300 meters and occur on the volcanic outcrops that periodically protrude through the sediment cover along the strike of the rift zone. These sites are alligned with the caldera at Deception Island which has active hot springs. These are the first submarine hydrothermal sites discovered in Antarctica and as such represent unique research opportunities. This project will return to the Strait to further map and sample these areas. There are several compelling reasons to believe that further exploration of vent systems in the Bransfield will yield exciting new information: (1) Bransfield Strait is a back-arc rift system and it is likely that the vent fluids and mineral deposits associated with venting in this setting are unlike anything sampled so far from submarine vents. (2) Preliminary evidence suggests that venting in the Bransfield occurs in two different volcanic substrates: andesite and rhyolite. This situation provides a natural laboratory for investigating the effects of substrate chemistry on vent fluid composition. (3) Bransfield Strait is isolated from the system of mid-ocean ridges and has a relatively short history of rifting (approximately 4 my). So, while the region straddles the Atlantic and Pacific, vent biota in the Strait may well have a distinct genealogy. Biochemical information on vent species in the Bransfield will add to our knowledge of the dispersal of life in the deep ocean. In the past such discoveries have led to the identification of new species and the isolation of previously unknown biochemical compounds. (4) The fire and ice environments of hydrothermal sites in the Bransfield may prove to be the closest analog for primordial environments on Earth and extraterrestrial bodies. The Bransfield Strait is one of the most productive areas of the world's oceans and lies close to the Antarctic continent, far removed from the mid-ocean ridge system. The combination of organic-rich sediment and heat produced by volcanism in this back- arc setting creates a situation conducive to unusual fluids, unique vent biota, and exotic hydrothermal deposits. Collaborative awards: OPP 9725972 and OPP 9813450