Investigating the influence of lithology and water depth on the composition and distribution of sulphides at the worlds deepest known vent sites.

研究岩性和水深对世界上已知最深喷口处硫化物成分和分布的影响。

• 批准号: NE/I012613/1
• 负责人: Stephen Roberts
• 金额: $ 4.74万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI012613%2F1
• 关键词: Investigating; influence; lithology; water; depth

The start of the Age of Metal marked a step-change for mankind. Today, our entire technological society is dependent on metals. But it all started with copper. One of the main sources of this metal in the ancient world was Cyprus in the eastern Mediterranean. Cyprus is named after the Greek word for copper. The island's secret was the Troodos ophiolte, an ancient fragment of oceanic crust that was uplifted to form a mountain range. Here, eighty six million years ago, high-temperature hydrothermal vents deposited large mineral ore bodies on the seafloor. Below the seabed, these were rich in copper minerals, deposited by the hot vent fluids as they mixed with cold seawater. Today, modern hydrothermal vents, their ore deposits, and exotic animals are well known as striking examples of geology in action. But we know relatively little about what determines the distribution and composition of the ore deposits. We think that vent fluids become rich in valuable base metals deep beneath mid-ocean ridges, where pressures are 5000 atmospheres and temperatures reach ~500 degrees Celsius. Under these conditions, seawater is supercritical (i.e. the vapour phase behaves like a fluid) and is so reactive that it can easily dissolve rocks. We also think that the composition of those dissolving rocks is important. Different rocks have different metals in them and this affects the composition and value of the ore deposits. But until now, it has been impossible to sample hydrothermal systems under these pressure and temperature conditions. In April 2010, we made the extraordinary discovery of hydrothermal activity in the deepest mid-ocean ridge on Earth. Within the Cayman Trough, deep beneath the Caribbean Sea, we found vents at 5000m gushing out supercritical fluids at nearly 500 degrees Celsius. These are the hottest ever found, and are close to the conditions normally found where seawater meets magma chambers deep below the seafloor. With another expedition already scheduled for 2012, we have a unique opportunity to use this natural laboratory to test predictions about the distribution and composition of ore deposits formed from such high-temperature supercritical fluids. The significance of this work is multi-fold. Economically, we can apply the knowledge gained from this unique study to predict other, more accessible ore deposits on land and at sea. Already, deep-sea extraction companies are starting to explore seafloor ore deposits. The information we gather from this study will help predict the future viability of these deposits. Our new data will also help inform governments and NGOs (e.g. the United Nations International Seabed Authority) of how to protect these sites and ensure that only sustainable exploration is ever planned. Scientifically, we will gain a new understanding of the role of pressure, temperature and rock composition in the formation of ore deposits. We will also revise our estimates of the exchange of heat and fluids between the ocean and seafloor. This exchange helps explain why the sea is salty and the Earth's climate has been in balance. Our exciting work, in such an extreme environment, will continue to engage the public's imagination and help promote science and technology to tomorrow's generation.

金属时代的开始标志着人类的一个转变。今天，我们整个科技社会都依赖金属。但这一切都是从铜开始的。古代这种金属的主要来源之一是地中海东部的塞浦路斯。塞浦路斯以希腊语中的铜命名。这个岛的秘密在于Troodos ophiolte，这是一块古老的海洋地壳碎片，它被抬升形成了山脉。在这里，8600万年前，高温热液喷口在海底沉积了大型矿体。在海床下，这些岩石富含铜矿物，这些矿物是由热喷口流体与冷海水混合后沉积下来的。今天，现代的热液喷口、其中的矿藏和外来动物都是众所周知的地质作用的显著例证。但我们对决定矿床分布和组成的因素所知相对较少。我们认为，在海洋中脊深处，压力为5000个大气压，温度达到500摄氏度的地方，喷口流体富含有价值的贱金属。在这种条件下，海水是超临界的（即气相表现得像流体），而且反应性很强，很容易溶解岩石。我们还认为，这些溶解岩石的组成很重要。不同的岩石含有不同的金属，这影响了矿床的组成和价值。但到目前为止，在这种压力和温度条件下对热液系统进行采样是不可能的。2010年4月，我们在地球上最深的大洋中脊发现了热液活动。在加勒比海深处的开曼海槽中，我们发现5000米深的火山口喷出了温度接近500摄氏度的超临界流体。这是迄今为止发现的最热的温度，接近海底深处海水与岩浆房相遇的正常温度。2012年的另一次考察已经安排好了，我们有一个独特的机会利用这个自然实验室来测试关于由这种高温超临界流体形成的矿床的分布和组成的预测。这项工作具有多重意义。从经济上讲，我们可以应用从这项独特的研究中获得的知识来预测陆地和海上其他更容易开采的矿床。深海开采公司已经开始勘探海底矿藏。我们从这项研究中收集的信息将有助于预测这些矿床的未来生存能力。我们的新数据还将帮助政府和非政府组织（例如联合国国际海底管理局）了解如何保护这些地点，并确保只计划进行可持续的勘探。在科学上，我们将对压力、温度和岩石成分在矿床形成中的作用有新的认识。我们还将修订我们对海洋和海底之间热和流体交换的估计。这种交换有助于解释为什么海水是咸的，为什么地球的气候一直处于平衡状态。在这样一个极端的环境下，我们激动人心的工作将继续激发公众的想象力，并帮助向下一代推广科学技术。

项目成果

Talc-dominated seafloor deposits reveal a new class of hydrothermal system.

• DOI: 10.1038/ncomms10150
• 发表时间: 2015-12-22
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Hodgkinson MR;Webber AP;Roberts S;Mills RA;Connelly DP;Murton BJ
• 通讯作者: Murton BJ

The formation of gold-rich seafloor sulfide deposits: Evidence from the B eebe hydrothermal vent field, C ayman T rough

富金海底硫化物矿床的形成：来自开曼群岛 Beebe 热液喷口场的证据

• DOI: 10.1002/2017gc006922
• 发表时间: 2017
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Webber A

The influence of spreading rate, basement composition, fluid chemistry and chimney morphology on the formation of gold-rich SMS deposits at slow and ultraslow mid-ocean ridges

扩散速率、基底成分、流体化学和烟囱形态对慢速和超慢速洋中脊富金 SMS 矿床形成的影响

• DOI: 10.1007/s00126-017-0762-4
• 发表时间: 2017
• 期刊: Mineralium Deposita
• 影响因子: 4.8
• 作者: D. Knight R