Cruise support for Dr Christopher Smith-Duque, shipboard petrologist on IODP Expedition 329

世界上的海洋和海底是地球上探索最少的地区。尽管覆盖了地球表面的70%以上，但目前只有几百个钻孔和疏浚点代表了我们对海底的全部采样。在世界上最大的洋流系统南太平洋环流中，采样的缺乏程度比地球上任何其他地区都要严重。上一次系统地从南太平洋这一地区的海底回收材料的科学考察是在130多年前的英国皇家海军挑战者号考察（1872-1876）期间。综合海洋钻探计划（IODP）第329远征队提供了一个独特的机会，可以发现海底下生命的性质和范围，并了解在地球上最大、勘探最少的地区之一运行了1亿多年的地质过程。JOIDES决议的样带将覆盖11,000公里的海洋，从塔希提岛的帕皮提到新西兰的奥克兰，为期66天，将从7个地点收集沉积物岩心，并在3个地点钻探海洋地壳的玄武岩。在船上，我将成为一个国际科学家团队的一员，使用多学科的方法来描述海底沉积物的地质和生物性质，以及在东太平洋隆起中洋脊形成的潜在火山岩。南太平洋环流特别令人感兴趣，因为这是一个数百万年来海洋生物活动极低的区域。IODP 329考察队将确定：1)在环流内的海底下有什么生命，如果有的话，生命发生在什么样的栖息地和条件下；2)海洋在控制从中心到环流边缘的横断面海底下的栖息地方面所起的作用。例如，来自地表附近的死亡生物量的积累如何影响海底的生命；3)独立于光合作用过程的海底沉积物和基底内的生命范围；4)海底岩石的地质和不断演变的热驱动海水/岩石化学相互作用如何影响海底的可居住性和生命分布。作为第329远征队中唯一的一名岩石学家，我的任务是描述和描述沉积物下面的火山岩。这些玄武岩熔岩是在南东太平洋隆起的岩浆喷发时形成的，洋中脊形成了大部分的太平洋基底。这些熔岩后来冷却下来，这些地点经过数百万年的时间从活跃的山脊移动到现在的位置。在第329次探险中对岩石的描述和分析将使我能够推断熔岩喷发的风格并对岩石类型进行分类。我的职责还包括描述和解释海水如何与海洋基底相互作用，以及海水-玄武岩热和化学交换的条件。新的矿物是由热液蚀变的热驱动化学过程形成的，这种化学过程在海水和岩石之间交换元素和化合物。这些新矿物形成于岩石碎片之间的空隙、冷却的裂缝和被称为小泡的气泡中，这些小泡曾经被火山喷发时从岩浆中逸出的气体占据。由于岩浆被海水快速冷却而形成的火山玻璃也可以被替换，在熔岩缓慢冷却过程中形成的火成岩矿物也可以被替换。海水和玄武岩之间的许多反应释放出化学物质和能量，为海底原始微生物生命创造了潜在的栖息地。描述这些蚀变特征对于了解海洋基底的生物定植和潜在的生命范围是必要的。

The world's oceans and the seafloor are the most poorly explored regions of Earth. Despite covering over 70% of the Earth's surface, only a few hundred drilled holes and dredge sites currently represent the entirety of our sampling of the sub-seafloor. More so than any other region on Earth there remains a dearth of sampling in the South Pacific Gyre, the world's largest ocean current system. The last scientific expedition to systematically recover material from the ocean floor in this region of the South Pacific Ocean was over 130 years ago during the HMS Challenger Expedition (1872-1876).Integrated Ocean Drilling Program (IODP) Expedition 329 represents a unique opportunity to discover the nature and extent of life below the seafloor and to understand the geological processes that have operated for over 100 million years in one of the largest, most poorly explored regions of the Earth. The JOIDES Resolution's transect, will cover 11,000 km of ocean over a period of 66 days from Papeete, Tahiti to Auckland, New Zealand and will collect sediment cores from 7 sites and drill into the basalts of the oceanic crust at 3.Aboard ship, I will be part of an international team of scientists using a multi-disciplinary approach to characterise the geological and biological nature of seafloor sediments and the underlying volcanic rocks that formed at the East Pacific Rise mid-ocean ridges. The South Pacific Gyre is of particular interest because this has been a region of extremely low biological activity within the oceans for many millions of years.IODP Expedition 329 will determine: 1) What, if any, life occurs beneath the sea floor within the gyre and in what habitats and conditions does life occur; 2) The role the ocean plays in controlling habitats beneath the seafloor across a transect from the centre to the edge of the gyre. For example, how does the accumulation of dead biomass from near the surface affect life in the ocean floor; 3) The extent of life within sea floor sediment and basement that is independent of the photosynthetic process, and 4) How the geology of sub-seafloor rocks, and the evolving thermally driven seawater/rock chemical interactions affect the habitability of the seafloor and distribution of life.My role as the sole petrologist sailing on Expedition 329 will be to describe and characterise the volcanic rocks that occur beneath the sediments. These basaltic lavas formed during eruptions of magma at the southern East Pacific Rise, the mid-ocean ridges that has formed much of the Pacific Ocean basement. These lavas have since cooled and the sites moved over millions of years away from the active ridge to their present locations. Describing and analysing the rocks during Expedition 329 will allow me to infer the styles of lava eruptions and classify the rock types.My role will also include describing and interpreting how seawater interacts with oceanic basement and the conditions of seawater-basalt thermal and chemical exchange. New minerals are formed by thermally driven chemical process known as hydrothermal alteration that exchanges elements and compounds between seawater and rock. These new minerals form in voids between fragments of rock, in cooling fractures and within bubbles known as vesicles that were once occupied by gases escaping from the magmas during eruption. Volcanic glass formed by the very rapid quenching of magma by seawater can also be replaced as can the igneous minerals that were formed during the slower cooling of the lava. Many of the reactions between seawater and basalts release chemicals and energy that create potential habitats for primitive microbial sub-seafloor life. Describing these alteration features will be imperative for understanding the biological colonization and potential extent of life within oceanic basement.