UK-IODP Moratorium Award for Rosalind Coggon - Co-chief scientist IODP Exp 390/393

海洋化学反应了一些基本过程之间不断变化的平衡，比如造山、侵蚀和风化、气候变化和生物进化，这些过程在整个地球历史上都影响着地球表面。因此，过去海水化学的可靠记录为了解地球未来的演变提供了至关重要的信息。为了从这些记录中研究过去气候或构造的特征，我们必须量化其他海洋输入和输出，包括与海底海洋地壳的化学交换。海洋地壳是由海底火山形成的洋中脊形成的，每2亿年就会重新覆盖地球表面的三分之二。然而，它仍然相对未被开发，只有使用潜水器或科学海洋钻探才能进入。这样的探索揭示了海水在冷却的海洋地壳的裂缝中循环，与岩石发生反应，将热量和化学物质输送到海洋。在山脊上，这是通过壮观的“热液”温泉发生的，但从数量上讲，更重要的反应发生在巨大山脊两侧的低温流体流动中。在大洋中脊火山活动期间，地幔中的二氧化碳气体从岩浆中释放到海洋和大气中。在“热液循环”中，当流体穿过地壳时，碳酸钙（CaCO3）就会形成，将二氧化碳储存在岩石中。因此，洋中脊洋壳的形成和演化使碳在地球系统中的长期循环成为可能。不幸的是，我们不知道热液交换在老化的海洋地壳中持续了多长时间，因此它如何影响海洋化学或影响气候的长期c循环，主要是因为我们缺乏不同年龄的海洋地壳岩心。然而，我们已经证明，热液碳酸盐记录了它们形成的流体的化学性质，可以用来确定过去的海洋化学和条件。国际海洋发现计划（IODP）的390和393探险队将在南大西洋的六个地点进行取样，以恢复700万至6100万年前在大西洋中脊形成的海洋地壳。我将使用这些岩芯中的岩石和矿物来开发过去海洋化学的新记录，并量化热液对海洋和长期全球碳循环的贡献。

Ocean chemistry reflects the shifting balance between fundamental processes such as mountain building, erosion and weathering, climate change, and biological evolution that have influenced Earth's surface throughout its history. Reliable records of past seawater chemistry therefore provide information crucial to understanding the future evolution of our planet. To investigate signatures of past climate or tectonics from these records we must quantify the other ocean inputs and outputs, including chemical exchanges with the underlying ocean crust.Ocean crust is produced along the submarine volcanic mid-ocean ridges repaving two-thirds of Earth's surface every 200 million years. However, it remains relatively unexplored, accessible only using submersibles or scientific ocean drilling. Such exploration revealed that seawater circulates through cracks in the cooling ocean crust, reacts with the rocks, transporting heat and chemicals to the oceans. At the ridges this occurs through spectacular 'hydrothermal' hot springs, but quantitatively more important reactions occur during lower-temperature fluid flow on the vast ridge flanks. During mid-ocean ridge volcanism CO2 gas from the mantle is released from the magma to the oceans and atmosphere. During 'hydrothermal circulation' calcium carbonate (CaCO3) forms from the fluid as it passes through the crust, storing CO2 in the rock. The formation and evolution of ocean crust at mid-ocean ridges therefore enables long-term C-cycling through the Earth system. Unfortunately, we do not know how long hydrothermal exchange persists in aging ocean crust, and hence how it affects ocean chemistry or the long-term C-cycle that influences climate, primarily because we lack drill core of ocean crust of different ages. However, we have shown that the hydrothermal carbonates record the chemistry of the fluids they form from and can be used to determine past ocean chemistry and conditions. International Ocean Discovery Program (IODP) Expeditions 390 and 393 will drill a transect of six sites across the South Atlantic, recovering ocean crust formed at the Mid-Atlantic ridge between 7 and 61 million years ago. I will use rocks and minerals from these cores to develop new records of past ocean chemistry and quantify hydrothermal contributions to the oceans and the long-term global carbon cycle.