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

海洋化学反映了基本过程之间不断变化的平衡，如造山、侵蚀和风化、气候变化和生物进化，这些过程在整个历史上影响了地球表面。因此，过去海水化学的可靠记录为了解我们星球的未来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，包括与底层海洋地壳的化学交换。海洋地壳沿着海底火山洋中脊产生，每隔2亿年重新铺设三分之二的地球表面。然而，它仍然相对未被开发，只能使用潜水器或科学海洋钻探才能进入。这种探索表明，海水通过冷却的海洋地壳的裂缝循环，与岩石发生反应，将热量和化学物质输送到海洋。在山脊处，这是通过壮观的“热液”温泉发生的，但在数量上，更重要的反应发生在广阔的山脊侧翼的低温流体流动期间。在洋中脊火山活动期间，来自地幔的二氧化碳气体从岩浆释放到海洋和大气中。在“热液循环”过程中，碳酸钙（CaCO3）在流体穿过地壳时形成，将CO2储存在岩石中。因此，洋中脊洋壳的形成和演变使地球系统中的碳循环得以长期进行。不幸的是，我们不知道热液交换在老化的海洋地壳中持续多久，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的钻孔岩心。然而，我们已经表明，热液碳酸盐记录了它们形成的流体的化学性质，并可用于确定过去的海洋化学和条件。国际海洋发现计划（IODP）第390和393号探险队将在南大西洋的六个地点进行钻探，恢复700万至6100万年前在中大西洋海岭形成的洋壳。我将利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.