Accretion of superfast spreading oceanic crust: Participation in IODP Expedition 335

海洋地壳覆盖了近三分之二的地球表面。它是在洋中脊由上涌地幔中形成的岩浆凝固而产生的。这些岩浆被储存在洋脊轴下方的岩浆室中，在那里它们结晶产生下洋壳。岩浆输入和结晶提供的热量驱动海底热液系统，通过岩石圈-水圈交换控制海洋化学，并为化学合成生态系统提供能量。然而，重建下地壳的岩浆过程已被证明是具有挑战性的，主要是由于严重有限的可及性。迄今为止，只研究了来自破碎地壳的下地壳部分，仍然不确定这些部分在多大程度上代表完整地壳。因此，为了了解大部分地壳的形成，恢复完整的下洋壳将是向前迈出的重要一步，赤道太平洋的科学海洋钻探（IODP孔1256 D）已经穿透了上地壳，到达了上地壳-下地壳的边界。IODP Expedition 335将加深这个洞，恢复完整的下大洋地壳的第一部分。这一部分将产生下地壳演化的前所未有的观点，从岩浆房过程和由此产生的地壳形成，其随后的冷却和海洋热液流体的蚀变。这一建议寻求资金的PI加入远征335，在那里他将担任火成岩岩石学家。他将描述和解释深成岩，这代表了下地壳的积木，使用它们的成分和纹理，使有关地壳增生过程中的岩浆房过程的一阶观测。此外，他将定义在巡航后研究期间进行测试的假设，并采取必要的样本以实现巡航后研究目标。

Oceanic crust covers nearly two thirds of the Earth's surface. It is generated at mid-ocean ridges by the solidification of magmas formed in the upwelling mantle. These magmas are stored in magma chambers below the ridge axis, where they crystallise to yield the lower oceanic crust. The heat provided by magma input and crystallisation drives seafloor hydrothermal systems, which control ocean chemistry through lithosphere-hydrosphere exchange, and provide energy for chemosynthetic ecosystems. Reconstructing the magmatic processes in the lower crust has proven challenging, however, primarily due to severely limited accessibility. Only lower crustal sections from dismembered crust have been studied to date, and it remains uncertain to which extent these sections are representative for intact crust. Thus, in order to understand the formation of a large part of the Earth's crust, the recovery of intact lower oceanic crust would be a major step forward.Scientific ocean drilling in the Equatorial Pacific Ocean (IODP Hole 1256D) has penetrated the upper crust, reaching the upper crust-lower crust boundary. IODP Expedition 335 is set to deepen the hole, recovering the first section of intact lower oceanic crust. This section will yield an unprecedented view of lower crustal evolution, from magma chamber processes and the resulting formation of the crust to its subsequent cooling and alteration by ocean-derived hydrothermal fluids.This proposal seeks funding for the PI to join Expedition 335, where he will serve as igneous petrologist. He will describe and interpret the plutonic rocks, which represent the building blocks of the lower crust, using their composition and textures to make first-order observations about the magma chamber processes during crustal accretion. In addition, he will define hypotheses to test during post-cruise research, and take the necessary samples to achieve the postcruise research objectives.