Time scales for vertically moving axial magma chambers at fast-spreading ocean ridges and involved magmatic reactions: Insights from IODP Site 1256

大洋扩张中心的地球动力学模型表明，快速扩张海脊下的轴向岩浆室(AMC)是一种瞬变现象，在不同的时间尺度上上下移动，到目前为止还很难量化。由于IODP多巡航任务“超快扩张地壳”(1256站点，赤道东太平洋隆起)，现在似乎可以直接估计这些时间尺度。探险312成功地钻探了一个化石传导边界层(CBL)：夹在辉长岩和席状岩之间的一层变质的“花岗状”岩脉，为获得AMC/岩脉过渡运动的基本时间信息提供了可能性。通过将现代扩散模拟工具应用于“花岗岩”岩墙层内的那些相，这些相被处于较高位置的AMC的热印记变质，我们的目的是限制AMC的垂直运动的时间尺度。在AMC向上移动到先前的热液岩脉期间，预计会发生巨大的反应，导致同化和停顿。我们试图通过实验模拟这些过程，以了解/量化相应的岩浆反应机制，以评估一个通用的模型，即在快速扩张的山脊下MORB的污染是如何进行的。

Models on the geodynamics of oceanic spreading centers imply that the axial magma chambers (AMC) under fast-spreading ridges are transient phenomena, moving up and down in distinct time scales which are only poorly quantified up to now. Thanks to IODP multi-cruise mission "Superfast Spreading Crust" (Site 1256, equatorial East Pacific Rise), a direct estimation of these time scales seems now possible. Expedition 312 drilled successfully a fossil conductive boundary layer (CBL): a horizon of metamorphosed, "granoblastic" dikes sandwiched between gabbros and sheeted dikes, providing the potential to obtain fundamental temporal information of the movements of the AMC/Dike transition. By applying modern tools of diffusion modeling to those phases within the "granoblastic" dike horizon, which were metamorphosed by the thermal imprint of the AMC in a high position, we aim to constrain the time scales of vertical movements of AMC's. During upward moving of an AMC into previously hydrothermalized dikes, vast reactions are expected causing assimilation and stoping. It is our attempt to simulate these processes experimentally, in order to understand/quantify the mechanism of the corresponding magmatic reactions for evaluation a general model, how contamination of MORB under fast-spreading ridges proceeds.