MARGINS: Hydrothermal Circulation Within Subducting Ocean Crust: Implications for Subduction Zone Temperatures

本研究旨在探讨俯冲地壳内热液循环对俯冲带温度的影响。了解俯冲带温度对于理解控制地震活动上倾和下倾极限的过程、描述俯冲带流体流动系统以及了解俯冲物质的命运非常重要。在俯冲之前，海洋地壳的热液冷却已经被记录下来，并且可以对俯冲带的温度产生深远的影响。然而，俯冲地壳内部热液循环在控制这些温度中的作用尚未得到研究。本项目的主要目标是评估这些影响的程度。本研究将包括：1)将流体和热耦合输运模型应用于俯冲带问题；2)检验沉积物分布、收敛速度和俯冲几何形状对俯冲带热液循环的作用。将解决的关键问题包括：1)热液循环能持续到俯冲带多远？2)哪些因素有利于俯冲地壳中热液循环的持续或停止？3)这种环流的热后果是什么？通过对俯冲地壳内热液循环的研究，将有助于更好地认识俯冲带温度的控制作用。这对于了解加利福尼亚北部等地区的油气生成以及估计俯冲边缘的地震和海啸风险非常重要。其他更广泛的影响包括培养博士生。

The goal of this study is to examine the influence of hydrothermal circulation in subducting crust on subduction zone temperatures. Knowledge of subduction zone temperatures is important for understanding processes controlling the updip and downdip limits of seismicity, characterizing subduction zone fluid flow systems, and understanding the fate of subducted material. Hydrothermal cooling of ocean crust prior to subduction has been documented and can have profound effects on subduction zone temperatures. However, the role of hydrothermal circulation within subducting crust in controlling these temperatures has not been studied. The primary goal of this project is to evaluate the magnitude of these effects..This study will consist of 1) adapting a coupled fluid and heat transport model to subduction zone problems, and 2) examining the roles of sediment distribution, convergence rate, and subduction geometry on subduction zone hydrothermal circulation. Key questions that will be addressed include 1) How far into a subduction zone can hydrothermal circulation persist? 2) What factors favor persistence versus cessation of hydrothermal circulation in subducting crust? and 3) What are the thermal consequences of this circulation?By examining hydrothermal circulation within subducting crust, this study will lead to better understanding of the controls on subduction zone temperatures. This is important for understanding hydrocarbon generation in settings like northern California, and estimating the earthquake and tsunami risk on subduction margins. Other broader impacts involve training of a Ph.D. student.