Collaborative Research: Petrological controls on continental uplift: static- and reactive-transport modeling of hydration-driven de-densification

人们对在稳定的低地大陆内部形成广阔的高海拔高原的地质过程知之甚少。然而，这种抬升可能对整个地球系统的许多方面产生深远的影响，包括大气环流和生物多样性。最终，高原隆升的原因是由地壳和岩石圈内的深层过程驱动的，但由于无法进入，这些过程仍然是谜。最近提出的一个假说认为，在名义上干燥的下地壳中加入含水流体和/或水，可能会引起矿物反应，导致密度和体积发生重大变化，导致膨胀，从而使地表隆起。然而，这些变化的幅度作为岩石成分，添加的流体比例和地球表面以下的深度的函数是无法量化的。拟议的研究通过对从美国科罗拉多高原收集的岩石进行实验室分析和计算建模来解决这一知识缺口，以产生一个新的预测工具箱，该工具箱可以限制全球任何地质情景中地壳水合作用的地形影响。这项研究将培养一名新的博士生，两名来自代表性不足背景的本科生，并促进两名美国早期职业研究人员之间的新合作。地壳水合作用的构造效应知之甚少，由于缺乏现实的建模框架来量化流体-岩石相互作用在中低地壳变质条件下的岩石物理效应。这项研究的目的是直接解决这个问题，采用最近开发的算法，量化的开放和封闭的岩石学系统，使用平衡热力学的演变。将产生1-D和2-D算法，以量化压力、温度、大块岩石密度、水化状态和表面隆起之间的关系，这些算法可应用于发生流体-岩石相互作用的任何地壳环境。这也将解决封闭和开放系统的地质情景，考虑到小规模和短期的流体流入（如结晶岩浆），以大规模，连续的流体流入（如俯冲板的脱挥发分）。通过测量从科罗拉多高原地壳不同水平暴露的天然样品中的矿物成分和水含量，用电子探针微区分析、电子背散射衍射和二次离子质谱法测定，对洲际高原形成的预测将得到地面验证。这项工作的结果将有助于破译其隆升的驱动力，在新生代和从俯冲的法拉隆板块释放的流体之间的中间岩石圈地幔和下/中大陆地壳的分割程度。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The geological processes that form broad, high-elevation plateaus in otherwise stable and low-lying continental interiors are poorly understood. Yet, such uplift can have profound effects on many aspects of the whole earth system, including atmospheric circulation and biodiversity. Ultimately, the causes of plateau uplift are driven by deep-seated processes within the Earth's crust and lithosphere, but due to inaccessibility, such processes remain enigmatic. A recently proposed hypothesis suggests that the addition of hydrous fluids and/or water to nominally dry lower crust could cause mineral reactions that result in significant changes in density and volume, leading to expansion and therefore surface uplift. However, the magnitude of these changes as functions of rock composition, proportion of fluid added, and depth below the Earth's surface are unquantified. The proposed study addresses this knowledge gap by performing laboratory analysis on rocks collected from the Colorado Plateau, USA, and computational modeling to produce a new predictive toolbox that can constrain the topographic effects of crustal hydration in any geological scenario worldwide. This research will train one new PhD student, two undergraduate students from underrepresented backgrounds, and promote new collaboration between two US-based early-career researchers.The tectonic effects of crustal hydration are poorly understood, owing to the absence of realistic modeling frameworks for quantifying the petrophysical effects of fluid-rock interaction at middle- to lower-crustal metamorphic conditions. This research aims to directly address this issue by employing recently developed algorithms that quantify the evolution of open and closed petrological systems using equilibrium thermodynamics. Both 1-D and 2-D algorithms will be produced that quantify the relationships between pressure, temperature, bulk-rock density, hydration state, and surface uplift, which can be applied to any crustal environment where fluid-rock interaction takes place. This will also address both closed- and open-system geological scenarios, considering small-scale and short-term fluid influx (e.g. crystallizing magmas) to large-scale, continuous fluid influx (e.g. devolatilization of a subducting slab). Predictions made for intercontinental plateau formation will be ground-truthed by measuring mineral compositions and water contents within natural samples exposed from different levels of the Colorado Plateau crust, as determined by electron probe microanalysis, electron backscatter diffraction, and secondary ion mass spectrometry. The results of this work will assist in deciphering the driving force for its uplift during the Cenozoic and the extent to which fluids released from the subducted Farallon slab were partitioned between the intermediate lithospheric mantle and the lower/middle continental crust.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.