Deep-crustal Reactive Fluid Flow in the Mesozoic White-Inyo Magmatic Arc, California

加利福尼亚州中生代白伊尼奥岩浆弧中的深地壳反应流体流动

• 批准号: 1321519
• 负责人: Peter Nabelek
• 金额: $ 22.66万
• 依托单位: University of Missouri-Columbia
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-15 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1321519&HistoricalAwards=false
• 关键词: Deep; crustal; Reactive; Fluid; Flow

Water, besides being obviously present on the Earth?s surface, is also an integral part of the deep continental crust. In the crust, water is bound-up structurally in minerals and occurs in pore spaces of rocks, even many kilometers below the Earth's surface. During tectonic events, such as plate subductions and continental collisions, water is released from minerals during metamorphic reactions, and together with pore water can serve as a medium for heat transport and can promote weakening of rocks that are undergoing deformation. In this project, the Principal Investigator and students will study fluid flow that has occurred during the Mesozoic era in the White-Inyo Range of eastern California. During this era, the White-Inyo Range was buried deep within the western margin of North American crust that was experiencing metamorphism, magmatism, and volcanism as the oceanic Farallon tectonic plate was subducting beneath the continent. Geologic evidence in the range suggests that deep-crustal fluids promoted the emplacement of granitic plutons, by enhancing deformation of their host rocks, and were responsible for hydrothermal alteration of the crust within the range. The PI and students will study the Mesozoic hydrothermal system by analyzing the thermodynamic equilibrium relationships among preserved metamorphic minerals in collected rocks, by analyzing fluid-induced shifts in the ratios of carbon and oxygen in carbonate minerals, and by computer simulations. It is expected that the key factor that influenced the geometry of fluid flow and potential advective heat transport was variable permeability of rocks within the White-Inyo range. The expected outcome of the project will be a better understanding of the influence that deep-crustal fluids have on the geologic development of continental margins.The White-Inyo Range is an excellent example of an exhumed continental magmatic arc. Magmatism in the arc occurred during two time periods, 180-165 Ma and 102-83 Ma ago, and it overlapped in time with magmatism in the Sierra Nevada Range. Previous structural and metamorphic studies have established that the plutons intruded a regional anticline that contains greenschist-facies shales, limestones, calcareous argillites, and sandstones. Intrusion of the plutons generated heterogeneous hydrodynamic systems, with heterogeneous fluid flow stemming from variable permeabilities and foliations of the rocks. In the project, mineral equilibria, metamorphic reactions, and C and O isotope ratios in carbonate minerals will be used to determine which rocks experienced syn-metamorphic fluid flow. These petrologic and geochemical portions of the project will be the foundation for computer simulations of reactive fluid flow, on both contact-aureole and regional scales, within the magmatic arc. The computer simulations will couple fluid flow with heat transport and metamorphic reactions, and they will include provisions for latent heat of crystallization of melts, heats of metamorphic reactions, and for fluids generated by the reactions and plutons. The project will have an impact on understanding conductive and advective heat transport within magmatic arcs and on the role that fluids have on promoting deformation and recrystallization of rocks in the deep continental crust.

水除了明显存在于地球表面之外，也是深层大陆地壳不可分割的一部分。在地壳中，水在结构上与矿物质结合在一起，存在于岩石的孔隙空间中，甚至存在于地球表面以下数公里处。在板块俯冲和大陆碰撞等构造事件中，水在变质反应过程中从矿物中释放出来，与孔隙水一起可以作为热传输介质，并可以促进正在变形的岩石的弱化。在这个项目中，首席研究员和学生将研究加利福尼亚州东部怀特-因约山脉中生代时期发生的流体流动。在这个时代，怀特-因约山脉深埋在北美地壳的西缘，随着大洋法拉隆构造板块俯冲到大陆之下，北美地壳正在经历变质作用、岩浆作用和火山活动。该山脉的地质证据表明，深部地壳流体通过增强其宿主岩石的变形，促进了花岗岩体的侵位，并导致了该山脉内地壳的热液蚀变。首席研究员和学生将通过分析收集的岩石中保存的变质矿物之间的热力学平衡关系、分析流体引起的碳酸盐矿物中碳和氧比例的变化以及计算机模拟来研究中生代热液系统。预计影响流体流动几何形状和潜在平流热传输的关键因素是 White-Inyo 范围内岩石的可变渗透率。该项目的预期成果将是更好地了解地壳深部流体对大陆边缘地质发育的影响。White-Inyo Range 是发掘出的大陆岩浆弧的一个极好的例子。弧内的岩浆活动发生在180-165Ma和102-83Ma前两个时期，并且与内华达山脉的岩浆活动时间重叠。先前的构造和变质研究已经确定，岩体侵入了包含绿片岩相页岩、石灰岩、钙质泥岩和砂岩的区域背斜。岩体的侵入产生了非均质流体动力系统，由于岩石的可变渗透率和叶理而产生非均质流体流动。在该项目中，将利用碳酸盐矿物中的矿物平衡、变质反应以及 C 和 O 同位素比来确定哪些岩石经历了同变质流体流动。该项目的这些岩石学和地球化学部分将成为岩浆弧内接触光环和区域尺度上反应流体流动的计算机模拟的基础。计算机模拟将流体流动与热传输和变质反应耦合起来，并将包括熔体结晶潜热、变质反应热量以及反应和深成体产生的流体的规定。该项目将对了解岩浆弧内的传导和平流热传输以及流体在促进深部大陆地壳中岩石变形和再结晶方面的作用产生影响。