Aqueous Aluminosilicate Complexing in Deep-Crustal and Upper-Mantle Fluids

深地壳和上地幔流体中的水铝硅酸盐络合

• 批准号: 0711521
• 负责人: Craig Manning
• 金额: $ 30.32万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711521&HistoricalAwards=false
• 关键词: Aqueous; Aluminosilicate; Complexing; Deep; Crustal

The geochemical evolution of high-pressure, high-temperature igneous and metamorphic environments is strongly influenced by the effects of fluids on solid minerals in the Earth. Evidence for these effects can be found in fluid inclusions in minerals, elemental and isotopic shifts, and veins and metasomatic features in samples from deep settings, including mantle xenoliths, diamonds, arc magmas, and rocks associated with subduction that are exhumed, as well as a wide range of regional metamorphic terranes. Unfortunately, modeling of high-pressure fluid-rock interaction is difficult because the physical chemistry of deep, dense fluids remains highly uncertain. This project will support a set of experimental studies that target a complexing hypothesis for dense fluids in the interior of the Earth. It is expected that the results from this study will provide new insights into the novel chemistry of dense aqueous fluids, while helping support the mentoring of undergraduate and graduate students, continued international collaboration and incorporation of the results into the UCLA's Advanced Petrology class. A key problem is that in H2O-rich high-pressure fluids there is growing evidence for formation of polymerized oxygen coordinated polynuclear complexes. Examples include H6Si2O7 dimers, H5AlSiO6, and albite-like molecules. Such species are poorly understood, chiefly because their concentrations are negligible in most upper- to mid-crustal hydrothermal settings; however, at high P and T, polymerized species may be much more abundant. Polynuclear complexes are potentially important because they elevate solubility of all elements. In particular, they provide coordination environments that permit dissolution of elements that are otherwise relatively insoluble in H2O (e.g., Al, Ti, Zr). This project will support an experimental investigation into key aspects of the hypothesized complexing. Hydrothermal piston-cylinder experimental studies will target interactions between Si, Al, and alkalis. These components are present at the highest concentrations in dense fluids. The high-pressure (5-20 kbar) and high-temperature (600-900°C) experimental work will include: (1) calibration of Si polymerization at very low Si concentration using the zircon-baddeleyite silica buffer; (2) determination of Al hydrate speciation in H2O based on corundum solubility as a function of pH; (3) investigation of Al-Si complexing through measurement of corundum solubility changes with aqueous Si concentration; (4) characterization of fluid compositions in the haplogranite-H2O system; and (5) determination of rutile solubility in Na-Al-Si-H2O solutions.

流体对地球固体矿物的作用强烈影响着高压高温岩浆变质环境的地球化学演化。这些效应的证据可以在矿物中的流体包裹体、元素和同位素的变化以及深部环境样品中的矿脉和交代特征中找到，包括地幔捕虏体、钻石、弧岩浆和与俯冲有关的岩石，以及广泛的区域变质岩石。不幸的是，高压流体与岩石相互作用的建模很困难，因为深层致密流体的物理化学仍然高度不确定。该项目将支持一系列针对地球内部致密流体复杂假设的实验研究。 预计这项研究的结果将为致密水性流体的新化学提供新的见解，同时帮助支持本科生和研究生的指导，继续国际合作并将结果纳入加州大学洛杉矶分校的高级岩石学课程。 一个关键的问题是，在H2O丰富的高压流体中，有越来越多的证据表明形成聚合氧配位多核配合物。实例包括H6 Si 2 O 7二聚体、H5 AlSiO 6和钠长石样分子。这些物种知之甚少，主要是因为它们的浓度是可以忽略不计的，在大多数上地壳到中地壳热液设置，但是，在高P和T，聚合的物种可能更加丰富。多核配合物具有潜在的重要性，因为它们提高了所有元素的溶解度。特别地，它们提供配位环境，其允许溶解否则相对不溶于H2O的元素（例如，Al、Ti、Zr）。这个项目将支持一个实验调查的关键方面的假设复杂。水热活塞缸实验研究将针对硅，铝和碱之间的相互作用。这些组分在稠密流体中的浓度最高。高压（5-20 kbar）和高温（600-900°C）的实验工作将包括：（1）使用锆斜锆石二氧化硅缓冲剂在非常低的Si浓度下校准Si聚合;（2）基于作为pH的函数的水溶解度确定Al水合物在H2O中的形态;（3）Al-Si络合作用的研究：（4）单斜花岗岩-H_2O体系流体组成的表征;金红石在Na-Al-Si-H_2 O溶液中溶解度的测定。