Thermodynamics of Aluminous Amphiboles

9706326埃文斯这个项目将把无铝“四边形”角闪石的结晶学和热力学性质的PI工作扩展到含铝正交角闪石系列和单斜角闪石系列，这两个系列都广泛存在于结晶岩中。在700o-1000oC和高压下平衡前后，将对包含一定范围的镁/铁比和铝含量的天然样品进行X射线单晶结构修正。位置散射和键长数据将与组成数据相结合，以提供作为温度函数的八面体和四面体位置有序性的描述。这些复杂的角闪石的吉布斯能量被写成显式地包括测量的构型熵，以及端元、倒易和倒易有序项。实验、热化学和自然相平衡数据提供了额外的限制。这些数据可以计算涉及角闪石和其他矿物的岩浆和亚固相线系统的相图，以前已经为这些矿物建立了一致的热力学模型。

9706326 Evans This project will extend the PIs work on the crystallographic and thermodynamic properties of the aluminum-free "quadrilateral" amphiboles into the Al-bearing orthorhombic gedrite series and the monoclinic hornblende series, both of which occur widely in crystalline rocks. X-ray single crystal structure refinements will be done on suites of natural samples encompassing a range of Mg/Fe ratios and Al-contents, prior to and after equilibration at 700o-1000oC and high pressure. Site scattering and bond length data will be incorporated with compositional data to provide a description of octahedral and tetrahedral site order-disorder as a function of temperature. The Gibbs energy of these complex amphiboles is written to explicitly include the measured configurational entropy, as well as end-member, reciprocal and reciprocal-ordering terms. Experimental, thermochemical and natural phase equilibrium data provide additional constraints. These data allow calculation of phase diagrams for magmatic and subsolidus systems involving amphiboles and other minerals for which there are previously developed consistent thermodynamic models.