Metamorphic Evolution of Mid-To-Deep Levels of the Continental Crust in Northern Idaho

该提案要求继续支持一项研究计划，该计划致力于了解爱达荷州北部暴露的北美科迪勒拉的热和构造历史。P.I.和俄勒冈大学的研究生先前的研究表明，在爱达荷州基岩北部的泥质和钙质岩石中记录了三次主要的变质事件。这些事件的构造、矿物学和化学证据为大陆地壳的演化提供了重要的资料。本文的研究将有助于提高我们对变质史的认识，以及对变质作用、变形作用和深部作用之间关系的认识。地热测量和地球气压测量将采用一种新的方法，同时解决矿物共生所隐含的所有平衡。研究带状矿物，特别是石榴石，以估计进变质作用的P-T时间路径和与隆升有关的减压路径。这种计算将用一种计算平衡矿物组合和成分的新方法进行测试，该方法使用自由能量最小化算法。流体-岩石的相互作用也将通过层间钙质和泥质成分的仔细研究来检验。本文将根据有关H2O-CO2-NaCl体系中矿物和含水物质热力学性质的新数据，研究与高盐流体相平衡的钙质岩石的相平衡关系。建立了一种描述矿物方石与富盐流体组成关系的新模型，并将其应用于自然地质体。将进行稳定同位素分析，以便更充分地描述与各种岩石组成反应的流体的性质、来源和数量。同位素年龄测定将试图了解多重变质作用的时间，以及变质作用与侵入岩的关系。

This proposal requests continued support for a research program devoted to understanding the thermal and tectonic history of the North American Cordillera as exposed in northern Idaho. Previous studies by the P.I. and graduate students at the University of Oregon, have demonstrated that three major metamorphic events are recorded in pelitic and calcareous rocks north of the Idaho Batholith. Structural, mineralogical and chemical evidence for these events provide important data hearing on the evolution of the continental crust. The propose research will be directed toward improving our understanding of the metamorphic history, and the relationships between metamorphism, deformation and plutonism. Geothermometry and geobarometry will be carried out using a new approach which solves all equilibria implied by a mineral paragenesis simultaneously. Zoned minerals, especially garnet, will be studied in order to estimate the P-T time path of prograde metamorphism, and the decompression path associated with uplift. Such calculations will be tested with a new method of calculating equilibrium mineral assemblages and compositions with a free energy minimization algorithm. Fluid- rock interactions will also be examined by careful studies of interlayered calcareous and pelitic compositions. The phase equilibrium relations in calcareous rocks, which equilibrated with very saline fluids, will be examined in the light of new data bearing on the thermodynamic properties of minerals and aqueous species in the system H2O-CO2-NaCl. A new model describing the compositional relations among the mineral scapolite and NaCl-rich fluid will be developed and applied to the natural occurrences. Stable isotopic analyses will be undertaken in order to more fully characterize the nature, source and amounts of fluid reacting with a variety of rock compositions. Isotopic age determinations will be made in an attempt to learn the timing of multiple metamorphism, and the relationship of metamorphism of intrusion of the Idaho Batholith.