Applications of Radiogenic Isotope Geochemistry to Studies of Igneous and Hydrothermal Processes

这是为了继续支持应用于热液作用、硅质岩浆系统和地幔地球化学的三个不同的放射成因同位素地球化学研究项目。1.对热液作用的研究将侧重于进一步发展确定流体运动的时间和规模的技术。这些技术可包括流体包裹体测年、硫化物测年、碳酸盐、磷酸盐和副矿物过度生长的测年，以及包括硫化物和萤石在内的各种热液相的稀土元素分析。研究将集中在美国和英国的密西西比河谷型(MVT)矿床和与岩体有关的矿化。2.硅质岩浆系统的研究将集中在使用Rb-Sr技术测定岩浆分异的年龄，通过从喷发年龄解析分异年龄来确定岩浆室的居住时间，以及研究硅质系统内的质量转移。美国和其他地方的许多系统都被选为研究对象。3.目前对喀麦隆线下地幔地球化学的研究将扩展到利用来自不同火山中心的熔岩和/或超镁铁捕虏体来研究微量元素作为岩石圈年龄函数的富集化过程。此外，使用40Ar-39Ar测定年轻MORB的年龄的技术正在开发中。

This is for continued support of three separate programs of research in radiogenic isotope geochemistry as applied to hydrothermal processes, silicic magma systems and mantle geochemistry. 1. The research in hydrothermal processes will emphasize the further development of techniques for determining the timing and scales of fluid movement. These techniques may include dating of fluid inclusions, dating of sulfides, dating of carbonates, phosphates and accessory mineral overgrowths, and REE analysis of a variety of hydrothermal phases including sulfides and fluorite. Research will be concentrated on MIssissippi Valley Type (MVT) deposits and pluton-related mineralization in the U.S. and U.K. 2. Studies of silicic magma systems will focus on dating of magma differentiation using Rb-Sr techniques, the longevity of magma chamber residence by resolving differentiation ages from eruption ages, and the study of mass transfer within silicic systems. A number of systems in the U.S. and elsewhere have been chosen for study. 3. Current research on the geochemistry of the mantle under the Cameroon line is to be expanded to study trace element enrichment processes as a function of lithospheric age using lavas and/or ultramafic xenoliths from various volcanic centers. In addition, techniques for dating young MORB using 40Ar-39Ar are being developed.