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

这是为了继续支持放射性成因同位素地球化学应用于热液过程、硅岩浆系统和地幔地球化学的三个独立研究项目。1. 热液过程的研究将强调进一步发展确定流体运动时间和规模的技术。这些技术包括流体包裹体测年、硫化物测年、碳酸盐测年、磷酸盐测年和伴生矿物测年，以及各种热液相（包括硫化物和萤石）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。硅质岩浆系统的研究将侧重于利用Rb-Sr技术确定岩浆分异的年代，通过从喷发年龄求解分异年龄来确定岩浆房居住的寿命，以及研究硅质系统内的传质。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大到利用来自不同火山中心的熔岩和/或超镁铁质捕虏体研究作为岩石圈年龄函数的微量元素富集过程。此外，利用40Ar-39Ar测定年轻MORB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.