Hydrous Volatiles in Upper Mantle Minerals

挥发性组分的浓度和化学形态 在地球上地幔的地质作用中起着重要的作用 流程. 尽管它们很重要，但我们对其知之甚少。 各种地球化学储层的实际储存模式。 以前，红外光谱法用于确定 在辉石、石榴子石和橄榄石中，存在数量不等的OG 在碱性岩浆中以捕虏体的形式被带到地球表面。 初步迹象表明，这些化合物的OH浓度 矿物与它们的形成过程有关， 因此可以反映环境含水挥发物活性。 PI计划 为了确定重要地幔矿物的实际OH含量， 集中在南部非洲的次大陆地幔上 他们将使用各种方法校准IR方法。 这将使他们能够以绝对值量化 这些岩石中OH的矿物间分配， 提供D/H比率。 为了将观察到的OH含量 样品的挥发性活动的来源，他们将 测量合成生长的石榴石的OH含量， 控制压力、温度和挥发分的条件 活塞缸装置中的活动。 结果 希望能对理解 挥发分在上地幔中的分布以及它们如何 表现在熔体生成和俯冲过程中。

The concentration and chemical speciation of volatile components in the Earth's upper mantle play an important role in geologic processes. Despite their importance, we know little about their actual modes of storage in the various geochemical reservoirs. Previously, infrared spectroscopy was used to establise that variable quantities of OG occur in pyroxenes, garnet and olivine brought to the Earth's surface as xenoliths in alkalic magmas. Preliminary indications are that the OH concentration of these minerals is correlated with their environmmet of formation and may thus reflect ambient hydrous volatioe activity. The PIs plan to determine the actual OH content of important mantle minerals, concentrating on the subcontinental mantle of southern Africa. They will calibrate the IR method using a variety of methods. This will allow them to quantify in absolute terms the abundance of inter-mineral partitioning of OH in these rocks and perhaps to provide D/H ratios. In order to relate the observed OH contents of the samples to volatile activity of the sources, they will measure the OH contents of garnets grown synthetically under controlled conditions of pressure, temperature and volatile activity in a piston cylinder apparatus. The results are expected to have an important bearing on understanding how volatiles are distributed in the upper mantle as well as how they behave int eh processes of melt generation and subduction.