Collaborative Research: Growth and Modification of the Tanzanian Lithosphere

9600030切斯利为了研究构造过程对岩石圈的影响，计划对坦桑尼亚克拉通内外的捕虏体进行详细检查。 岩石学，矿物化学，温压，主要和微量元素地球化学的调查，最重要的是，Os同位素组成的选择捕虏体将有助于表征坦桑尼亚岩石圈地幔的组成和垂直和横向范围的地幔。 全岩和铬铁矿矿物分离的Os同位素测量将限制这些岩石中熔体提取的最小年龄，因此岩石圈形成的时间。 此外，在橄榄岩中的Re-Os系统的硅酸盐和碳酸盐交代作用的影响将通过比较铬铁矿的结果（这应该产生初始的Os同位素组成）与全岩数据，这可能会记录增强的Re/Os比由于交代重新引入的Re进行评估。 这些岩石学和地球化学数据将有助于限制目前正在坦桑尼亚进行的地震和重力调查得出的岩石圈结构模型。 此外，将这些新的地球物理数据与本文概述的岩石学和地球化学研究相结合，将有助于描绘岩石圈地幔生长和改造所涉及的重要过程。

9600030 Chesley To investigate the influence of tectonic processes on cratonic lithosphere, a detailed examination of xenoliths both on and off the Tanzanian craton is planned. Investigation of the petrography, mineral chemistry, thermobarometry, major and trace element geochemistry and, most importantly, Os isotopic compositions on selected xenoliths will serve to characterize the composition of the Tanzanian lithospheric mantle and the vertical and lateral extent of cratonic mantle. Os isotopic measurements on whole rock and chromite mineral separates will constrain the minimum age of melt extraction in these rocks, hence timing of lithosphere formation. In addition, the effects of silicate and carbonatite metasomatism on the Re-Os systematics in peridotites will be evaluated by comparison of the chromite results (which should yield the initial Os isotopic composition) with whole rock data, which may record enhancement of the Re/Os ratio due to metasomatic re-introduction of Re. These petrologic and geochemical data will help constrain models of lithosphere structure derived from seismic and gravity surveys that are currently underway in Tanzania. Furthermore, integration of these new geophysical data with the petrological and geochemical studies outline here will allow delineation of the important processes involved in lithospheric mantle growth and modification.