High-Pressure Study of Some Large Ions in Mantle Minerals

提出的研究是在高压和高温下对富钾和富氟矿物/相进行的实验研究，这些矿物/相可能在地球上地幔的可变含水环境中稳定。这项研究将从一对化合物开始，它们已被证明在这样的地球条件下是稳定的，但在其他方面还没有得到充分的了解；这些相包括钾长石（KAlSi3O8onH2O），钾长石的含水类似物，以及KMgF3，一种钙钛矿结构相，用作硅酸盐钙钛矿的类似物。该研究将1)确定这些相在矿物（流体）组合中压力和温度稳定性的上限范围，这些相适用于已知的地幔岩石和可能俯冲到地幔中的候选地壳岩石；2)表征这些相的组成、OH含量和结构状态；3)确定组成元素的相间分配。其他将被纳入实验的相包括氟长云母、辉生云母、氟钾辉长石和钾长石，本研究知识的结果也将提高对其稳定性条件的认识。实验将在walker型多砧仪上进行，产品将通过电子探针、扫描电镜和阴极发光成像、x射线衍射和FT-IR光谱相结合的方法进行分析。这项研究的结果将用于改进对地幔储层中钾和氟的储存的预测，而不是将这些元素划分为流体和熔体。

9903203Harlow The proposed research is an experimental investigation at high pressure and temperature of potassium- andfluorine-rich minerals/phases that may be stable in variably hydrous environments of Earth's upper mantle. The study will start with a pair of compounds that have been demonstrated to be stable at such Earth conditions but are otherwise inadequately understood; these phases include K-cymrite (KAlSi3O8onH2O), the hydrous analog of K-feldspar, and KMgF3, a perovskite-structure phase used as an analog for silicate perovskites. The research will 1) determine the upper range of pressure and temperature stability of these phases in mineral(fluid assemblages appropriate to known mantle rocks and to crustal rocks that are candidates for subduction into the mantle, 2) characterize the phases with respect to composition, OH content, and structural state, and 3) determine the inter-phase partitioning of constituent elements. Other phases to be included in experiments will be fluorphlogopite, phengitic mica, fluor-K-richterite, and K-feldspar, and results from this study knowledge will improve the knowledge of their stability conditions as well. Experiments will be carried out in Walker-type multianvil apparati, and products will be analyzed by a combination of electron microprobe, scanning-electron microscopic and cathodoluminescence imaging, x-ray diffraction, and FT-IR spectroscopy. Results from the research will be used to improve predictions of the storage of potassium and fluorine in reservoirs in the mantle as compared to the elements' partitioning into fluids and melts.