A Laser Ablation ICPMS-Based Study of Postcumulus Processes in Hydrous and Dry Mafic Cumulates

智力优势：在分离结晶（堆积）过程中由矿物堆积形成的火成岩分布广泛，拥有经济矿产资源，并提供岩浆房物理和化学过程的记录。积云记录了积云（那些建立晶体堆）和积云后（那些修改晶体堆）过程的化学和结构证据。拟议的研究将使用激光烧蚀ICP-MS（LA-ICPMS）原位微量元素分析，以记录后积云过程的重要性和矿物磷灰石的分析，以了解这些系统中挥发性成分的演变。这项研究将对玄武岩液体形成的堆积物进行研究，并将蒙大拿州斯蒂尔沃特复杂的岩石与瑞典里曼和埃里克斯贝格辉长岩中的岩石进行对比，前者是从相对干燥的液体中结晶出来的。对斯蒂尔沃特的单斜辉石和埃里克斯贝格的角闪石的硅晶的初步研究表明，微量元素的变化多达三个数量级。通过绘制造孔晶的成分变化图，可以记录填隙液的成分演化和空间分布。间隙磷灰石的卤素含量对于理解堆积岩中挥发分的后期演化和出溶具有重要意义。LA-ICPMS分析磷灰石将提供一种手段，这些系统的微量元素的演变，他们的volatile evolution.Broader影响：这项工作将提供一个基本的理解，在部分熔融的岩石中运作的过程。这些过程的知识对于了解含有贵金属（铂和钯）和贱金属（特别是铬和镍）的重要矿石资源的成因至关重要。理解这些过程也是解释这些岩石及其组成矿物的化学性质的核心。考虑到几乎所有来自月球和火星的样本都与待研究的岩石相似，这项工作也可能会促进我们对这些天体的理解。这项工作也将有助于建立一个经验性的理解，如何微量元素之间的结晶岩浆和生长晶体在一个延长的生长历史的单晶分配。

Intellectual Merit: Igneous rocks formed by the accumulation of minerals during fractional crystallization (cumulates) are widely distributed, host economic mineral resources, and provide a record of the physical and chemical processes in magma chambers. Cumulates record chemical and textural evidence of both cumulus (those that build the crystal pile) and postcumulus (those that modify the crystal pile) processes. The proposed study will use in situ trace-element analyses by laser ablation ICP-MS (LA-ICPMS) to document the importance of postcumulus processes and analyses of the mineral apatite to understand the evolution of volatile components in these systems. The research will be conducted on cumulates formed from basaltic liquids and will contrast rocks from the Stillwater complex, Montana that crystallized from a relatively dry liquid with those from the Rymmen and Eriksberg gabbros, Sweden that crystallized from a wet liquid. Preliminary studies of oikocrysts of clinopyroxene from the Stillwater and amphibole from the Eriksberg reveal as much as three orders of magnitude variation in trace elements. By mapping the compositional variation in oikocrysts the compositional evolution and spatial distribution of the interstitial liquid can be documented. The halogen content of interstitial apatite has proven to be valuable for understanding the late-stage evolution and exsolution of volatiles in cumulates. LA-ICPMS analyses of apatite will provide a means of relating the trace-element evolution of these systems to their volatile evolution.Broader Impacts: This work will provide a fundamental understanding of the processes that operate in a partially molten rock. Knowledge of these processes is essential for understanding the genesis of important ore resources that host precious (platinum and palladium) and base metal (especially chromium and nickel). Understanding these processes is also central to interpreting the chemistry of these rocks and their constituent minerals. Given that nearly all of our samples from the Moon and Mars are similar to the rocks to be studied, the work is likely to advance our understanding of these bodies as well. The work will also help to establish an empirical understanding of how trace elements are partitioned between crystallizing magmas and growing crystals over an extended growth history for a single crystal.