Assimilation of the Mantle and Altered Crust by Oceanic Magmas

玄武岩岩浆对火成岩、变质岩和沉积岩的同化作用是火山活动不可避免的结果，而洋岛和不断扩张的大洋裂谷中捕虏体(外来岩石碎片)的存在证明了洋火山作用期间确实发生了同化作用。对同化过程知之甚少，熔融、解体或扩散进入或流出被同化的物质是主导过程，这将取决于被同化的物质的类型、岩浆与该物质相互作用的动力学以及岩浆的温度和成分。这里支持的实验将研究第一个问题：当与熔融的玄武岩接触时，各种地幔矿物和蚀变矿物的熔融、解体或扩散。实验结果将用电子探针和同位素稀释质谱仪进行化学分析。初步实验产生了意想不到的有趣结果，进一步的工作将确定模拟海山、洋岛和不断扩大的裂谷玄武岩的主要元素和微量元素化学的重要性。该项目将得到120,470美元的支持，为期2年。

Assimilation of igneous, metamorphic, and sedimentary rocks by basalt magma is an unavoidable consequence of volcanic activity, and the presence of xenoliths (foreign rock fragments) in ocean island and propagating ocean rifts is evidence that assimilation does occur during oceanic volcanism. The process of assimilation is poorly understood and whether melting, disintegration, or diffusion into or out of the material being assimilated is the dominant process will depend on the type of material being assimilated, on the kinetics of magma interaction with that material, and on the temperature and composition of the magma. The experiments supported here will investigate the first of these problems; the melting, disintegration, or diffusion from various mantle minerals and alteration minerals, when placed in contact with molten basalt. The products of the experiments will be chemically analyzed by electron microprobe and isotope dilution mass spectrometry. Preliminary experiments have produced unexpected and interesting results, and further work will determine the importance of assimulation to the major and trace element chemistry of seamount, ocean island, and propagating rift basalts. This project will be supported at $120,470 for 2 years.