Experimental Investigation of H2O, Cl, CO2 and SO2 Solubilities in Rhyolite and Andesite Melts at Shallow Crustal Conditions

摘要为了更好地了解岩浆脱气如何影响火山爆发和地球上许多金属矿床的形成，将通过实验确定硅酸盐岩浆中挥发物水、二氧化碳、硫和氯的溶解度。像这样的挥发物对地幔、地壳、大气和海洋储层的演化至关重要；储层内部和储层之间通过流体和岩浆的化学流动性；岩浆脱气过程与火山喷发和矿床的生成有关。岩浆输送挥发物的能力是硅酸盐熔体中挥发物溶解度的直接函数，一旦这些挥发物溶解度超过了一个或多个流体相，就会从熔体中析出。目前对岩浆流体析出作用的了解仅限于含有一种或两种挥发物的系统，因此提出的研究将系统地研究：(1)流纹岩和安山岩熔体中（水、二氧化碳和氯）和（水、二氧化硫和氯）的溶解度，以及(2)氯如何分布在这些地质上重要的熔体和含有这些挥发物的流体之间。氯在硅酸盐熔体和流体之间的分布程度特别令人感兴趣，因为这种挥发物是岩浆的常见成分，对矿化过程很重要，它的行为对岩浆脱气过程提供了关键的限制，因为大气中的氯会破坏臭氧的稳定并影响其他大气过程。溶解度数据将通过在压力和温度条件下进行的热液实验产生，这些实验条件代表了地壳浅层岩浆的脱气过程，实验结果将通过成熟的方法进行分析。拟议调查的智力价值来自与以下相关的实验数据：(1)对硅酸盐熔体挥发溶解度机理的解释；(2)计算挥发溶解度并预测岩浆脱气过程的模型；(3)基于硅酸盐熔体包裹体（硅酸盐玻璃的微观样品，代表被困硅酸盐熔体）研究的岩浆脱气行为的地球化学研究。这些数据也将对解决氯对地球大气和气候影响的模型有用。拟议的调查还具有更广泛的意义，因为这些数据、它们与科学的相关性以及它们与社会的相关性将通过美国自然历史博物馆的展览和公共项目共享。科学研究的成果和重要性通过标本、电子媒体和其他媒体在博物馆的常设展厅向公众展示；以地质过程为重点的系列讲座；并通过与参加nsf支持的本科生研究经历项目的暑期实习生的互动。

AbstractTo better understand how magmatic degassing influences explosive volcanic eruptions and the generation of many of Earth's metallic mineral deposits, the solubilities of the volatiles water, carbon dioxide, sulfur, and chlorine in silicate magmas will be determined experimentally. Volatiles like these are fundamentally important to the evolution of the Earth's mantle, crust, atmosphere, and ocean reservoirs; chemical mobility, via fluids and magmas, within and between these reservoirs; and magmatic degassing processes related to volcanic eruption and the generation of mineral deposits. The capacity of magmas to transport volatiles is a direct function of volatile solubilities in silicate melts, and once these volatile solubilities are exceeded one or more fluid phases exsolve from melts. Current understanding of magmatic fluid exsolution is limited to systems containing just one or two of these volatiles, thus the proposed study will investigate systematically: (1) the solubilities of (water, carbon dioxide, and chlorine) and (water, sulfur dioxide, and chlorine) in rhyolite and andesite melts, and (2) how chlorine is distributed between these geologically important melts and fluids containing these volatiles. The extent to which chlorine is distributed between silicate melt and fluids is of particular interest, because this volatile is a common component of magmas, it is important to mineralizing processes, its behavior provides key constraints on processes of magmatic degassing, and because chlorine in the atmosphere destabilizes ozone and affects other atmospheric processes.The solubility data will be generated through hydrothermal experiments conducted at pressure and temperature conditions that are representative of magmas that degas in the shallow crust, and the products of the experiments will be analyzed by well-established methodologies. The intellectual merit of the proposed investigation springs from the experimental data which are relevant to: (1) the interpretation of volatile solubility mechanisms in silicate melts, (2) models that allow computation of volatile solubilities and predict processes of magmatic degassing, and (3) ongoing geochemical investigations of magmatic degassing behavior based on studies of silicate melt inclusions (which are microscopic samples of silicate glass that are representative of trapped silicate melt). These data will also be useful for models addressing the impact of chlorine on Earth's atmosphere and climate.The proposed investigation also has broader significance because the data, their relevance to science, and their relevance to society will be shared through exhibits and public programs at the American Museum of Natural History. The results and importance of scientific research are presented to the general public through specimens, electronic media, and other media in the museum's permanent exhibition halls; lecture series focused on geologic processes; and through interactions with summer interns participating in an NSF-supported Research Experiences for Undergraduate Students program.