Collaborative Research: Content and Behavior of Sulfur in Silicic Magma and Links to Generation of Sulfur-rich Ore-forming Fluids of Porphyry Cu-Mo-Au Deposits

这个项目将确定富含硅的岩浆是如何在火山爆发或产生矿床的热液中释放大量硫的。这些岩浆应具有较低的含硫能力。我们将测试这些假设，即它们将硫储存在硬石膏（硫酸钙）斑晶和蒸汽泡中，或者仅仅将硫传输在来自更深的、缺乏硅的岩浆的水泡中。将研究几个以火山为主到以岩体为主的古代系统的岩浆和矿床，包括：科罗拉多州的圣路易斯卡尔德拉；秘鲁的Yanacocha火山和相关的金矿；内华达州的耶林顿岩基及其斑岩铜矿床。水、硫、氯和磷灰石（磷酸钙）和玻璃包裹体（“冷冻”熔体）等矿物的微量金属含量将通过二次离子质谱法和激光烧蚀-电感耦合等离子体质谱法等方法测定。硫和氢的同位素比值也将被测量。这些数据将有助于估计硅酸盐熔体中挥发性和微量金属的含量，并显示这些化学成分是如何获得和损失的。该项目将招收最多四名研究生进行论文研究，最多四名本科生进行实地和实验室研究。这项研究的社会意义包括了解大型硅质岩浆如何对全球气候影响产生平流层硫，以及了解一些铜和其他矿产资源是如何生产的。

This project will determine how silica-rich magmas release massive amounts of sulfur during volcanic eruptions or in hydrothermal fluids that produce ore deposits. These magmas should have low sulfur-carrying capacity. We will test the hypotheses that they store sulfur in anhydrite (calcium-sulfate) phenocrysts and vapor bubbles or merely transmit sulfur in aqueous bubbles derived from deeper, silica-poor magmas. Magmas and ore deposits from several ancient volcanic-dominated to plutonic-dominated systems will be studied including: San Luis Caldera, Colorado; Yanacocha Volcanics, Peru, and related gold deposits; and the Yerington batholith, Nevada, and its porphyry copper deposits. The water, sulfur, chlorine and trace-metal contents of minerals such as apatite (calcium-phosphate) and glass inclusions ("frozen" melt) will be determined by secondary ion mass spectrometry and laser ablation-inductively coupled plasma mass spectrometry and other methods. Isotopic ratios of sulfur and hydrogen will also be measured. These data will allow estimation of the volatile and trace metal contents of silicate melts, and show how these chemical components were acquired and lost. The project will engage up to four graduate students in thesis studies and up to four undergraduate students in field and laboratory research. The societal relevance of the research includes understanding how large silicic magmas contribute stratospheric sulfur with global climatic impact and understanding how some copper and other mineral resources are produced.