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

该项目将确定富含二氧化硅的岩浆如何在火山爆发或产生矿床的热液流体中释放大量硫。这些岩浆应该具有低的硫承载能力。我们将测试的假设，他们存储在硬石膏（硫酸钙）斑晶和蒸汽泡硫或仅仅传输来自更深的，二氧化硅贫岩浆的水泡硫。将研究几个古代火山为主的系统到深成岩为主的系统的岩浆和矿床，包括：科罗拉多的圣路易斯火山口;秘鲁的亚纳科查火山和相关的金矿;以及内华达州的耶灵顿岩基及其斑岩铜矿。磷灰石（磷酸钙）和玻璃夹杂物（“冻结”熔体）等矿物的水、硫、氯和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及其他方法确定。还将测量硫和氢的同位素比率。这些数据将允许估计硅酸盐熔体的挥发性和微量金属含量，并显示这些化学成分是如何获得和丢失的。 该项目将吸引多达四名研究生进行论文研究，并吸引多达四名本科生进行实地和实验室研究。该研究的社会意义包括了解大型岩浆如何贡献平流层硫对全球气候的影响，以及了解一些铜和其他矿产资源是如何产生的。

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.