Origin of Anomalous Sulfur in Volcanic Eruptions: A Study Utilizing the SHRIMP Ion Microprobe

本文研究了近期富含SO2的火山喷发产物中硫化物和硬石膏晶体的微观硫同位素变异性。Pinatubo)。硬石膏现在被认为是许多富含SO2的硅质岩浆喷发产物中的重要相，但关于硬石膏的幼晶性质和包裹体性质以及SO2从熔体中释放的机制仍存在疑问。这些问题的答案需要关于喷发产物中硬石膏和硫化物晶体的硫同位素组成的数据。对虾是解决这些问题的理想工具。SHRIMP初步结果排除了在单阶段岩浆结晶过程中形成全部硬石膏的可能性。虾将被用来评估硬石膏在这些喷发中是否通常是混合来源的。这项研究将有助于限制S火山喷发前的岩浆化学和排气行为，并确定先前存在的外来硫的偶然再动员是否是过去和现在火山喷发向大气中注入大量改变气候的二氧化硫的关键成分。

A study is proposed of the microscopic sulfur isotopic variability of sulfide and anhydrite crystals in the eruption products of recent SO2-rich volcanic eruptions (El Chichon, Nevado del Ruiz, Mt. Pinatubo). Anhydrite is now recognized as an important phase in the eruption products of many SO2-rich silicic magmas, but questions still remain about the juvenile vs. xenocrystic nature of the anhydrite and the mechanism of SO2 release from the melt. The answers to these questions require data on the sulfur isotopic composition of anhydrite and sulfide crystals in the eruption products. The SHRIMP is an ideal tool to apply to these problems. Preliminary SHRIMP results rule out formation of all anhydrite in a single-stage magmatic crystallization process. The SHRIMP will be used to assess whether anhydrite is generally of mixed origins in these eruptions. The study will help constrain pre-eruptive magma S chemistry and degassing behavior, as well as resolve whether fortuitous remobilization of pre-existing extraneous sulfur is a critical component of past and present volcanic eruptions which injected significant amounts of climate-altering SO2 into the atmosphere.