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

本文研究了近期富so2火山喷发产物（El Chichon, Nevado del Ruiz, Mt. Pinatubo）中硫化物和硬石膏晶体的微观硫同位素变化。硬石膏是许多富SO2硅质岩浆喷发产物中的一个重要阶段，但硬石膏的幼晶与异晶性质以及熔融释放SO2的机制仍然存在疑问。这些问题的答案需要火山喷发产物中硬石膏和硫化物晶体的硫同位素组成数据。虾是应用于这些问题的理想工具。初步的SHRIMP结果排除了在单阶段岩浆结晶过程中形成所有硬石膏的可能性。SHRIMP将用于评估在这些喷发中硬石膏是否通常是混合起源的。这项研究将有助于限制喷发前岩浆的化学性质和脱气行为，以及确定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偶然重新激活是否是火山喷发的关键组成部分。

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.