Stable Isotopic Study of Sulfur Degassing During the Climactic and Pre-Climactic Eruptions of Mt. Mazama, Crater Lake, Oregon

9814559曼德维尔在火山气体中，二氧化硫（SO2）对气候影响的潜力最大，因为它在爆发时直接注入平流层，缓慢转化为亚微米H2SO 4气溶胶，在平流层停留时间长。 H2SO 4气溶胶负荷导致的气候6845+/- 50年。B. P.火山喷发俄勒冈州火山口湖的马扎马估计为2 x 10^14克，比最近火山爆发时释放的大约多一个数量级。Pinatubo，但以前没有研究过Mazama岩浆中硫的来源。硫同位素数据将用于根据地球硫储层的特征同位素特征（即，地幔、地壳、流星/热液）和可能由于广泛脱气而发生的同位素变化的量化。本研究的目的包括：1）验证山核桃d34 S值升高的假设。马扎马火山灰是开放系统脱气的结果; 2）定量的硫，从体积的喷发岩浆脱气的量; 3）在岩浆温度下的硫同位素分馏因子的实验测定;和4）证明硫同位素数据的适用性，以表征古火山灰脱气风格。 最重要的是，在这项研究中获得的稳定同位素数据将描绘过去爆发性火山活动释放的SO2的可能来源，并将有助于我们了解地幔，地壳，水圈和大气之间的硫循环。

9814559MandevilleOf the volcanic gases, sulfur dioxide (SO2) has the greatest potential for climatic impact due to its direct injection to the stratosphere during explosive eruptions, its slow conversion to submicron H2SO4 aerosol and long residence time in the stratosphere. H2SO4 aerosol loading resulting from the climactic 6845+/- 50 yr. B.P. eruption of Mt. Mazama, Crater Lake, Oregon is estimated at 2 x 10^14 grams, approximately one order of magnitude more than was released during the recent eruption of Mt. Pinatubo, yet there have been no previous studies of the source of sulfur in Mazama magmas. Sulfur isotopic data will be used to delineate the source(s) of dissolved sulfur in Mazama magmas based on the characteristic isotopic signatures of the Earth's sulfur reservoirs (i.e., mantle, crustal, meteoric/hydrothermal) and quantification of isotopic shifts which may have occurred due to extensive degassing. Objectives of the proposed research include: 1) testing the hypothesis that elevated d34S values in Mt. Mazama tephra are the result of open-system degassing; 2) quantifying the amount of sulfur that degassed from the volume of erupted magma; 3) experimental determination of sulfur isotopic fractionation factors at magmatic temperatures; and 4) demonstrating the applicability of sulfur isotopic data to characterize degassing style in ancient tephra. Most importantly, stable isotopic data obtained in this study will delineate the likely source(s) of SO2 released by past explosive volcanism and will contribute towards our understanding of sulfur recycling between the mantle, crust, hydrosphere and atmosphere.