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Chalcophile elements track the fate of sulfur at Kīlauea Volcano, Hawai’i
Geochimica et Cosmochimica Acta ( IF 5 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.gca.2020.05.018
Penny E. Wieser , Frances Jenner , Marie Edmonds , John Maclennan , Barbara E. Kunz

Abstract Chalcophile element concentrations in melt inclusions and matrix glasses may be used to investigate low pressure degassing processes, as well as sulfide saturation during crustal fractionation, and mantle melting. Erupted products from Kīlauea Volcano, Hawaiʻi, record three stages of sulfide saturation (in the mantle, crust, and within lava lakes), separated by episodes of sulfide resorption (i.e., sulfide undersaturation) during ascent through the thick Hawaiian lithosphere, and during syn-eruptive degassing. The presence of residual sulfides in the mantle source throughout the melting interval accounts for the high S concentrations of Kīlauean primary melts (1387–1600 ppm). Residual sulfides retain chalcophile elements during melting, decoupling the variability of these elements in high MgO melts from that of lithophile elements. Decompression associated with magma ascent through the thick Hawaiian lithosphere drives an increase in the sulfide concentration at sulfide saturation (SCSS2−), resulting in shallow storage reservoirs (∼1–5 km depth) being supplied with sulfide-undersaturated melts. A drop in temperature, coupled with major element changes during the fractionation of olivine, causes the SCSS2− to decrease. Combined with an increase in melt S contents during fractionation, this initiates a second stage of sulfide saturation at relatively high MgO contents (∼12 wt%). Syn-eruptive degassing of S drives the resorption of sulfides in contact with the carrier liquid. The covariance structure of Cu, MgO and Ni contents in melt inclusions and matrix glasses indicates that the dissolution of sulfides effectively liberates sulfide-hosted Cu and Ni back into the melt, rather than the vapour phase. The contrasting behaviour of Cu, Ni, Se and S during sulfide resorption indicates that the chalcophile element signature of the Kīlauean plume is largely controlled by silicate melt-vapour partitioning, rather than sulfide-vapour partitioning. The participation of dense sulfide liquids in shallow degassing processes may result from their direct attachment to buoyant vapour bubbles, or olivine crystals which were remobilized prior to eruption. Sulfide resorption obscures the textural and chemical record of sulfide saturation in matrix glasses, but not in melt inclusions, which are isolated from this late-stage release of chalcophile elements. The partitioning of S between the dissolving sulfide, melt and the vapour phase accounts for approximately 20% of the total S release into the atmosphere.

中文翻译:

硫磺元素在夏威夷基拉韦厄火山追踪硫磺的命运

摘要 熔体包裹体和基质玻璃中的亲硫元素浓度可用于研究低压脱气过程,以及地壳分馏和地幔熔融过程中的硫化物饱和度。夏威夷基拉韦厄火山的喷发产物记录了硫化物饱和的三个阶段(在地幔、地壳和熔岩湖中),在上升穿过厚厚的夏威夷岩石圈期间和同步期间被硫化物吸收(即硫化物不饱和)事件分开- 喷发脱气。在整个熔化区间地幔源中残留硫化物的存在是基拉韦厄初级熔体的高 S 浓度(1387-1600 ppm)的原因。残余硫化物在熔化过程中保留亲硫元素,将这些元素在高 MgO 熔体中的可变性与亲石元素的可变性分离。与岩浆上升穿过厚厚的夏威夷岩石圈相关的减压驱动硫化物饱和度 (SCSS2-) 处的硫化物浓度增加,导致浅层储层(约 1-5 公里深)供应硫化物欠饱和熔体。温度下降,加上橄榄石分馏过程中主要元素的变化,导致 SCSS2- 降低。结合分馏过程中熔体 S 含量的增加,这在相对较高的 MgO 含量(~12 wt%)下引发了硫化物饱和的第二阶段。S 的协同喷发脱气驱动与载液接触的硫化物的再吸收。熔体夹杂物和基体玻璃中 Cu、MgO 和 Ni 含量的协方差结构表明,硫化物的溶解有效地将硫化物主体的 Cu 和 Ni 释放回熔体中,而不是气相。Cu、Ni、Se 和 S 在硫化物再吸收过程中的对比行为表明,基拉韦厄羽流的亲硫元素特征主要受硅酸盐熔体-蒸汽分配而不是硫化物-蒸汽分配控制。稠密的硫化物液体参与浅层脱气过程可能是由于它们直接附着在浮力蒸气泡或火山爆发前重新移动的橄榄石晶体上。硫化物再吸收掩盖了基质玻璃中硫化物饱和的结构和化学记录,但在熔体夹杂物中没有,这是与这种后期亲硫元素释放分离的。S 在溶解硫化物、熔体和气相之间的分配约占释放到大气中的 S 总量的 20%。Cu、Ni、Se 和 S 在硫化物再吸收过程中的对比行为表明,基拉韦厄羽流的亲硫元素特征主要受硅酸盐熔体-蒸汽分配而不是硫化物-蒸汽分配控制。稠密的硫化物液体参与浅层脱气过程可能是由于它们直接附着在浮力蒸气泡或火山爆发前重新移动的橄榄石晶体上。硫化物再吸收掩盖了基质玻璃中硫化物饱和的结构和化学记录,但在熔体夹杂物中没有,这是与这种后期亲硫元素释放分离的。S 在溶解硫化物、熔体和气相之间的分配约占释放到大气中的 S 总量的 20%。Cu、Ni、Se 和 S 在硫化物再吸收过程中的对比行为表明,基拉韦厄羽流的亲硫元素特征主要受硅酸盐熔体-蒸汽分配而不是硫化物-蒸汽分配控制。稠密的硫化物液体参与浅层脱气过程可能是由于它们直接附着在浮力蒸气泡或火山爆发前重新移动的橄榄石晶体上。硫化物再吸收掩盖了基质玻璃中硫化物饱和的结构和化学记录,但在熔体夹杂物中没有,这是与这种后期亲硫元素释放分离的。S 在溶解硫化物、熔体和气相之间的分配约占释放到大气中的 S 总量的 20%。硫化物吸收过程中的 Se 和 S 表明基拉韦厄羽流的亲硫元素特征主要受硅酸盐熔体-蒸汽分配控制,而不是硫化物-蒸汽分配控制。稠密的硫化物液体参与浅层脱气过程可能是由于它们直接附着在浮力蒸气泡或火山爆发前重新移动的橄榄石晶体上。硫化物再吸收掩盖了基质玻璃中硫化物饱和的结构和化学记录,但在熔体夹杂物中没有,这是与这种后期亲硫元素释放分离的。S 在溶解硫化物、熔体和气相之间的分配约占释放到大气中的 S 总量的 20%。硫化物吸收过程中的 Se 和 S 表明基拉韦厄羽流的亲硫元素特征主要受硅酸盐熔体-蒸汽分配控制,而不是硫化物-蒸汽分配控制。稠密的硫化物液体参与浅层脱气过程可能是由于它们直接附着在浮力蒸气泡或火山爆发前重新移动的橄榄石晶体上。硫化物再吸收掩盖了基质玻璃中硫化物饱和的结构和化学记录,但在熔体夹杂物中没有,这是与这种后期亲硫元素释放分离的。S 在溶解硫化物、熔体和气相之间的分配约占释放到大气中的 S 总量的 20%。
更新日期:2020-08-01
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