Sulfur from the subducted slab dominates the sulfur budget of the mantle wedge under volcanic arcs
Sulfur from the subducted slab dominates the sulfur budget of the mantle wedge under volcanic arcs
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来自俯冲板片的硫主导了火山弧下地幔楔的硫收支
DOI：
10.1016/j.epsl.2022.117948
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发表时间：
2023
影响因子：
5.3
通讯作者：
Aiuppa, A.
中科院分区：
文献类型：
--
作者：
Taracsák, Z.;Mather, T.A.;Ding, S.;Plank, T.;Brounce, M.;Pyle, D.M.;Aiuppa, A.
硫在地球系统中起着至关重要的作用，影响着生物、气候、成矿和氧化还原过程。俯冲带在全球硫循环中起着关键作用。由于氧化地幔来源或岩浆分异，弧形岩浆的硫含量比大洋中脊玄武岩(MORBs)更高，氧化程度更高。熔体氧化态和硫含量可能相互关联，因为硫在板片-地幔相互作用中是一种潜在的氧化剂。在这里，我们使用熔体包裹体(MI)来确定来自中美洲火山弧(CAVA)沿线三个火山中心的原始弧岩浆的硫同位素组成(δ34S)：富戈(危地马拉)、塞罗尼格罗(尼加拉瓜)和图里亚尔巴(哥斯达黎加)。这三个地点采样了全球弧岩浆微量元素的大部分变化：BA/La比值从22(图里亚尔巴)到118(塞罗内格罗)不等。熔化δ34S的值介于-0.5‰和+4.9‰之间。均质和自然淬火的MIS的硫含量和δ34S值重叠，表明后包埋过程不影响所研究的MIS的硫含量和硫同位素比值。脱气导致有限的硫同位素分馏；计算的气熔同位素分馏系数在0.998-1.001之间。我们的模型计算预测，沿洞穴的大多数火山气体的δ34S介于-1‰和+6‰之间，随着脱气过程的进行，34S变得丰富。我们估计Fuego、Cerro Nero和Turrialba的初始熔体δ34S值分别为+0.70±1.4‰、+2.2±1.0‰和+1.6±0.8‰(两个标准误差)。所有这些值都高于MORBs(-0.9MORb)。将富含34S的氧化板条物质添加到地幔楔体中，可以解释上升的弧原生熔体δ34S和在全球观察到的弧岩浆的氧化条件。根据物质平衡，洞穴下方的地幔楔体中存在δ34S介于+2‰~+5‰之间的板片组分，使局部弧地幔S的含量分别增加到360±30ppm和462±11ppm。模拟表明，地幔楔体中40-70%的硫来自板片来源的组分。板片俯冲作用有望在其地质历史上对地球硫循环和地幔氧化状态的演化产生重大控制作用。
Sulfur is of a crucial importance in the Earth system influencing biological, climate, ore-forming, and redox processes. Subduction zones play a key role in the global sulfur cycle. Arc magmas have higher sulfur contents and are more oxidised than mid-ocean ridge basalts (MORBs) due to either an oxidised mantle source or magma differentiation. Melt oxidation state and sulfur content may interrelate, as sulfur is a potential oxidising agent during slab-mantle interaction. Here, we use melt inclusions (MIs) to determine the sulfur isotopic composition (δ34S) of primary arc magmas from three volcanic centres along the Central American Volcanic Arc (CAVA): Fuego (Guatemala), Cerro Negro (Nicaragua), and Turrialba (Costa Rica). These three locations sample much of the global arc magma trace element variability: Ba/La ratios range from 22 (Turrialba) to 118 (Cerro Negro). Meltδ34S values are between -0.5‰ and +4.9‰. Sulfur contents andδ34S values of homogenised and naturally quenched MIs overlap, indicating post-entrapment processes do not affect sulfur contents and sulfur isotope ratios in the studied MIs. Degassing causes limited sulfur isotope fractionation; calculated gas-melt isotope fractionation factors are between 0.998-1.001. Our model calculations predict that most volcanic gases along the CAVA haveδ34S between -1‰ and +6‰, becoming enriched in34S as degassing progresses. We estimate initial meltδ34S values for Fuego, Cerro Negro, and Turrialba to be +0.7±1.4‰, +2.2±1.0‰, and +1.6±0.8‰ (two standard errors), respectively. All these values are elevated compared to MORBs (-0.9‰). Addition of oxidised slab material enriched in34S to the mantle wedge can explain elevated arc primary meltδ34S and the oxidising conditions observed in arc magmas globally. Based on mass balance, a slab component withδ34S between +2‰ to +5‰ is present in the mantle wedge under the CAVA, elevating local arc mantle S contents to 360±30 ppm at Fuego, 462±11 ppm at Cerro Negro. Modelling suggests that 40-70% of sulfur in the mantle wedge originates from a slab-derived component. Slab subduction is expected to have major control on the evolution of Earth's sulfur cycle and mantle oxidation state over its geological history.