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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Sulfur isotope systematics of basaltic lavas from Indonesia: implications for the sulfur cycle in subduction zones
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Sulfur isotope systematics of basaltic lavas from Indonesia: implications for the sulfur cycle in subduction zones

机译：印度尼西亚玄武岩熔岩的硫同位素系统：对俯冲带硫循环的影响

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摘要

We report sulfur isotope compositions of basaltic and basaltic andesite lavas from selected volcanoes in the Indonesian arc system covering the spectrum from low-K tholeiitic to high-K calc-alkaline compositions. The results of 25 samples from seven volcanoes, which are associated with different subduction regimes, show a range in δ~(34)S values of +2.0-+7.8‰ (VCDT) with an average of +4.7 ± 1.4‰ (1σ). Averages and within-suite with n = 7, respectively) are comparable to those of the entire sample set. Sulfur concentrations are low (mostly between 2 and 74 ppm, average = 19 ppm) and do not show correlations with sulfur isotope composition and whole-rock chemistry, or systematic changes with time in any of the lava suites. From model calculations we infer that basaltic magmas will undergo sulfur isotope fractionation during degassing, most commonly towards lower δ~(34)S values, but that the extent is limited at P-T conditions and oxidation states of interest. Hence, δ~(34)S signatures of basaltic lavas will generally be within a few permil from primary magmatic values, even in cases of extensive sulfur loss. Consequently, magmas in the Indonesian are system originate from mantle sources that are enriched in ~(34)S relative to MORB and OIB sources and are likely to have δ~(34)S values of about +5-+7‰. The enrichment in ~(34)S is considered to reflect addition of slab-derived material, presumably from sediments rather than altered oceanic crust, with fluids being the most likely transport medium. Absence of correlation between δ~(34)S values of Indonesian basalts and chemical proxies for source components or processes at the slab-wedge interface suggests that sulfur isotopes are relatively insensitive to variations in subduction setting and dynamics. This is supported by the modest range in δ~(34)S of the Indonesian volcanoes studied despite significant variations in the nature and amount of subducted material, and by the similarity with average ~(34)S enrichments in other oceanic arc systems.
机译：我们报告了印尼弧系统中选定火山的玄武岩和玄武质安山岩熔岩的硫同位素组成，涵盖了从低K胆甾型到高K钙碱性组成的光谱。来自七个火山的25个样本的结果与不同的俯冲方式有关，结果显示δ〜（34）S值的范围为+ 2.0- + 7.8‰（VCDT），平均值为+4.7±1.4‰（1σ） 。平均值和套房内的n = 7）分别与整个样本集相当。硫的浓度很低（通常在2至74 ppm之间，平均值= 19 ppm），并且与硫同位素组成和全岩石化学或任何熔岩组中随时间的系统变化都没有关系。从模型计算中我们可以推断出，玄武岩岩浆在脱气过程中会经历硫同位素分馏，最常见的是朝较低的δ〜（34）S值方向转变，但其程度仅限于P-T条件和感兴趣的氧化态。因此，即使在大量硫磺流失的情况下，玄武岩熔岩的δ〜（34）S标记通常也将与原始岩浆值相差几密耳。因此，印尼岩浆系来自地幔源，相对于MORB和OIB源，地幔源富含〜（34）S，δ〜（34）S值可能约为+ 5- + 7‰。 〜（34）S的富集被认为反映了板坯衍生材料的添加，大概是来自沉积物，而不是改变了的海洋地壳，而流体是最可能的传输介质。平板-楔形界面处印尼玄武岩的δ〜（34）S值与源组分或过程的化学近似值之间没有相关性，这表明硫同位素对俯冲环境和动力学变化相对不敏感。尽管俯冲物质的性质和数量存在显着变化，但所研究的印度尼西亚火山的δ〜（34）S的适度范围以及与其他大洋弧系中平均〜（34）S富集的相似性都支持了这一点。

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