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首页> 外文期刊>Contributions to Mineralogy and Petrology >Volatile (Cl, F and S) and major element constraints on subduction-related mantle metasomatism along the alkaline basaltic backarc, Payenia, Argentina
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Volatile (Cl, F and S) and major element constraints on subduction-related mantle metasomatism along the alkaline basaltic backarc, Payenia, Argentina

机译：挥发性（CL，F和S）和沿着碱性玄武岩BASARC，Payenia，Argentina的潜水相关型幔型弥撒的主要因素限制

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摘要

We present data on volatile (S, F and Cl) and major element contents in olivine-hosted melt inclusions (MIs) from alkaline basaltic tephras along the Quaternary Payenia backarc volcanic province (similar to 34 degrees S-38 degrees S) of the Andean Southern Volcanic Zone (SVZ). The composition of Cr-spinel inclusions and host olivines in Payenia are also included to constrain any variations in oxygen fugacity. The variation of potassium, fluorine and chlorine in MIs in Payenia can be modelled by partial melting (1-10%) of a variously metasomatised mantle. The high chlorine contents in MIs (up to 3200 ppm) from Northern Payenia require addition of subduction-related fluids to a mantle wedge, whereas volatile signatures in the southern Payenia are consistent with derivation from an enriched OIB source. Cl and Cl/K ratios define positive correlations with host olivine fosterite content (Fo(80-90)) that cannot be explained by olivine fractionation, degassing and/or degree of mantle melting. Neither can the correlation between SiO2 and TiO2 in the MIs and host olivine Fo-content be explained by magmatic differentiation processes. Instead these correlations essentially require a south to north mantle source transition from a low Mg# pyroxenite (from recycled eclogite) to a high Mg# fluid metasomatised peridotite. The Cl/K and S/K ratios in Payenia MIs extend from enriched OIB-like signatures (south) to Andean SVZ arc like signatures (north). We show that the northward increase in S, Cl and S/K is coupled to a northward increase in melt oxidation states and thus in Fe3+/Fe-tot ratios in the magmas. The increase in oxidation state also correlates with an increase of Mn/Fe (olivine) ratios. We calculate that 25% of the apparent north-south pyroxenite-peridotite source variation in Payenia (based on olivine Mn/Fe ratios) can be explained by the south to north variation in melt oxidation states.
机译：我们展示挥发性（S，F和Cl）的数据以及沿着第四纪养老尼亚山脉Volcanic省的碱性玄武岩Tephras（类似于Andean的34度S-38度）南部火山区（SVZ）。还包括Cr-Spinel夹杂物和寄生蛋白寄生虫的组成，以限制氧气不足的任何变化。养老腺癌中钾，氟和氯的变异可以通过各种熔融的碎屑（1-10％）进行模拟。来自京尼尼亚北部的MIS中的高氯含量（高达3200 ppm）需要向地幔楔加入潜水潜水液，而南京氏菌菌的挥发性签名与来自富集的OIB源的衍生物一致。 Cl和Cl / K比定义与宿主橄榄石的含量（FO（80-90））定义阳性相关性，其不能通过橄榄石分馏，脱气和/或裂缝熔化程度解释。 SiO2和TiO2之间的相关性既不能通过岩浆分化过程解释MIS和核橄榄石FO含量。相反，这些相关性基本上需要南方的北方地幔源从低Mg＃型辉曲岩（从再生的eNlogite）转变为高Mg＃液体脱模的恒星。 Payenia MIS中的Cl / K和S / K比从丰富的OIB的签名（南）延伸到Andean SVZ弧，如签名（北）。我们表明，S，Cl和S / K的向北增加与熔融氧化状态的向北增加，从而在岩浆中的Fe3 + / Fe-Totios。氧化状态的增加也与Mn / Fe（Olivine）比的增加相关。我们计算京尼尼亚（基于Olivine Mn / Fe比率）的表观北北曲率源性变化的25％可以通过南方到熔融氧化态的北方变异。

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