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首页> 外文期刊>Contributions to Mineralogy and Petrology >Metamorphic degassing of carbonates in the contact aureole of the Aguablanca Cu-Ni-PGE deposit, Spain
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Metamorphic degassing of carbonates in the contact aureole of the Aguablanca Cu-Ni-PGE deposit, Spain

机译：西班牙Aguablanca Cu-Ni-PGE矿床接触金针中碳酸盐的变质脱气

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Analysis of magmatic and sedimentary rocks of several large igneous provinces has demonstrated that the release of gas during plutonic-metamorphic processes may be linked to global climate change and mass extinctions. Aguablanca, one of the largest Cu-Ni-PGE deposits in Europe, formed during the Variscan orogeny when a mafic magma intruded limestones and shales, creating a contact aureole composed of marble, skarn and hornfels. Our petrological and geochemical investigation of the aureole provides evidence that a combination of the two processes led to the formation of the ore deposit: The assimilation of terrigenous sediments supplied S to the magma while the assimilation of carbonates changed the oxygen fugacity and decreased the solubility of sulfur in the magma. The metamorphic assemblages in the contact aureole are directly related to heterogeneity of the protolith and particularly to the original proportions of calcite and clay. We modeledcarbon dioxide degassing during contact metamorphism and showed that pure limestone is relatively unproductive because of its high reaction temperature. The presence of clay, however, leads to the formation of calc-silicates and significantly enhances CO_2 degassing. Our estimations suggest that degassing of the Aguablanca contact aureole released about 74.8 Mt of CO_2, a relatively low volume that we attribute to the composition of the host rock, mainly a pure limestone. A far larger volume of carbon dioxide was emitted by the contact metamorphism of dolostones in the contact aureole of Panzhihua (part of Emeishan large igneous province, SW China). We propose that the level of emission of carbon dioxide depends strongly on the nature of the protolith and has to be considered when predicting environmental impact during the emplacement of large igneous provinces.
机译：对几个火成岩大省的岩浆和沉积岩进行的分析表明，在古生变质过程中释放的气体可能与全球气候变化和大灭绝有关。 Aguablanca是欧洲最大的Cu-Ni-PGE矿床之一，形成于瓦里斯卡造山运动期间，当时黑铁质岩浆侵入石灰岩和页岩，形成了由大理石，矽卡岩和角铁组成的接触金针。我们对金针的岩石学和地球化学研究提供了证据，表明这两个过程的结合导致了矿床的形成：陆源沉积物的同化作用将S供应给岩浆，而碳酸盐的同化作用则改变了氧气的逸度并降低了其溶解度。岩浆中的硫。接触性金刚烷中的变质组合与原石的异质性直接相关，尤其与方解石和粘土的原始比例有关。我们对接触变质过程中的二氧化碳脱气进行了建模，结果表明纯石灰石由于其较高的反应温度而相对而言没有生产能力。但是，粘土的存在导致形成钙硅酸盐，并显着增强了CO_2脱气。我们的估算表明，对Aguablanca接触性金刚烷进行脱气后，释放出约74.8 Mt的CO_2，这归因于基质岩（主要是纯石灰岩）的成分，相对较低。在攀枝花（峨眉山大火成岩省的一部分）的接触极中，白云岩的接触变质作用释放出大量二氧化碳。我们建议，二氧化碳的排放水平在很大程度上取决于原石的性质，在预测大火成岩省份进驻期间对环境的影响时必须加以考虑。

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