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首页> 外文期刊>Journal of South American earth sciences >An overview of monogenetic carbonatitic magmatism from Uganda, Italy, China and Spain: Volcanologic and geochemical features
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An overview of monogenetic carbonatitic magmatism from Uganda, Italy, China and Spain: Volcanologic and geochemical features

机译：乌干达，意大利，中国和西班牙的单基因碳岩性岩浆作用概述：火山岩和地球化学特征

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We address general features of carbonatite monogenetic volcanic fields located in continental settings which are peculiar being associated with kamafugites or melilite-bearing leucitites. Instructive examples are the Toro Ankole in Uganda, West Qinling in China, and Campo de Calatrava in Spain and the Intra-mountain Ultra-alkaline Province (IUP) of Italy. Maars are the typical volcanic forms, occurring in isolation or in clusters along fault systems. Concentric-shelled juvenile lapilli and bombs, having a upper-mantle peridotite kernel, are unique to this type of volcanism. These pyroclasts are interpreted as the result of deep-seated fragmentation of magma having a high carbon dioxide-water (CO_2/H_2O) ratio. The presence of discrete, large peridotitic nodules implies a high-velocity propagation of magma, while the associated large CO_2 emission suggests a high proportion of juvenile CO_2. Magma fragmentation is inferred to occur as a consequence of explosive CO_2 exsolution at the upper mantle level (diatresis) followed by immiscibility. Based on field evidence, carbonatitic maar formation could be due to violent CO_2 expansion and does not require phreatomagmatic phenomena. Extrusive carbonatites and associated rocks represent very primitive melts having a distinct High Field Strength Elements (HFSE) distribution, the source of which is related to enriched mantle. Carbonated peridotite is a stable paragenesis at depths of 400-600 km; thus, primary carbonatitic silicate magma can be produced at these depths as a consequence of rising deeper melt/fluids that are trapped at the transition zone. In our opinion, carbonatitic carbon is linked to the primary process of deep-mantle differentiation and Earth's core degassing.
机译：我们讨论了位于大陆环境中的碳酸盐岩单基因火山场的一般特征，这些火山岩特有的是与卡马富吉特岩或含陨石的白云母有关的。例如，乌干达的Toro Ankole，中国的西秦岭，西班牙的Campo de Calatrava和意大利的山内超碱性省（IUP）。马氏岩是典型的火山形式，沿断层系统孤立或成簇出现。具有上地幔橄榄岩核的同心炮弹少年拉皮利和炸弹是这类火山活动所独有的。这些破火山岩被解释为具有高二氧化碳-水（CO_2 / H_2O）比的岩浆的深层破碎的结果。离散的大的橄榄岩结节的存在意味着岩浆的高速传播，而相关的大CO_2排放则表明幼年的CO_2比例很高。推断岩浆碎裂是由于上地幔层上的CO_2爆炸性爆炸（渗析）和随后的不溶混而发生的。根据现场证据，碳酸盐马来岩的形成可能是由于剧烈的CO_2膨胀，不需要发岩浆现象。挤压碳酸盐岩和伴生岩石代表着非常原始的熔体，具有独特的高场强元素（HFSE）分布，其来源与地幔富集有关。碳酸橄榄岩在400-600 km深度是一种稳定的共生作用。因此，由于被困在过渡区的更深的熔体/流体上升，在这些深度上可以产生初级碳酸盐硅酸盐岩浆。我们认为，碳酸盐碳与地幔深层分化和地球核心脱气的主要过程有关。

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