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首页> 外文期刊>Contributions to Mineralogy and Petrology >The importance of talc and chlorite “hybrid” rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction mélange of New Caledonia
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The importance of talc and chlorite “hybrid” rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction mélange of New Caledonia

机译：滑石和绿泥石“混合”岩石对于通过俯冲带进行挥发物再循环的重要性；新喀里多尼亚高压俯冲混杂岩的证据

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摘要

The transfer of fluid and trace elements from the slab to the mantle wedge cannot be adequately explained by simple models of slab devolatilization. The eclogite-facies mélange belt of northern New Caledonia represents previously subducted oceanic crust and contains a significant proportion of talc and chlorite schists associated with serpentinite. These rocks host large quantities of H2O and CO2 and may transport volatiles to deep levels in subduction zones. The bulk-rock and stable isotope compositions of talc and chlorite schist and serpentinite indicate that the serpentinite was formed by seawater alteration of oceanic lithosphere prior to subduction, whereas the talc and chlorite schists were formed by fluid-induced metasomatism of a mélange of mafic, ultramafic and metasedimentary rocks during subduction. In subduction zones, dehydration of talc and chlorite schists should occur at sub-arc depths and at significantly higher temperatures (∼ 800°C) than other lithologies (400–650°C). Fluids released under these conditions could carry high trace-element contents and may trigger partial melting of adjacent pelitic and mafic rocks, and hence may be vital for transferring volatile and trace elements to the source regions of arc magmas. In contrast, these hybrid rocks are unlikely to undergo significant decarbonation during subduction and so may be important for recycling carbon into the deep mantle.
机译：平板脱挥发分的简单模型不能充分解释流体和微量元素从平板到地幔楔的转移。新喀里多尼亚北部的榴辉岩相混杂带代表以前俯冲的洋壳，并且含有大量与蛇纹岩有关的滑石和绿泥石片岩。这些岩石中含有大量的H 2 O和CO 2 ，并可能将挥发物输送到俯冲带的深层。滑石和绿泥石片岩和蛇纹岩的块状岩石和稳定的同位素组成表明，蛇纹岩是在俯冲之前由海洋岩石圈的海水变化形成的，而滑石和绿泥石片岩是由流体诱导的黑铁质混杂岩的交代作用形成的，俯冲过程中的超基性岩和准沉积岩。在俯冲带，滑石和绿泥石片岩的脱水应该发生在亚弧深度，并且温度（〜800℃）要比其他岩性（400〜650℃）高得多。在这些条件下释放的流体可能携带高含量的痕量元素，并可能触发相邻的胶质岩和镁铁质岩石的部分熔融，因此对于将挥发性和微量元素转移到弧岩浆源区可能至关重要。相反，这些杂化岩石在俯冲过程中不太可能发生明显的脱碳作用，因此对于将碳循环到深地幔中可能很重要。

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