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首页> 外文期刊>Contributions to Mineralogy and Petrology >High-Ti amphibole as a petrogenetic indicator of magma chemistry: evidence for mildly alkalic-hybrid melts during evolution of Variscan basic–ultrabasic magmatism of Central Iberia
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High-Ti amphibole as a petrogenetic indicator of magma chemistry: evidence for mildly alkalic-hybrid melts during evolution of Variscan basic–ultrabasic magmatism of Central Iberia

机译：高钛角闪石作为岩浆化学的成岩指示剂：中伊比利亚中部瓦里斯坎碱性-超碱性岩浆作用演化过程中轻度碱-混合熔体的证据

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摘要

Central Iberian Variscan granite batholiths and anatectic complexes are punctuated by coeval stocks of hydrous, high-K calc-alkaline, ultrabasic to intermediate rock series. Despite their overall calc-alkaline affinity, the mafic–ultramafic members contain high-Ti amphibole oikocrysts rimmed by lower-Ti amphibole ± cummingtonite and high-Ti amphibole replacing early phlogopite. To understand the factors controlling the saturation of high-Ti amphibole in the parental magmas, clinopyroxene-melt, phlogopite-melt and amphibole-melt relationships are reviewed. This analysis reveals that for melts with intermediate compositions, the affinity of TiO2 for amphibole rises in alkalic magmas. Accordingly, mildly alkalic trachytoid to subalkaline medium- to high-K andesite and dacite compositions are estimated for interstitial high-Ti amphibole-saturated melts. Amphibole Ce/Pb ratios reveal a mantle–crust hybrid nature for interstitial melts with subalkaline trachytoid compositions. The hydrous character of the Variscan basic magmas favoured an overall magmatic evolutionary trend with a low rate of variation of Na2O with respect to silica during amphibole crystallization. Communicated by M. W. Schmidt.
机译：伊比利亚中部的瓦里斯卡纳花岗岩基岩和高酸性复合物被含水，高K钙碱性，超碱性至中级岩石系列的同期储层所打断。尽管它们总体上具有钙碱性亲和力，但铁镁-超镁铁质成员仍然含有高钛角闪石长方晶石，而高钛角闪石±cummingtonite和高钛角闪石代替了早期金云母。为了了解控制母体岩浆中高钛角闪石饱和度的因素，综述了斜辉石-熔体，金云母-熔体和闪石-熔体的关系。该分析表明，对于具有中间成分的熔体，碱性岩浆中TiO 2 对闪石的亲和力增加。因此，对于间质性高Ti闪闪石饱和熔体，估计了中等碱度的曲奇线状至亚碱性，中度至高K的安山岩和钠长石成分。角闪石的铈/铅比率显示出含碱碱性次摆线化合物的间隙熔体的地幔-壳杂性。 Variscan基本岩浆的含水特征有利于总体岩浆演化趋势，在闪石结晶过程中Na 2 O相对于二氧化硅的变化率低。由M. W. Schmidt沟通。

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