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首页> 外文期刊>Geosciences >Modification of the Continental Crust by Subduction Zone Magmatism and Vice-Versa: Across-Strike Geochemical Variations of Silicic Lavas from Individual Eruptive Centers in the Andean Central Volcanic Zone
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Modification of the Continental Crust by Subduction Zone Magmatism and Vice-Versa: Across-Strike Geochemical Variations of Silicic Lavas from Individual Eruptive Centers in the Andean Central Volcanic Zone

机译：俯冲带岩浆作用和副版本对大陆壳的改造：来自安第斯中部火山带各个喷发中心的硅质拉瓦斯的跨层地球化学变化

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摘要

To better understand the origin of across-strike K2O enrichments in silicic volcanic rocks from the Andean Central Volcanic Zone, we compare geochemical data for Quaternary volcanic rocks erupted from three well-characterized composite volcanoes situated along a southeast striking transect between 21° and 22° S latitude (Aucanquilcha, Ollagüe, and Uturuncu). At a given SiO2 content, lavas erupted with increasing distance from the arc front display systematically higher K2O, Rb, Th, Y, REE and HFSE contents; Rb/Sr ratios; and Sr isotopic ratios. In contrast, the lavas display systematically lower Al2O3, Na2O, Sr, and Ba contents; Ba/La, Ba/Zr, K/Rb, and Sr/Y ratios; Nd isotopic ratios; and more negative Eu anomalies toward the east. We suggest that silicic magmas along the arc front reflect melting of relatively young, mafic composition amphibolitic source rocks and that the mid- to deep-crust becomes increasingly older with a more felsic bulk composition in which residual mineralogies are progressively more feldspar-rich toward the east. Collectively, these data suggest the continental crust becomes strongly hybridized beneath frontal arc localities due to protracted intrusion of primary, mantle-derived basaltic magmas with a diminishing effect behind the arc front because of smaller degrees of mantle partial melting and primary melt generation.
机译：为了更好地了解安第斯中部火山岩带硅质火山岩中横贯走向的K 2 O富集的起源，我们比较了沿一条沿线分布的三个特征明确的复合火山喷发的第四纪火山岩的地球化学数据。纬度介于21°和22°之间的东南走向样带（Aucanquilcha，Ollagüe和Uturuncu）。在给定的SiO 2 含量下，随着距电弧前沿距离的增加，熔岩喷发显示出较高的K 2 O，Rb，Th，Y，REE和HFSE含量; Rb / Sr比;和Sr同位素比。相反，熔岩系统地显示出较低的Al 2 O 3 ，Na 2 O，Sr和Ba含量。 Ba / La，Ba / Zr，K / Rb和Sr / Y比;钕同位素比;以及向东的负Eu异常。我们认为，弧前的硅质岩浆反映了相对年轻的镁铁质组成的两性源岩的融化，中，深地壳的年龄越来越长，而长晶质的组成也越来越长，其中剩余矿物学逐渐向长石富集。东。总体而言，这些数据表明，由于地幔部分融化和初生熔岩的程度较小，由于地幔起源的原始玄武岩岩体长期侵入，使得大陆壳在前弧弧下强烈地杂化，作用逐渐减弱。

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