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首页> 外文期刊>Contributions to Mineralogy and Petrology >Erupted cumulate fragments in rhyolites from Lipari (Aeolian Islands)
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Erupted cumulate fragments in rhyolites from Lipari (Aeolian Islands)

机译：利帕里（风神群岛）流纹岩中爆发的累积碎片

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Over the last similar to 267 ky, the island of Lipari has erupted magmas ranging in compositions from basaltic andesites to rhyolites, with a notable compositional gap in the dacite field. Bulk geochemical and isotopic compositions of the volcanic succession, in conjunction with major and trace elemental compositions of minerals, indicate that the rhyolites were dominantly generated via crystal fractionation processes, with subordinate assimilation. Radiogenic (Sr, Nd, and Pb) and stable (O) isotopes independently suggest <= 30 % of crustal contamination with the majority of it occurring in mafic compositions, likely relatively deep in the system. Within the rhyolites, crystal-rich, K2O-rich enclaves are common. In contrast to previous interpretations, we suggest that these enclaves represent partial melting, remobilization and eruption of cumulate fragments left-over from rhyolite melt extraction. Cumulate melting and remobilization is supported by the presence of (1) resorbed, low-temperature minerals (biotite and sanidine), providing the potassic signature to these clasts, (2) reacted Fo-rich olivine, marking the presence of mafic recharge, (3) An(38-21) plagioclase, filling the gap in feldspar composition between the andesites and the rhyolites and (4) strong enrichment in Sr and Ba in plagioclase and sanidine, suggesting crystallization from a locally enriched melt. Based on Sr-melt partitioning, the high-Sr plagioclase would require similar to 2300 ppm Sr in the melt, a value far in excess of Sr contents in Lipari and Vulcano magmas (50-1532 ppm) but consistent with melting of a feldspar-rich cumulate. Due to the presence of similar crystal-rich enclaves within the rhyolites from Vulcano, we propose that the eruption of remobilized cumulates associated with high-SiO2 rhyolites may be a common process at the Aeolian volcanoes, as already attested for a variety of volcanic systems around the world.
机译：在过去的一次类似267 ky的过程中，利帕里岛喷发了岩浆，其成分从玄武岩安山岩到流纹岩，在达菲石场中有明显的成分缺口。火山演替的大体地球化学和同位素组成，加上矿物的主要和微量元素组成，表明流纹岩主要是通过晶体分级分离过程产生的，并具有次要的同化作用。放射性（Sr，Nd和Pb）同位素和稳定的（O）同位素独立表明地壳污染的<= 30％，其中大部分发生在镁铁质成分中，可能在系统中相对较深。在流纹岩中，富含晶体，富含K2O的飞地很常见。与以前的解释相反，我们认为这些飞地代表了流纹岩熔体提取留下的累积碎片的部分熔化，移动和喷发。 （1）吸收的低温矿物（黑云母和山铁矿）的存在支持了熔体的迁移和迁移，为这些碎屑提供了钾的特征;（2）富Fo的橄榄石反应，标志着镁铁质补给的存在，（ 3）（38-21）斜长石，填补了安山岩和流纹岩之间的长石成分的空隙，并且（4）斜长石和Sanidine中Sr和Ba的强烈富集，表明从局部富集的熔体中结晶。基于Sr熔体分配，高Sr斜长石在熔体中需要约2300 ppm的Sr，该值远远超过Lipari和Vulcano岩浆中的Sr含量（50-1532 ppm），但与长石的熔化相一致。丰富的积累。由于来自Vulcano的流纹岩中存在类似的富含晶体的飞地，因此我们提出，与高SiO2流纹岩相关的固定累积物的喷发可能是风成火山的普遍过程，因为已经证明了周围的各种火山系统世界。

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