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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Contrasting records from mantle to surface of Holocene lavas of two nearby arc volcanic complexes: Caburgua-Huelemolle Small Eruptive Centers and Villarrica Volcano, Southern Chile
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Contrasting records from mantle to surface of Holocene lavas of two nearby arc volcanic complexes: Caburgua-Huelemolle Small Eruptive Centers and Villarrica Volcano, Southern Chile

机译：从地幔到地表的对比记录是附近两个弧形火山群的全新世熔岩：智利南部的卡博格-韦勒莫勒小火山喷发中心和比利亚里卡火山

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Most of the small eruptive centers of the Andean Southern Volcanic Zone are built over the Liquine-Ofqui Fault Zone (LOFZ), a NS strike-slip (>1000 km length) major structure, and close to large stratovolcanoes. This contribution compares textural features, compositional parameters, and pre- and syn-eruptive P,T conditions, between basaltic lavas of the Caburgua-Huelemolle Small Eruptive Centers (CHSEC) and the 1971 basaltic andesite lava of the Villarrica Volcano located 10 km south of the CHSEC. Olivines and clinopyroxenes occur as phenocrysts and forming crystal clots of the studied lavas. They do not markedly show compositional differences, except for the more scattered composition of the CHSEC clinopyroxenes. Plagioclase in CHSEC lavas mainly occur as phenoaysts or as microlites in a glass-free matrix. Two groups of plagioclase phenoaysts were identified in the 1971 Villarrica lava based on crystal size, disequilibrium features and zonation patterns. Most of the CHSEC samples exhibit higher La-N/Yb-N and more scattered Sr-Nd values than 1971 Villarrica lava samples, which are clustered at higher Nd-143/Nd-144 values. Pre-eruptive temperatures of the CHSEC-type reservoir between 1162 and 1165 +/- 6 degrees C and pressures between 10.8 and 11.4 +/- 1.7 kb consistent with a deep-seated reservoir were obtained from olivine-augite phenocrysts. Conversely, olivine-augite phenocrysts of 1971 Villarrica lava samples record pre-eruptive conditions of two stages or pauses in the magma ascent to the surface: 1208 +/- 6 degrees C and 6.3-8.1 kb +/- 1.7 kb (deep-seated reservoir) and 1164-1175 +/- 6 degrees C and <= 1.4 kb (shallow reservoir). At shallow reservoir conditions a magma heating prior to the 1971 Villarrica eruption is recorded in plagioclase phenocrysts. Syn-eruptive temperatures of 1081-1133 +/- 6 degrees C and 1123-1148 +/- 6 degrees C were obtained in CHSEC and 1971 Villarrica lava, respectively using equilibrium olivine-augite microlite pairs. The LOFZ could facilitate a direct transport to the surface of the CHSEC magmas and explain the observed differences with the pre-eruptive conditions of the 1971 Villarrica lava. (C) 2015 Elsevier B.V. All rights reserved.
机译：安第斯山脉南部火山带的大多数小型喷发中心都建在利奎因-奥基断裂带（LOFZ）之上，这是北非走滑带（长度大于1000公里）的主要结构，并靠近大型平流火山。该贡献比较了Caburgua-Huelemolle小火山喷发中心（CHSEC）的玄武岩熔岩与1971年位于比拉里卡火山以南10公里处的1971年的Villarrica火山的玄武安山岩熔岩之间的质地特征，成分参数以及火山喷发前和协同条件CHSEC。橄榄石和clinopyroxenes形成为隐晶，形成研究熔岩的晶体凝块。除了CHSEC斜环茂金属的分散程度更大以外，它们没有明显的成分差异。 CHSEC熔岩中的斜长石酶主要以酚醛或微晶形式存在于无玻璃基质中。根据晶体大小，不平衡特征和分区模式，在1971年Villarrica熔岩中鉴定出两组斜长石表型。与1971 Villarrica熔岩样品相比，大多数CHSEC样品表现出更高的La-N / Yb-N和更分散的Sr-Nd值，后者以较高的Nd-143 / Nd-144值聚类。 CH橄榄型储层的火山喷发前温度在1162至1165 +/- 6摄氏度之间，压力在10.8至11.4 +/- 1.7 kb之间，与深层储层相一致。相反，1971年Villarrica熔岩样品的橄榄石-镁橄榄石隐晶记录在岩浆上升到地表的两个阶段或间歇前的喷发前条件：1208 +/- 6摄氏度和6.3-8.1 kb +/- 1.7 kb（深部）储罐）和1164-1175 +/- 6摄氏度且<= 1.4 kb（浅储罐）。在浅层油藏条件下，斜长石隐伏特隆记录了1971年比利亚里卡火山爆发前的岩浆加热。在CHSEC和1971 Villarrica熔岩中，分别使用平衡橄榄石-橄榄石微岩对获得了1081-1133 +/- 6摄氏度和1123-1148 +/- 6摄氏度的协同温度。 LOFZ可以促进直接输送到CHSEC岩浆的表面，并解释与1971年Villarrica熔岩喷发前条件所观察到的差异。 （C）2015 Elsevier B.V.保留所有权利。

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