ABSTRACT

The Sinemurian Marifil Volcanic Complex at Sierra de Pailemán, located in the east part of the North Patagonian Region, Argentina, includes five lithofacies and three volcanic events. The volcanic activity begins with subaerial pyroclastic-fall deposits, massive lapilli tuffs with eutaxitic textures, and subaerial silicic domes’ emplacement. The upper part of the sequence is formed by pyroclastic fall deposits that pass to massive lapilli tuffs and rhyolitic lava flows. These lithofacies indicate the collapse of explosive eruption columns, coeval with small silicic domes’ emplacement, and lava-flows’ eruption. The volcanic episode at Sierra de Pailemán was generated during continuous magmatic activity because no erosional or unconformity surfaces were recognized. The Marifil Volcanic Complex’s age at Sierra de Pailemán is 191.2 ± 1.3 Ma (Sinemurian) and belongs to the V0 phase of volcanism. These rocks are high-K rhyolites, possibly produced by partial melting of the lower crust, promoted by fluids derived from a subducted plate in back-arc settings that change to an intraplate setting. The Lu-Hf isotopes suggest the possibility of magma mixing in the source and recycling or re-melting of a more evolved crust related to subduction zones. The Lower Jurassic magmatic activity in the western North Patagonian Region and the Patagonian Cordillera of Argentina and Chile correspond to continental arcs.

摘要

位于阿根廷北巴塔哥尼亚地区东部的 Sierra de Pailemán 的 Sinemurian Marifil 火山群包括五个岩相和三个火山事件。火山活动始于陆上火山碎屑沉积物、具有共生质地的大量青金石凝灰岩和陆上硅质圆顶的就位。该序列的上部是由火山碎屑沉积物形成的，这些沉积物通过大量的青金石凝灰岩和流纹岩熔岩流。这些岩相表明爆炸性喷发柱的坍塌，与小硅质圆顶的就位和熔岩流的喷发同时发生。Sierra de Pailemán 的火山事件是在持续的岩浆活动期间产生的，因为没有发现侵蚀或不整合面。Sierra de Pailemán 的 Marifil 火山群的年龄为 191.2 ± 1。3 Ma（Sinemurian），属于火山活动的V0阶段。这些岩石是高钾流纹岩，可能是由下地壳的部分熔融产生的，由来自弧后环境中俯冲板块的流体推动，这些流体变为板内环境。Lu-Hf 同位素表明岩浆在源头混合的可能性，以及与俯冲带相关的更演化地壳的再循环或重新熔化的可能性。北巴塔哥尼亚地区西部和阿根廷、智利巴塔哥尼亚山脉的下侏罗统岩浆活动对应大陆弧。Lu-Hf 同位素表明岩浆在源头混合的可能性，以及与俯冲带相关的更演化地壳的再循环或重新熔化的可能性。北巴塔哥尼亚地区西部和阿根廷、智利巴塔哥尼亚山脉的下侏罗统岩浆活动对应大陆弧。Lu-Hf 同位素表明岩浆在源头混合的可能性，以及与俯冲带相关的更演化地壳的再循环或重新熔化的可能性。北巴塔哥尼亚地区西部和阿根廷、智利巴塔哥尼亚山脉的下侏罗统岩浆活动对应大陆弧。