ABSTRACT

Here we define the Comallo volcanic sedimentary complex of the western North Patagonian Massif. It is composed by two members that include 9 lithofacies and 7 facies associations. The lower member is represented by massive and stratified lapilli tuffs, lithic and tuffaceous breccias, coherent andesite-dacite lava-flows, andesitic breccias, and massive crystalline limestones. The upper member consists of red conglomerates, parallel and cross-stratification sandstones, and mudstones. The lower member is interpreted as having been deposited by dilute and dense pyroclastic currents, block and ash deposits and lava-flow, and hypersaline lacustrine environments. The upper member is considered to have been deposited in fluviatile environments. A new U-Pb age of 192.0 ± 3.0 Ma (Sinemurian) was obtained for this complex. It is coeval with several volcanic sedimentary units that crop out along the western North Patagonian Massif, the Neuquén basin and the Extraandean Chubut in pull-apart or rift depocentres. The movements of the NW-SE strike-slip faults that border the northern and southern limits of the Comallo depocentre made possible the development of a pull-apart basin as well as the volcanism and the fluvial system. This and other coeval units were deposited in similar environmental conditions along the North Patagonian Massif, the Neuquén basin and the extraandean Chubut, indicating a similar tectonomagmatic setting, in a tensional rear-arc during Lower Jurassic times.

摘要

在这里，我们定义了北部北巴塔哥尼亚地块的Comallo火山沉积复合体。它由包括9个岩相和7个相的协会的两个成员组成。下半部的代表是块状和分层的青金石凝灰岩，岩性和凝灰质角砾岩，连贯的安山岩-针铁矿熔岩流，安山角砾岩和块状结晶灰岩。上部由红色砾岩，平行和交叉分层的砂岩和泥岩组成。下部构件被解释为是由稀疏和密集的火山碎屑流，块状和灰分沉积，熔岩流以及高盐度湖泊环境沉积的。上部被认为已沉积在易挥发的环境中。该复合物的新U-Pb年龄为192.0±3.0 Ma（Sinemurian）。它与几个火山沉积单元同时期，沿着北部巴塔哥尼亚地块，内乌肯盆地和Extraandean Chubut沿拉脱或裂谷沉积中心分布。NW-SE走滑断层的运动与Comallo沉积中心的北部和南部边界接壤，这使得拉脱盆地的发展以及火山作用和河流系统成为可能。这个和其他同时代的单位在北侏罗纪时期的拉张后弧中，在北巴塔哥尼亚地块，内乌肯盆地和陆外丘布河的相似环境条件下沉积，表明构造构造相似。NW-SE走滑断层的运动与Comallo沉积中心的北部和南部边界接壤，这使得拉脱盆地的发展以及火山作用和河流系统成为可能。这个和其他同时代的单位在北侏罗纪时期的拉张后弧中，在北巴塔哥尼亚地块，内乌肯盆地和陆外丘布河的相似环境条件下沉积，表明构造构造相似。NW-SE走滑断层的运动与Comallo沉积中心的北部和南部边界接壤，这使得拉脱盆地的发展以及火山作用和河流系统成为可能。这个和其他同时代的单位在北侏罗纪时期的拉张后弧中，在北巴塔哥尼亚地块，内乌肯盆地和陆外丘布河的相似环境条件下沉积，表明构造构造相似。