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首页> 外文期刊>Journal of Volcanology and Geothermal Research >A major resurgent caldera in southern Mexico: the source of the late Eocene Tilzapotla ignimbrite
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A major resurgent caldera in southern Mexico: the source of the late Eocene Tilzapotla ignimbrite

机译：墨西哥南部的主要死灰复燃：晚始新世Tilzapotla火成岩的来源

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The Tilzapotla caldera constitutes the first discovery of a major Tertiary collapse volcanic structure south of the Mexican Volcanic Belt. Although it is spatially associated with silicic ignimbrites in a region relatively distant from the extensive ignimbritic province of the Sierra Madre Occidental (SMO), it is among the largest collapse calderas documented in Mexico. The caldera is defined by a 33 x 24 km semi-elliptical structure that encircles the largest exposures of the Tilzapotla ignimbrite and corresponds to the structural margin rather than the topographic rim. A central uplifted block limited by NW-trending faults is the main indication of a resurgent stage. The caldera structural margin is surrounded by extensive exposures of Cretaceous marine sequences that structurally define a broad elliptical dome (45 x 35 km) originated in the first stage of the caldera evolution. There is evidence showing that the 34 Ma Tilzapotla ignimbrite represents the climatic event of the caldera collapse. It is constituted by a massive sequence of crystal vitric tuff with conspicuous euhedral biotite and abundant quartz. The intra-caldera facies is intercalated with mega- and meso-breccias of limestone and anhydrite fragments derived from the slumping of the caldera wall during the caldera collapse. The overlying sequence includes post-collapse ignimbrites as well as amphibole and pyroxene bearing dacitic to andesitic lava flows. The age (33 to 32 Ma) and isotopic signatures of these lava flows indicate a resurgent event related with the input of more primitive magmas into the magma chamber. The rectilinear northeastern and southwestern segments of the structural margin of the caldera correspond to NW-trending tectonic lineaments that are part of a regional strike-slip system, active at the time of the caldera formation. We interpret that the NW tectonic structures defined zones of weakness that accommodated the caldera collapse in the northeastern and southwestern segments of the caldera structural margin.
机译：Tilzapotla破火山口是墨西哥火山带以南主要的第三纪塌陷火山构造的首次发现。尽管在空间上它与硅质火成岩在空间上相关，而该地区离西马德雷山脉广泛的火成岩省（SMO）相对较远，但它是墨西哥有记载的最大坍塌火山口之一。破火山口是由一个33 x 24 km的半椭圆形结构定义的，该结构包围Tilzapotla火成岩的最大暴露区域，并且对应于结构边缘而不是地形边缘。受西北趋势断裂限制的中央隆起块是复苏阶段的主要标志。破火山口的结构边缘被白垩纪海洋序列的大量暴露所包围，这些白垩纪海洋序列在结构上限定了起源于破火山口演化第一阶段的宽椭圆形圆顶（45 x 35 km）。有证据表明34 Ma Tilzapotla的火成岩代表了破火山口倒塌的气候事件。它由大量的玻璃状凝灰岩，显着的黑面黑云母和丰富的石英构成。破火山口内的相间夹有石灰岩和大型角砾岩角砾岩，以及在破火山口倒塌时源自破火山口壁坍塌的硬石膏碎片。上覆序列包括塌陷后的火成岩以及闪闪的和闪闪的火山岩和安山岩熔岩流。这些熔岩流的年龄（33至32 Ma）和同位素特征表明，与更多原始岩浆输入岩浆室内有关的死灰复燃事件。破火山口结构边缘的直线东北和西南段对应于西北走向的构造构造，这些构造构造是区域走滑系统的一部分，在破火山口形成时活跃。我们解释说，西北构造构造定义了弱化区域，以适应破火山口结构边缘的东北和西南段的破火山口塌陷。

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