CERRO-XALAPAXCO - AN UNUSUAL TUFF CONE WITH MULTIPLE EXPLOSION CRATERS, IN CENTRAL MEXICO (PUEBLA)
CERRO-XALAPAXCO - AN UNUSUAL TUFF CONE WITH MULTIPLE EXPLOSION CRATERS, IN CENTRAL MEXICO (PUEBLA)
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DOI：
10.1016/0377-0273(94)90073-6
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发表时间：
1994-11-01
影响因子：
2.9
通讯作者：
SIEBE, C
中科院分区：
文献类型：
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作者：
ABRAMS, MJ;SIEBE, C
Xalapaxco凝灰岩锥位于墨西哥中部La Malinche层状火山的东北侧。异常多的（10个）爆炸坑，集中在火山锥的中央和上坡一侧，暴露出分层涌流沉积物和大量下降沉积物的交替层。火山锥的形态及其沉积物的特征表明，在火山喷发期间，有大量地下水参与其中。导致圆锥体形成的火山喷发穿过了一个冲积扇，冲积扇的源头是拉马林奇火山山顶附近冰川雕刻的峡谷。这个巨大的峡谷是在反复的冰川时期被切割出来的，最后一次冰川时期大约在8500年前结束。目前的冲积扇主要由拉马林奇冰川-流质安山岩/英安岩物质改造而成。上升的岩浆在石灰岩基底和冲积扇的上覆夹层火山碎屑和冰川-河流沉积物中遇到了大量地下水。短暂的呼吸火山喷发产生了涌流和空降沉积物。锥层中发现的捕虏体由英安岩和安山岩碎屑、石灰岩、燧石和罕见的火成岩碎片组成。没有一种幼年物质可以被明确地识别出来，但最有可能是由与拉马林奇熔岩在质地和组成上相似的斑状英安岩代表的。多个火山口的形成是对短暂喷发期间水和岩浆供应变化的反应。因此，理想的岩浆/水比存在的位置在时间和空间上都发生了变化。对陨石坑直径/深度比的分析表明，活动从锥的中心向西部的外围转移。由于水文环境的配置，在火山喷发的后期，从拉马林奇火山上坡一侧的扇面流出的地下水比从火山锥下方流出的地下水要多。在目前干燥的环境中，凝灰岩锥在层状火山斜坡上的明显异常位置可以用喷发时普遍存在的更潮湿的气候条件来解释。
The Xalapaxco tuff cone is located on the northeast flank of La Malinche stratovolcano in central Mexico. An unusually large number (10) of explosion craters, concentrated on the central and on the uphill side of the cone, expose alternating beds of stratified surge deposits and massive fall deposits. The morphology of the cone and the characteristics of its deposits point to the involvement of significant quantities of groundwater during its eruption. The phreatomagmatic eruptions which led to the cone's formation pierced an alluvial fan, whose source is a glacially carved canyon near the summit of La Malinche volcano. The large canyon was cut during repeated glacial episodes, the last of which ended ca. 8500 years ago. The present alluvial fan mostly consists of reworked glacio-fluviatile andesite/dacite material from La Malinche. Rising magma encountered substantial amounts of groundwater within the limestone basement and in overlying intercalated pyroclastic and glacio-fluviatile deposits of the alluvial fan. Short-lived phreatomagmatic eruptions produced surge and airfall deposits. Xenoliths found in the cone beds are composed of dacite and andesite clasts, limestone, chert, and rare ignimbrite fragments. No juvenile material could be unequivocally identified, but is represented most probably by porphyritic dacite similar in texture and composition to La Malinche lavas. The multiple craters were formed as a response to changes in water and magma supply during the short-lived eruption. Hence, the locations where ideal magma/water ratios existed to fuel phreatomagmatic explosions shifted in time and space. Analysis of diameter/depth ratios of the craters indicates that the activity shifted from the center of the cone to its periphery in the west. Due to the configuration of the hydrographic environment, more groundwater flowing from La Malinche was available from the fan on the uphill side than below the cone at later stages of the eruption. The apparently anomalous position of the tuff cone on the slopes of a stratovolcano in a presently dry environment can be explained by more humid climatic conditions prevailing at the time of eruption.