Monogenetic volcanoes fed by interconnected dikes and sills in the Hopi Buttes volcanic field, Navajo Nation, USA
Monogenetic volcanoes fed by interconnected dikes and sills in the Hopi Buttes volcanic field, Navajo Nation, USA
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DOI：
10.1007/s00445-016-1005-8
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发表时间：
2016-02
影响因子：
3.5
通讯作者：
J. Muirhead;A. Eaton;G. Re;J. White;M. Ort
中科院分区：
文献类型：
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作者：
J. Muirhead;A. Eaton;G. Re;J. White;M. Ort
虽然单成因火山场对世界各地的主要城市构成危险，但它们的浅岩浆补给源（<500米深）很少暴露，因此了解甚少。在这里，我们调查暴露在霍皮巴特斯火山场，亚利桑那州，揭示其岩浆馈线系统的性质的岩脉和岩床。浅曝光揭示了侵入和喷发之间的过渡带在350米的同喷发表面。结合野外和卫星观测，我们确定了三种类型的浅层岩浆系统：（1）岩脉为主，（2）岩床为主，（3）相互连接的岩脉岩床网络。利用火山碎屑岩和其他喷发中心（例如，maar-diatremes）呈NW-SE走向，与区内岩脉走向平行。因此，我们推断堤坝为许多喷发提供了燃料。在转变为海侵（斜坡）岩床的地方也观察到岩脉。在本研究中，对岩脉（最大体积为1.90 × 106 m3）和岩床（最小体积为8.47 × 105 m3）的可观测体积的估计表明，霍皮丘的岩床至少占古地表350 m范围内浅侵入体积（总计2.75 × 106 m3）的30%。我们还发现了碟形岩床，这在传统上与单成因火山岩场无关。我们的研究表明，浅馈线在单成因领域可以形成几何复杂的网络，特别是那些侵入差固结沉积岩。我们的结论是霍皮Buttes火山喷发主要是由西北-东南-罢工堤防。然而，碟形岩床也发挥了重要作用，通过运输岩浆进出喷发管道调制喷发。岩床的发展可能伴随着分米量级的地表隆起。我们推断，这里描述的霍皮孤峰的特征馈线系统可能是其他地方的单成因场的基础，特别是在岩浆与浅，往往是弱的沉积岩相交的地方。这项研究的结果支持越来越多的证据表明，浅底床的重要作用，在积极的单成领域。
Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (<500 m depth) are rarely exposed and, therefore, poorly understood. Here, we investigate exposures of dikes and sills in the Hopi Buttes volcanic field, Arizona, to shed light on the nature of its magma feeder system. Shallow exposures reveal a transition zone between intrusion and eruption within 350 m of the syn-eruptive surface. Using a combination of field- and satellite-based observations, we have identified three types of shallow magma systems: (1) dike-dominated, (2) sill-dominated, and (3) interconnected dike-sill networks. Analysis of vent alignments using the pyroclastic massifs and other eruptive centers (e.g., maar-diatremes) shows a NW-SE trend, parallel to that of dikes in the region. We therefore infer that dikes fed many of the eruptions. Dikes are also observed in places transforming to transgressive (ramping) sills. Estimates of the observable volume of dikes (maximum volume of 1.90 × 106m3) and sills (minimum volume of 8.47 × 105m3) in this study reveal that sills at Hopi Buttes make up at least 30 % of the shallow intruded volume (∼2.75 × 106m3total) within 350 m of the paeosurface. We have also identified saucer-shaped sills, which are not traditionally associated with monogenetic volcanic fields. Our study demonstrates that shallow feeders in monogenetic fields can form geometrically complex networks, particularly those intruding poorly consolidated sedimentary rocks. We conclude that the Hopi Buttes eruptions were primarily fed by NW-SE-striking dikes. However, saucer-shaped sills also played an important role in modulating eruptions by transporting magma toward and away from eruptive conduits. Sill development could have been accompanied by surface uplifts on the order of decimeters. We infer that the characteristic feeder systems described here for the Hopi Buttes may underlie monogenetic fields elsewhere, particularly where magma intersects shallow, and often weak, sedimentary rocks. Results from this study support growing evidence of the important role of shallow sills in active monogenetic fields.