Subglacial, phonolitic volcanism at Hoodoo Mountain volcano, northern Canadian Cordillera
Subglacial, phonolitic volcanism at Hoodoo Mountain volcano, northern Canadian Cordillera
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加拿大科迪勒拉山脉北部胡杜山火山的冰下、声石火山活动
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
R. G. Anderson
中科院分区：
文献类型：
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作者：
B. Edwards;J. Russell;R. G. Anderson
摘要：胡杜山火山（HMV）是一座第四纪火山岩火山，位于加拿大不列颠哥伦比亚省西北部海岸山脉伊斯库特河北岸。它的活动跨越了过去 10 万年，可能最近才爆发过 9 ka，体积约为 17 平方公里。纵观其历史，大部分火山活动都直接受到冰川的影响，这就是其引人注目的形态和火山沉积物的原因。火山的物理发展至少包括六个阶段：（1）约85ka的冰下喷发； (2) 80ka左右的冰层喷发； (3) 约 80 至 54 ka 之间的陆上（？）火山碎屑喷发； (4) 大约 54ka 的地面喷发； (5) 54 至 30ka 之间的冰下喷发； (6) 大约 9ka 的地面、冰河后喷发。在 HMV 10 万年的历史中，HMV 熔岩的化学和矿物成分仍然有限。所有样品均为响沸石或粗面岩，含有碱长石、单斜辉石和磁铁矿的（微）斑晶。样品几乎全部是霞石和acmite 标准样品。与原始地幔值相比，HMV样品的稀土元素浓度富集10-100倍，并且具有中等的负Eu异常。现场观测、岩石学数据集和热力学模型支持通过分步结晶和中地壳压力下的地壳同化相结合，从碱性橄榄石玄武岩中推导出 HMV 的声乐石岩浆。与分异相关的岩浆密度的随之变化使得来自停滞在地壳中的玄武岩母岩浆的声石岩浆持续浮升和喷发。在这种环境下，伴随着科迪勒拉冰盖波动的岩石静压的微小变化可能会通过充满岩浆的地壳岩石圈的“冰川泵送”来放大火山活动。
Abstract.Hoodoo Mountain volcano (HMV) is a Quaternary phonolitic volcano situated on the north side of the Iskut River, in the Coast Mountains of northwestern British Columbia, Canada. Its activity spans the last 100,000 years, it may have erupted as recently as 9 ka, and it encompasses a volume of approximately 17 km3. Throughout its history, much of the volcanic activity has been directly affected by glaciers, which accounts for its striking morphology and volcanic deposits. The physical development of the volcano includes at least six stages: (1) subglacial eruptions at about 85 ka; (2) ice-confined eruptions at about 80 ka; (3) subaerial(?) pyroclastic eruptions between about 80 and 54 ka; (4) subaerial effusive eruptions at about 54 ka; (5) subglacial eruptions between 54 and 30 ka; and (6) subaerial, post-glacial eruptions at about 9 ka. The chemical and mineralogical compositions of HMV lavas remained limited throughout the 100,000-year history of the HMV. All samples are phonolite or trachyte with (micro-) phenocrysts of alkali-feldspar, clinopyroxene, and magnetite. Samples are almost exclusively nepheline and acmite normative. Compared with primitive mantle values, samples from HMV are 10–100 times enriched in rare earth element concentrations and have moderate negative Eu anomalies. Field observations, petrological data sets, and thermodynamic modeling support derivation of the phonolite magmas at HMV from alkali olivine basalt by a combination of fractional crystallization and crustal assimilation at mid-crustal pressures. The attendant changes in magma density related to differentiation permitted the continued buoyant ascent and eruption of phonolitic magmas derived from basaltic parental magmas that stalled in the crust. In this environment, the slight changes in lithostatic pressure accompanying fluctuations in Cordilleran ice sheets could amplify volcanism by "glacial pumping" of the magma-charged crustal lithosphere.