DOI: 10.1016/j.earscirev.2019.103031
论文题名: “Pipe vesicles” in basalt: Trails left by dense immiscible melt droplets sinking through a viscous basal thermal boundary layer
作者: Sheth H.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2020
卷: 201 语种: 英语
中文关键词: Basalt
; Flood basalt
; Liquid immiscibility
; Pipe vesicles
; pāhoehoe
; Volcanism
英文关键词: basalt
; boundary layer
; droplet
; immiscibility
; lava flow
; mineralization
; volcanism
英文摘要: Pipe vesicles, tubular cavities found in the basal parts of pāhoehoe lava flows worldwide, constitute one of their fundamental primary structures. Like other vesicles, pipe vesicles have been ascribed to gas bubbles, whether rising buoyantly through viscous lava or trapped in an inward-moving solidification front. These models involve special and unrealistic conditions and still poorly explain characteristic features of pipe vesicles. In a new model proposed here, pipe vesicles are postulated to be hollow trails left by droplets of dense, immiscible iron-rich silicate or sulphide melt sinking through a viscous thermal boundary layer just above the lower chilled margin of a pāhoehoe flow unit. Driven by gravity, the droplets sink vertically in static lava, but obliquely in mobile lava, such as lava undergoing gravitational spreading. Viscous and fluid dynamic forces tend to deform the sinking droplets and resist their motion. The characteristic inverted-Y, inverted-V and lambda (λ) shapes of individual pipe vesicles reflect downward branching, with a large droplet breaking up in partially crystallized, highly polymerized basalt in the basal thermal boundary layer. Pipe vesicles do not yield lava flow directions even on a local (centimeters to meters) scale, but are indirect indicators of widespread liquid immiscibility processes in basalts and potential commercial Fe-Cu-Ni mineralization. As pipe vesicles are not vesicles (cavities left by gas escape), a new term is necessary, and the term “vermiform pāhoehoe”, having good descriptive power but no genetic connonations, is suggested for pāhoehoe with “pipe vesicles”. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/166253
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
Recommended Citation:
Sheth H.. “Pipe vesicles” in basalt: Trails left by dense immiscible melt droplets sinking through a viscous basal thermal boundary layer[J]. Earth Science Reviews,2020-01-01,201