{"title":"Magma mixing between rhyolite and pseudotachylite as the origin for the Glencoe ‘Flinty Crush Rock’","authors":"David P Dobson, Viorela Martinescu","doi":"10.1144/sjg2023-016","DOIUrl":null,"url":null,"abstract":"The Glencoe caldera is a well-studied example of a caldera system exposed to intermediate depths along the glacially excavated glen. We present a first quantitative assessment of clast-size population and matrix chemistry from the flinty crush rock which occurs on the main ring faults. Size-shape metrics of clasts differ from those of a ‘normal’ pseudotachylite from the Outer Hebrides. Both samples display good power-law clast size populations, once allowance is made for dissolution of a portion of clasts into the melt which contained them, with fractal dimensions of 2.7 and 4.0 respectively for the Outer Hebrides and Glencoe samples respectively.\n Mass-balance calculations of flinty crush rock matrix chemistry imply an origin by mixing between rhyolite and pseudotachylite which was derived from semipelitic host rock. This means that the flinty crush rock was transported some distance from the point of frictional heating, as previously proposed, since semipelitic rocks are not present at the surface at Stob Mic Mhartuin but are likely to be present at depth. This transport, and mixing with rhyolite magma, would have provided the time and thermal energy for clast dissolution beyond that possible during normal pseudotachylite generation and quenching on fault wall rocks. \n \n Supplementary material:\n https://doi.org/10.6084/m9.figshare.c.7084992\n","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.5000,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Scottish Journal of Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1144/sjg2023-016","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The Glencoe caldera is a well-studied example of a caldera system exposed to intermediate depths along the glacially excavated glen. We present a first quantitative assessment of clast-size population and matrix chemistry from the flinty crush rock which occurs on the main ring faults. Size-shape metrics of clasts differ from those of a ‘normal’ pseudotachylite from the Outer Hebrides. Both samples display good power-law clast size populations, once allowance is made for dissolution of a portion of clasts into the melt which contained them, with fractal dimensions of 2.7 and 4.0 respectively for the Outer Hebrides and Glencoe samples respectively.
Mass-balance calculations of flinty crush rock matrix chemistry imply an origin by mixing between rhyolite and pseudotachylite which was derived from semipelitic host rock. This means that the flinty crush rock was transported some distance from the point of frictional heating, as previously proposed, since semipelitic rocks are not present at the surface at Stob Mic Mhartuin but are likely to be present at depth. This transport, and mixing with rhyolite magma, would have provided the time and thermal energy for clast dissolution beyond that possible during normal pseudotachylite generation and quenching on fault wall rocks.
Supplementary material:
https://doi.org/10.6084/m9.figshare.c.7084992
期刊介绍:
Although published only since 1965, the Scottish Journal of Geology has a long pedigree. It is the joint publication of the Geological Society of Glasgow and the Edinburgh Geological Society, which prior to 1965 published separate Transactions: from 1860 in the case of Glasgow and 1863 for Edinburgh.
Traditionally, the Journal has acted as the focus for papers on all aspects of Scottish geology and its contiguous areas, including the surrounding seas. The publication policy has always been outward looking, with the Editors encouraging review papers and papers on broader aspects of the Earth sciences that cannot be discussed solely in terms of Scottish geology.
The diverse geology of Scotland continues to provide an important natural laboratory for the study of earth sciences; many seminal studies in geology have been carried out on Scottish rocks, and over the years the results of much of this work had been published in the Journal and its predecessors.
The Journal fully deserves its high reputation worldwide and intends to maintain its status in the front rank of publications in the Earth sciences.