Magma mixing between rhyolite and pseudotachylite as the origin for the Glencoe 'Flinty Crush Rock'
Magma mixing between rhyolite and pseudotachylite as the origin for the Glencoe 'Flinty Crush Rock'
复制标题
流纹岩和假速岩之间的岩浆混合是格伦科“燧石碎岩”的起源
DOI：
10.1144/sjg2023-016
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发表时间：
2024
影响因子：
0.7
通讯作者：
Dobson D
中科院分区：
文献类型：
--
作者：
Dobson D
格伦科破火山口是一个研究充分的例子，破火山口系统暴露在中间深度沿着冰川挖掘峡谷。我们提出了第一个定量评估的碎屑大小的人口和基质化学从坚硬的破碎岩石发生在主环断层。碎屑的大小形状的度量不同于那些“正常”pseudotachylite从外赫布里底群岛。这两个样品显示良好的幂律碎屑大小的人口，一旦津贴是溶解的一部分碎屑到熔体中，包含他们，与分形维数为2.7和4.0的外赫布里底群岛和格伦科样品分别。燧石破碎岩石基质化学的质量平衡计算意味着起源于流纹岩和假玄武玻璃岩之间的混合，来自半泥质寄主岩石。这意味着坚硬的压碎岩石被运送到距离摩擦加热点一定距离的地方，如前所述，因为半泥质岩石不存在于Stob Mhic Mhartuin的表面，但可能存在于深度。这种迁移，以及与流纹岩岩浆的混合，为碎屑溶解提供了时间和热能，超过了断层围岩上正常假玄武玻璃岩生成和淬火过程中可能提供的时间和热能。补充材料：模拟结果、坚硬破碎岩石样品中基质的主要元素组成和补充图可在https://doi.org/10.6084/m9.figshare.c.7084992上获得
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 that 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 that contained them, with fractal dimensions of 2.7 and 4.0 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 that 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, as semipelitic rocks are not present at the surface at Stob Mhic 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:Results of simulations, major element compositions of the matrix in the flinty crush rock sample and a supplementary figure are available at https://doi.org/10.6084/m9.figshare.c.7084992