Detailed internal structure and along-strike variability of the core of a plate boundary fault : the Highland boundary fault, Scotland
| Autor: | Billy Andrews, Lucy McKay, Timothy D. Raub, Zoe K. Shipton, Adrian J. Boyce, Rebecca J. Lunn |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
geography
geography.geographical_feature_category 010504 meteorology & atmospheric sciences Geology Fault (geology) 010502 geochemistry & geophysics 01 natural sciences Core (optical fiber) Plate tectonics Sinistral and dextral TA Clastic rock Earthquake rupture Petrology 0105 earth and related environmental sciences Terrane Wall rock |
| ISSN: | 0016-7649 |
| Popis: | The Highland Boundary fault near Stonehaven, NE Scotland, provides a rare opportunity to study the internal fault structure of a well-exposed, along-strike section of an ancient plate boundary fault. As in many plate boundaries, serpentinite juxtaposes quartzo-feldspathic crustal rocks of distinct terranes. We report, for the first time, the complex internal structure of the Highland Boundary fault core, comprised of four structurally and chemically distinct clay-rich units that remain unmixed. Despite the evidence for internal strain, relatively intact clasts of wall rock and microfossils are preserved within the clay. The fault core clay minerology is consistent with a shallow, low-temperature authigenesis derived from shear-enhanced chemical reactions between wall rocks of contrasting chemistry during sinistral strike-slip. The observed structure is comparable to those of other major weak-cored plate boundaries (e.g. the San Andreas fault). Through detailed mapping, we demonstrate that the internal structure of a plate boundary fault core can vary in thickness and composition along-strike over centimetre- to metre-length scales. Earthquake rupture mechanics critically depend on the physical properties of fault rock assemblages. Therefore, models that investigate rupture propagation at active plate boundaries should incorporate, or else assess tolerance and sensitivity to, variable fault core thickness and composition. Supplementary material: Further X-ray diffraction (XRD) analytical data are available at https://doi.org/10.6084/m9.figshare.c.4663640 |
| Databáze: | OpenAIRE |
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