Fault Rocks of the Moine Thrust Zone: Microstructures and Textures of Selected Mylonites

In this paper, the microstructures typifying the common mylonites found in the Moine Thrust Zone at Eriboll are presented along with c-axis quartz textures. Typical cataclasite microstructures are also depicted. The study revealed that the deformation and softening mechanisms in fault rocks can change with increasing shear strain. It also revealed that strain can be extremely inhomogeneous on the microscale at high shear strains. There is evidence for episodic pulses of brittle behaviour which has been associated with possible seismic behaviour within the zone. The contribution concludes by outlining the microstructural and textural features that can be used to determine the direction of shearing in a mylonite zone.

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Fault Rocks of the Moine Thrust Zone: A Guide to Their Nomenclature

Textures and Microstructures ◽

10.1155/tsm.4.211 ◽

1982 ◽

Vol 4 (4) ◽

pp. 211-221 ◽

Cited By ~ 17

Author(s):

S. White

Keyword(s):

Shear Strain ◽

Country Rock ◽

Fault Zones ◽

Fault Rocks ◽

Fine Grained ◽

Fine Grain ◽

Simple Set ◽

Thrust Zone ◽

Moine Thrust Zone

The aim of this article is to extract from the existing literature a consistent nomenclature that can be used in the description of coherent fault rocks. The nomenclature is dealt with in this paper. Typical microstructures illustrating each is presented in a later paper (White et al ., 1982). It will be shown that a simple set of nomenclature can be extracted from the literature, so long as genetic connotations are kept to a minimum. The sequence, with increasing shear strain is country rock–protomylonite–blastomylonite–mylonite–ultramylonite if the rock has a well developed foliation; country rock–protocataclasite–cataclasite–ultracataclasite if it is without a foliation.It is emphasized that a mylonite is basically a fine-grained schist that has formed within fault zones. It is the association with faulting that distinguishes a mylonite from a fine grain schist.

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118. Fault rocks from Ben Arnaboll, Moine thrust zone, northwest Scotland

Fault-related Rocks ◽

10.1515/9781400864935.382 ◽

1998 ◽

pp. 382-391 ◽

Cited By ~ 1

Keyword(s):

Fault Rocks ◽

Thrust Zone ◽

Moine Thrust Zone

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Terranes

Geological Society London Memoirs ◽

10.1144/gsl.mem.1992.013.01.03 ◽

1992 ◽

Vol 13 (1) ◽

pp. 1-4 ◽

Cited By ~ 25

Author(s):

B. J. Bluck ◽

W. Gibbons ◽

J. K. Ingham

Keyword(s):

Hanging Wall ◽

Fault System ◽

Upper Proterozoic ◽

Lower Proterozoic ◽

Central Highland ◽

Thrust Zone ◽

Lower Palaeozoic ◽

Moine Thrust Zone ◽

Shallow Marine Sediments ◽

Northern Highlands

AbstractThe Precambrian and Lower Palaeozoic foundations of the British Isles may be viewed as a series of suspect terranes whose exposed boundaries are prominent fault systems of various kinds, each with an unproven amount of displacement. There are indications that they accreted to their present configuration between late Precambrian and Carboniferous times. From north to south they are as follows.In northwest Scotland the Hebridean terrane (Laurentian craton in the foreland of the Caledonian Orogen) comprises an Archaean and Lower Proterozoic gneissose basement (Lewisian) overlain by an undeformed cover of Upper Proterozoic red beds and Cambrian to early mid Ordovician shallow marine sediments. The terrane is cut by the Outer Isles Thrust, a rejuvenated Proterozoic structure, and is bounded to the southeast by the Moine Thrust zone, within the hanging wall of which lies a Proterozoic metamorphic complex (Moine Supergroup) which constitutes the Northern Highlands terrane. The Moine Thrust zone represents an essentially orthogonal closure of perhaps 100 km which took place during Ordovician-Silurian times (Elliott & Johnson 1980). The Northern Highlands terrane records both Precambrian and late Ordovician to Silurian tectonometamorphic events (Dewey & Pankhurst 1970) and linkage with the Hebridean terrane is provided by slices of reworked Lewisian basement within the Moine Supergroup (Watson 1983).To the southwest of the Great Glen-Walls Boundary Fault system lies the Central Highlands (Grampian) terrane, an area dominated by the late Proterozoic Dalradian Supergroup which is underlain by a gneissic complex (Central Highland Granulites) that has been variously interpreted as either older

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