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The Late Proterozoic Torridon Group Applecross Formation in the foreland of the Moine Thrust Belt, NW Scotland, contains deformation bands, three fracture sets (from oldest to youngest A, B, and L) defined by orientation, crosscutting relations, and progressively less quartz cement in younger sets, and joints. Set A crosscuts deformation bands and strikes north-south. Set B has trimodal orientation defining three linked subsets that formed concurrently. Set L strike ranges from NE-SW to ENE-WSW, in parent crack-wing crack arrays that formed progressively; these are more abundant near small-displacement, oblique-slip faults that offset the overlying Cambrian Eriboll Formation and the Moine Thrust Belt. Applecross sandstones have low fracture abundance, possibly a consequence of low elastic moduli (Young's modulus 2.3-17.0 GPa, most values <6.9 GPa) and moderate to high subcritical crack index (45-78), resulting from compacted soft lithic grains and clay-mineral cements. Low abundance contradicts models that postulate persistent incipient failure by subsurface fracture. The fracture sequence resembles that found in the overlying Cambrian Eriboll Formation quartzarenites, implying that no widespread late Proterozoic fracture sets exist in this part of the Applecross Formation, an uneventful record for a rock profoundly resistant to brittle deformation.

Cambrian Eriboll Formation sandstones of the Ardvreck Group that crop out west of the Moine Thrust Zone contain joints and quartz-filled or quartz-lined fractures that resemble cemented joints. Of the fractures containing quartz, five sets strike north, NW to WNW, NE, west and north; according to crosscutting relations this is a progression from the oldest to the youngest set. Sets include opening-mode microfractures, partly visible in transmitted light as fluid-inclusion planes and sharply defined as microveins using SEM-based cathodoluminescence (CL). Dating the oldest north-striking set, using inferred quartz accumulation rates, fluid inclusions and burial history, suggests that these fractures mark a Palaeozoic east-west least horizontal stress trajectory in Laurentia. The youngest two sets of porous fractures are associated with faults that cut and postdate the Moine Thrust Zone. Data indicate that at depth in basins, pervasive fracture systems arising from discrete loading events are ephemeral owing to fracture porosity destruction by cementation.