RT Journal Article
SR Electronic
T1 Laurentian palaeostress trajectories and ephemeral fracture permeability, Cambrian Eriboll Formation sandstones west of the Moine Thrust Zone, NW Scotland
JF Journal of the Geological Society
JO Journal of the Geological Society
FD Geological Society of London
SP 349
OP 362
DO 10.1144/0016-76492008-061
VO 166
IS 2
A1 Laubach, S.E.
A1 Diaz-Tushman, Kira
YR 2009
UL http://jgs.lyellcollection.org/content/166/2/349.abstract
AB 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.