Paleofluid-flow in a foreland basin, Northern Appalachians: from syntectonic flexural extension to Taconian overthrusting

Structural relationship of fracture sets combined with fluid-inclusion data and isotopic composition of vein infill help constrain the P-T history of the Quebec foreland basin. Results suggest that a warm (60 degrees C), low salinity fluid of meteoric origin migrated through fracture networks and no rmal faults in the Ville de Quebec rocks during the extensional collapse of the outer shelf in the lowermost Caradocian. This fluid was progressively mixed with a warmer (150-160 degrees C) high salinity, basinal fluid associ ated with hydrocarbon gases and fluids. P-T modelling of inclusions related to the second pulse suggests a 3-4 km maximum burial depth for rocks of th e Quebec Promontory Nappe that we equate with thrusting of the nappe over t he autochthonous margin and/or overthrusting by the Chaudiere Nappe. (C) 20 00 Elsevier Science B.V. All rights reserved.