PALEOPLUMBING AND REMAGNETIZATION ALONG FAULTS IN SCOTLAND

Chemical remanent magnetizations (CRMs), interpreted to be late Paleozoic to Mesozoic in age, are reported from many Precambrian and Paleozoic rocks in Scotland. We investigated the Moine Thrust Zone (MTZ), Highland Boundary (HB), Great Glen (GG), and Southern Uplands (SU) in Scotland and found multiple CRMs and associated diagenetic alteration in and around the fault zones except for the SU Fault. The MTZ contains four CRMs (Devonian, Permian, Mesozoic, and Early Tertiary) in different lithologies and sections of the fault zone from Skye to Durness. In addition, CRMs residing in hematite are present in vein sets associated with the MTZ that are Triassic (north-south veins) and Jurassic (east-west veins) in age near the MTZ and are interpreted as representing two brecciation and fluid flow events that are related to extension in the Mesozoic. The GG fault contains Permian and Cretaceous CRMs along different segments that were caused by fluid events that precipitated hematite. A Permian hematite CRM is present along the HB fault. These CRMs can be attributed to post orogenic activity which released heat during regional crustal extension in the Permian, hydrothermal activity associated with Tertiary intrusions, Devonian and Carboniferous igneous activity, and extension in the Mesozoic. In contrast, we did not isolate a CRM from Carboniferous limestones at several localities along SU fault. The reason the rocks directly around the SU fault do not contain a CRM and was apparently not a fluid conduit is an open unresolved question. Fractured, mineralized, and folded limestones (Carboniferous) deformed by the Southerness Fault at Southerness, south of the SU fault, however, contain magnetizations with southerly directed declinations and shallow negative inclinations that are either pre-tilting or syn-tilting. They are interpreted to be Permian CRMs residing in magnetite related to fluid migration along the Southerness Fault in the Late Permian. These results suggest that fractured and permeable segments along most of the major faults in Scotland were conduits for fluids at different times from the Paleozoic to the Cenozoic, and may have provided a paleoplumbing system for Scotland.