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Specific Techniques for Dating of Fluids and Fluid Flow |
School of Geology and Geophysics, The University of Oklahoma, Norman, OK 73019, USA
Palaeomagnetic and geochemical data, and petrographic observations from Palaeozoic rocks in the Arbuckle Mountains provide data on the timing and pathways of fluid flow events. The lower part of the Upper Cambrian Reagan Sandstone, the basal palaeoaquifer in the Palaeozoic section, and the upper part of underlying 525 Ma Colbert Rhyolite are geochemically altered and contain two late Palaeozoic secondary magnetizations. The rhyolite as well as the overlying strata contain apparent primary Cambrian magnetizations. One of the secondary magnetizations (D = 150°, I = 5°,
95 = 5°, 45% tilt corrected) resides in hematite and is interpreted to be a chemical remanent magnetization (CRM) that formed due to hematite authigenesis as a result of fluid migration. The other secondary magnetization (D = 146°, I = 17°, 95 = 4°, 80% tilt corrected) resides in magnetite and is older than the CRM in hematite on the basis of the pole positions. The origin of this magnetization is more ambiguous and could have been caused by hot fluids resetting previously formed magnetite. Evidence for alteration by fluids includes secondary mineralization of calcite, hematite and quartz in veins, depletion/enrichment of elements in the rhyolite, and authigenic hematite cement in the lower Reagan Sandstone. Fluids also migrated along fractures during multiple episodes in the late Palaeozoic, locally remagnetizing and altering younger Palaeozoic strata in the Arbuckle Mountains.
