PHYSICS OFTHE EARTH AND P LAN ETA RY _________ INTERIORS ELSEVIER Physics of the Earth and Planetary Interiors 85 (1994) 3—13 Geochemical constraints on the origin of secondary magnetizations in the Cambro-Ordovician Royer Dolomite, Arbuckle Mountains, southern Oklahoma R.D. Elmore a,* K. Cates a G. Gao b L. Land b a School of Geology and Geophysics, University of Oklahoma, Norman, OK 73019, USA b Department of Geological Sciences, University of Texas at Austin, Austin, TX 78713, USA Received 2 September 1993; revision accepted 6 January 1994 Abstract Geochemical and paleomagnetic results from Cambro-Ordovician Royer Dolomite in the Arbuckle Mountains, southern Oklahoma, suggest a connection between dolomite type and magnetizations. One dolomite type, which is most common in the vicinity of the Arbuckle Anticline, has a dull luminescence, low ~18Ovalues, coeval to slightly lower 87Sr/86Sr ratios and contains an easterly Cambro-Ordovician magnetization in magnetite. To the southeast, closer to the Ouachita Mountain front, most of the Royer dolomite contains a southeasterly and shallow magnetization in magnetite that is interpreted to be Late Paleozoic in age. In contrast to the other dolomites, these dolomites contain abundant authigenic K-feldspar and pyrite, radiogenic 87Sr/86Sr ratios, and have a bright (red) luminescence, all of which are consistent with alteration by basinal fluids. At one site, a stromatolitic bioherm, dolomites similar to those at the Arbuckle Anticline are surrounded by the altered dolomites. The distribution of specimen directions at this site is streaked between a Cambro-Ordovician and Late Paleozoic direction. The results of this study suggest a connection, either direct (by causing precipitation) or indirect (by increasing permeabilities for another fluid), between a radiogenic fluid and a chemical magnetization in magnetite. The relatively unaltered dolomites at the stromatolitic bioherm site escaped the almost pervasive alteration and remagnetization caused by the basinal fluids close to the Ouachita Mountains, a potential source for the fluids. 1. Introduction 1989; Elmore and McCabe, 1991; Elmore et at., 1993a). Most of these secondary magnetizations Secondary magnetizations that reside in mag- are pervasive in rock units and many are synfold- netite are common in sedimentary rocks and their ing (see McCabe and Elmore, 1989). Several origin is controversial (e.g. McCabe and Elmore, mechanisms have been proposed for these mag- netizations, including chemical processes (e.g. _______ McCabe et al., 1989), thermoviscous processes * Corresponding author. (Kent, 1985), and strain (Hudson et a!., 1989). 0031-9201/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSDI 003 1-9201(94)05044-X