| Paper No. 114-0 | ||
| PALEOMAGNETIC DATING OF MINERALIZATION AT RED DOG AND THE MESOZOIC TECTONIC HISTORY OF THE BROOKS RANGE, ALASKA | ||
|
LEWCHUK, Michael T., School of Geology and Geophysics, Univ of Oklahoma, 100 East Boyd Street, Norman, OK 73019, mlewchuk@ou.edu, LEACH, David, USGS, MS 973, Federal Center, Denver, CO 80225, SYMONS, David, Department of Earth Sciences, Univ of Windsor, 401 Sunset, Windsor, ON N9B 3P4, Canada, and ELMORE, R. Douglas, Geology and Geophysics, Univ Oklahoma, 100 East Boyd St, Norman, OK 73019-1009 Paleomagnetic methods have isolated two ancient magnetizations in and around the Paleozoic shale hosted Red Dog ore deposit in northern Alaska. A shallow southerly magnetization was found in rocks dominated by galena and sphalerite while a much steeper, westerly magnetization was found in rocks that have substantial quartz replacement. Based on inclination only, the shallow magnetization formed at equatorial latitudes and the steeper magnetization at high latitudes. The steep magnetization is similar to secondary magnetizations of Mesozoic age found previously throughout the Brooks Range and geochemical considerations require that the quartz formed during deep burial in the Mesozoic. Thus the quartz-rich rocks are recording regional remagnetization associated with quartz replacement during the Mesozoic. The older magnetization, in Zn/Pb ores lacking quartz replacement, is presumably the recording the age of the mineralization at an equatorial latitude. Further interpretations are dependent upon hypotheses for the Mesozoic tectonic history of the Brooks Range. If the Brooks Range was a part ancestral North America but rotated counter-clockwise by 50-70° coincident with the opening of the Canada Basin, then the shallow magnetization is contemporaneous with the age of the host rocks. Thus the main Zn/Pb mineralization is syngenetic and formed during the Carboniferous. Hypotheses that preclude counter-clockwise rotation of the Brooks Range and instead consider it an accreted terrane could allow for a younger magnetization age and an epigenetic origin for the ore. However this would require several thousand kilometers of northward translation. Thus we favor the hypothesis of a syngenetic Zn/Pb ore followed by counter-clockwise rotation of the Brooks Range during the Mesozoic. | ||
|
GSA Annual Meeting, November 5-8, 2001
General Information for this Meeting | ||
| Session No. 114 Sediment-Hosted Lead-Zinc Deposits: Roles of Basin Evolution, Tectonics, and Geochemistry in Ore Genesis I Hynes Convention Center: 306 8:00 AM-12:00 PM, Wednesday, November 7, 2001 | ||
© Copyright 2001 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions. | ||