The history of remagnetization of sedimentary rocks: deceptions, developments and discoveries
Published:January 01, 2013
Rob Van Der Voo, Trond H. Torsvik, 2013. "The history of remagnetization of sedimentary rocks: deceptions, developments and discoveries", Remagnetization and Chemical Alteration of Sedimentary Rocks, R. D. Elmore, A. R. Muxworthy, M. M. Aldana, M. Mena
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Remagnetizations have been recognized ever since magnetizations in rocks were demonstrably shown to have been acquired at a much later time than the formation or deposition of the rocks themselves. There was mention of remagnetizations as early as the 1950s, and in the 1960s the concept was frequently hypothesized as an explanation for repetitions and loops in apparent polar wander paths. In this paper, remagnetization features and processes are organized by magnetic carrier: hematite, magnetite, Fe-sulphides and goethite. Selected case histories are presented which are chosen in order to reveal important diagnostics, although many origins of remagnetizations are still obscure or incompletely known.
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Remagnetization and Chemical Alteration of Sedimentary Rocks
Chemical remagnetization is a very common phenomenon in sedimentary rocks and developing a greater understanding of the mechanisms has several benefits. Acquisition of a secondary magnetization is usually tangible evidence of a diagenetic event that can be dated by isolation of the chemical remanent magnetization and comparison of the pole position to the apparent polar wander path. This can be important because diagenetic investigations are frequently limited by the difficulty in constraining the time frames in which most past events have occurred. Remagnetization can commonly obscure a primary magnetization; developing a better understanding of remagnetization could improve our ability to uncover primary magnetizations. Many chemical remagnetization mechanisms have been proposed, including those associated with chemical alteration by a number of different fluids (orogenic, basinal and hydrocarbons), burial diagenetic processes (clay diagenesis and maturation of organic matter) or other processes. This paper summarizes our current knowledge of these chemical remagnetization mechanisms, with a focus on examples where there is a connection with chemical alteration.