Rock magnetic properties of remagnetized Palaeozoic clastic and carbonate rocks from the NE Rhenish massif, Germany.

Several rock magnetic properties are reported for remagnetized biohermal carbonate rocks, platform carbonate rocks and siliciclastic rocks from the NE Rhenish massif, Germany. Thermal demagnetization of a triaxial isothermal remanent magnetization (IRM) applied at room temperature identifies a variety of magnetic minerals in the sample set. Magnetite is the predominant magnetic phase and carries a Late Palaeozoic remagnetization component and can be accompanied by haematite and pyrrhotite as the carrier of remagnetization. High haematite contents are characteristic for samples carrying a remagnetization of Triassic age. Zero field heating of remanence acquired at 10 K indicates significant contribution from magnetic material with blocking temperatures between 10 and 100 K. The Verwey transition at 120 K is much more pronounced in siliciclastic rocks than in carbonate rocks and is presumably related to the presence of detrital multidomain (MD) magnetite. Samples from biohermal carbonate rocks have hysteresis properties with highandratios similar to those from remagnetized carbonate rocks from North America. In those lithologies, the intensity decrease of a low temperature IRM during heating from 10 to 100 K combined with the absence of paramagnetic minerals, high hysteresis ratios, magnetic viscosity and frequency dependence of susceptibility give strong evidence for the presence of superparamagnetic (SP) magnetite. This supports the hypothesis of a chemical remagnetization event in the NE Rhenish massif during the Late Carboniferous. The rock magnetic properties of siliciclastic rocks are characterized by high amounts of paramagnetic material and MD magnetite. MD material obscures the contributions of other material to the bulk magnetic properties completely in most siliciclastic rocks and partly in platform carbonate rocks. [ABSTRACT FROM AUTHOR]