Open AccessLate Carboniferous to Permian remagnetization of Devonian limestones in the Ardennes: Role of temperature, fluids, and deformation
Author(s) -
Zegers T. E.,
Dekkers M. J.,
Bailly S.
Publication year - 2003
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2002jb002213
Subject(s) - geology , permian , carboniferous , pyrrhotite , magnetite , remanence , paleomagnetism , illite , natural remanent magnetization , devonian , massif , mineralogy , paleozoic , geochemistry , petrology , paleontology , clay minerals , magnetization , pyrite , magnetic field , physics , structural basin , quantum mechanics
To test various remagnetization mechanisms in unmetamorphosed to very low grade metamorphic carbonates, we integrated paleomagnetic and rock magnetic data of Devonian carbonates with geological observations in the well‐studied Rhenohercynian Belt of France and Belgium. Paleomagnetic results from 42 sites show that there are three separate remanence components. Hysteresis measurements that are consistent with unremagnetized limestones and the low paleotemperature of the Boulonnais area (<55°C) indicate that component B is a primary Middle Devonian natural remanent magnetization (NRM). Prefolding to postfolding Carboniferous component C and postfolding Early Permian component P both occur throughout the Ardennes and Brabant Massif. Rock magnetic results indicate that component P is carried by pyrrhotite and component C is carried by a magnetite mix that straddles the single‐domain‐multidomain grain‐size range (10–30 nm). The relative intensity factor, R i , defined as ln(intensity P/intensity C), shows a marked spatial correlation with the southern of two Mississippi Valley‐type (MVT) ore districts. This, in combination with the timing of remagnetization, suggests that component P pyrrhotite formed as a result of percolation of MVT fluids through these carbonates. Fine‐grained magnetite formation, as a by‐product of smectite‐to‐illite conversion in the presence of host‐rock‐buffered internal fluids during deformation, is the most likely remagnetization mechanism for component C. Pressure solution deformation processes may have enhanced the smectite‐to‐illite conversion and hence remagnetization.