Towards Absolute dating of Fluid-Flow Remagnetizations: Initial results from Variscan Carbonates

Absolute dating of remagnetization events remains the holy grail in paleomagnetism, with the potential to unlock thousands of rock units for new tectonic, metamorphic, and paleointensity studies. Constraining the timing of remagnetizations is especially crucial for understanding fluid flow and mineralogical transformations in orogenic systems.

As a first step toward dating fluid-flow–related remagnetizations, we investigate three Cambrian carbonate units from the northwestern Iberian Peninsula—Tamames, Láncara, and Vegadeo—remagnetized during the Carboniferous. Our goal is to identify, characterize, and ultimately constrain the age of these fluid-induced remagnetization events.

In this presentation we will show an integration of rock magnetism, paleomagnetism, mineralogical, and geochronology results. Magnetic characterization includes room-temperature and low-temperature hysteresis cycles, IRM acquisition curves, First‑Order Reversal Curve diagrams (FORC), thermomagnetic curves, thermal and AF demagnetization, and anisotropy of magnetic susceptibility (AMS). In addition, targeted mineral separation procedures were performed to obtain magnetic sulfide fractions for Re–Os geochronology. The identification and spatial distribution of magnetic phases were examined using scanning electron microscopy (SEM) and quantum diamond microscopy (QDM), allowing us to distinguish primary from secondary magnetic minerals and to evaluate textural evidence of fluid-rock interaction. Complementary U–Pb carbonate geochemistry provides independent age constraints to compare with paleomagnetic and Re–Os datasets.

Together, these results initiate the development of a robust framework for identifying, characterizing, and dating fluid-induced remagnetizations, offering new insights into the tectonic and mineralogical evolution of Iberia’s orogenic systems.