Conodont colour alteration indices (CAI) of Upper Ordovician limestones from the Iberian Peninsula

摘要: Conodont colour alteration index (CAI) data in Upper Ordovician rocks from several areas of the Variscan domain Iberian Peninsula indicate conditions ranging diagenesis to low-grade metamorphism. In most areas, where studies using other indicators, such as illite crystallinity (IC) or vitrinite reflectance are lacking, CAI method has permitted a preliminary estimation metamorphic grade. Almaden syncline (Central-Iberian Zone), IC available, thermal inferred agree with those obtained by method. Puertollano–Almuradiel syncline, interval primarily fluid inclusions (270–370°C) overlaps considerably that (180–340°C). general, cleavage is present anchizonal epizonal conditions, whereas diagenetic ≥ 2.5, scarce. The conodont texture changes increasing metamorphism, and apatite recrystallisation appears general 5. Variation values within single sample and/or short stratigraphic distances observed at localities due hydrothermal activity.