title: Challenges in Interpreting 40Ar/39Ar Age Spectra: Clues from Hydrothermally Altered Alkali Feldspars
abstract: Integrated 40Ar/39Ar and U-Pb geochronology, combined with microstructural analysis of Early Cretaceous volcanics from eastern China, challenge conventional interpretations of flat 40Ar/39Ar age spectra. K-feldspar sample JD-1K (122.12 ± 0.81 Ma) preserves magmatic sanidine characteristics (homogeneous composition, disordered monoclinic structure), while hydrothermally altered perthite JD-2K yields a flat plateau age of 99.83 ± 0.73 Ma (~20 Ma younger than coeval K-feldspar, biotite, and zircon 
journal: Geosciences