Titanite Petrochronology Records Secular Temperature and Fluid Evolution During Ductile Deformation: An Example From Late Cretaceous Shear Zones in the Eastern Transverse Ranges

Quantifying the timing and conditions of ductile deformation is essential for quantitative models lithospheric deformation. Yet, directly constraining these variables documenting how they change during a single event remain difficult. We present titanite microstructural, zoning, trace-element, U-Pb data from <m-scale mylonitic shear zones in Eastern Transverse Ranges, CA (Joshua Tree National Park) that record (a) (b) evolution within single, punctuated event. Titanite grains sheared plutonic rocks yield bimodal distribution dates (∼151 ∼75 Ma) interpreted as independently constrained pluton crystallization zone ages, respectively. Synkinematic neocrystallization at Ma documents early ∼640–710°C under hydrous fluid conditions. Recrystallized rims with indistinguishable neocrystallized Zr-in-titanite temperatures 600–610°C higher F contents, suggesting became more halogen-rich brine progressed system cooled. Chemical zoning related to fluid-driven recrystallization occurs tandem lattice misorientations partially fully reset bent titanite, implying reactive flow ultimate mechanism by which are deformed dislocation creep. These document (e.g., ∼1–3 Myr) phase high-temperature accompanied local emplacement demonstrate petrochronology can capture multiple, discrete reactions associated crustal weakening affect rheological zones.