Geochronology and thermal history of the Mount Everest massif Available to Purchase

New in situ apatite U–Pb and mica Rb–Sr and ⁴⁰Ar/³⁹Ar geochronology outline a break in geochronology within the Mount Everest massif at an elevation of c. 8000 m. Above the break, most chronometers record dates from the Eocene epoch, whereas below, most dates are from the Middle Miocene epoch. Raman spectroscopy of carbonaceous material and Ti-in-biotite-based thermometry results outline a break in temperatures at the same elevation. From the summit downwards, temperatures increase to a maximum of c. 500°C at c. 8500 m before decreasing to c. 400°C at c. 7900 m. The coinciding breaks in the independent datasets are interpreted to reflect movement along a previously unrecognized structure, here termed the Adrishya thrust that was active c. 18 Ma. The Adrishya thrust may reflect re-equilibration of the evolving orogenic wedge, perhaps further influenced by cooling and strain localization structurally away from the exhuming orogenic core.