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The Gangdese batholith emplaced from the Cretaceous to Eocene in southern Tibet has been widely regarded as the major constituent of an Andean-type convergent margin resulting from northward subduction of the Neo-Tethyan oceanic lithosphere under Asia. While the Gangdese batholith consists predominantly of calc-alkaline rocks, we identify from the eastern part of the batholith a suite of epidote-bearing granodiorites that shows adakitic geochemical characteristics, marked with apparently higher La/Yb and Sr/Y, and lower Y and HREE, than other Gangdese rocks and common arc magmas. SHRIMP zircon U–Pb analyses of two of the samples yielded ²⁰⁶Pb/²³⁸U dates of 80.4±1.1 and 82.7±1.6 (2σ) Ma, which constrain the emplacement ages of the adakitic rocks. Trace element modeling suggests that these rocks originated from partial melting of a garnet amphibolite source that, on the basis of the Sr and …