The Geology and Thermochronology of Cretaceous Magmatism of Southeastern Vietnam

Abstract

Geological, mineralogical–petrographic, and geochronological studies (U/Pb, Rb/Sr, and Ar/Ar isotope dating) of igneous complexes of the Dalat Zone identified two stages, which reflect a change in the geodynamic regime. The first, Late Jurassic, stage corresponded to a suprasubduction setting with formation of volcanic sequences of the Deobaoloc complex: calc-alkali basaltic andesites, andesites, dacites, their tuff breccias, and tuffs. The second, Albian–Coniacian, stage of the transform setting was related to a sliding zone of tectonic plates, activation of general left-lateral shear deformations at the continent–ocean boundary, and formation of paleovolcanic structures and related Dinhquan granitic batholiths (113 ± 0.6 Ma), Ancroet granites (97 ± 0.4 Ma), Deoca monzogranodiorites (90.4 ± 0.3 Ma), and Cana leucogranite–alaskites (86.8 ± 1.5 Ma). The thermochronological analysis and mathematical modeling indicate that the live period of parental granitic magma in a transform geodynamic setting was Δt of ~27 Ma and differentiation in the deep source resulted in origination of the final Cana leucogranite-alaskitic intrusive stocks with Au–Mo ± Cu mineralization.