Archean records in the Kontum Complex (Central Vietnam) and implications for Precambrian crustal evolution in Indochina

Abstract

Zircon U-Pb age-clusters of ∼3.5 Ga and ∼3.2 Ga with εHf(t) = +1.0 ∼−13.5 and THfDM = ∼3.4–4.0 Ga are documented from plagioclase amphibolites in the Kham Duc rock-unit of the Kontum Complex, Indochina. These data provide evidence for a Paleoarchean crustal nucleus that is in part synchronous with, as well as older than, the Yangtze basement of the South China Block. In addition, the presence of ∼2.2 Ga, ∼1.85 Ga and ∼1.42 Ga age-records in the complex correlate with those in the southern Yangtze, suggesting their connection at the time of Nuna assembly and breakup. These data reveal a similar Paleoarchean-Mesoproterozoic crustal evolution among Indochina, Yangtze, Australia and NW Laurentia. The Ordovician-Silurian and Triassic tectonothermal events in the Kontum Complex link to the breakup of the Indochina Block from the northern margin of Gondwana prior to accretion to Asia.