U-Pb Zircon ages of Granodiorits of the Dien Binh complex in the Kon Tum massif and its tectonic significances

Abstract

Diorite and granodiorite of the Dien Binh Complexare distributed in the western margin of the Kon Tum Massif and are believed to haveformed in relationto the subduction of ancient oceanic lithosphere under the Kon Tum Massif during the Early Paleozoic. Although some previous studies have investigatedthe timing of Dien Binh magmatic emplacement, however, its tectonic setting andsignificancein regional tectonics remain controversial. This paperpresents newU-Pb zircon age datingresults fromtwo granodioritic samples ofthe Dien Binh complex collectedin the west of Kon Tum province. The 206Pb/238U weighted mean ages are441.4 ± 1.8 Ma (2σ, MSWD =1.4, n=16) and 446.2 ± 1.9 Ma (2σ, MSWD=0.93, n=12). The new age data together with previously analyzed age data from themagmatic complex indicate that the I-type granodiorite of the Dien Binh complex has formed during ca. 438–455 Ma, which iscoeval with the Tra Bong I-type granodiorite (ca. 440 –447 Ma), Chu Lai S-type granite (ca. 430–452 Ma) in the Kon Tum Massif. In combination of the timing of Early Paleozoic magmatism (e.g., S-type granite), regional metamorphism, and sedimentary stratigraphy in the Indochina Block supports that the amalgamation of the Kon Tum Massif and the Truong Son Belt began around the late Middle Ordovician to the early Late Ordovician. The analysis results in this study, combined with regional geological data, confirm the existence of coeval I-type and S-type magmatic rocks that were formed during the post-collision orogeny along the Tam Kỳ -Phước Sơn suture zone