Geochemistry and Petrogenesis of Kong Chro Granitoid, Kontum Massif, Central Vietnam

The Kong Chro granitoid exhibits a uniform body and is distributed in the southeastern part of the Kontum massif, belonging to the Indochina block. The lithological composition includes granite, biotite hornblende granite, and granodiorite, which are characterized by a pinkish-gray color and fine to coarse grains. The major minerals comprise plagioclase (30–35%), K-feldspar (30–35%), quartz (20–30%), biotite (<10%), and hornblende (<5%), while accessory minerals include zircon, apatite, ore minerals, and sphene. The Kong Chro granitoid has high SiO2 (69.65–73.70 wt %), and medium Al2O3 (13.45–14.00 wt %) with an aluminum saturation index (A/CNK) range of 0.92–1.03. It is high CaO (0.71–2.05 wt %), high Fe2 $${\text{O}}_{3}^{{\text{t}}}$$ (1.78–3.24 wt %), low MnO (0.02–0.09 wt %), generally high MgO (0.13–0.57 wt %), high TiO2 (0.12–0.32 wt %), and low P2O5 (0.02–0.10 wt %). Trace elements display obvious negative anomalies for Ba, Nb, P, and Ti, as well as obvious positive anomalies for Th, K, Pb, and Y. The notable negative anomalies of Ba, P, and Ti are attributed to the fractional crystallization of plagioclase, apatite, ilmenite, and titanomagnetite, while the positive anomaly of K is linked to the fractional crystallization of K-feldspar. U−Pb zircon isotopic analysis using the LA-ICP-MS method yields an average 206Pb/238U age of 236.5 Ma, corresponding to the late Triassic period. The formation process of the Kong Chro granitoid may be related to the collisional events between the Indochina and South China blocks during the Permian-Triassic period.