Geochemical characteristics and tectonic significance of OIB-type basalts in the Nagong area, southern Tibet

The basalts of the Sangxiu Formation are widely distributed across the Nagong area of southern Tibet, particularly along the Rongbu–Gudui fault and its secondary faults. High-precision testing and analysis of the basalts reveal SiO2 contents ranging from 43.7 to 47.71%, and initial 87Sr/86Sr and 143Nd/144Nd ratios of 0.706135–0.708093 and 0.512521–0.512706, respectively; eNd(t) values are − 1.18 to + 2.57. These data are consistent with the characteristics of ocean island basalts (OIB) and Emeishan high-Ti basalts. Large ion lithophile elements (LILEs) such as Rb and Ba, as well as high field strength elements (HFSEs) such as Nb, Ta, and Zr, are enriched, and there is no obvious Eu negative anomaly. These results indicate that the Sangxiu basalts are OIB-type alkaline basalts formed through interactions with the lithospheric mantle as well as partial melting of the asthenospheric mantle in relation to a mantle plume. Additional comparative analysis of the regional Cuomei Large Igneous Province (CLIP) and other rocks related to the Kerguelen hotspot suggests that the Nagong basalts belong to the CLIP in relation to the earliest Kerguelen hotspot activity.