Plutonic: Volcanic associations in the Tu Le Basin and Phan Si Pan uplift, Northwest Vietnam

Abstract

Major and trace elements and whole rock Sr–Nd isotope data of Late Permian silicic plutonic and volcanic rocks from the Phan Si Pan–Tu Le region in NW Vietnam were studied in order to establish their petrogenetic relationship with the magmatic rocks of the Song Da zone (NW Vietnam) and the alkaline silicic rocks of the Panxi area of the Emeishan large igneous province (ELIP) in SW China. The granites and rhyolites have geochemical characteristics of anorogenic granites (e.g. high Fe# and high Ga/Al) and are further subdivided based on mineralogy. The Phu Sa Phin and Muong Hum granites contain sodic to sodic–calcic amphiboles and sodic pyroxene, while the Phan Si Pan granite does not. The Phu Sa Phin and Muong Hum granites occasionally show peralkaline to metaluminous compositions, while the Phan Si Pan granites and the Tu Le rhyolites have metaluminous to peraluminous compositions. The chondrite-normalized REE patterns and the primitive mantle- normalized spidergrams (enrichment in high field strength elements) are similar to those of the Song Da silicic rocks. The eNd(t) values range from weakly negative to moderately positive values (−2.2 to +2.2), suggesting the silicic rocks may be assimilated by basement rocks during magma emplacement. Permian magmatic rocks in the Phan Si Pan–Tu Le region are petrologically, geochemically and geochronologically comparable to those of the inner zone of ELIP.