Geochemistry and petrogenesis of Late Ladinian OIB-like basalts from Tabai, Yunnan Province, China

Abstract

Major and trace elements analysis has been carried out on the Late Ladinian Tabai basalts from Yunnan Province with the aim of studying their petrogenesis. Their SiO2 contents range from 43.63 wt.% to 48.23 wt.%. The basalts belong to the weakly alkaline (average total alkalis Na2O+K2O=3.59 wt.%), high-Ti (3.21 wt.% to 4.32 wt.%) magma series. The basalts are characterized by OIB-like trace elements patterns, which are enriched in large ion lithosphile elements (LILE) including Rb and Ba, and display negative K, Zr and Hf anomalies as shown on the spider diagrams. The Tabai basalts display light rare-earth elements (LREE) enrichment and are depleted in heavy rare-earth elements (HREE) on the REE pattern. Those dates indicate that the parental magma of the Tabai basalts was derived from low-degree (1%–5%) partial melting of garnet peridotite. The magma underwent olivine fractional crystallization and minor crustal contamination during their ascent. The Tabai basalts were related to a relaxation event which had triggered the Emeishan fossil plume head re-melting in the Middle Triassic.