Cretaceous volcanic rocks of the South Tethyan suture zone, Pakistan: implications for the Réunion hotspot and Deccan Traps

Abstract

The location, ages, and geochemical characteristics of marine volcanic rocks preserved in the South Tethyan suture zone of Pakistan suggest that the Réunion hotspot was active off northwestern Greater India well before the emplacement, far to the south, of the Deccan flood basalts, the great bulk of which were erupted at 65–66 Ma and are widely believed to be associated with the hotspot’s plume-head phase. Most of the suture zone samples have Nd–Pb–Sr isotopic ratios (e.g. age-corrected ϵNd(t)=+3.0 to +4.6) close to those expected for modern-type Réunion source mantle in the Late Cretaceous, and their incompatible element patterns resemble those of recent Réunion shield lavas. 40Ar–39Ar incremental heating yields ages of 73.4–72.0 Ma. Nevertheless, unless even older ages are discovered among the suture zone rocks, a pre-Deccan marine phase of Réunion hotspot activity on the Tethyan side of Greater India can be accommodated within the framework of the plume-head model.