Sources of the Karoo and Etendeka LIPs

The Earth's geological record holds evidence for dozens of cataclysmic magmatic episodes, when unfathomable amounts of lava—flood basalts—erupted to the surface over (geologically) short time intervals. One of these events took place at ~180 Ma during the Jurassic period in the Gondwana supercontinent. Over 4 million cubic kilometers of lavas and intrusives erupted in what today constitutes parts of southern Africa, Antartica and the Falklands, forming what is called the Karoo large igneous province (LIP). A similar event took place in western Africa at ~130 Ma, forming the Etendeka LIP.

The enormous scale and repeated occurrence of LIPs points to an important process in the Earh's interior. For surface dwellers, LIPs can be disastrous and are suspected to have caused several mass extinctions through the release of climate-perturbing gases. We want to better understand how and why LIPs form.

In this project (part of the Research Council of Finland-funded GEMS-project, led by the Karoo guru Dr. Arto Luttinen), we use both short-lived (Nd-142, W-182) and long-lived radiogenic isotope systems (of Sr, Nd, Hf, Os and Pb) to get a better grasp of the nature of the mantle source of the Karoo and Etendeka LIPs. In particular, measurable variations in the Nd-142 and W-182 systematics could have only been generated in the first 500 Ma and 60 Ma of Earth history, respectively. Detection of Nd-142 or W-182 anomalies in Karoo rocks would give us a clues to the potentially ancient nature and origin of LIP sources.

The geochemical information will be used in the project to inform geodynamic models of mantle convection and melting aiming to simulate LIP formation.