SPP - SAMPLE

Section 4.2 is involved in the SAMPLE programme with three main projects as PI or co-PI:

Composition and melting conditions of primary mantle magmas at the volcanic rifted margin of southern Africa
The aim of this project is to determine the composition of primary magmas in the Etendeka volcanic province of Namibia and to estimate the intensive parameters of melt generation in the mantle source. The main methods are micro-analysis of phenocryst minerals and melt inclusions within them, combined with petrologic modelling.

Contact: Dr. Robert Trumbull

Structures and mechanisms of dyke emplacement at a volcanic rifted margin
Continental rifting along the South Atlantic protomargins was accompanied by injection of basaltic dyke swarms on a large scale. In this joint project with the Karlsuhe Institute of Technology we examine the geometric distribution and orientation of dyke swarms in NW Namibia, determine their ages with radiometric dating, and investigate magma flow directions from anisotropy of magnetic susceptibility. We combine this with geochemical and petrologic analysis of selected dykes to unravel the complexities of crustal extenstion and magma emplacement at a volcanic rifted margin.

Contact: Dr. Robert Trumbull (GFZ), Prof. Reinhard Greiling (KIT)

The role of mantle plumes in the formation of Large Igneous Provinces: constraints from noble gases

Large igneous provinces (LIPs) are thought to have formed by magmatism resulting from decompressional melting of plume heads. Mantle plumes are upwellings of mantle material in focused conduits considered to originate from deep within the mantle. Plume heads are the leading ends of such upwellings. However, the evidence for this theory of LIP formation is mixed and has been challenged lately. In this context noble gas isotopes are important as a discriminator of deep-mantle origin because of the large and indicative isotope variations existing between the various terrestrial reservoirs. One of the main arguments for a plume origin of Continental Flood Basalt (CFB) magmas is excess ³He compared to MORB. High ³He/⁴He ratios have been found, e.g., in the Afar and Columbia River CFB provinces. Noble gas data from the Paraná-Etendeka LIP (in Brazil and Namibia on either side of the South Atlantic) do not exist and the He isotope data available from the Tristan da Cunha hotspot are not very meaningful. Thus we perform a noble gas study of samples from Etendeka and Tristan da Cunha to constrain the mantle components involved in the formation of CFB and hotspot lavas and to shed some light on the role of plumes in LIP formation.

Contact: Dr. Samuel Niedermann