The Parana-Etendeka Province David W. Peate Department of Earth Sciences, The Open University, Milton Keynes, United Kingdom Stratigraphic data and ^Ar-39Ar ages for the Early Cretaceous Parani- Etendeka flood basalts indicate that the main magmatic episode lasted for several m.y. (129-134 Ma) and was linked to the northward opening of the South Atlantic Ocean, but with some earlier magmatism (135-138 Ma) found inland far from the eventual oceanic rift. The regional distribution of distinct high-TiN (Urubici, Pitanga, Paranapanema, Ribeira) and low-TiN (Gramado, Esmeralda) magma types in the lavas and associated dyke swarms implies that magma generation occurred over a wide area and involved different mantle sources. Low MgO contents (3-7 wt%) indicate extensive fractional crystallisation, and upper crustal assimilation was important in the evolution of the Gramado magmas. However, Parani basalts that are considered to be uncontaminated by crust have trace element and isotope characteristics (e.g. NbLa < 0.8; ENA < 0) and major element features that appear to require mantle sources distinct from those of oceanic basalts. The minor, late-stage, Esmeralda magma type is an exception, requiring a component from incompatible-element- depleted asthenosphere. The role of the Tristan mantle plume appears to have been largely passive, with conductive heating facilitating mobilisation of old lithospheric material. Significant rhyolitic eruptions (>I000 km3) that can be correlated across the Atlantic Ocean accompanied the final magmatic phase in the southeast Parana and the Etendeka. The flood basalts post-date most estimates for the Jurassic-Cretaceous boundary, ruling out any link to a faunal extinction. INTRODUCTION Vandoros, 19671. The Rio Grande Rise and Walvis Ridge in the South Atlantic Ocean are interpreted as representing The extensive Parani lava field in central South the fossil trace of the Tristan mantle plume and they con- America and the minor Etendeka remnant in Namibia once nect the flood basalt exposures of the Parani and the formed a single magmatic province [Erlank et al., 1984; Etendeka, respectively, to the present magmatic activity of Bellieni el al., 1984al that was associated with the opening the plume found on the islands of the Tristan da Cunha of the South Atlantic Ocean during the Early Cretaceous. group and Gough (Figure 1) [O'Connor and Duncan, This Parani-Etendeka province ranks as one of the largest 1990; Gallagher and Hawkesworth, 19941. This associa- extant continental large igneous provinces (LIPS), with a tion has bolstered models that stress an important role for preserved volume in excess of 1 x 106 km3 [Cordani and the Tristan plume in generating the flood basalts [e.g., Morgan, 1981; White and McKenzie, 1989; Peate et a/., Large Igneous Provinces: Continental, Oceanic, and Planetary 19901. Flood Volcanism Before the 1960s. numerous papers on the petrograph! Geophysical Monograph 100 Copyright 1997 by the American Geophysical Union and general geological setting of the Parani lavas were 217