Browsing by Author "Turunen, Sanni"

This study describes a series of picritic lavas from the Luenha River, Mozambique, related to the Karoo large igneous province. The reservoirs for the African Karoo-related flood basalts are not well known. There are no previously documented primitive volcanic rocks related to them. In this study, picritic lavas from the Luenha River are found to be primitive and to exhibit a HREE-undepleted trace element signature, similar to those of African flood basalts. Significant within-series variation is observed in REE concentrations and Sr isotopic compositions, and can be modelled as a result of crustal contamination of a primitive melt. The high deltaNb values (0,4–0,6), low TiO2 concentrations (0,3–1,0 wt. %), high-Al spinel cores, chondritic isotopic ratios in the most primitive samples and smooth, HREE-undepleted PM-normalized trace element compositions could be derived by high-degree, shallow depth partial melting of a source other than depleted upper mantle. Luenha picrites might represent a parental melt for the Karoo shallow source lavas and may facilitate characterization of their mantle sources. Major element compositions were analysed by X-ray fluorescence method (XRF), trace elements by inductively coupled plasma mass spectrometer (ICP-MS), mineral chemistry by electron probe microanalyzer (EPMA) and isotopic ratios for Sr and Nd were measure with thermal ionization mass spectrometer (TIMS). A polarization microscope was used for petrography.