Figure 3
From: Bilateral geochemical asymmetry in the Karoo large igneous province
Correlation between ΔNb and contamination-sensitive incompatible element and isotopic ratios. ΔNb values versus (a) La/Nb, (b) Th/Nb, (c) initial 87Sr/86Sr and (d) initial εNd in Karoo CFBs. Plausible parental magma types with MORB-like (D-picrites23 and Ahlmannryggen (AR)29 dykes for South Karoo CFBs; P-dykes44,48 for North Karoo CFBs) and SCLM-like (E-picrites18,20,25,28 for South Karoo) characteristics are indicated. Compositions of possibly related mantle source components (depleted mantle DM68; estimated South Karoo SCLM; chondritic primitive mantle PM69; non-chondritic primitive mantle PMNC49,50; enriched mantle EM1 based on Walvis Ridge from http://georoc.mpch-mainz.gwdg.de/georoc/) are illustrated. Compositions of OIB-like South Karoo dykes23,29 are shown for comparison. The influence of lithospheric contamination and compositions of possible lithospheric contaminants are schematically indicated [silicic rocks of Kaapvaal crust from http://georoc.mpch-mainz.gwdg.de/georoc/; Karoo sandstone37; Archaean crust18; SCLM-sourced melts L1 (Vestfjella lamproite, South Karoo)64 and L2 (Leucite Hills lamproite, Wyoming)65. TA error is estimated total analytical error (Methods). The isotopic compositions are calculated at 180 Ma, apart from L1 (160 Ma), and DM, PM, PMNC, and EM1 reservoirs and L2 (present-day values).
