The application of a ThHfTa diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary Volcanic Province

摘要: The recently proposed [1] ThHfTa diagram is shown in the light of considerable additional data to be a sensitive indicator tectonic environment which an unknown lava (basic silicic) was erupted. With presently available it now possible distinguish calc-alkaline lavas from island arc tholeiites. Some fields different environments have been enlarged and boundaries between modified slightly, but conclusions drawn by Wood et al. are still supported data. It not discriminate E-type MORB andtholeiitic within-plate basalts using this diagram, when used conjunction with ZrTiY triangular [23] (as originally suggested [1]) these magma types can distinguished. The effects bulk lower upper crustal contamination alkali basalt on Th, Hf, Ta radiogenic isotope concentrations residual liquids calculated detail. ratios extremely processes. Data published Thompson co-workers [2,5] for Tertiary Skye, Scotland, illustrate complexity develop petrogenic model lavas. These calculations suggest that use isotopic alone estimate extent particular has suffered fraught errors should interpreted care.