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Fig. 9 | Swiss Journal of Geosciences

Fig. 9

From: Triassic magmatism on the transition from Variscan to Alpine cycles: evidence from U–Pb, Hf, and geochemistry of detrital minerals

Fig. 9

Detrital chromian spinel compositional variation diagrams of the Val Sabbia Ss. Red circles represent translucent grains and black crosses represent opaque grains: a Ternary plot of the major trivalent cations in chromian spinel. Fields compiled by Cookenboo et al. (1997) and references therein: i) Alaskan-type; ii) Stratiform field shows compositional range of spinels in ultramafic bodies produced by fractional crystallisation in the crust; iii) Abyssal and Alpine-type peridotites field includes chromian spinel of mantle melting origin as ultramafic xenoliths, abyssal dunites, spinel-plagioclase peridotites and Alpine-type peridotites. b Discrimination between volcanic and mantle spinel using Al2O3 and Fe2+/Fe3+ values. SSZ: suprasubduction zone; MORB-p: Mid-ocean ridge-type peridotites (Kamenetsky et al. 2001). c Spinel field diagram Al2O3 vs TiO2; ARC: arc; CFB: continental flood basalts; MORB: mid-ocean ridge basalts; MORB-p: MORB-type peridotites; OIB: oceanic island basalts; SSZ: suprasubduction zone (fields from Kamenetsky et al. 2001, and Hu et al. 2014). d Typical spinel compositions from various sea-floor and continental crust origin. No scale implied. Modified from Cookenboo et al. (1997). See detailed compositional diagrams in the Online Resource 5

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