The oceanic affinities of some alpine mafic rocks based on their Ti-Zr-Y contents

摘要: Ophiolite-Chert complexes containing ultramafics, mafic dykes and pillow lavas, overlain by radiolarian cherts other pelagic sediments are significant features of mountain belts, especially in the Alpine-Himalayan chain (Vine & Hess 1970), Caledonides (Bird et al. 1971). The sedimentology fauna similarity igneous succession with inferred oceanic structure consistent hypothesis that these tectonically emplaced fragments crust upper mantle 1970). Elsewhere orogenic rocks aspect frequently found without full ophiolite being present. Although broadly similar to lavas it has not proved possible establish genetic affinities such their major element chemistry (Vallance 1969). It recently been proposed basaltic may be distinguished ratios three elements, Ti, Zr Y which have shown insensitive alteration affecting elements during metamorphism up greenschist facies (Cann 1971; Pearce Cann Five magma types (number analyses given parentheses) considered Cann; island arc andesites (12), tholeiites (14), ocean alkali basalts (8), tholeiite (13) mid-ocean ridge (39). Using discriminant analysis they constructed functions lava types. Analyses were X-ray fluorescence on pressed powder pellets. On this basis, samples supposed