SUBDUCTION-RELATED GRANITIC-ROCKS OF TAIWAN

Late Cretaceous granitic rocks constitute an essential part of the pre -Tertiary Tananao metamorphic basement complex of Taiwan. They are dom inantly of granodiorite to quartz monzonite composition. Most granitic rocks are peraluminous (A/CNK > 1.0 and normative corundum > 1%) and display moderately fractionated LREE and relatively unfractionated HRE E patterns with negative Eu anomalies. On a primitive mantle-normalize d trace-element diagram, they show a significant Nb depletion which is typical of the calc-alkaline magmatism from the subduction-zone envir onment. They fall within the volcanic are field on the discrimination diagram of Pearce, Harris and Tindle (1984). The lack of systematic in ter-element relationships suggests that the role of fractional crystal lization is not significant and that these granitic rocks were derived from heterogeneous protoliths. Geochemical data suggest Taiwan granit ic rocks are contaminated I-type and I-type granites related to the su bduction of the Paleo-Pacific plate beneath the eastern margin of the Eurasia plate during late Mesozoic time. Copyright (C) 1996 Elsevier S cience Ltd