Nature and significance of plutonic clasts in Devonian conglomerates of the New England Fold Belt

Abstract

Abstract Granite, adamellite, granodiorite, quartz monzodiorite and quartz diorite clasts, together with much more abundant basic and intermediate volcanic detritus, occur in Devonian conglomerates in the New England Fold Belt, N.S.W. The plutonic material is of calc‐alkaline type, characterised overall by high Fe/Mg ratios and low LIL abundances, and is geochemically more closely allied to plutonic rocks from island arcs than to those emplaced in continental crust. Small intrusive bodies emplaced within the volcanic chain to the west, which supplied most of the Devonian sedimentary material, are inferred to be the source of the plutonic debris. Geo‐chemical characters and palaeogeographic relationships indicate that the clasts were not derived from Late Silurian gabbro‐diorite‐granodiorite intrusions in the northern part of the Lachlan Fold Belt. The absence of accompanying metasedimentary hornfels or metamorphic basement detritus also argues against a Lachlan source and a source in a basement terrain to the west of the New England Fold Belt.