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Durham University

Department of Earth Sciences

Profile

Publication details for Professor Yaoling Niu

Bruce, M.C., Niu, Yaoling, Harbort, T.A. & Holcombe, R.J. (2000). Petrological, geochemical and geochronological evidence for a Neoproterozoic ocean basin recorded in the Marlborough terrane of the northern New England Fold Belt. Australian Journal of Earth Sciences 47: 1053-1064.

Author(s) from Durham

Abstract

Petrological, geochemical and radiogenic isotopic data on ophiolitic-type rocks from the
Marlborough terrane, the largest (~700 km2) ultramafic–mafic rock association in eastern Australia,
argue strongly for a sea-floor spreading centre origin. Chromium spinel from partially serpentinised
mantle harzburgite record average Cr/(Cr 1 Al) = 0.4 with associated mafic rocks displaying depleted
MORB-like trace-element characteristics. A Sm/Nd isochron defined by whole-rock mafic samples
yields a crystallisation age of 562 6 22 Ma (2s). These rocks are thus amongst the oldest rocks so far
identified in the New England Fold Belt and suggest the presence of a late Neoproterozoic ocean
basin to the east of the Tasman Line. The next oldest ultramafic rock association dated from the New
England Fold Belt is ca530 Ma and is interpreted as backarc in origin. These data suggest that the
New England Fold Belt may have developed on oceanic crust, following an oceanward migration
of the subduction zone at ca540 Ma as recorded by deformation and metamorphism in the Anakie
Inlier. Fragments of late Neoproterozoic oceanic lithosphere were accreted during progressive
cratonisation of the east Australian margin.