Volume 38: January - December 1997

Issue 7: July 1997

Abstract

Eclogites and Blueschists of the Pam Peninsula, NE New Caledonia: a reappraisal

  • Eclogites and Blueschists of the Pam Peninsula, NE New Caledonia: a reappraisal

    • GL. Clarke, JC. Aitchison2 and D. Cluzel3

    1Department of Geology and Geophysics, University of Sydney, Sydney, NSW 2006, Australia and 2Department of Earth Sciences, University of Hong Kong, Pokfulam Road, Hong Kong3Laboratoire de Geologie, Universite Francaise du Pacifique, BP 4477, Noumea, New CaledoniaCorresponding author Email: geoffc@ucc.s.oz.au

    ABSTRACT

    High-P rocks of the Pam Peninsula, NE New Caledonia, are divided into three zones: (1) an uppermost ferroglaucophane-lawsonite zone of Cretaceous to Eocene metasediments and metavolcanics of the Diahot terrane that experienced peak conditions involving P=7-9 kbar and T=400+-58oC; (2) albite-epidote-omphacite zone Diahot terrane rocks that experienced blueschist facies conditions of P=12.6+-1.2 kbar and T=570+-36oC; (3) lowermost metabasic eclogites of uncertain age that form the Pouebo terrane which experienced high-P conditions of P-23.9+-3.0 kbar and T 600oC. Eclogite occurs as metre- to kilometre-scale pods in coarse-grained hydrous mineral-rich 'glaucophanite' formed during hydration and decompression of the Pouebo terrane. Metamorphism and deformation were consequent to 44-51 Ma Eocene convergence, when sedimentary and ophiolitic nappes were thrust over the eclogites in a SW direction; white mica ages constrain metamorphism to have ended by 37+-1 Ma. Large steps in metamorphic grade are coincident with SW-dipping and NE-dipping faults that separate the three zones and were formed during two stages: (1) comparatively slow uplift and hydration of the Pouebo terrane before it was juxtaposed with the albite-epidote-omphacite zone at P 14 kbar; (2) comparatively rapid uplift of both the Pouebo terrane and the albite-epidote-omphacite zone to form a domal core of eclogite flanked by significantly lower-grade rocks to the SW and NE.

    Keywords: blueschist; eclogite; high-P metamorphism; New Caledonia; thermobarometry

    Pages: 843 - 876

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