Journal of Petrology | Volume 38 | Number 7 | Pages 843-876 | 1997
© Oxford University Press 1997
Eclogites and Blueschists of the Pam Peninsula, NE New Caledonia: a Reappraisal
1 Department of Geology and Geophysics, University of SydneySydney, NSW 2006, Australia
2 Department of Earth Sciences, University of Hong KongPokfulam Road, Hong Kong
3 Laboratoire de Géologie, Université FranÇaise du PacifiqueBP 4477, Noumea, New Caledonia
Received May 8, 1996; Revised typescript accepted February 19, 1997
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Abstract |
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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±58°C; (2) albite–epidote–omphacite zone Diahot terrane rocks that experienced blueschist facies conditions of P=12.6±1.2 kbar and T=570±36°C; (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 600°C. Eclogite occurs as metre- to kilometre-scale pods in coarse-grained hydrous mineral-rich ‘glaucophanite’ formed during hydration and decompression of the Pouébo 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 Pouébo 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.
KEY WORDS: blueschist; eclogite; high-P metamorphism; New Caledonia; thermobarometry
* Corresponding author Email: geoffc{at}ucc.s.oz.au
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