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Neodymium and strontium isotope study of ophiolite and orogenic lherzolite petrogenesis

1980; Elsevier BV; Volume: 47; Issue: 1 Linguagem: Inglês

10.1016/0012-821x(80)90104-1

1385-013X

Pierre Richard, Claude J. Allègre,

Geochemistry and Elemental Analysis

Neodymium isotopic analyses have been measured on nine ophiolites and four orogenic lherzolites. εNd varies from +12 to +3 in the ophiolites and from +18 to +2 in the orogenic lherzolites. The majority of the analyses plot on a εNd-εSr correlation line as defined by Nd and Sr isotopic analyses of oceanic basalts. However, certain ophiolitic and lherzolitic samples exhibit high87Sr/86Sr ratios and as such lie to the right of the correlation line towards seawater compositions. From these data one can postulate several origins for ophiolites including that of mid-ocean ridges and ocean islands. If the orogenic lherzolites are interpreted as representative of the mantle occurring below active ridges a more complex model is required involving mantle heterogeneity and multi-episodic chemical fractionation starting prior to 2 Ga ago.