Abstract

Ophicalcite, a breccia of controversial origin composed of serpentinite fragments in pink calcite, caps paleotopographic ridges of ophiolite in Ligurian nappes of northern Italy. Abundant geopetal fabrics within the calcite suggest a sedimentary origin in contrast with previously proposed magmatic and hydrothermal origins. The restriction of ophicalcite to paleotopographic highs, upward increase in carbonate versus host rock, absence of fossils, and presence of caliche-like fabrics favor a pedogenic origin rather than an origin by recrystallization of pelagic ooze. Ultramafic rocks were thus subaerially exposed in certain areas prior to radiolarite deposition. If this interpretation is correct, certain long-held views of the environmental significance of ophiolite sequences should be re-evaluated.

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