Seawater Alteration of Pillow Lavas, Bay of Islands Ophiolite Complex, Western Newfoundland

Abstract

<p>The pillow lavas of the lower Crabb Creek area or the Bay of Islands Ophiolite complex exhibit geochemical and petrographic characteristics similar to metamorphosed mid-ocean ridge basalts. Depletions of Ca and Mg and the enrichment or K, P, Na, Si and H2O are the result of hydrothermal alteration and the metasomatic influence seawater on fresh basalts.</p> <p>All samples exhibit typical low grade, greenschist Facies metamorphic mineral assemblages. 'Fresh', moderately altered and severely altered suites can be recognized by the degree or degradation of the phenocryst and matrix phases. Immobile trace elements show these metabasalts to originally be ocean-floor tholeiites .</p>