Importance of alteration of volcanic material in the sediments of deep sea drilling site 323: chemistry, 18O 16O and 87Sr 86Sr

J. R. Lawrence*, J. I. Drever, T. F. Anderson, H. K. Brueckner

*Corresponding author for this work

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65 Citations (Scopus)

Abstract

A downhole decrease in 18O, Mg2+ and K+, an increase in Ca2+ and a low 87Sr 86Sr ratio of 0.7067 in the pore fluids of DSDP site 323 were caused principally by the alteration of volcanic material. These chemical and isotopic patterns were produced by the alteration, in order of decreasing importance of: a 60-m thick basal layer of volcanic ash; the underlying basalts; and igneous components in the 640-m thick upper sequence composed largely of terrigenous material. A significant portion of the alteration of the ash in the basal sequence must have occurred before the deposition of the upper sediments, perhaps under the influence of advecting solutions. The rest of the alteration occurred during the deposition of the thick upper sediments. Mass balance considerations and the low δ18O values of most of the alteration products suggest that much of the later alteration occurred progressively over the last 13 Myr. The principal alteration products were smectite, potassium feldspar, clinoptilolite and calcite.

Original languageEnglish
Pages (from-to)573-588
Number of pages16
JournalGeochimica et Cosmochimica Acta
Volume43
Issue number4
DOIs
Publication statusPublished - 1979
Externally publishedYes

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