The size distribution of framboidal pyrite in modern sediments

An indicator of redox conditions

R. T. Wilkin, H. L. Barnes, Susan Louise Brantley

Research output: Contribution to journalArticle

557 Citations (Scopus)

Abstract

Pyrite framboids are densely packed, generally spherical aggregates of submicron-sized pyrite crystals. In this study, a survey was made of framboid size distributions in recently deposited sediments from euxinic (Black Sea; Framvaren Fjord, Norway; Pettaquamscutt River Estuary, Rhode Island, USA), dysoxic (Peru Margin), and oxic (Wallops Island, Virginia, USA; Great Salt Marsh, Delaware, USA) environments. Pyrite framboids in sediments of modern euxinic basins are on average smaller and less variable in size than those of sediments underlying dysoxic or oxic water columns. Down-core trends indicate framboid size distribution is a sediment property fixed very early during anoxic diagenesis, generally within the top few centimeters of burial. Size distributions in modern sediments are comparable with those in ancient sedimentary rocks, evidence that framboid size is preserved through advanced stages of diagenesis and lithification. It is proposed that where secondary pyrite growth is limited, as to preserve primary pyrite textures, framboid size distribution may be used to indicate whether fine-grained sedimentary rocks were deposited under oxic or anoxic conditions. The Crystal Size Distribution Theory relates framboid size to growth time and rate. On the basis of this theory, the characteristic smaller sizes of framboids in sediments of modern euxinic basins reflect shorter average growth times relative to oxic or dysoxic environments. In euxinic environments, framboid nucleation and growth occurs within anoxic water columns, and growth times are, on average, shorter because of hydrodynamic effects than when framboid nucleation and growth occurs within anoxic sediment porewaters underlying oxic water columns. A maximum framboid growth time of 0.4 years is indicated for framboids forming in the water columns of euxinic basins.

Original languageEnglish (US)
Pages (from-to)3897-3912
Number of pages16
JournalGeochimica et Cosmochimica Acta
Volume60
Issue number20
DOIs
StatePublished - Jan 1 1996

Fingerprint

redox conditions
pyrite
Sediments
sediment
water column
Sedimentary rocks
Water
nucleation
diagenesis
sedimentary rock
Anoxic sediments
euxinic environment
Nucleation
basin
crystal
lithification
sediment property
Crystals
anoxic sediment
Distillation columns

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

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title = "The size distribution of framboidal pyrite in modern sediments: An indicator of redox conditions",
abstract = "Pyrite framboids are densely packed, generally spherical aggregates of submicron-sized pyrite crystals. In this study, a survey was made of framboid size distributions in recently deposited sediments from euxinic (Black Sea; Framvaren Fjord, Norway; Pettaquamscutt River Estuary, Rhode Island, USA), dysoxic (Peru Margin), and oxic (Wallops Island, Virginia, USA; Great Salt Marsh, Delaware, USA) environments. Pyrite framboids in sediments of modern euxinic basins are on average smaller and less variable in size than those of sediments underlying dysoxic or oxic water columns. Down-core trends indicate framboid size distribution is a sediment property fixed very early during anoxic diagenesis, generally within the top few centimeters of burial. Size distributions in modern sediments are comparable with those in ancient sedimentary rocks, evidence that framboid size is preserved through advanced stages of diagenesis and lithification. It is proposed that where secondary pyrite growth is limited, as to preserve primary pyrite textures, framboid size distribution may be used to indicate whether fine-grained sedimentary rocks were deposited under oxic or anoxic conditions. The Crystal Size Distribution Theory relates framboid size to growth time and rate. On the basis of this theory, the characteristic smaller sizes of framboids in sediments of modern euxinic basins reflect shorter average growth times relative to oxic or dysoxic environments. In euxinic environments, framboid nucleation and growth occurs within anoxic water columns, and growth times are, on average, shorter because of hydrodynamic effects than when framboid nucleation and growth occurs within anoxic sediment porewaters underlying oxic water columns. A maximum framboid growth time of 0.4 years is indicated for framboids forming in the water columns of euxinic basins.",
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The size distribution of framboidal pyrite in modern sediments : An indicator of redox conditions. / Wilkin, R. T.; Barnes, H. L.; Brantley, Susan Louise.

In: Geochimica et Cosmochimica Acta, Vol. 60, No. 20, 01.01.1996, p. 3897-3912.

Research output: Contribution to journalArticle

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