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TitleEvolution of sedimentary basins as recorded in silica concretions: an example from the Ionian zone, western Greece
AuthorPe-Piper, GORCID logo; Piper, D J WORCID logo; Bourli, N; Zelilidis, A
SourceMinerals vol. 11, issue 7, 763, 2021 p. 1-16, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210348
PublisherMDPI AG
Mediapaper; on-line; digital
File formatpdf; html
Lat/Long WENS 19.0000 22.0000 40.1667 37.8333
Subjectssedimentology; mineralogy; Science and Technology; Nature and Environment; sedimentary basins; basin evolution; concretions; silica; diagenesis; salt tectonics; bedrock geology; lithology; sedimentary rocks; limestones; clastics; nodules; cherts; fluid dynamics; fluid flow; Ionian Zone; Phanerozoic; Mesozoic; Cretaceous
Illustrationslocation maps; photographs; photomicrographs; plots
ProgramGSC Atlantic Division
Released2021 07 15
AbstractChert concretions in thick limestone successions preserve a more complete paragenetic sequence of diagenetic minerals than their host limestone and interbedded shale. The goal of this study was to test the possible presence of a high-temperature mineralising system in the Ionian basin of western Greece. Upper Cretaceous chert nodules were sampled at Araxos, where rocks are highly faulted and uplifted by salt diapirism, and on Kastos Island, on the flanks of a regional anticline. Chert concretions have microporosity produced by recrystallisation of opal to quartz and fractures produced in the brittle chert during basin inversion. Diagenetic mineral textures were interpreted from backscattered electron images, and minerals were identified from their chemistry. Diagenetic minerals in pores and veins include sedimentary apatite (francolite), dolomite, Fe-chlorite, Fe oxide-hydroxide mixtures, sphalerite, barite and calcite. Sphalerite is restricted to Araxos, suggesting that inferred basinal fluids were hotter and more saline than at Kastos. At Araxos, the Fe oxide-hydroxide also includes minor Cu, Zn, and Ni. Whether the transported metals were derived from sub-salt clastic rocks and basement, or from enriched Mesozoic black shales, is unclear. The effectiveness of this novel approach to understanding fluid flow history in thick limestone successions is validated.
Summary(Plain Language Summary, not published)
Hard concretions in limestone, termed chert, preserve a record of fluid flow through the rocks. In this case study, there is evidence for fluids that precipitate ores of lead and zinc, which are otherwise unknown in this region.

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