Evolution of Sedimentary Basins as Recorded in Silica Concretions: An Example from the Ionian Zone, Western Greece

Chert 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 Gre...

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Bibliographic Details
Published in:Minerals (Basel) 2021-07, Vol.11 (7), p.763
Main Authors: Pe-Piper, Georgia, Piper, David J. W., Bourli, Nicolina, Zelilidis, Avraam
Format: Article
Language:English
Subjects:
Anticlines
Apatite
Backscattering
Barite
Calcite
Chert
Cherts
Chlorite
Concretions
Copper
Cretaceous
Diagenesis
Diapirism
Dolomite
Dolostone
Electron imaging
Fluid dynamics
Fluid flow
Fluids
Fractures
Francolite
High temperature
Iron
Limestone
Mesozoic
Metals
Microporosity
Mineralogy
Minerals
Nickel
Nodules
pores
Quartz
Recrystallization
Rocks
Sedimentary basins
Sedimentary rocks
Sedimentary structures
Shale
Silica
Silicon dioxide
Sphalerite
veins
Zinc
Zincblende
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Summary:Chert 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.
ISSN:2075-163X
2075-163X
DOI:10.3390/min11070763