Origin of the Coloured Karst Fills in the Neogene Extensional System of NE Iberia (Spain)

Karst fills from the onshore Penedès Basin and offshore València Trough display red, pink, orange and ochre colours. Their Mössbauer spectra indicate that Fe3+ contained in goethite is the dominant species in reddish-pink fills, whereas Fe2+ contained in dolomite and clays is more dominant in the or...

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Bibliographic Details
Published in:Minerals (Basel) 2021-12, Vol.11 (12), p.1382
Main Authors: Travé, Anna, Rodríguez-Morillas, Noelia, Baqués, Vinyet, Playà, Elisabet, Casas, Lluís, Cantarero, Irene, Martín-Martín, Juan, Gómez-Rivas, Enrique, Moragas, Mar, Cruset, David
Format: Article
Language:English
Subjects:
Apatite
Basins
Carbon dioxide
carbonate diagenesis
Carbonates
Cement
Chlorite
Colour
coloured karst fills
Dolomite
Dolostone
Dominant species
Fault lines
Feldspars
Fluctuations
fracture and vug porosity
geochemistry
Goethite
Groundwater table
Illite
Illites
Ilmenite
Interlayers
Iron
Kaolinite
Karst
Magnetite
Neogene
Offshore
Oil fields
Pyrite
Sediments
Smectites
Stratigraphy
Strontium 87
Strontium isotopes
Water table
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Summary:Karst fills from the onshore Penedès Basin and offshore València Trough display red, pink, orange and ochre colours. Their Mössbauer spectra indicate that Fe3+ contained in goethite is the dominant species in reddish-pink fills, whereas Fe2+ contained in dolomite and clays is more dominant in the orange and ochre ones. The lower δ13C values and higher 87Sr/86Sr ratios of the karst fills with respect to their host carbonates can reflect the input of soil-derived CO2 and an external radiogenic source into the karst system. This geochemical composition, together with the non-carbonate fraction of the fills, consists of authigenic and transported illite, illite-smectite interlayers, as well as kaolinite, chlorite, pyrite, quartz, ilmenite, magnetite, apatite and feldspar, account for a mixed residual-detrital origin of fills. This polygenic origin agrees with that of the terra rossa sediments described worldwide. The different colours of karst fills are attributed to fluctuations in the water table, which control the Eh/pH conditions in the karst system. Thus, reddish colours reflect low water table levels and oxidising episodes, and orange and ochre ones reflect high water table levels and more reducing episodes. The greenish colours of fills could be related to fluctuations in the Fe3+/Fe2+ ratio.
ISSN:2075-163X
2075-163X
DOI:10.3390/min11121382