Chemical and hydrological evolution of the Mulhouse potash basin (France): are "marine" ancient evaporites always representative of synchronous seawater chemistry?

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dc.contributor.authorCendón, DIen_AU
dc.contributor.authorAyora, Cen_AU
dc.contributor.authorPueyo, JJen_AU
dc.contributor.authorTaberner, Cen_AU
dc.contributor.authorBlanc-Valleron, MMen_AU
dc.date.accessioned2009-07-22T01:40:32Zen_AU
dc.date.accessioned2010-04-30T05:04:26Zen_AU
dc.date.available2009-07-22T01:40:32Zen_AU
dc.date.available2010-04-30T05:04:26Zen_AU
dc.date.issued2008-07-15en_AU
dc.date.statistics2008-07-15en_AU
dc.description.abstractBrine reaction processes were the most important factors controlling the major-ion (Mg, Ca, Na, K, SO4, and Cl) evolution of brines in the Oligocene, Mulhouse basin (France) evaporite basin. The combined analysis of fluid inclusions in primary textures by Cryo-SEM-EDS with sulfate-delta S-34, delta O-18 and Sr-87/Sr-86 isotope ratios reveals hydrothermal inputs and recycling of Permian evaporites, particularly during advanced stages of evaporation in the Salt IV member. The lower part of the Salt IV evolved from an originally marine input. The basin was disconnected from direct marine inputs and a series of sub-basins formed in an active rift setting where tectonic variations influenced sub-basin interconnections and chemical signatures of input waters. Sulfate-delta S-34 shows Oligocene marine-like signatures at the base of the member. However, enriched sulfate-delta O-18 reveals the importance of synchronous re-oxidation processes. As evaporation progressed other non-marine and/or marine-modified inputs from neighbouring basins became more important. This is demonstrated by increases in K concentrations in brine inclusions and Br in halite, sulfate isotopes trends and Sr-87/Sr-86 ratios. The recycling of previously precipitated evaporites of Permian age was increasingly important with evaporation. This supports the connection of the Mulhouse basin to basins situated north of Mulhouse. The brine evolution eventually reached sylvite precipitation. The chemical signature of the resulting brines is not compatible with global seawater chemistry changes. The fast rate of intra and inter basin brine variations as well as the existence of contemporaneous brines with different chemical signatures, supports our interpretation. The existence of diverse non-marine inputs and associated internal chemical changes to the brine preclude the use of trapped-brine inclusions in reconstructing Oligocene seawater chemistry, without previously identifying all inputs. The general hydrological evolution of the Mulhouse basin is explained as a restricted sub-basin with a first marine stage. This gradually changed to a similar to 40% marine source at the beginning of evaporite precipitation, with the rest of inputs non-marine. The general proportion of solutes did not change greatly over evaporite precipitation. However, as the basin restriction increased the originally marine inputs changed to continental or marine-modified inputs from neighbouring basins north of Mulhouse basin. © 2008, Elsevier Ltd.en_AU
dc.identifier.citationCendón, D. I., Ayora, C., Pueyo, J. J., Taberner, C., & Blanc-Valleron, M. M. (2008). Chemical and hydrological evolution of the Mulhouse potash basin (France): are "marine" ancient evaporites always representative of synchronous seawater chemistry?. Chemical Geology, 252(3-4), 109-124. doi:10.1016/j.chemgeo.2008.01.019en_AU
dc.identifier.govdoc1288en_AU
dc.identifier.issn0009-2541en_AU
dc.identifier.issue3-4en_AU
dc.identifier.journaltitleChemical Geologyen_AU
dc.identifier.pagination109-124en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.chemgeo.2008.01.019en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/1549en_AU
dc.identifier.volume252en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectEvaporitesen_AU
dc.subjectSeawateren_AU
dc.subjectRock-fluid interactionsen_AU
dc.subjectFranceen_AU
dc.subjectBrinesen_AU
dc.subjectEvolutionen_AU
dc.titleChemical and hydrological evolution of the Mulhouse potash basin (France): are "marine" ancient evaporites always representative of synchronous seawater chemistry?en_AU
dc.typeJournal Articleen_AU
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