M�tamorphisme hydrothermal en faci�s salins et p�n�salins sur l'exemple du complexe salif�re de l'extr�me Nord Tunisien

Crampon, N.

doi:10.1007/bf00375735

Cited by 11 publications

(2 citation statements)

References 2 publications

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“…The authors concluded that the trapping temperature for these inclusions was> 150 °C (assuming low pressure and halite‐supersaturated fluids) and possibly 300 °C (if halite crystals were mechanically trapped and pressure was in excess of 1·5 kbar). Crampon (1973) studied a few inclusions in albite from evaporitic carbonate rocks of northern Tunisia. He reported homogenization temperatures of 240–264 °C and 287 °C, respectively, and 37 wt% NaCl equivalent.…”

Section: Discussionmentioning

confidence: 99%

Authigenic albite in carbonate rocks – a tracer for deep‐burial brine migration?

Spötl¹,

Longstaffe²,

Ramseyer³

et al. 1999

Sedimentology

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Euhedral, post‐depositional albite from the Eastern and Western Alps, the western Carpathians and some Greek islands was examined petrographically and geochemically to gain insights into the nature of feldspar reactions in carbonate rocks. This study focuses on coarsely crystalline, homogeneously nucleated albite in order to avoid problems related to the presence of inseparable detrital material in fine‐grained albite varieties. All albite samples show a very restricted compositional variability and are typically ≥ 99 mol% Ab component. Unit‐cell parameters determined by Rietveld analysis are slightly more variable than previously accepted, but confirm high Al–Si ordering characteristic of low albite. The oxygen isotopic composition of albite ranges from + 19·4‰ to + 28·3‰ VSMOW. There is no direct relationship between the δ18O value and the inferred temperature of albite formation, nor is there one with stoichiometry. The coarse crystal size (up to several millimetres in diameter), petrographic evidence showing albite cross‐cutting stylolites, greater abundance of albite in carbonate rocks subject to high‐grade diagenetic or weak metamorphic overprinting and available fluid inclusion data suggest that albite precipitation is favoured at higher temperatures in carbonates than in sandstones. Pore fluids were invariably brines, as suggested by the inferred high positive δ18Ofluid values, the common association of albite‐bearing carbonates and evaporites and reports of saline fluid inclusions in albite. The presence of authigenic albite may thus be a useful tracer of palaeobrine–carbonate reactions, particularly in deep‐burial and incipient metamorphic settings.

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Section: Discussionmentioning

confidence: 99%

Authigenic albite in carbonate rocks – a tracer for deep‐burial brine migration?

Spötl¹,

Longstaffe²,

Ramseyer³

et al. 1999

Sedimentology

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“…Carbonates associated with evaporites or influenced by evaporite-derived saline pore fluids, however, commonly show neoformation of K-feldspar (along with albite), in particular where burial conditions reached incipient rock metamorphism (Perrenoud 1952;Ftichtbauer 1958;Crampon 1973;Kulke 1978;Brauckmann 1984;Perthuisot & Guilhaumou 1983;Ktirmann 1993). Previous dating efforts relied on conventional K-Ar dating (Bellon & Perthuisot 1977, 1980, but with the exception of the pioneering work by Hearn & Sutter (1985) no systematic studies have been conducted.…”

Section: Dating Feldspar Authigenesis L" 4~ Evidencementioning

confidence: 98%

Authigenic potassium feldspar: a tracer for the timing of palaeofluid flow in carbonate rocks, Northern Calcareous Alps, Austria

Spötl

Kunk

Ramseyer

et al. 1998

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Feldspar is a common authigenic constituent in Permian carbonate rocks which occur as tectonically isolated blocks within the evaporitic Haselgebirge m61ange in the Northern Calcareous Alps (NCA). Coexisting with pyrite, anhydrite, (saddle) dolomite, magnesite, fluorite and calcite, K-feldspar and minor albite record an event of regionally extensive interaction of hot brines with carbonate rocks. Detailed petrographic, crystallographic and geochemical studies reveal a variability in crystal size and shape, A1-Si ordering, elemental and stable isotopic compositions of the K-feldspar, which is only partially consistent with the traditional view of authigenic feldspar as a well-ordered, compositionally pure mineral. 4~step-heating measurements of authigenic potassium feldspar from several localities yield two age populations, an older one of 145-154 Ma, and a younger one of c. 90-97 Ma. Most age spectra reflect cooling through the argon retention temperature interval, which was rapid in some localities (as indicated by plateau ages) and slower in others. Rb-Sr isotope data are more difficult to interpret, because in many K-feldspar samples they are controlled largely by Sr-bearing inclusions. The Jurassic 4~dates are interpreted as minimum ages of feldspar growth and hence imply that fluid-rock interaction is likely to be simultaneous with or to slightly predate m61ange formation. Deformation associated with the closure and subduction of the Meliata-Hallstatt ocean south of the NCA during the Upper Jurassic is regarded as the principal geodynamic driving force for both enhanced fluid circulation and m61ange formation. Some localities were reheated beyond the argon retention temperature for microcline during mid-Cretaceous nappe stacking of the NCA, thus obliterating the older signal.The almost ubiquitous presence of basinal fluids, and their complex interaction with sedimentary rocks, is amply documented by a wealth of both direct (e.g. deep crustal drilling) and indirect (e.g. mineralization) observations. Placing precise constraints on the absolute timing of individual reactions between palaeoftuids and the host rock, however, remains a major challenge, particularly in carbonate lithologies. Many studies of diagenesis have relied on isotopic dating of authigenic K-mica, which is a standard method in the study of sandstones, but its use is severely limited in carbonate rocks, because interpretation and integration of these results with paragenetic information is often ambiguous, and because detrital contamination poses a major problem.

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Metamorphic Fluids: The Evidence from Fluid Inclusions

Crawford¹,

Hollister²

1986

Advances in Physical Geochemistry

105

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M�tamorphisme hydrothermal en faci�s salins et p�n�salins sur l'exemple du complexe salif�re de l'extr�me Nord Tunisien

Cited by 11 publications

References 2 publications

Authigenic albite in carbonate rocks – a tracer for deep‐burial brine migration?

Authigenic albite in carbonate rocks – a tracer for deep‐burial brine migration?

Authigenic potassium feldspar: a tracer for the timing of palaeofluid flow in carbonate rocks, Northern Calcareous Alps, Austria

Metamorphic Fluids: The Evidence from Fluid Inclusions

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