Basinal fluids

The flK-f of plagioclase from MORB is generally lower than that of back-arc basin igneous rocks. Therefore, the higher m +/mY + of midoceanic ridge fluids compared with back-arc basin fluids could be explained in terms of Na-feldspar/K-feldspar/hydro-thermal fluids equilibrium. 

Goodfellow, W.D. 2000. Sedimentary basinal fluid compositions, anoxic oceans and the origin of sedex Zn-Pb deposits Abstract Volume (Geological Association of Canada), 25, unpaginated. 

Jacquot, E., Fritz, B. Leroy, J. 1999. Geochemical modelling of interactions between crystalline basement and basin fluid applied to the geothermal HDR plant of Soultz-sous-Forets (Alsace, France). Terra Abstracts, 1, 586. EUG X Strasbourg, France. March 28-April I, 1999. 

Sulfur can exist in aqueous solution in at least five oxidation states, but data on sulfur species in basinal fluids are limited primarily to sulfate, S(V1), and sulfide, S(-ll). Sulfate (SOl ) wiU be discussed here, and hydrogen sulfide (H2S) and bisulfide (HS ) will be discussed in Section 5.16.7. 

Sedimentary formation waters have long been invoked as ore-forming fluids in a number of distinctly different geologic settings. Although ore deposit classification schemes vary, the following have been genetically associated with basinal fluids (i) Mississippi-Valley-type lead, zinc, copper, barium, and fluoride deposits (ii) shale-hosted lead, zinc, and barium deposits (iii) rift-basin and redbed copper deposits ... 

Fluid inclusion studies have shown that basinal fluids responsible for depositing fluorite ore... 

Davisson M. K. and Criss R. E. (1996) Na-Ca-Cl relations in basinal fluids. Geochim. Cosmochim. Acta 60, 2743-2752. 

Gregg, J. M., Shelton, K. L., and Bauer, R. M., 1992, Geochemical and fluid inclusion evidence for regional alteration of Upper Cambrian carbonates by basinal fluids in southern Missouri source rocks in the southern Midcontinent in 1990 symposium on source rocks in the southern Midcontinent, Norman, OK, p. 313-320. 

The origin of saline formation water in sedimentary basins has been problematical since it was first recognized that basinal fluids typically contain dissolved solids in concentrations considerably in excess of seawater. Vast differences in major-ion ratios quickly dispelled early assiunptions that basinal fluids were connate and represented buried seawater (Chave, 1960). Since then, different mechanisms have been advocated to account for the composition of subsurface water, and indeed, different mechanisms probably operate in basins with different lithologies and different burial histories. In some cases saline formation water may evolve in near isochemical rock—water systems during burial, as increasing temperature and pressure induce reactions which transfer components from the solid to the dissolved state. At the other end of the spectrum, fluid bearing no resemblance to the interstitial burial water may be imported from another part of the basin, or even from outside the basin, for example, by meteoric recharge, and modified by rock—water interaction. 

Gao, G., Land, L.S. Folk, R.L. (1992) Meteoric modification of early dolomite and late dolomitization by basinal fluids. Upper Arbuckle Group, Slick Hills, southwestern Oklahoma. Bull. Am. Xsi. Petrol. Geol., 76, 1649-1664. 

Oil and gas field waters have long been used in diagenetic studies, primarily as vehicles for understanding basin fluid flow, oil migration pathways, evolution of water composition, and reservoir com-partmentalization. However, water samples used for these purposes must be original formation water, not mixed with drilling mud or with injected fluids such as fracture fluid, waterflood water, or other fluids used for enhanced oil recovery (EOR),... 

Crystalline basement in southern Norway contains oil inclusions with hydrocarbons and dark carbonaceous solids [139], Analysis shows C1-C5 gaseous hydrocarbons, and complex hydrocarbon in two quartz veins, and are thought to have been derived from overlying sedimentary rocks by the deep percolation of basinal fluids [139],... 

Blake and Jackson 1968, 1969 Kharaka et al. 1983 Palmer and Drummond 1986 Bell 1991 Bell et al. submitted). The fact that the acidic and anionic forms of acetic acid have different decarboxylation rates is consistent with the established behavior of other carboxylic acids (Gould 1959 Clark 1969 Richardson and O Neal 1972). However, in experiments conducted with starting solutions of intermediate pH (6-8), in which both the acid and anion forms were present, a dramatic increase in the overall rate was observed. This observation is of great importance in modeling the stability of acetic acid in sedimentary basin fluids where the pH falls between 4 and 8. A mechanism was proposed (Bell et al. 1993) that describes adequately the pH dependence in the observed first-order rate constant however, this mechanism requires further verification. 

Schleusener JL, Barnes HL, Drummond SE, Palmer DA (1988) Activation parameters and low temperature half-lives for the decarboxylation of acetate in sedimentary basin fluids. Geol Soc Am Abstr Programs 20 150 Schulte MD, Shock EL (1993) Aldehydes in hydrothermal solution standard partial molal thermodynamic properties and relative stabilities at high temperatures and pressures. Geochim Cosmochim Acta (in press)... 

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