Evaporites basinal

Evaporite Basin Sulfur Deposits. Elemental sulfur occurs in another type of subsurface deposit similar to the salt-dome stmctures in that the sulfur is associated with anhydrite or gypsum. The deposits are sedimentary, however, and occur in huge evaporite basins. It is befleved that the sulfur in these deposits, like that in the Gulf Coast salt domes, was derived by hydrocarbon reduction of the sulfate material and assisted by anaerobic bacteria. The sulfur deposits in Italy (Sicily), Poland, Iraq, the CIS, and the United States (western Texas) are included in this category. 

The great evaporite basin deposits of elemental sulfur in Poland were discovered only in 1953 but have since had a dramatic impact on the economy of that country which, by 1985, was one of the world s leading producers (p. 649). The sulfur occurs in association with secondary limestone, gypsum and anhydrite, and is believed Ui be derived from hydrocarbon reduction of sulfates assisted 1 bacterial action. The H2S so formed is consumed by other bacteria to produce sulfur as waste — this accumulates in the bodies of the bacteria until death, when the sulfur remains. 

Gulf Coast region of the USA and Mexico, and from the evaporite basin deposits in west Texas, Poland, the former USSR and Iran. 

As a test of our ability to calculate activity coefficients in natural brines, we consider groundwater from the Sebkhat El Melah brine deposit near Zarzis, Tunisia (Perthuisot, 1980). The deposit occurs in a buried evaporite basin composed of halite (NaCl), anhydrite (CaSC>4), and dolomite [CaMg(CC>3)2]. The Tunisian government would like to exploit the brines for their chemical content, especially for the potassium, which is needed to make fertilizer. 

Maps of the conterminous United States (a) evaporite basins and districts and (b) distribution of gypsum/anhydrite, sait, and evaporite karst. Karst is iimestone or doiomite that has been eroded by dissoiution. Source From Johnson, K. S. (1997). Carbonates and Evaporites 12, 2-13. 

Whelan, J.F., Rye, R.O., deLorraine W., Ohmoto, H. 1990 Isotopic Geochemistry of a Mid-Proterozoic Evaporite Basin Balmat, New York. American Journal of Sdence, 290, 396-424... 

Typical marine water contents of Br are 65 ppm. The first chloride salt precipitated in an evaporite basin is halite (70-75 ppm Br). Bromine content of halite increases to >230 ppm Br as the first potassium mineral crystallizes (Valyashko 1956). 

We emphasize that it is not anhydrous salts but salt hydrates (and gas hydrates) that have this important thermal insulating property. Cool climates, which tend to support high hydration states, favor this type of process. Cold evaporitic basins are ideal, and so we find that Mars is where this phenomenology is most likely to have widespread relevance. 

The same phenomenology must be important locally on Earth, too, where thick evaporite deposits of hydrated salts and local thick beds of methane clathrate in permafrost or seafloor sediments should influence the thermal environment of the crust. The predicted control on the crust s thermal state by hydrate deposits should have consequences for the localization of hydrothermal springs around and within evaporite basins, hydrothermal metamorphism... 

Sanford W. E. and Wood W. W. (1991) Brine evolution and mineral deposition in hydrological open evaporite basins. Am. J. Sci. 291, 687-710. 

Halite = NaCl (salt, formed in evaporite basins)... 

D2. Multiple-cycle weathering, including particularly dissolution of earlier marine or terrestrial evaporites (e.g. modem Qaidam Basin, China and Chott el Djerid, Tunisia), both of which are nested above earlier terrestrial evaporite basins)... 

Cendon, D.I., Peryt, T.M., Ayora, C., Pueyo J.J. Tabemer, C. (2004) The importance of recycling processes in the Middle Miocene Badenian evaporite basin (Carpathian foredeep) palaeoenvironmental implications. Palaeogeography, Palaeoclimatology, Palaeoecology 212, 141-158. 

Logan, B.W. (1987) The Macleod evaporite basin, Western Australia. American Association of Petroleum Geologists, Memoir 44, 140 pp. 

Evaporative lakes are common in midcontinent regions in Australia, the western United States, southwest Canada, and Africa, for example. Depending upon the extent of evaporation and the amounts and compositions of inflowing waters, the first precipitates are calcite and, perhaps, dolomite, which may be followed by gypsum/anhydrite, then halite, and finally more complex sulfate, carbonate and halide salts (cf. Holland 1978 Berner and Berner 1987 Faure 1991). Similar sequences of mineral precipitates may accumulate in restricted evaporite basins in equatorial areas (Berner and Berner 1987). 

Rock units involved in salt-dissolution studies in western Oklahoma and nearby areas are mainly of early Guadalupian (Permian) age. These strata make up a thick sequence of red beds and evaporites deposited in and near a broad, shallow inland sea that extended north and northeast of the carbonate platform that bordered the Midland Basin (Fig. 1) (Mills, 1942 Clifton, 1944 Ham, 1960 Johnson, 1967). Evaporites, mainly salt (halite) and gypsum (or anhydrite), were precipitated from evaporating seawater as layers on the sea floor or grew as coalescing crystals and nodules in a host of mud just below the depositional surface. Thick red-bed shales, siltstones and sandstones were deposited around the perimeter of the evaporite basin, and some of these also extended as blanket deposits across the basin. Many thin red-bed clastic units are interbedded with the evaporites. 

Four basic requirements are necessary for salt dissolution to occur here, or in other evaporite basins for that matter (Johnson et al., 1977) ... 

Ayora, C., J. Garcia-Veigas J.-J. Pueyo, 1994a X-Ray microanalysis of fluid inclusions and its application to the geochemical modeling of evaporite basins. Geoch. Cosmoch. Acta. 58 43-55. 

Fanlo, 1. C. Ayora, 1998. The evolution ofthe Lorraine evaporite basin implications forthe chemical and isotope composition ofthe Triassic ocean. Chem. Geol. 146 135-154. 

Petrichenko, 0. L, T. M. Peryt A V. Poberegsky, 1997. Peculiarities of gypsum sedimentation in the Middle Miocene Badenian evaporite basin of Carpathian Foredeep. Slovak Geol. Mag. 3 ... 

The evaporitic depositional environments are extremely sensitive to sea-level changes. Complete desiccation of evaporite basins follow slight drops in sea level, whereas sea-level rises quickly eliminate evaporitic deposition altogether. 

Sr, B contents constant increase of their contents in the profile indicate stable evaporation conditions their variations episodes connected with the fresh water inflows to the evaporite basin and its dilution ... 

Kasprzyk A., 2003 - Sedimentological and diagenetic patterns of anhydrite deposits in the Badenian evaporite basin of the Carpathian Foredeep, southern Poland. Sedimentary Geology, 158 (3-4) 167-194. 

James, R., Allen, D. E., and Seyfried, W. E. (2003). Experimental Study of Alteration of Oceanic Crust and Terrigenous Sediments at Moderate Temperatures. Geochim. Cosmochim. Acta, 681-691. Jordan, T. E., Munoz, N., Hein, M., Lowenstein, T., Godfrey, L., and Yu, J. (2002). Active Faulting and Folding Without Topographic Expression in an Evaporite Basin, Chile. Geol. Soc. Am. Bull. 114(11), 1406-1421. 

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