Gypsum secondary

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. 

A priori considerations. An extensive review of the form and mineralogy of the secondary cave deposits is provided by Hill and Forti (1997), but also see Ford and Williams (1989). By far the most useful speleothems for geological purposes are the most common forms stalactites, stalagmites and flowstones composed of calcite, and occasionally aragonite. Other deposits that have been used to derive useful information include travertines, gypsum crusts, calcite veins and scalenohedral calcite (dog-tooth spar). 

Mineralogical analyses suggest that gypsum and hydrobasaluminite are major secondary precipitates found within the DTMF, with trace amounts of gersdoffite and ferrihydrite also present. Electron microprobe analyses indicates a strong co-location between As, Ni, and Fe, which... 

The initial quarrying, primary, and secondary crushing and screening of raw materials are nol shown in the flowsheet. See also Gypsum. 

Geologic sources of sulfur include primary and secondary sulfide minerals as well as chemically precipitated sulfate minerals. In sedimentary rocks, sulfur is often concentrated. Examples include pyritic shales, evaporites, and limestones containing pyrite and gypsum in vugs and lining fractures. In many cases, these rocks can be both the source of organic matter as well as sulfate for the biogeochemical reduction of sulfate to occur. 

It is possible that a variety of secondary phases may precipitate in the lungs or in the macrophages, or may form reaction rinds on sulfide particles, as the result of sulfide oxidation or soluble salt dissolution in vivo. For example, phosphate (present in high concentrations in both the lung and macrophage fluids) may combine with calcium, aluminum, iron, lead, or other metals released from the salts to precipitate a variety of less soluble phosphate phases. Other secondary phases might include hydroxides or hydroxysulfates of aluminum or iron, or sulfates such as gypsum. 

Caves act as repositories for secondary deposits of many kinds, some locally derived such as breakdown from collapse of cavern roofs, some transported such as sand and silt carried by underground streams, and some the result of chemical deposition in the cavern void space such as calcite and gypsum speleothems. Textbooks on karst hydrology commonly provide descriptions and overall classifications of cave sediments (e.g. Bogli,... 

G) Palustrine micritic limestone infilled by a dark secondary micrite associated with gypsum crystals. Simplified chart showing the evaporite precipitation sequence from waters of various compositions. 

Other minor constituents are authigenic pyrite which appears as framboides or separate crystals secondary gypsum, mainly as vein filling detrital quartz grains and authigenic feldspar (microcline). 

Concretions similar to those found in the Lower Marsh sediments occur locally along the banks and beds of creeks on the Upper Marsh, and in some saltmarsh pans, but are otherwise absent. Both in situ and reworked concretions occur in the intertidal flat sediments just beyond the seaward edge of the Lower Marsh. The reworked concretions are often partly oxidised and contain a range of secondary minerals including akaganeite, gypsum and goethite (Pye, 1988). 

The Ca—Mg—HCO3- and Ca—Mg—SO4-type groundwater from the glacial drift aquifers reflects the dissolution of calcite and dolomite by carbonic acid formed in the soil zone, and the production and leaching of secondary gypsum through oxidation of sulfide in the presence of calcite or dolomite under conditions of partial saturation. In cases where the content of carbonates is low, silicate mineral weathering potentially occurs. 

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