Pyrite cement

If substantial arsenic is present in a sandstone or conglomerate, it may occur in hematite or other iron (oxy)(hydr)oxide cements or coatings on mineral grains. Arsenic may also be enriched in sandstones, conglomerates, and other clastic sedimentary rocks if hydrothermal or other secondary sulfide minerals are present (e.g. St. Peter Sandstone, (Gotkowitz et al., 2001) arsenian pyrite cement in the Marshall Sandstone of the Michigan Basin, USA, (Kolker et al., 2000 Szramek, Walter and McCall, 2004)). Sections of the St. Peter Sandstone in eastern Wisconsin, USA, are enriched in sulfide minerals and contain about 500 mg kg-1 of arsenic. In contrast, unmineralized portions typically have <10 mg kg-1 (Gotkowitz et al., 2001). If present in sedimentary rocks, hydrothermal sulfide deposits often tend to concentrate in veins and faults more than the rock matrices. 

Sulphur isotopic ratios were measured on two samples from Murgental and Altishofen (Lower Freshwater Molasse). In the pervasive pyrite cements from Murgental, both the edge and the centre of a patch were measured, yielding cdt (Canyon Diablo Troilite) values of -14.4%o and +1.1 %o, respectively. In Altishofen, two spots of mica replacement were measured, yielding 6 S cdt values of-28.1%0 and -22.1%o. 

Well Depth (mRKB) Formation Quartz clasts K-feldspar clasts Plagio- clase clasts Mica clasts Heavy minerals Carbon- ate fossils Plant frag- ments Clay clasts Clay matrix Pyrite cement Authi- genic kaolinite Authi- genic illite Calcite cement Siderite cement Dolomite cement Quartz cement Porosity Grain size (mm)... 

Several lines of evidence suggest the involvement of TSR. Partially dissolved remnants of early diagenetic anhydrite cement are found embedded in quartz cement (Fig. 12). Fluid inclusion data indicate that nodular quartz cement with anhydrite inclusions (Fig. 15) formed at elevated temperatures, suggesting that anhydrite dissolution may have coincided with high temperature TSR. Post-pyrobitumen carbonate and pyrite cements and nodules are also present in the Norphlet and may represent late diagenetic precipitates associated with TSR. Pyrite cement from the Norphlet has sulphur isotope ratios that are identical to those of the Pine Hill Anhydrite (Table 3) and within the range reported for Jurassic seawater (Hoefs... 

Because calcium oxide comprises about 65% of Pordand cement, these plants are frequendy situated near the source of their calcareous material. The requisite silica and alumina may be derived from a clay, shale, or overburden from a limestone quarry. Such materials usually contain some of the required iron oxide, but many plants need to supplement the iron with mill scale, pyrite cinders, or iron ore. Silica may be supplemented by adding sand to the raw mix, whereas alumina can be furnished by bauxites and Al202-rich flint clays. 

Verkieselung,/. silicification. verkiesen, v.t. gravel, ballast pyritize. verkitten, .i. cement, lute seal. 

Other types of cements include anhydrite, barite, pyrite, iron hydroxides haematite, albite and apatite and are subordinate. 

Cement, dry process Cement, wet process, 44% water Limestone calcination Dolomite calcination Alumina preparation Barium sulfide preparation Ignition of inorganic pigments Iron pyrite roasting... 

Figure 1730. Kilns and hearth furnaces Walas, 1959). (a) Temperature profiles in a rotary cement kiln, (b) Space velocities in rotary kilns, (c) Continuous lime kiln for production of approximately 55tons/24hr. (d) Stirred salt cake furnace operating at 1000°F, 11-18 ft dia, 6-10 tons salt/24 hr. (e) Multiple-hearth reactor one with 9 trays, 16 ft dia and 35 ft high roasts 1250 lb/hr iron pyrite. (f) Siements-Martin furnace and heat regenerators a hearth 13 ft wide and 40 ft long makes 10 tons/hr of steel with a residence time of 10 hr.

Sedimentary rocks with the highest arsenic concentrations largely consist of materials that readily sorb or contain arsenic, such as organic matter, iron (oxy)(hydr)oxides, clay minerals, and sulfide compounds. Arsenian pyrite and arsenic-sorbing organic matter are especially common in coals and shales. Ironstones and iron formations are mainly composed of hematite and other iron (oxy)(hydr)oxides that readily sorb or coprecipitate arsenic. Iron compounds also occur as cements in some sandstones. Although almost any type of sedimentary rock could contain arsenic-rich minerals precipitated by subsurface fluids (Section 3.6.4), many sandstones and carbonates consist almost entirely of minerals that by themselves retain very little arsenic namely, quartz in sandstones and dolomite and calcite in limestones. 

After lixiviation of the sulphate, oxide, or chlorides obtained by these methods, the copper is precipitated by the process already described. If the cement copper thus obtained contains over 55 per cent, of the metal, it is refined directly, if the percentage is lower, it is first smelted with matte or calcined copper pyrites. 

Figure 8 Conglomerate consisting of several types of pyrite together with zircon, chromite, and other heavy minerals. The large pyrite grain in the right part of the figure is a complex assemblage of older pyrite grains which have been cemented by younger pyrite (source Ramdohr, 1958).

Figure 14 Partially crushed foraminifer with chambers filled by chlorite cement (chi), kaolinite (k), and pyrite (py) cements. Reactions evident in these anomalously large pores are indicative of reactions that may also proceed in smaller pores throughout the shale. Frio Fomiation, Oligocene, South Texas. Backscattered electron image.

Figure 18. Wavelength-dispersive electron microprobe image of a cluster of pyrite framboids within coal from the Black Warrior basin Alabama. Bright colored areas show the presence of arsenic, nickel, and sulfur. Arsenic is concentrated in epigenetic overgrowths and cement surrounding the framboids, while the diagenetic framboid interiors them.selves contain little or no arsenic. This indicates that the arsenic was added after earliest diagenesis.

Pyrite and marcasite are the major minerals forming the sulfide cement, as identified by XRD and optical microscopy. These sulfides occur as both well-formed cubes and anhedral masses. Arsenic-rich areas (up to 1% by weight as estimated by EDS) occur in the pyrite and marcasite crystals as well as in iron hydroxides, but no separate arsenopyrite phase has been identified. Colloidal size (10-20 nm) iron hydroxide phases were identified using TEM. TEM-EDS analysis showed qualitative differences in arsenic, nickel, and zinc in the iron hydroxides on a nanometer scale. 

Among the largest users of agglomeration technologies are iron and steel mills and their raw material suppliers, the cement industry and fertilizer producers. In the first area flotation concentrates and ores that were upgraded by other methods, fine or dusty pyrite cinders, red mud from bauxite processing, filter... 

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