Minerals detrital

Mineral Matter in Goal. The mineral matter (7,38) in coal results from several separate processes. Some comes from the material inherent in all living matter some from the detrital minerals deposited during the time of peat formation and a third type from secondary minerals that crystallized from water which has percolated through the coal seams. 

The metal budget of any individual shale horizon reflects a variable admixture of materials with a number of end member compositions. Even where the sulfide component of a sample is >10%, conventional discrimination plots used to identify and quantify hydrothermal input such as Co/Ni ratio (e.g., Meyer et al., 1990) or rare earth element plots (e.g., Johannesson et al., 2006) are hindered in their application due to dilution by the nonsulfide silicate detrital minerals. 

Coal contains detrital minerals that were deposited along with the plant material, and authigenic minerals that were formed during coalification. The abundance of mineral matter in coal varies considerably with its source, and is reported to range between 9.05 and 32.26 wt% (Valkovic 1983). Minerals found in coal include (Table 2) aluminosilicates, mainly clay minerals carbonates, such as, calcite, ankerite, siderite, and dolomite sulphides, mainly pyrite (FeS2) chlorides and silicates, principally quartz. Trace elements in coal are commonly associated with one or more of these minerals (see Table 2). 

The problem is certainly more complex at conditions of low temperature and pressure where thermal energy is low and slight fluctuations in configurational energy can probably provide metastable crystallization as experienced often in the laboratory. However, we will retain the general principle that authigenic minerals will more closely represent equilibrium phases than will detrital minerals inherited from other geological cycles. 

Sepiolite and palygorskite have a rather special composition and seem to be related to specific mineral parageneses. They appear to be stably associated with montmorillonite, corrensite, serpentine, chert, sulfates, carbonates and various salts. They are found in deposits typified by processes of chemical precipitation or solution-solid equilibria (Millot, 1964) and are therefore rarely associated in sediments with large quantities of detrital minerals. Their chemical environment of formation is in all evidence impoverished in alumina and divalent iron. Their frequent association with evaporites, carbonates and cherts indicate that they came from solutions with high chlorinity. 

The lithophile elements are those that generally occur in silicate phases and include among others Si, Al, Ti, K, Na, Zr, Be, and Y. These would be expected to occur in coals in some combination with the silicate minerals kaolinite, illite, other clay minerals, quartz, and stable heavy detrital minerals. 

The Antarctic coal beds are apparently less persistent, and locally may be thicker, than many of the beds in Paleozoic coal fields of North America. It is hazardous to generalize about petrographic composition from hand specimens that are available from many of the coal beds, but one obtains the impression that dull, moderately dull, and midlustrous attrital layers are more prevalent than in Paleozoic coal of the Northern Hemisphere. Vitrain bands tend to be relatively sparse and thin fusain chips and partings generally are present and may be abundant. Many coal specimens are relatively impure, apparently owing to well-dispersed detrital mineral matter. 

Bone coal impure coal that contains much clay or other fine-grained detrital mineral matter. 

Hodges KV, Ruhl KW, Wobus CW, Pringle MS (2005) l"Ar/v,Ar thermochronology of detrital minerals. Rev Mineral Geochem 58 239-257... 

Secondary porosity results from the dissolution of carbonates in the subsurface environment. It can occur both in limestones and in sandstones where carbonate cements of original labile detrital minerals are dissolved. Because the formation of secondary porosity can substantially enhance the reservoir properties of sediments, it has received considerable attention from the petroleum industry. 

Detrital minerals minerals introduced by weathering of parent rock materials (e.g., feldspar). 

The possible associations of trace and minor elements with clays are summarized by Finkelman (14). These include Al, Sc, Ti, Cl, Cr, La, Mg, and Fe. Iron, Co, Ni, Zn, As, and Ag all have chalcophile tendencies and may associate with pyrite or other sulfides. Uranium may be largely associated with the organic part of the coal but can also be associated with a diverse suite of uranium minerals (14). Other elements, such as Ru, Ce, and Sm are concentrated in the margins of the seam suggesting an association with detrital minerals. 

Geochemical evidence suggests that there were delays of several hundred million years between the rise of oxygenic photosynthesis, the oxygenation of the atmosphere, and the oxygenation of the deep ocean. Photosynthesis (evidenced by cyanobacterial microfossils and biomarkers) rose as early as 3.5 Ga (billion years before present (Schopf, 1993)) and had been sofidly established by 2.7—2.5 Ga (Brocks et al, 1999 KnoU, 1996 Schopf, 1993 Summons et al, 1999). Data from red beds, detrital mineral deposits, and sulfur isotopes indicate the rise of atmospheric oxygen around 2.4 Ga (Bekker et al, 2004 Chandler, 1980 Des Marais et al, 1992 ... 

Brewer I. D. (2001) Detrital-mineral thermochronology investigations of Orogenic denudation in the Himalaya of central Nepal. PhD, The Pennsylvania State University. 

Stock J. D. and Montgomery D. R. (1996) Estimating paleore-lief from detrital mineral age ranges. Basin Res. 8, ill- ill. 

The slowness of surface-reaction-controlled rate dissolution results in metastability—the tendency of minerals to persist for geologically long periods under conditions greatly different from those under which they are thermodynamically stable. This is illustrated dramatically where detrital minerals formed at high temperatures by... 

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