Sedex

Commercially available instruments include the SEsitive Detector of Exothermic processes (SEDEX) [103,104], SIKAREX [106], with a typical sensitivity of 0.5 W/kg), and RADEX [102, 108]. This equipment can also be run inisothermal and scanning modes. 

The equipment is quite adequate for screening purposes. In its simplest form (i.e., a glass tube in an oven), it is a relatively low cost technique that can be assembled with standard laboratory equipment. However, the simple test set-up provides no quantitative thermal data for scale-up purposes, but only T0 values. The more advanced instruments like the SEDEX and SIKAREX, which are also isoperibolic calorimetry equipment, acquire specific thermal stability data that can be used for scale-up. Furthermore, the small autoclave tests provide gas evolution data. 

As discussed in Section 2.3.1.2, SEDEX [103, 104] and SIKAREX [106] instruments are also used isothermally. In the case of the SIKAREX, the temperature of the sample is held by a heating coil at constant temperature by establishing a constant rate of heat exchange to the jacket (held about 50 to 100°C below the sample temperature). By measuring the electrical input, a negative copy of the reaction heat profile is obtained. Typical sensitivity of the equipment is 0.5 W/kg operating with a sample size of 10 to 30 g and in a temperature range of 0 to 300°C. 

Hakl, J., "Advanced SEDEX (Sensitive Detector of Exothermic Processes)," Ther-mochimici Acta, 80,109 (1984). 

Hakl, J., "Sensitive Detector of Exothermic Processes (SEDEX)," Thermochimici Acta, 38,253 (1980). 

The Sikarex safety calorimeter system and its application to determine the course of adiabatic self-heating processes, starting temperatures for self-heating reactions, time to explosion, kinetic data, and simulation of real processes, are discussed with examples [1], The Sedex (sensitive detection of exothermic processes) calorimeter uses a special oven to heat a variety of containers with sophisticated control and detection equipment, which permits several samples to be examined simultaneously [2]. The bench-scale heat-flow calorimeter is designed to provide data specifically oriented towards processing safety requirements, and a new computerised design... 

Analysis of dry twigs revealed areas of Zn enrichment with associated elements (Cd, Tl and Mn) that show a spatial relationship to areas of Pb enrichment (with Fe, Hg, REE, Al, and Ti), especially south of Tsuius Creek. A strong Pb/Zn zonation is typical of Broken Hill-type Sedex mineralization. Of particular note were localized high Tl values. 

Keywords SEDEX deposit, Yukon Territory, acid rock drainage, mineral exploration vectors, groundwater. 

The Selwyn Basin in the Yukon Territory of Canada hosts major SEDEX Zn-Pb sulphide deposits, the biggest being the relatively large ( 90.4 Mt) deposits at Howard s Pass Y), owned by Selwyn Resources (Morganti 1979 Goodfellow 2004). This research focuses on the surficial geochemical expression of the XY deposit, one of the 13 known orebodies within the Howards Pass district. 

Geological Setting The XY deposit is a stratiform Zn-Pb-dominated massive sulfide SEDEX orebody (Goodfellow 2004). It is situated near the base of the Duo Lake Formation within the Road River Group (Morganti 1979). The Duo Lake Formation is comprised predominantly of carbonaceous, sulfidic shales, with subsidiary cherty and phosphatic components in the strata immediately surrounding the ore horizon (Goodfellow et al. 1983). The Duo Lake Formation is underlain by carbonates of the Rabbitkettle Formation, which outcrop in parts of the valley in... 

Goodfellow, W. D. (2004). Geology, genesis and exploration of SEDEX deposits, with emphasis on the Selwyn Basin, Canada. In Deb, M. Goodfellow, W.D. (ed) Sediment-hosted Lead-Zinc Sulphide Deposits Attributes and Models of Some Major Deposits of India, Australia and Canada. Dehli, India, Narosa Publishing House, 24-99. 

SEDEX deposits of northern Australia (e.g., McArther River, Century, Lady Loretta), the lithogeochemical halos extend several hundred meters into the overlying stratigraphy and several kilo-... 

Fig 3. Regional stratiform alteration in dolomitic shales lateral to SEDEX Zn-Pb-Ag deposits. 

Carne, R.C. Catthro, R.J. 1982. Sedimentary exhalative (sedex) zinc-lead deposits, northern Canadian Cordillera. Canadian Institute of Mining and Metallurgy, Bulletin, 75, 66-78. 

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. 

Keywords Manganese, SEDEX, Balmat-Edwards, Distal exhalative, Adirondack Lowlands... 

Irish-type SEDEX deposits are carbonate-hosted stratiform to stratabound sulfide deposits that occur as syngenetic exhalative to early diagenetic replacement bodies (Coleman et al. 1989). Many SEDEX deposits have formed in Proterozoic intracontinental rifts and Phanerozoic deposits occur in similar... 

Most SEDEX deposits are not precipitated directly adjacent to their feeder zone (Sangster 2002) therefore the geochemical zonation of distal products provides a valuable exploration tool. Manganese halos have been well documented for the Tynagh mine in... 

Lydon, J.W. 1996. Sedimentary exhalative sulphides (Sedex). In Eckstrand, O.R., Sinclair, W.D., Thorpe, R.I. (eds.), Geoiogy of Canadian Minerai Deposit Types. Geological Survey of Canada, Geology of Canada, 8, 130-152. 

Sangster, D.F. 2002. The role of dense brines in the formation of vent-distal sedimentary-exhalative (SEDEX) lead-zinc deposits field and laboratory evidence. Mineraiium Deposita, 37, 149-157. 

Most processes listed in Box 23.1 have been discussed before. However, the term describing the settling of suspended particles, k Ct, and the exchange between the water and the sediments, sedex [C qd - Ct ], need further explanation. A detailed discussion follows in Section 23.2. First, we discuss the fate of vinyl acetate in a pond (Illustrative Example 23.1) for which the solute-particle interaction is not important. 

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