Mineralized areas

Under a homestead theory of subsurface rights, the first finder of a mineral area would have claim to the entire recognized deposit. In the case of oil and gas, the geologic unit is the entire resei voir, however shaped, as long as it can be proven to be contiguous. Separate and distinct resei voirs in the same general area, whether vertical or horizontal, would require separate and distinct discoveiy and claim. Alien wells draining a claimed reservoir would be liable for trespass if the homesteader can reasonably prove invasion (whether by well... 

Sato, Kazuo, Delevaux, M.H. and Doe, B.R. (1981) Lead isotope measurements on ores, igneous, and sedimentary rocks from the Kuroko mineralization area. Geochem. J., 15, 135-140. 

It is thought that submarine hydrothermal alteration of basalt took place in the Besshi-subtype mineralization area in Sanbagawa. However, no study on the hydrothermal alteration of basalt (basic schist) has been carried out and it is clearly necessary. The contact metamorphosed rocks and sulfide ores caused by Tertiary granitic intrusion are found in deeper part of the Besshi mine and Makimine mine (Tatsumi, 1952 Kase, 1972). 

Mineral exploration, the search for economic ore deposits, requires somewhat different reference samples than those used in ore valuation. Soil or sediment and water samples are frequently used in the search when mineralized areas of abundant outcrop or those covered only by thin locally derived overburden are being evaluated. In such cases, it is virtually impossible not to detect the mineralization from an analysis of ore elements in these types of samples. Later, as the mineral deposits closest to the surface were exploited and then played out, new deposits occurred at progressively greater depths, and these sample types were less and less effective as markers in the search (Hoffman 1989). 

New exploration techniques, and new reference materials in support of them, were needed. One major change was in the use of ore pathfinder elements, rather than the ore elements themselves, for exploration purposes. For example, instead of analyzing samples for the primary Au ore element, samples were analyzed for As, Hg, and W pathfinders that pointed to hidden gold deposits. The pathfinder elements occur in association with ore veins, but have a much broader spread than the mineralized area itself. However, measurement of the pathfinder elements requires methods with better detection limits than were needed in earlier exploration programs, as the pathfinders typically are not as enriched as the ore elements, in comparison to baseline crustal levels. 

Acid drainage is a persistent environmental problem in many mineralized areas. The problem is especially pronounced in areas that host or have hosted mining activity (e.g., Lind and Hem, 1993), but it also occurs naturally in unmined areas. The acid drainage results from weathering of sulfide minerals that oxidize to produce hydrogen ions and contribute dissolved metals to solution (e.g., Blowes et al., 2005). 

The most important control on the chemistry of drainage from mineralized areas (once we assume access of oxygen to the sulfide minerals) is the nature of the nonsulfide minerals available to react with the drainage before it discharges to the surface (e.g., Sherlock et al., 1995). These minerals include gangue minerals in the ore, the minerals making up the country rock, and the minerals found in mine dumps. The drainage chemistry of areas in which these minerals have the ability to neutralize acid differs sharply from that of areas in which they do not. 

In the calculation, reaction of 1 cm3 of pyrite consumes about 3.4 cm3 of calcite, demonstrating that considerable quantities of buffering minerals may be required in mineralized areas to neutralize drainage waters. 

Ficklin, W. H., G. S. Plumlee, K. S. Smith and J. B. McHugh, 1992, Geochemical classification of mine drainages and natural drainages in mineralized areas. In Y. K. Kharaka and A. S. Maest (eds.), Water-Rock Interaction. Balkema, Rotterdam, pp. 381-384. 

Suspended sediments in mineralized areas SEDIMENTS (pg/kg dry weight)... 

This contribution summarizes state-of-the-science with respect to USGS research on the hydrogeochemistry of trace-element mobilization and attenuation from mineralized areas during transport in surface and ground waters. The primary aspects are ... 

Surface water samples were also collected at a number of sites throughout the Ruby Creek watershed although only data collected from active stream flow were utilized here. The surface water data was also categorized into background areas (n=13) and sites downstream from mineralization area (n=21). 

Table 2. Significant differences between median (mg/L) background (BACK) and mineralized(MINER) area in ground and surface water in the Ruby Creek Watershed...

Fore LS. 2003. Biological assessment of mining disturbance on stream invertebrates in mineralized areas of Colorado. In Simon TP, editor. Biological response signatures indicator patterns using aquatic communities. Boca Raton (FL) CRC Press, p 347-370. 

Groundwater arsenic problems in nonmined mineralized areas are less common, but Boyle et al. (1998) found concentrations up to... 

The drainage basin of the Clark Fork, an eastern tributary of the Columbia River, has been affected for long distances by the copper mining and ore treatment processes that were conducted at Butte and Anaconda, Montana, for about 125 years, ending in 1982. Conditions in this stream have been described (28). A more recent paper (29) pointed out that many streams in mineralized areas had relatively high metal concentration prior to the beginning of niining activity. 

The sedimentary section of the U.S. southern midcontinent consists in large part of Paleozoic platform carbonate rocks interbedded with shale and subordinate sandstone. As documented below, a large volume of the Paleozoic carbonate rocks in this region is enriched in arsenic, as well as lead, zinc, copper, cobalt, molybdenum, and nickel compared to surrounding carbonate strata (Erickson et al., 1981 Lee and Goldhaber, 2001). In plan view this trace-mineralized area extends over thousands of square kilometers. The widespread metal enrichment process was related to the formation of much more spatially localized ore districts. These districts consist of economic concentrations of the ore elements zinc and lead, and to a lesser extent copper, cobalt, and barium that occur in the platform... 

In contrast to the extensive data collected on trace-mineralized rocks between ore districts, less information is available on the arsenic contents of the ore deposits. Because iron sulfide minerals are typically gangue phases, they are commonly ignored in trace element studies of ore deposits, which tend to focus on ore minerals such as sphalerite and galena. Therefore, there have not been extensive analyses for arsenic in iron sulfides in many of the MVT ore districts or trace-mineralized areas. However, a few studies on trace element contents in iron sulfides from the Ozark region have been performed. Wu et al. (1996) analyzed 80 pyrite and marcasite samples from the Viburnum Trend of the Southeast Missouri Lead District and found arsenic in concentrations of 2 to 900 ppm. Bhati and Hagni (1980) also analyzed iron sulfide minerals from this area, but did not publish results for arsenic. Hagni (1993) described the relatively rare occurrence of nickel-arsenic-sulfide ores from the Magmont-West ore deposit of the Viburnum Trend. Leach et al. (1995) list arsenic as a trace constituent in ores from the Northern Arkansas and Southeast Missouri MVT ore districts, but without abundances specified. 

The regional fluid-flow described above produced widespread diffuse trace mineralization over large areas of the U.S. Midcontinent. In addition to this diffuse mineralization, specific paleohydrologic processes can lead to somewhat more intense element enrichment, ranging from economic ore deposits down to sub-economic but nonetheless significant concentrations of ore and gangue minerals. Because arsenic can accompany MVT mineralization, these more intensely mineralized areas are important to identify because they may be particularly susceptible to enviromnental impacts. 

Historically, high-As groundwaters have mostly been associated with mining and mineralized areas, and the affected areas have been quite localized (a few km ). Areas of geothermal activity are also often associated with As-rich groundwaters and this can affect quite large areas (Smedley and Kinniburgh, 2002). 

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