Geologic Setting

Reactions illustrate that oxidation of Fe—As disulfide group and As-sulfide minerals is the primary release process for As. Liberation of As by carbonation of realgar and orpiment in contact with high pH groundwaters may contribute locally to elevated contents of As in groundwater, especially where As is decoupled from Fe. Released metals are sequestered in secondary minerals by sorption or by 

Foley and Ayuso (2008) suggest that typical processes that could explain the release of arsenic from minerals in bedrock include oxidation of arsenian pyrite or arsenopyrite, or carbonation of As-sulfides, and these in general rely on discrete minerals or on a fairly limited series of minerals. In contrast, in the Penobscot Formation and other metasedimentary rocks of coastal Maine, oxidation of arsenic-bearing iron—cobalt— nickel-sulfide minerals, dissolution (by reduction) of arsenic-bearing secondary arsenic and iron hydroxide and sulfate minerals, carbonation and/or oxidation of As-sulfide minerals, and desorption of arsenic from Fe-hydroxide mineral surfaces are all thought to be implicated. All of these processes contribute to the occurrence of arsenic in groundwaters in coastal Maine, as a result of the variability in composition and overlap in stability of the arsenic source minerals. Also, Lipfert et al. (2007) concluded that as sea level rose, environmental conditions favored reduction of bedrock minerals, and that under the current anaerobic conditions in the bedrock, bacteria reduction of the Fe-and Mn-oxyhydroxides are implicated with arsenic releases. 

The five soil profiles obtained for this study (Ayuso el al., 2006) contain unstratified clay to boulder-sized constituents (generally up to about 10 cm). Soil, till, and 

Lead arsenate (acid) PbHAs04 Pfaltz and Bauer Inc., 1976 18.395 1.18026 2.46083 

Acme arsenate of lead (basic)a Pb5 OH9 (As04) 3 PBI/Gordon Corp., Acme Quality Paints 17.070 1.10352 2.38394 

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Other excellent summaries describing what is known of the formation processes and geological setting of these deposits have also been assembled (30—32). Listings of nodule compositions for these and other areas have been compiled (33,34). Eor many sites these data are available as computer databases (qv) maintained by the NOAA National Geophysical Data Center in Boulder, Colorado. 

Calculations for prospective areas with structures not yet tested by drilling, or assessments on the basis of the general geological setting of a basin. 

Sato, Takeo (1974) Distribution and geological setting of the Kuroko deposits. Mining Geology Special Issue, 6, 1-16. 

Seki, Y. (1993) Geologic setting of the Takatama gold deposit, Japan an example of caldera-related epithermal gold mineralization. Resource Geology Special Issue, 14, 123-136. 

Tanimura, S., Date, J., Takahashi, T. and Ohmoto, H. (1983) Geologic setting of the Kuroko deposits, Japan. 

An experimental study at 350°C on the interaction between NaCl solution and graywacke which occurs widely in island arc geologic setting indicates that the final solution contains (0.6-0.7) ppm As (Bischoff et al., 1981). Analytical data on As concentration of hydrothermal solution at back-arc basins are few. Arsenic concentration of hydrothermal solution at Lau Basin is 6.0-8.2 ppm (Foquet et al., 1991). We can also estimate As concentration of hydrothermal solution based on the solubility data on orpiment and realgar because these As-bearing minerals are common in back-arc basin deposits (e.g., Okinawa Trough, Kuroko deposits). 

Table 1.18 Major uranium resources of the world numbered in sequence on the basis of their geological setting and arranged according to their approximate economic significance.

The site-specific requirements for landfill remediation should be developed before beginning design or selection of cover type. Site-specific requirements depend on numerous site-specific factors, including landfill history waste type, quantity, and age climate geologic setting local surface water and groundwater use and regulatory requirements. 

Smith, K. S., W. H. Ficklin, G. S. Plumlee and A. L. Meier, 1992, Metal and arsenic partitioning between water and suspended sediment at mine-drainage sites in diverse geologic settings. In Y. K. Kharaka and A. S. Maest (eds.), Water-Rock Interaction. Balkema, Rotterdam, pp. 443M-47. 

Geological Setting The Talbot VMS Cu-Zn prospect is situated in the eastern extension of the Paleoproterozoic Flin Flon Belt (1.92 -1.88 Ga), north-western Manitoba (Stern et al. 1999). The prospect is located just northeast of Lake Talbot, about 160 km SE of Flin Flon (Fig. 1). Mineralization is hosted by medium to high-grade... 

Sampling sites were selected based on the regional soil survey and a related study in seven sub-areas, each with coverage of several dozen to hundreds of square kilometers and with representative geological setting and geochemical characteristics. Rice and cultivation layer soil at 146 sites were sampled at a density of one site per square kilometer during rice harvest season, October 2006. 

Geological Setting The geology of the study area consists of Cretaceous sedimentary, volcanic, granitic, ultramafic (serpentinite), and carbonate rocks containing a magnetite-rich pipe and basic dykes (Fig. 1). The sedimentary rocks are intruded by felsic volcanic, granitic and ultramafic rocks,... 

Each ore type described in Section 18.6.2 require different flowsheets and reagent schemes, which is dictated by the mineral composition of the ore and the geological setting, as well as the type of PGM carrier minerals. 

A number of general and site-specific considerations must be made in devising a rational, cost-effective aquifer restoration program tailored to the site s unique hydro geologic setting. ... 

Air sparging Injects air below the water table and captures it above the water table to extract volatile contaminants and promote biodegradation Can be inefficient in low-permeability zones and complex geologic settings Typically limited to depths less than 30 ft Multicomponent mixtures can adversely affect extractability... 

Steam-enhanced extraction Injects steam above and/or below water table to promote volatilization of contaminants Can be inefficient in low permeability zones or complex geologic settings... 

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