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TitleA XAS study of arsenic speciation in waste materials from lode gold deposits
AuthorPercival, J B; Parsons, M B; Chen, N; Beauchemin, S; Kwong, Y T J
SourceMicro et Nano Scientiæ Mare Magnum, XIV International Clay Conference, Book of abstracts, volume 1, Oral sessions; by Associazione Italiana per lo Studio delle Argille; 2009 p. 266
Year2009
Alt SeriesEarth Sciences Sector, Contribution Series 20080632
MeetingXIV International Clay Conference; Castellaneta Marina; IT; June 14-20, 2009
Documentbook
Lang.English
Mediapaper
Subjectsgeochemistry; metallic minerals; spectroscopy; arsenic; arsenic geochemistry; gold; mesothermal deposits; mine waste products; mercury; mineralization; analytical methods; mines; tailings; oxidation; iron oxides; x-ray absorption spectroscopy
ProgramEnvironment and Health
AbstractGold production at two historic mine camps (Nova Scotia and British Columbia) have resulted in the production of tailings and other waste products with elevated concentrations of As and Hg. Their distribution in the receiving environment has been documented as part of a larger study examining the processes that control their fate and transport. Results will be used to characterize the environmental signature of these and other similar mesothermal gold mineralizations to build geoenvironmental ore deposit models and support on-going environmental management initiatives aimed at reducing risks to human and ecosystem health.
Both mine camps processed Au-bearing ore using Hg-amalgamation and/or cyanidation during the late 19th and early to mid 20th centuries. Exploration and production continue today sporadically. Gold occurs in veins and is associated with a host of sulphide minerals including arsenopyrite, galena, sphalerite, chalcopyrite, pyrrhotite, and stibnite (B.C. camp only). Gangue minerals include mainly quartz and carbonate minerals (calcite, dolomite, and ankerite at NS mines) with subordinate feldspar, mica and chlorite.
Synchrotron X-ray absorption spectroscopy (XAS) was used to investigate the As speciation in a variety of bulk samples including tailings, sediments, sludges and precipitates. Fluorescence experiments using Lytle and single element Vortex Si-drift detectors were carried out on the Hard X-ray Micro-Analysis (HXMA) beamline at the Canadian Light Source (CLS), University of Saskatchewan. Several spectra (3-10) were collected and averaged for each of the 10 reference minerals and compounds and 33 samples. The As K-edge X-ray absorption near-edge structure (XANES) spectra were used to characterize speciation of As within the tailings. Results on tailings from N.S. indicate the presence of scorodite, and adsorbed AsV. Sediment samples from B. C. indicate that in an active drift AsV sorbed to amorphous Fe-oxides dominates, whereas in another (inactive) drift, As-I, AsIII and AsV occur. In a sediment sample from a settling pond near the second drift, As-I >> AsV whereas in amorphous Fe-oxide samples, near the portal, AsV >>As-I. In a sample characterized by a surface biofilm and Fe-oxides, AsIII was found. The oxidative dissolution of sulphide minerals and As-bearing phases like arsenopyrite from exposed surfaces in both these drifts results in an increased solubility for As and Fe with subsequent precipitation of amorphous Fe-oxides enriched with oxidized As species but the presence of organics may inhibit the complete As oxidation reaction.
GEOSCAN ID226340