CGRG Bibliography of Canadian Geomorphology
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Author : Grasby, S.E.; and Hutcheon, I.
Date : 2002.
Title : Modern thermal springs and hydrothermal ore deposits in the southern Canadian Cordillera.
Publication : Geological Association of Canada and Mineralogical Association of Canada Joint Annual Meeting, May 27 - 29, 2002. Saskatoon, Saskatchewan.
Issue :
Page(s) :
Abstract
Ore models for hydrothermal Ag-Pb-Zn deposits in the southern Canadian Cordillera typically invoke the mixing of deep-seated fluids with relatively shallow circulating, sulphide rich meteoric waters, along major Eocene extension faults. The best analogue for studying this relatively shallow portion of the circulation system is modern thermal springs. Thermal springs in southern British Columbia are restricted to six major Eocene or later brittle fault systems. These faults provide an anomalous high permeability flow path that allows for deep circulation of meteoric water. The depth of circulation, and thus temperature, is largely influenced by local geothermal gradient and fault plane geometry. The modern distribution of thermal springs is consistent with ore models in that they 1) show preferential deep circulation of meteoric water along Eocene extension faults, and 2) have estimated circulation depths, up to 5 km, similar to depths proposed for mineralization. Both sulphate and sulphide occur in thermal springs, with SO4 being the dominant form. Concentrations are highly variable in the springs examined (11 ? 1670 mg/l SO4, 0 ? 123 mg/l H2S). High sulphate values in these springs are mainly derived from dissolution of evaporite minerals from associated carbonate host rocks. Stable isotope data indicate this sulphate is reduced to HS- by bacterial sulphate reduction. ?34S values for sulphide ore minerals (0 to -13?) are consistent with the range of values for HS- in thermal spring along the Columbia River Fault (-0.8 to ?12.9?). Mass flux calculations indicate that individual modern thermal-spring systems can transport up to 285 tons of reduced sulphur per year. Given the approximately one million tons of Pb-Zn ore produced from the deposits along the Slocan Lake Fault, with an associated 0.3 million tons of sulphur, it would take an individual thermal spring system ~ 1000 years to transport that amount of sulphur to depth. Thus relatively minor flow systems can play a significant role in forming major ore deposits.
Bibliography of Canadian Geomorphology