Overview of SEDEX Pb-Zn deposits

CIM Vancouver 2006
Wayne Goodfellow,
Abstract SEDEX (SEDimentary EXhalative) deposits are important resources for Zn and Pb, accounting for 50% and 60% of the world's reserves of these elements, respectively. Major Canadian past-producers include Sullivan, Duncan, Faro and Grum. In addition to Zn and Pb, other economic commodities include Ag and Cu.

SEDEX deposits are sulphide bodies composed predominantly of Zn and Pb, bound in sphalerite and galena. SEDEX are syngenetic, stratiform and shale-hosted deposits. They consist of vent-distal and vent-proximal facies. The former is composed of interbedded sphalerite, galena, iron sulphides and clastic sediments, and latter of variably veined, infilled and replaced bedded sulphides.

SEDEX deposits occur in intracratonic and epicratonic rifts within reduced marine basins. They are restricted to rocks younger than two billion years and formed during discrete periods in the Proterozoic and Phanerozoic. The architecture of sedimentary basins is characterized by a syn-rift phase of rapid subsidence and clastic sedimentation that is followed by a post-rift phase of fine-grained clastic and carbonate sedimentation in basins and platforms.

Exploration vectors for SEDEX deposits consist of synsedimentary faults, local fault-controlled third-order basins, anoxic water columns, widespread hydrothermal alteration (muscovite, carbonates, and tourmaline), and laterally and vertical extensive distal sediments that are mineralogical and chemically zoned about seafloor vents.
Keywords: SEDEX, syngenetic, intracratonic rifts, shale-hosted, epicratonic rifts, Pb-Zn, stratiform
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