Sedimentary exhalative deposits
) are ore deposits
which are interpreted to have been formed by release of ore-bearing hydrothermal
fluids into a water reservoir (usually the ocean
), resulting in the precipitation of stratiform
SedEx deposits are the most important source of lead
, a major contributor of silver
The palaeoenvironmental setting and palaeogeologic setting of these ore deposits sets them apart from other lead, zinc or tungsten deposits which generally do not share the same source
morphologies as SedEx deposits.
SedEx deposits are distinctive in that it can be shown that the ore minerals
were deposited in a marine second-order basin environment, related to discharge of metal
into the seawater. This is distinct from other Pb-Zn-Ag and other deposits which are more intimately associated with intrusive or metamorphic processes or which are trapped within a rock
matrix and are not exhalative.
The process of ore genesis
of SedEx mineralisation is varied, depending on the type of ore which is deposited by sedimentary exhalative processes.
- Source of metals is sedimentary strata which carry metal ions trapped within clay and phyllosilicate minerals and electrochemically adsorbed to their surfaces. During diagenesis, the sedimenary pile dehydrates in response to heat and pressure, liberating a highly saline formational brine, which carries......