Abstract -
We present the results of studies of the structural
geology of three mines in the Irish Zn-Pb orefield, Galmoy,
Lisheen and Silvermines which support a model invoking
the existence of normal fault relay zones at fault segment
boundaries to be responsible for the localisation of up-fault
fluid flow of metal-bearing fluids, and their entrapment
within stratiform dolomite breccias. We show that, these
structures occur in deposit-related fault systems over a
broad range of scales which tend to reflect the mechanical
stratigraphy of the host rocks, yet only relay zones with
a particular size:displacement ratio are likely to have
contributed significantly to the localisation of up-fault fluid
flow. Moreover, their precise geometrical arrangement may
have favoured the flow of ore fluids into the hangingwall,
where Irish Zn-Pb deposits are observed, or to ascend the
fault to higher levels, possibly reaching the sea floor.
Abstract of talk given to:
Structural Geology and Resources 2012, Australian Institute of Geologists (AIG), Kalgoorlie, September 2012.