The Maragorik prospect is an
example of high sulphidation, Cu/Au
mineralisation occurring at a high
level in the hydrothermal system. As
extensive ash deposits blanket the
region, controlled-source audio
magneto-tellurics (CSAMT), in conjunct-
ion with bulldozer trenching, have been
used to delineate subsurface geology.
Fluid upflow has occurred along EW
structures dilated by rotation on the
bounding major NW lineaments. Rising
hydrothermal fluids have exploited
permeable horizons in contact with the
upflow structures. This lithological
control is evident as ledges of
silicification and peripheral clay
alteration, at high levels in the
system. As is typical of high
sulphidation systems, a two phase fluid
consists of an initial rapidly moving
vapour-dominated phase, followed by a
liquid-dominated phase. Much of the
zoned and overprinted silica to clay
alteration is developed from the
vapour-dominated fluid. Mineral
deposition occurs as a result of
brecciation of the competent silic-
ification by liquid phase fluids. Such
mineralisation is of restricted volume
in ledges proximal to the feeder
structures.
The style of alteration and
mineralisation are indicative of a very
low temperature and hence a high level
system. Thus, although high sulphid-
ation systems are inferred to develop
from porphyry-related magmatic fluids,
such a source at Maragorik is
interpreted to be very deeply buried.