Seafield Resources'
offshore placer gold project covers c.10 000 km2 of the
Westland
continental shelf between Karamea and Jacksons Head, from the low-water mark out
to the 120 m isobath (Figure 1). De Beers Marine (DBM), the marine diamond
subsidiary of the De Beers Group, will carry out the project with geological
input from Placer Solutions (PSL). DBM bring a wealth of expertise and advanced
technology to the project, developed during their 20 years of exploration and
mining of diamond placers on the Atlantic shelf of southern Africa, where they have also maintained a strong
environmental record.

Glaciers and
high-energy rivers emanating from the Southern Alps have transported substantial
quantities of gold bearing sediment onto the Westland continental shelf during Pleistocene
glacial periods, when fluvial gradients are steeper, sea level is c.120 m lower
and most of the shelf is exposed. These deposits have been extensively reworked
by the advancing shoreline and marine processes during interglacial marine
transgressions, and most are now buried beneath a variable thickness of
post-glacial marine sand, silt and mud. DBM will use side-scan sonar, swath
bathymetry, Chirp sub-bottom profiling and a magnetometer to map the sea floor
and sediments beneath it, guided by PSL's predictive geological model for gold
distribution on the shelf. Cactus grab and vibro-core samples will be used to
ground-truth the geophysics and provide stratigraphic, sedimentological and gold
distribution data for incorporation into the geological model. Areas of interest
identified by the geophysical and sampling data will be investigated in more
detail, with closer-spaced geophysics and Mega-drill sampling to a maximum
sediment depth of 20 m beneath the sea floor. These samples will be raised to
the ship with air-lift suction technology, processed onboard for mineralogical
and grade information, then returned to the sea floor. Environmental baseline
data will be gathered from Van Veen grab samples of seabed sediment taken
throughout the area during the prospecting programme.