20 - 100 million tonne IOCG type oxide Cu-Au
200 - 300 million tonne porphyry Cu-Au deposit
The Sierra Pintada property, consisting of fourteen exploration
claims totaling approximately 3300 hectares, is located in
the Chilean Coastal cordilleran copper-gold belt 650 kilometers
north of Santiago and is readily accessible from the town
of Vallenar 30 km to the east. The property covers a 15 kilometer
strike length of a several hundred kilometer long major structure
zone along which there are numerous centers of past high grade
copper, gold, silver and cobalt mining e.g. Carrizal Alto
District passed production approximately 450,000 tonnes of
copper and 1.5 million ounces of gold. The high grade copper-gold
veins, mantos and stock works previously worked on the Sierra
Pintada property are most probably within the Early Cretaceous
Metallogenic Belt which includes the Andacollo and Los Mantos
de Punitaqui Mines.
All claims are owned 100% by Minera IPBX Limitada, the whole
owned Chilean exploration arm of International PBX Ventures
Geology and Mineralisation
The property covers 15 kilometers of the structural contact
between late Paleozoic meta-volcanic and meta-sedimentary
rocks which form the Coastal Metamorphic complex to the west
and Late Cretaceous diorites to granodiorites of the Franja
Central to the east. This NNE trending zone is up to 100 metres
wide with northerly trending splays and wherever it emerges
from beneath overburden is the center of numerous prospect
pits, adits and workings to depths of 50 metres on high grade
Cu-Au (Ag, +/- Co) and Au-Cu (Ag) fissure veins from 1-5 metres
width. The material previously mined typically graded 3-5%
Cu + 1-5 gpt Au for the former and 10-50 gpt Au + 1-5% Cu
for the later.
There are at least four mining districts
of from 2-4 km strike length occur along the 25 km of strike
of the structure zone identifiable south of Freirina. The
northern most La Gloria and Totora districts are covered by
the Sierra Pintada project claims.
These claims cover two strongly mineralised
zones within the main structure zone. The western most Viña
zone consist of a 50 - 100 metre wide zone of shearing and
brecciation within strongly hematite-clay-limonite +/- quartz
altered volcanics and dioritic intrusives with wide spread
CuOx mineralisation. This zone has been extensively worked
along approximately 1500 m of strike and vertical range of
150 metres. The workings consist of trenches, adits and open
cuts from 1-10 metres wide on multi-directional high-grade
zones visibly grading 5% or more green copper minerals. The
workings concentrate in several high grade cores from 15-20
m wide. At a 2.75 gpcc density this worked section of the
core has a tonnage potential of about 10 million metric tonnes.
The structure is strong where it heads under pediment gravels
in both strike directions. The eastern most Gloria zone is
similar in all aspects to the Viña zone with the exception
that it shows weak green copper mineralisation in the surface
workings which according to local miners are on 'veins' grading
15-30 gpt gold.
Scattered old workings and hematite/clay
rich soils indicates that at least the Gloria gold-copper
zone probably does continue to the southwest beneath pediment
cover to the Totora district were a repeat situation of high
grade fissure and shear veins has been worked.
There are no published records of production from the old
mines or prior exploration activity. Reconnaissance scale
Government geological for the area suggest that most of the
mining activity occurred during the 1820's to 1890's i.e.
during the main mining period at Carrizal Alto. Hand cobbed
ore grading 5-10% copper and 15-50 gpt gold reportedly being
shipped to the Carrizal Bajo smelters.
During evaluation and acquisition of the
project claims a series of 33 representative chip and dump
samples were collected by Minera IPBX Limitada personnel.
The results area as follows:
Gloria Zone: Au 1.03 - 5.1 gpt (av. 2.58 gpt.) plus 0.02 -
1.59% Cu (av. 0.36%)
Viña Zone: Cu 0.92 - 8.00% (av. 2.59%) plus 0.12 -
1.82 gpt Au (av. 0.48 gpt)
These results are in line with verbal reports from local miners
of shipped grades of 15+ gpt gold from the Gloria Zone and
5%+ copper from the Viña Zone when the hand cobbing
reduction ratio of from 3-5:1 is taken in to account. The
locals also state that much of the gold was coarse free gold.
As mentioned above in the La Gloria mining district one section
of the Viña zone has been worked over a length of 1500
metres and vertical range of at least 150 metres. Considering
the two core sections of about 35 metres thickness and average
density of 2.75 gpcc, this section alone has an open ended
open pit tonnage potential of about 20 million tonnes. In
this same district the Gloria zone is exposed for at least
1700 metres and averages about 50 metres wide hence its near
surface open pit tonnage potential at this point is also about
20-30 million tonnes.
On a larger scale repeat deposits of
similar size may be encountered in the southern Totora district
and the overburden areas between the two districts. Also it
is possible that these districts are centered above deeper
Andacollo style porphyry systems as has been suggested for
Carrizal Alto to the north.