Andewa 3D-IP Chargeability Anomalies Doubled
in Total Area to Approx. 7km2
Frontier Resources Ltd is very pleased to announce that results from the remaining third of the 21 km2, grid-based, three-dimensional induced-polarity geophysical survey at the Andewa gold and copper Project in Papua New Guinea have doubled the total chargeability anomaly area (>30ms) to about seven square kilometres. The anomalies are open in several directions.
A very large sulphide mineralised system has been demonstrated by compelling 3D-IP chargeability anomalies from surface to >800m total depth, in three major, but discrete zones. The newly defined Ekhos chargeability anomaly is 3.3 km2 in area (at 150m below sea level), which is larger than the previously announced Core Chargeability Zone (CCZ) (3.0 km2) and the Ber anomaly (approx. 0.5 km2). Ekhos has developed into the largest and closest to surface 3D-IP chargeability anomaly at Andewa, with much of it very intense (>45ms). Each chargeability anomaly is surrounded by a sub-circular, high-resistivity anomaly that appears to merge near and/or off the edge of the grid, to become one ~ 6km diameter anomaly in the centre of the Mt Andewa caldera, representing probable silicification around the intrusions. There are strong correlations between known surficial gold and copper and the 3D-IP chargeability anomaly at Ekhos, however, most of that region has never been explored.
The CCZ and Ekhos chargeability anomalies are connected by an east-west trending zone and the Ekhos and Ber anomalies are located at higher elevations above sea level (than the CCZ). Deep drilling will be undertaken with Frontier’s diamond coring rig (to its approx.400m capability)
as soon as possible (April) to test the chargeability,
soil/rock, gold/arsenic/copper anomalies. A contract
rig may be utilised for deeper drill testing (to ~700m). A geophysical consultant is evaluating the data and is
defining conductive zones representing probable semi-
massive sulphide type mineralisation, which will be
initially drill targeted. Most soil and rock chip assays have now been received
(about 5,000 samples). Results are being collated/
plotted, evaluated and will be released as soon as
possible, likely in late February. Field technicians have been mobilised to site to
undertake infill grid-based sampling to better define
the gold and copper mineralised soil zones. Landowners are being briefed onsite tomorrow by the
Chairman/MD regarding the significance of these
results, future work plans and followed by a
celebratory ‘MuMu and SingSing’ (Feast and Party).
DETAILS
Three exceptionally extensive, voluminous and intense, 3D-IP
(three dimensional Induced Polarisation) chargeability anomalies
have demonstrated the presence of very large on-surface to
more than 800m deep sulphide systems at the Andewa gold and
copper Project on the island of New Britain in Papua New
Guinea. Please refer to figures 1, 2, 3, 4a-b, 5a-e, 6a-c and 7a-h
for detailed plans and cross sections.
The Andewa Valley is uninhabited (figure 2) with landowners
living outside the ‘caldera’ on the coast.
Seven ‘historic’ high-level gold prospects or anomalous areas
occur within a central 7 km by 2.5 km structural zone (figure 3).
Exploration has previously concentrated on only the Komsen
gold Prospect. Frontier has previously undertaken
The generalised shapes of the anomalies can be seen in figures
4a and b showing a pseudo 3D image (schematic) of the
chargeability and resistivity
zones (viewed from the
southeast to the northwest
and vice versa, respectively).
The IP and soil geochemistry
section lines are also shown
with topography represented
by dotted lines. The small
inset plan is a vertical
representation illustrating
the viewing direction.
no
exploration in the Ekhos ‘district’.
The orange sections are
strongly chargeable zones (>
30ms), the light green
regions represent relatively
low resistivity (<65 ohm-m)
and the darker green zones
represent relatively high
resistivity (>500 ohm-m). All
of these zones are interesting
for various reasons.
The >30ms chargeability
anomaly is approx. 4.5km
wide
The total area now known to
have anomalous chargeability
(>30ms) has doubled to
approximately seven square
kilometers. This consists of
three very large, spatially
related and intense
chargeability anomalies,
being the Core Chargeability
Zone (CCZ), Ber Zone and the
newly defined Ekhos Zone.
The total anomalous chargeability area is approximately 5,400m long (E-W) and 3,000m wide (N-S). The chargeability anomaly is NOT closed off to the NE of Ekhos, though it appears it could be closed off to the south (at depth). The CCZ chargeability anomaly is NOT closed off to its south on surface or at depth, however, its very intense core (>45ms) does appear to be adequately resolved.
The Ekhos chargeability anomaly is 3.3 km2 in area, which is larger than the previously announced CCZ (3.0 km2) and Ber areas (~0.5 km2) (at 150m below sea level). Ekhos has developed into the largest and closest to surface 3D-IP chargeability anomaly at Andewa, with much of it very intense at >45ms. The CCZ also has large anomalous areas at >45ms chargeability that extend to depths greater than the 800m modelled maximum.
Each major chargeability anomaly is surrounded by a sub-circular high-resistivity anomaly that appears to merge near the edge and off the grid, to become one approximately 6km diameter resistivity anomaly in the centre of the Mt Andewa caldera/ volcano, with ‘holes’ in it where the strong chargeability anomalies exist (figures 6a-c).
The resistivity and chargeability anomalies are generally mutually exclusive, but Ekhos has demonstrated coincident zones that are interesting drilling targets and the CCZ also has some at greater depth.
Resistivity likely reflects major hydrothermal fluid movement that resulted in silicification or quartz veining in ring, radial and other types of fractures associated with a major mineralised porphyry intrusion. The margins and more intense central sectors of the resistivity anomalies are also valid drill targets and will be compared to the soil geochemistry and assessed.
The Ekhos chargeability anomaly is very large, sub-equant and approximately 3,850m long x 1,750m wide.
Ekhos clearly demonstrates a very large, voluminous, cohesive and extensive sulphide system commencing on surface and becoming consistently very intense (>50ms) with depth. It averages about 1,000m wide and has a higher grade chargeability core zone that is approximately 2,400m long and 1,000m wide (at >30ms and 400m below topography - refer to plans in figures 5a-e and 6a-c plus specifically cross sections 7e, f, g & h). As a comparison, the CCZ is approximately 2,900m long ((NW to SE) and a maximum of 2,100m wide, averaging approximately 1,000m wide.
The Ekhos chargeability anomaly is pseudo saucer to cup shaped progressing SW to NE, in relation to both intensity and size, and it appears to depth limited to approximately 700m below surface. The CCZ in comparison is NOT depth limited and continues past the approximate 800m maximum modelled depth.
Frontier has previously drilled gold mineralisation at Komsen on the western margin of the CCZ from surface to a maximum depth of 320m below surface in a limited program, with drill intercepts containing significant base metals such as 1m of 19.0 g/t gold + 119.0g/t silver + 10.3% zinc + 0.22% copper, 2m of 5.43 g/t gold + 95 g/t silver + 11.1% zinc + 2.3% lead + 0.12% copper and 0.5m of 2.55 g/t gold + 36 g/t silver + 0.48% zinc + 0.19% copper.
The CCZ is located between the Komsen and Ekhos Prospects, where float rock samples assayed to 54.4 g/t gold + 990 g/t silver and outcrop rock samples assayed to 7.10 g/t gold. It is also marginal to the Samarung Prospect which had a historic float rock sample grading 37.2 g/t gold + 1.58% copper + 0.5 ppm platinum + 44 ppm palladium and numerous narrow auriferous veins and structures.
Mineralised and altered porphyry float rock has been noted in 2 locations and hypothesised in an Aster satellite evaluation, including a jarosite equivalent alteration zone, surrounded by a pyrophyllite clay alteration halo and a 1.1km diameter circular feature showing alunite equivalent clay alteration. Alunite can also be associated with High-Sulphidation epithermal gold systems, which can occur genetically related to porphyry mineralisation (at higher relative levels) and are also a valid target.
Chairman and Managing Director Peter McNeil M.Sc. commented:
Results from the last third of the three dimensional Induced Polarisation geophysical survey have dramatically enhanced the economic potential for precious and base metals at the Andewa Project. Frontier has demonstrated the presence of three enormous IP chargeability anomalies that likely reflect sulphide mineralisation within a major gold and copper mineralised system.
The soil and rock samples from the 2010 exploration program have now been received and are being compiled for release as soon as possible. Interrogation of the geochemical and geophysical data sets
is producing, high quality drilling targets in multiple prospect areas. Frontier has been remarkably successful with this exploration program defining chargeability anomalies over about 1/3 of the total 21 km2 grid area.
An extensive drilling campaign will commence as soon as possible (likely in April) to test these enormous and incredibly impressive IP chargeability, conductivity and resistivity anomalies.
Frontier’s previous surface and drilling programs have proven gold mineralisation at the Komsen Prospect from surface to a maximum depth of 320m below surface in a limited program, proving excellent lateral and vertical continuity in the structure, with drill results to 7.9m of 10.01g/t gold.
Some basic geological and geophysical discussion is warranted regarding what these geophysical results could mean. Please refer to the brief discussion below. The strong chargeability anomalies are in themselves valid and compelling drilling targets, as are their shoulders (or the transition zones between high and low intensity), for both precious and base metal deposits. The intensely chargeable zones likely reflect areas with much higher sulphide concentrations. A “sulphide system” means disseminated or wide-spread, electrically conductive sulphide minerals are present. It is not known what type or quantity of sulphides are causing the chargeability response, but it is almost certainly pyrite and/or base metal sulphides (not graphite). The strength of the chargeability anomaly is directly proportional to the total volume and type of sulphides that are present (ie. generally more sulphides = stronger chargeability anomaly). In a loose sense, the rocks become ‘chargeable with electricity’. If there are no sulphides (or graphite) the rocks cannot become ‘charged’ and are in effect ‘normal’. Pyrite is iron sulphide. It is the most common form of sulphide, but generally has no economic value. Base metal sulphides (primarily of copper +/- zinc and lead) and precious metals (gold and silver) are economically significant and are the exploration targets at Andewa. Conductivity anomalies probably represent semi-massive sulphides (because they ‘conduct’ electricity). The definition of a ‘World Class Deposit’ varies but is now generally considered to be about 4 million contained ounces of gold or copper equivalent. Gold and base metals have various three dimensional spatial relationships with pyrite/sulphides in different types of mineral deposits in these environments, depending on the precise physical and chemical conditions under which they formed. Higher grade zones of copper mineralisation sometimes contains lower total sulphides (less pyrite, but more base metal sulphides) and thus actually have lower total chargeability. As such, economically significant base metal sulphide zones could also occur adjacent to (not within) the highest chargeability anomalies. This means that the shoulders of the chargeability anomalies are also valid drilling targets.
It is possible that the copper and gold grades of the sulphide mineralisation will increase with depth and that the chargeability anomalies at / near surface represent structurally related mineralisation peripheral to major porphyry copper - gold mineralisation. Care should be exercised in the interpretation /significance of these anomalies. Drilling will provide a ‘definitive’ test of the multitude of geophysical, geochemical and structural targets.
The 3D-IP geophysical survey has been a remarkable success and has demonstrated there is excellent depth potential for possible gold and copper mineralisation associated with the intense sulphide systems /chargeability /conductivity and resistivity anomalies.
For information relating to Frontier Resources please visit our website at www.frontierresources.com.au or feel free contact me upon my return from Papua New Guinea.
FRONTIER RESOURCES LTD