Orbost drilling update - Oroya Mining Limited

ABN 16 009 146 794
24 April 2013
Company Announcements Office
Australian Securities Exchange
Orbost drilling update
• Three holes completed on western flank of Sunday Creek
• Results indicate main copper prospectivity is on eastern and northern flank
• Anomalous copper and molybdenum highlight potential of Pinnak anomaly
Oroya Mining Ltd (ASX:ORO) has concluded drilling in the second phase of exploration on
its Orbost porphyry copper project.
Three holes, for a total of 273m, have tested the potential for shallow copper deposits at
Sunday Creek, west of the original discovery holes. SC 306 was drilled to 126.3 metres
toward the centre of the HeliTEM anomaly when drilling was stopped short of the target by
excessive water loss.
All holes intersected highly altered, pyritic granite under thin thermally metamorphosed
sediments (hornfel), confirming that the HeliTEM anomaly was a response to strong
mineralisation in the granites. Assaying is underway, and, as previously announced, the
upper section of SC306 had low copper grades. Full results will be released when the
assays are received. Holes SC307 and SC308 had sodic alteration with pyrite and hole
SC306 intersected strongly pyritic sericite-chlorite alteration to the end of hole. This
zonation is encouraging and potassic alteration with copper would be expected toward the
centre in a classic porphyry system.
Historic hole SC302, on the eastern side, intersected potassic alteration and higher copper
values. Testing of the centre of the anomaly and postulated breccia pipe therefore remains
a priority. It will require drilling from a location near the creek, which will entail preparation of
a cultural heritage management plan. Additionally, exploration has not yet identified a
breccia pipe or source for the wide spread anomalous copper in the eastern section of the
Sunday Creek anomaly, although there are deep HeliTEM anomalies that might be caused
by such a feature. These will be objectives for another drilling round because they correlate
with high copper in the geochemical surveys. Environmental and cultural heritage surveys
will need to be commissioned to fully test this prospective area.
Soil and rock chip geochemical results from the area of the anomalies have been
reassessed with the drill results. This indicates that copper content in the soil and rock chips
is a good guide to the prospectivity for copper in the area. The findings support the
extension of geochemical surveys to cover the untested HeliTEM anomalies to determine
which are most prospective for copper prior to the next round of drilling. These anomalies
are the major western zone of Sunday Creek and Sardine Creek.
Suite 502, 140 Bourke Street, Melbourne, VIC 3000, Australia Ph: (03) 90777987
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The Pinnak anomaly is now a high priority target because previous geochemical surveys
have shown the Pinnak area to be highly anomalous. Rock chip sampling returned values
of up to 0.2% Cu, 0.6% Pb, 0.1% Mo and 0.8 ppm gold from scattered quartz stockwork
veins. Soil geochemistry found anomalous copper and molybdenum in the aureole around a
granitic core (figure 1). Importantly, these results coincide with the southern part of the
Pinnak HeliTEM anomaly, surveyed in 2012 (figure 2). Based on the Sunday Creek results,
the HeliTEM is likely to be caused by strong pyritic mineralisation. The zonation of the
geochemistry with EM results is very encouraging.
The picture that is emerging from the exploration is consistent with the porphyry copper
model derived from major granite intrusion. The Orbost results show zonation of
mineralogy, including higher pyritic areas and potassic or chlorite-sericite alterations. It is
encouraging that the HeliTEM is detecting areas of strong mineralisation, which can
become the focus for geochemical follow-up to guide the next round of drill tests.
Figure 1. Pinnak Prospect showing anomalous copper soil geochemistry with offset anomalous molybdenum values and
a broad Pb-Zn halo across the metamorphic aureole of the Feltis Farm Granite (Tonalite). Source: McHaffie, I.W. & Radojkovic, A.,
2001. Synthesis and evaluation of east Victorian soil and drainage geochemistry. Victorian Initiative for Minerals & Petroleum Report 73. Department of
Natural Resources and Environment.
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Figure 2. HeliTEM anomalies on Oroya's Orbost tenements.
ENDS
For Further information please contact
Dr Kevin Moriarty
Chairman
Oroya Mining Limited
+61 408 173 157
kevinm@oroya.com.au
DECLARATION OF COMPETENCY
The information in this report that relates to Exploration Targets and Exploration Results is based on information compiled by Dr
Kevin Moriarty, a Competent Person who is a Member of The Australasian Institute of Mining and Metallurgy. Dr Moriarty has
sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity
being undertaken to qualify as a Competent Person as defined in the 2004 Edition of the ‘Australasian Code for Reporting of
Exploration Results, Mineral Resources and Ore Reserves’. Dr Moriarty is a consultant geologist and Chairman of Oroya Mining
Limited. Dr Moriarty consents to the inclusion in the report of the matters based on his information in the form and context in
which it appears.
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