re: tyc lifting off now Thursday, 7 October 2004EXCEPTIONAL...

re: tyc lifting off now Thursday, 7 October 2004
EXCEPTIONAL METALLURGICAL RESULTS
ENHANCE BANKABLE FEASIBILITY STUDY ON
TETHYAN’S H4 PROJECT
Rapid Copper Extraction of Leach Ores Strengthens H4 Feasibility
Base metals group Tethyan Copper Company Limited (ASX: TYC) today reported exceptional
metallurgical test results from work carried out as part of a Bankable Feasibility Study at its H4
Copper Project. The H4 Project is slated as Tethyan’s “starter” project in the Reko Diq area in
Pakistan – an emerging copper province where the Company controls over 12 billion pounds of
copper and 9 million ounces of gold in JORC-compliant inferred and indicated resources.
The Bankable Feasibility Study contemplates a 40,000 tonne per annum copper mine at H4 with a
mine life of approximately 15 years. The operation would generate LME-grade copper metal on
site, using the well-proven process of bio-heap leaching followed by solvent extraction and
electro-winning of cathode copper metal.
Implications of the favourable test results, if reproduced on a mine-scale, include enhanced cash
flow generation due to the rapid copper extraction, lower production costs due to a reduction in
total acid consumption and a reduced requirement for post-leaching acid neutralisation, and lower
capital requirements due to a reduction in the total size of the leach pads.
The current series of 6 column leach tests commenced 3 months ago and have demonstrated quite
exceptional results, with copper extraction after only 90 days ranging from 64% to 88%. This
compares with expected ranges of 180-200 days for the same levels of copper extraction from
typical copper deposits around the world. These tests cover 6 different ore composites, defined by
the host rock type and the ratio of chalcocite to chalcopyrite. The excellent copper extraction rate
may be attributed to refinements in various operational parameters derived from the previous test
work. In particular the irrigation rate of the raffinate (the acid which is added to the columns) was
increased, while acid added at the agglomeration stage was decreased.
The copper extraction curves for these tests (see Graph 1) demonstrate a well-defined S-curve,
typical of bio-leach extraction graphs. Initial rapid copper extraction is due to the dissolution of
the chalcocite by the acid, and this is followed, after approximately 30 days, by renewed strong
extraction as bacterial activity surges.
Two previous rounds of column leach test work have been done. An initial column leach test was
carried out in 2001 and demonstrated favourable leaching characteristics, with 86% copper
recovery after 167 days. Two further column leach tests were started in early 2004, using a much
lower acid irrigation rate. The first of these, a composite sample of mixed chalcocite and
chalcopyrite ore (such as would be encountered at the lower boundary of the ore deposit) reached
a final 60% extraction after 150 days. The second column is still active after 200 days, with 78%
of the copper extracted.