OREAS 926

OREAS 926 is one of a suite of sixteen copper ore CRMs (OREAS 920 to OREAS
935) prepared from material from the CSA mine located near the town of Cobar in
central western New South Wales, Australia. The copper ore body is hosted by the
Early Devonian CSA Siltstone, a thinly bedded turbiditic sequence of
carbonaceous siltstones and mudstones with minor coarser units. The CSA
Siltstone is part of the Cobar Supergroup, consisting of lower syn-rift
sediments and upper post-rift sag phase sediments. The mineralisation is
structurally controlled and confined to a number of steeply dipping bodies
within a major shear zone on the eastern margin of the Early Devonian Cobar
Basin. It is characterised by low-grade greenschist alteration and epigenetic
low-grade mineralisation enveloping higher-grade shoots of vein complexes or
sub-massive to massive sulphides. The sulphides include chalcopyrite,
pyrrhotite, pyrite, sphalerite, galena, bornite and cubanite. Iron-rich chlorite
and silica are prominent alterations in the siltstone host.
Twenty two commercial analytical laboratories participated in the program to
characterise the analytes reported below. The following methods were employed
for method specific certification:

Four acid (HCl-HNO3-HF-HClO4) digestion with
ICP-OES, ICP-MS or AAS finish (19 laboratories);
Aqua regia digestion with ICP-OES, ICP-MS or AAS finish (19 laboratories);

Peroxide fusion with ICP-OES, ICP-MS or AAS finish (12
laboratories).