As part of the ongoing drilling, six rigs were operating prior to the Christmas shutdown.
More in-fill holes are planned at the Imbruminda and Omora deposits to help lift inferred resources to either the indicated or measured categories.
Marengo said the next resource estimate was scheduled for this quarter.
The project is 95km southwest of the provincial capital of Madang and is initially expected to produce 100,000 tonnes of contained copper plus 15,000t of contained molybdenum a year over a 20-year life but there is scope for considerable expansion.
Mining approvals are expected in the September quarter of 2013, construction is tipped to start 24 months later and the project is targeting production in 2016.