Drilling is undertaken to gain information from the subsurface, mainly through the collection of samples. These may be in the form of continuous core, as in most engineering and mineral exploration applications, or core over selected depth intervals of a drill hole, such as in oil exploration wells. Other types of drilling, such as auger, rotary or percussion drilling, produce cuttings or rock chips, which sample a given depth interval. An example is rotary air blast (RAB) drilling, often used in gold exploration, particularly on the mainland.
The Tasmanian Government is obligated under Part 6 (s.117-126) and s.187-191 of the Mineral Resources Development Act 1995 to maintain a library of drill core from mineral tenements and also to ensure that records of the drilling are collected and maintained by tenement holders. Both the core and the records may eventually become part of the Tasmania's geoscientific information base. There is no obligation for MRT to store core from engineering projects, but it is policy to do so where practicable.
There are different arrangements for information on drill hole samples and the samples themselves, usually drill core, from mineral tenements entering the public domain. Only public domain information and core is made available for public inspection.
The Tasmanian Government spent some $700,000 in 2000 from its Capital Investment Program for the extension and refurbishment of the Mornington core library operated by MRT.
There is currently core from about 3000 drill holes, totalling about 460 kilometres of core, housed in the library.
Drill core is the most valuable product of a mineral exploration program. The MRT collection has a replacement value of $46 million and is accessed regularly by mineral explorers. The collection has been used in recent years to accelerate the Beaconsfield mine redevelopment and the Arthur River magnesite project.
The assaying of old drill core for gold resulted in the discovery of the Henty Gold mine.
A significant part of research in economic geology is to identify signs of ore outside of the deposits themselves. The identification of these haloes of "altered" rock, that is rock affected by the mineralising processes, and the development of techniques to use in characterising the alteration to provide vectors to undiscovered mineral deposits, mean that drill core remains a valuable public asset long after its initial collection.
MRT's Core Library is located at 93 Mornington Drive, on Hobart's eastern shore.
Appointments can be made by telephoning (03) 6233 8406.
Core Library
