高温超伝導磁気センサーを用いた電磁探査技術による鉱床探査

抄録

JOGMEC completed construction of the SQUITEM, a three-channel TEM data acquisition system based on the HTS SQUID magnetic sensor in 2006. A HTS SQUID is a high-sensitivity magnetic sensor that has wide bandwidth, and offers high field sensitivity even at low frequencies. The SQUID magnetometer offers advantages over a conventional induction coil receiver in depth of investigation and detecting conductive targets especially in the presence of conductive overburden.
The magnetic field resolution of the SQUITEM is 300fT/ √Hz at 1kHz as measured in the field. A slew rate (6.8mT/sec in maximum) is sufficient to respond to square-wave primary-field variation in metal exploration. Frequency bandwidth from DC to 100kHz provides minimal distortion of the recorded signal.
JOGMEC applied the SQUITEM to metal exploration at the White Roo Prospect in the Border Project, west of Broken Hill, a JOGMEC/Minotaur Joint Venture. The joint venture was targeting Broken Hill Type Pb-Zn-Ag mineralization. Initial drilling had intersected pyrrhotite/chalcopyrite mineralization hosted within a mafic gneiss. A SQUITEM survey was conducted in October 2006 to investigate bedrock conductors highlighted by a conventional TEM survey. The SQUITEM survey concluded that the SQUITEM data was superior to the conventional TEM system with respect to depth of investigation. This is because the SQUITEM data profiles and inverted sections highlighted a conductive zone at depth that was not apparent in the conventional TEM data. Drilling of this bedrock conductor resulted in the intersection of pyrrhotite-chalcopyrite mineralization.