Orogenic Exploration Pty Ltd

Terowie South Diamond Project (Surrendered)

The Terowie South Diamond Project was aimed to testing a discrete gravity low anomaly below Hiles Lagoon, a flat, nearly circular playa lake, southeast of the town of Terowie. In 2000 Orogenic Exploration entered into a Joint Venture agreement with Alcaston Mining NL over Exploration Licence 2575. Hiles Lagoon is located near the centre of the Terowie Kimberlite Province.

Following final interpretation of a gravity survey by a Monash University student over Hiles Lagoon, a small hand auger drilling programme (two holes) was completed during September 1999. Unfortunately, the hand auger was not able to penetrate the current lacustrine sediments (maximum depth reached 4.5m). One auger sample for heavy mineral indicator study was collected and processed with the recovery of kimberlitic picroilmenite and Cr-spinel, together with olivine (not kimberlitic). These grains were then sent for microprobe analyses which have confirmed the interpretation.

To test the gravity anomaly a single angled diamond core drillhole as completed between 22 November to 3 December 2000. The total depth of the drillhole was 420 metres, with HQ coring commencing from 6 meters, and changing to NQ coring at 48 metres. The angled hole was collared on the southeast side of Hiles Lagoon and orientated to test the large discrete gravity anomaly beneath the lagoon. The diamond core drilling by Orogenic intersected two thin dykes beneath Hiles Lagoon. Due to the deep nature of the drillhole, unusually fresh samples were recovered of the olivine, phlogopite, clinopyroxene, melilitite, nepheline, and K-feldspar bearing dykes. Detailed petrology has confirmed the dykes are melanephelinite. Microprobe data shows the two dykes are not the source of the olivine grains recovered from the lake sediments during the hand auger program, but the diamond core drilling does show the gravity anomaly is probably due to depth variations in the lacustrine sediments beneath the lake. No diamond were recovered and the licence was surrendered on the 3 January 2004. Further details on the Terowie South Diamond Project can be found in Open File Envelope 9623 at the SARIG web site.

Hiles Lagoon olivine grain microprobe geochemistry