International Star, Inc.


Mineralization and Alteration

Gold mineralization at the Van Deemen prospect occurs primarily in gently-dipping zones of quartz-sericite-hematite-pyrite clay alteration of brecciated Precambrian gneiss. Alunite is locally present in minor amounts. The alteration zones are spatially associated with  rocks generally exhibiting an open style of brecciation. Stacked sheets of quartz breccia are often present in the gold zones, sometimes forming at the fault contact with the upper plate, and other times forming irregular lenses in the faulted gneiss. These quartz breccias often contain mixed fragment types including brecciated chunks of vein quartz. The matrix supporting the breccia fragments appears to be made up of finely pulverized rock flour subsequently replaced by fine-grained quartz. In these quartz breccia zones, sulphides {pyrite and arsenopyrite) occur in and near late-stage fractures. Surrounding the quartz breccia bodies are locally brecciated gneisses often severely sheared prior to alteration. The shearing has drawn the feldspars into lenses and augen into bands that alternate with others composed of strained quartz grains, all greatly elongated in parallel. The feldspars are usually pulverized during this shearing process and subsequently replaced by dense sericite. •The altered rock surrounding the tabular quartz-breccia bodies is often cut by comby quartz veins carrying considerable pyrite .and arsenopyrite (?) that is usually fully oxidized. In general, where there is an increase in the amount of open, brittle brecciation and hematite and limonite there is also an increase in the old content.

The quartz-sericite-hematite-pyrite alteration is widespread along the Van Deemen Fault. The area of alteration is more extensive than the gold zones (+0.010 o/t gold). Drill holes north of Areas III and IV have shown a relatively thick package of altered rocks paralleling the low-angle normal fault, but the altered rocks carry only weak, spotty gold mineralization. Drill data available to date suggest that the northeast-trending gold zones are surrounded by a relatively large area of alteration that is mostly barren of gold. In other words, the gold zones seem to occur as elongate, tabular bodies trending northeast within a much more extensive body of alteration.

It is possible that hydrothermal fluids were being introduced into the low-angle fault zone by a wide variety of footwall conduits producing a broad, sheet-like zone of alteration. It is also possible that the northeast-trending fault zones (accommodation zones ?} tapped a gold-bearing hydrothermal fluid source and acted as conduits carrying the precious metal into the favorable fault breccia host. Future exploration for gold mineralization at the Van Deemen will be concentrated on following out known gold zones to the northeast and southwest and identifying new gold trends.

The gold-related alteration and mineralization at the Van Deemen locally overprints zones of porphyry copper alteration as described by Wilkins (1984). In some instances it is difficult to discern one from the other or to which event a particular zone of alteration is related. In general, the porphyry alteration exhibits a phyllic alteration assemblage (quartz-sericite-pyrite), but usually lacks the hypogene earthy hematite, minor clays, and brecciation that is present in the mid-Tertiary (?) alteration. It has been suggested Van Deemen Fault zone might have simply overprinted a portion of a failed, gold-bearing porphyry copper system. However, the close spatial association of gold mineralization with the mid-Tertiary low angle normal fault, combined with thin section work showing much of the mineralization introduced after brittle, open-style brecciation, suggests that the gold was introduced during the mid-Tertiary event, and not with the Laramide porphyry event.

No ore microscopy work has been completed to date on the gold-bearing rocks at Van Deemen, so it remains an unknown as to how and where the gold occurs. Preliminary cyanide leach tests do indicate, however, that a good percentage of the gold is free and probably quite fine. In addition, the combination of detailed surface sampling and close-spaced drilling has indicated a weak to moderate supergene enrichment at the surface, another indication that much of the gold is probably native.