DELINEATION AND SIGNIFICANCE OF LITHO AND STABLE ISOTOPE GEOCHEMISTRY ALTERATION HALOS IN THE GIANT HOLLINGER-MCINTYRE GOLD MINE, TIMMINS, ONTARIO, CANADA

Geochemical alteration around the giant Hollinger-McIntyre-Coniaurum (HMC) gold deposit was evaluated using whole rock lithogeochemical and mineralogy data obtain from a suite of 556 rock samples and bulk stable isotope measurements made on 68 vein samples collected from the surface, 1,000 and 2,000 m levels of the mine. The wholerock data plots in both the calc-alkaline and tholeiitic fields and compositionally ranges from rhyolite, through dacite/andesite, to basalt. The Y vs. Zr and Al2O3 vs. TiO2 content of the felsic rocks indicate the Pearl Lake Cu-Au deposit is hosted by a quartz-feldspar porphyry that is distinct from all other felsic intrusive rocks in the both the mine and Porcupine camp.

Principal component analysis of the lithogeochemical data indicates there are four clusters of samples including two that are associated with gold mineralization. The mineralization related alterations suggest that the HMC deposit was formed by two events. Geochemical maps made with the kriging tools in ArcMap^© indicate that alteration is complex and varies with depth. Major and trace elements have both been added to and leached from the country rocks with some such as Ca, Na and Cu being good indicators as to the location of the gold ore bodies.

The δ¹³C of vein carbonate ranges between +1.8 and -9.6‰ and systematically increase from -3.5 at surface to -9.5‰ at 1,000 m below the Pearl Lake Porphyry. The δ¹⁸O values range from +9.0 to +18.1‰ and have a broad, near surface, enrichment zone south and east of the Pearl Lake intrusion. The range in carbonate isotope composition suggests a complex fluid history that could include a magmatic component.