Ian Borg

Metaturbidite-hosted orogenic gold deposits of the Meguma Supergroup, in Nova Scotia, Canada, are currently being developed as the increase in metal prices makes formerly uneconomic, bulk-minable, disseminated prospects such as the Touquoy deposit more feasible. Recent research suggests that there may be relationships between mineralization and organic carbon in certain regions. The purpose of this study is to explore the relationship between organic carbon and metal deposits in a prominent example of orogenic-type gold in Nova Scotia.

For this study, 11 core samples and 12 ground pulp samples selected from the ore zone of the Touquoy deposit for further analysis. Procedures include geochemical analysis, spot analysis with an electron microprobe, and reflected light microscopy. The literature surrounding organic carbon and metal deposits was also explored, and the findings were applied to the Touquoy deposit. Finally, the data set from this study was combined with two others to supplement the findings, and for the purposes of comparison.

The geochemistry of the Touquoy samples, in addition to samples from other data sets, show that there is a positive correlation between gold and carbon at the deposit scale, but a negative correlation at the metre scale. Additionally there is a weak positive correlation between arsenic and carbon. Other results support a previous interpretation that sericite alteration is the main hydrothermal alteration product.

The data suggest that Meguma sediments were deposited off an Andean-type arc setting, rather than a passive margin as previously suggested. Additionally, there is also between one and two orders of magnitude more carbon in mineralized zones, than in barren Goldenville rocks. The presence of monoclinic pyrrhotite within the deposit, in addition to gold’s close spatial association with arsenopyrite suggests there is a relationship between the two sulfides and warrants further study.

In conclusion, though sample size, and use of homogenized pulp samples prevented a clear relationship with carbon being laid out, the data of this study support the proposal of an ore deposit model which includes the interaction with organic carbon in the form of petroleum.

Keywords: organic carbon, gold, meguma, orogenic, arsenopyrite, petroleum
Pages: 98
Supervisor: Marcos Zentilli