| Title | Geology and controls on gold enrichment at the Horne 5 deposit and implications for the architecture of the gold-rich Horne Volcanogenic Massive Sulfide Complex, Abitibi Greenstone Belt, Canada |
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| Author | Krushnisky, A; Mercier-Langevin, P; Ross, P S; Goutier, J; McNicoll, V J; Jackson, S E ; Monecke, T; Yang, Z; Pilote, C; Moore, L |
| Source | Economic Geology 2022 p. 1-34, https://doi.org/10.5382/econgeo.4978 |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20210376 |
| Publisher | Society of Economic Geologists, Inc. |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Quebec |
| NTS | 32J; 32K; 32L; 32B; 32C; 32D; 32E; 32F; 32G; 42A; 42B; 42G; 42H; 42J; 42I |
| Area | Abitibi |
| Lat/Long WENS | -83.0000 -74.0000 50.5000 47.5000 |
| Subjects | metallic minerals; mineralogy; Science and Technology; Nature and Environment; general geology; gold; mineral enrichment; mineral deposits; Greenstone Belt |
| Illustrations | location maps; diagrams; photographs; charts; graphs |
| Program | Targeted Geoscience Initiative (TGI-6) Ore systems |
| Released | 2022 07 21 |
| Abstract | The Archean Horne 5 deposit, located in the Rouyn-Noranda district in the southern Abitibi greenstone belt, Canada, contains a total resource of 172.4 t Au (5.6 Moz) from 112.7 Mt of ore grading at 1.53
g/t Au. The deposit is part of the Au-rich Horne volcanogenic massive sulfide (VMS) complex that also includes the past-producing Horne mine (i.e., the Upper and Lower H zones plus small subsidiary lenses) that yielded 325.4 t Au (10.5 Moz Au) from
53.7 Mt of ore grading at 6.06 g/t Au. Combined, the Horne mine and Horne 5 deposit contain ~500 t Au (16 Moz), making them the world's single largest accumulation of VMS-related Au. The Horne 5 deposit consists of stacked lenses of massive to
semimassive sulfides alternating with extensive zones of disseminated and stringer sulfides. The mineralization is hosted within thick accumulations of steeply dipping dacitic to rhyodacitic volcaniclastic units of transitional to calc-alkaline
magmatic affinity. Dacitic-rhyodacitic synvolcanic units (lobes, sills, and/or domes) intrude the host succession, which is also crosscut by a series of post-ore mafic and younger intermediate to felsic feldspar ± quartz porphyry dikes. A broad and
diffuse halo of distal sericite-chlorite-epidote alteration extends outboard of intensely sericite-altered zones proximal to the sulfide lenses. Gold is interpreted to be synvolcanic on the basis of Au-rich massive sulfide clasts in the
volcaniclastic units, the presence of preserved Au-rich primary pyrite, Au zones limited to the sulfide envelope, crosscutting deformed but unaltered and barren dikes, and the absence of typical syndeformation, orogenic-style alteration and
mineralization despite overprinting high-strain corridors and faults. Gold is spatially associated with pyrite, sphalerite, and chalcopyrite, and its distribution is largely controlled by the higher porosity and permeability of the volcaniclastic
host rocks, which are interpreted to have facilitated hydrothermal fluid circulation in the subseafloor environment. Synvolcanic intrusions and fine-grained tuffs overlying auriferous zones also influenced the distribution of the mineralization by
acting as cap rocks to ascending fluids. Evidence suggests that Au enrichment at the Horne 5 deposit is due to efficient transport and precipitation of Au in the subseafloor environment, a favorable geodynamic setting (transitional to calc-alkaline
magmatism over thick crust), and possible input of magmatic fluids as suggested by high Te and Cu in the mineralization. Minor and very local remobilization of metals occurred in response to regional deformation and associated greenschist facies
metamorphism. The detailed study of the Horne 5 deposit geology and a review of the available information on the Horne mine and recent 3-D modeling indicate that the Horne 5 deposit may have formed higher in the stratigraphy than the Upper and Lower
H orebodies of the former Horne mine, which originally formed a single lens. Therefore, the Horne Au-rich VMS complex originally formed as a stacked system in which the Horne 5 deposit was deposited above the Upper and Lower H zones and not in a
distal or lateral position as previously proposed, indicating that a robust hydrothermal system was responsible for the formation of the world's largest Au-rich VMS complex. |
| Summary | (Plain Language Summary, not published)
This manuscript will be submitted to an external peer-reviewed scientific journal. The manuscript presents data (petrograhy, volcanic textures, ore
mineralogy, whole-rock lithogeochemistry, mineral chemistry, geochronology), detailed observations, and interpretations about the geology of the Horne 5 deposit located in Rouyn-Noranda in northwestern Quebec. The manuscript discusses the genesis of
the deposit and controls on gold enrichment processes of this polymetallic deposit. |
| GEOSCAN ID | 329133 |
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