|Title||Targeted Geoscience Initiative 4. lode gold deposits in ancient deformed and metamorphosed terranes: geological mapping and structural re-appraisal of the banded iron formation-hosted gold mineralization
in the Geraldton area, Ontario|
|Author||Tóth, Z; Lafrance, B; Dubé, B; Mercier-Langevin, P; McNicoll, V J|
|Source||Summary of field work and other activities 2013; by Ontario Geological Survey; Ontario Geological Survey, Open File Report 6290, 2013 p. 58.1 - 58.14|
|Links||OGS OFR 6290 Online - En ligne (pdf, 204
|Alt Series||Earth Sciences Sector, Contribution Series 20130269|
|Media||paper; on-line; digital|
|Area||Geraldton; Mosher Lake|
|Lat/Long WENS||-87.0000 -86.9208 49.6861 49.6708|
|Subjects||metallic minerals; structural geology; mineralization; iron formations; gold; mineral deposits; metamorphism; deformation; metavolcanic rocks; metasedimentary rocks; magnetite; folds; structural
analyses; structural controls; foliation; lithology; field relations; veins; alteration; Precambrian|
|Illustrations||geological sketch maps; photographs|
Geoscience Initiative (TGI-4), Gold Ore Systems|
Gold deposits hosted by Archean banded iron formation represent a key exploration target in Canada. As part of the Targeted Geoscience Initiative-4 Lode Gold project, the goal of
the project is to characterize the structural controls on gold mineralization and their footprints. The study area, the Beardmore-Geraldton Belt (BGB), is located along the boundary between the granite-greenstone Wabigoon and the sedimentary Quetico
subprovinces This area was chosen because of the on-going advanced exploration that provides access to large stripped outcrops showing the relationships between mineralization and structures as well as recent drill holes that provide access to new
information on the nature, distribution and chronology of the gold-bearing hydrothermal alteration, allowing to further increase our understanding of mineralizing processes in BIF-bearing Precambrian successions. During the summer of 2013 stripped
outcrops were mapped in detail and drill cores intersecting mineralized zones in different host rocks have been logged and sampled for petrography and lithogeochemistry.
All the three mapped strippings are located along the north limb of the
regional F2 Hard Rock anticline. Tight F1 folds are refolded by gentle to tight, S-shaped, F2 folds that are parasitic folds to the Hard Rock anticline. S-shaped F3 folding of S2 at the Headframe and OPP stripped outcrop suggests, local sinistral
shearing prior to dextral shearing during D4. D4 is a late, dextral transcurrent shearing event that produced multiple Z-shaped drag folds with a strong axial planar foliation and dextral shear bands.
Gold mineralization occurs as semi-massive
sulphide replacement associated with quartz-Fe carbonate veins at the OPP and Headframe East stripped outcrops. It is folded by S-shaped F2 folds suggesting that mineralization was emplaced either pre- or early-D2. Fe-carbonate alteration, is folded
by F1 folds. However, the mineralization exposed of the stripped outcrops does not show evidence of deformation by F1 folds. If this iron-carbonate alteration is associated with gold mineralization this would suggest the possibility of a pre-D2
presumably syn-D1 mineralization. Alternatively, this may suggest that there are several stages of iron-carbonate alteration. The stripped outcrops clearly expose the complexity of the structural setting of the gold deposits in the Geraldton district
with several generations of foliations and folds. Better defining the chronology of deformation in relationship with the emplacement of the bulk of the gold mineralization could impact on the understanding of the distribution and geometry of the
auriferous lodes and also help better define the key parameters responsible for their formation.
|Summary||(Plain Language Summary, not published)|
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience
knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. Gold deposits hosted by Archean banded iron formation represent a key exploration target in Canada. As part of the
Targeted Geoscience Initiative-4 Lode Gold project, the goal of the project is to characterize the structural controls on gold mineralization and their footprints in the Geraldton area. During the summer of 2013tripped outcrops were mapped in detail
and drill cores intersecting mineralized zones in different host rocks have been logged and sampled for petrography and lithogeochemistry. This report presents some of the key new data.