The Slocan property lies within the southern portion of the approximately 100 km long Valhalla-Passmore Gneiss Complex (Valhalla domal metamorphic core complex: Reesor, 1965; Little, 1960, 1985), which can be characterized as a structural culmination composed of a high grade metamorphic core with outward-dipping metamorphic layering and foliation, bordered by ductile/brittle shear zones or faults (Schaubs and Carr, 1998; Simony and Carr, 1996).

Metamorphic rocks of the Valhalla assemblage comprise a heterogeneous sequence of biotitic schist (pelitic schist) and quartzo-feldspathic gneiss (psammitic gneiss), amphibolite gneiss and minor marble, calc-silicate gneiss, quartzite, metaconglomerate and ultramafic rocks (Schaubs and Carr, 1998).

The Valhalla complex forms the footwall of the Valkyr and Slocan Lake shear zones (see Figure 3 and Figure 4). It consists of Castlegar Gneiss, metasedimentary rocks, Middle Devonian Trail Gneiss, Late Cretaceous Kinnaird Gneiss, Late Cretaceous Mulvey granodiorite, Paleocene Airy Quartz monzonite and Early Eocene Ladybird granite. The complex contains three sheets of supracrustal rocks identified as upper, middle and lower. The upper sheet consists of the “Valhalla assemblage” metasedimentary rocks sandwiched between Paleocene granitoids and the Mulvey granodiorite. The middle sheet and upper portion of the lower sheet are interlayered with Mulvey granodiorite.

The hanging wall of the Valkyr and Slocan Lake shear zones (so called upper plate) consists of Middle Paleozoic to Early Mesozoic rocks of allochtonous Quesnelia, Middle Jurassic and Late Cretaceous granitic rocks, Eocene College Creek granite and Middle Eocene Coryel syenite and granite. In the Passmore dome area, metasedimentary rocks within the upper sheet are overlain by Airy quartz monzonite (Figure 4) and are interpreted as being underlain by Mulvey granodiorite gneiss (Schaubs and Carr, 1998).

The Valhalla assemblage is proposed, based on the presence of distinctive laterally continuous marker units such as carbonate and metaconglomerate and similar lithologic ordering, to be inverted and correlative with part of the Paleozoic ancestral North American stratigraphic succession including Neoproterozoic Horsethief Creek Group, Eocambrian Hamill Group, Early Cambrian Badshot marble, Early Palaeozoic Lardeau Group, Mississippian Banded Limestone and Mississippian to Pennsylvanian Milford Group.

The ages of intrusive rocks in the Valhalla Complex are constrained to the Cretaceous-Tertiary by recent U-Pb dating of zircons. The complex is known to include three granitic sheets dated at 100 Ma, 62 Ma and 59 Ma that are interlayered with three paragneiss sheets of uncertain age. However, fabric and metamorphic studies of the predominantly metasedimentary rocks of the paragneiss sheets in the complex reveal a Late Cretaceous tectonic history, including extensive magmatism, upper amphibolite (garnet amphibolite) facies metamorphism (cordierite-sillimanite- K-spar subfacies), migmitization, penetrative foliation and localized strain on ductile thrust faults termed the Gwillim Creek shear zones (Schaubs and Carr, 1998).

Metamorphic rocks in the Valhalla Complex are highly deformed. Current thinking requires them to be polyfolded, with early F1 minor folds predating the Late Cretaceous S2 foliation and folding and folded by several generations of later minor folding (F3, F4). Alternatively, the concept of ‘flow folding’, with concurrent ongoing folding and refolding of earlier formed folds, may serve to explain much of the folding seen in the lower Valhalla Complex metamorphic rocks, particularly where the folding is confined to layer-parallel, laterally extensive zones. Narrow subvertical fold zones that appear to cut across the layering may be later than the ‘flow folding’.

The Valhalla and Passmore domal complexes occur in the footwall of and are bounded by, the shallowly-dipping, ductile Valkyr shear zone to the north, west and south, and the Slocan Lake fault to the east. The Valkyr Shear is an infered eastward rooting ductile normal fault, now reversed in dip, active between 59 and 54 Ma (Carr et al., 1987). Footwall rocks of the Valkyr Shear zone have accommodated most of the strain with mylonitic fabrics penetrative over a 2 to 2.5 km thick zone, whereas hanging wall rocks only show strain over 500 meters (Carr et al., 1987).

The Slocan Lake fault is an easterly directed, normal fault that shows brittle to ductile deformation and is slightly younger (54 to 45 Ma: Carr et al, 1987). An extensional origin is proposed for these structures, with the latest period of extension beginning in Eocene time causing a rapid exhumation (uplift and denudation) of the complex from mid-crustal levels of 10-20 km depth (Parrish et al., 1988). Thinning of the Valhalla assemblage by up to 60% during this exhumation is proposed (Schaubs and Carr, 1998).