Structure and evolution of the Heath Steele base metal sulfide orebodies, Bathurst Camp, New Brunswick, Canada

Abstract

A structural analysis of the base metal sulfide deposits at the Heath Steele mines, northern New Brunswick, is presented. The structural similarity of the deposits is defined and their relationships to one another discussed.The deposits are spatially associated with Ordovician sedimentary rocks, which are situated in an igneous rock complex comprising felsic and basic volcanics, volcaniclastics, and intrusives. The complex has been subjected to low-grade metamorphism and five generations of deformation (D1-Ds). The first two generations of deformation (D1 and D2) are represented by transposition foliations (S1 and S2). The present attitude of the S2 foliation is a result of recumbent folding (D3) and two generations of open folds with vertical axial planar cleavages striking northwest (S4 foliation) and northeast (S5 foliation). The S1 foliation is axial planar to conical F1 folds. Regionally, such folds have been associated with thrusting (D1) along the earliest recognized layering (So foliation). Vein swarms illustrate the local importance of solute mass transfer during this event, at the Heath Steele mines culminating in fracture-controlled alteration along a brittle-ductile deformation (D1) shear zone near the sulfide deposits, and development of metasomatic breccia in the sulfide deposits.Overall, the deposits occur along the So foliation, the contact between augen schists and the metasedimentary rocks, but massive sulfides are concentrated in F1 fold closures, forming pods and slabs parallel to the S1 foliation. This concentration reflects either mobilization of preexisting sulfides (during D1) or deposit formation by mineralization during D1. If the contact (in So) is nontectonic, a stratigraphic control on the location of the deposits is indicated and their association with iron-formation argues for a syngenetic origin. Conclusive evidence for these models has been obliterated by the intense deformation and solution transfer.

Ore Remobilization History of the Metamorphosed Rävliden North Volcanogenic Massive Sulfide Deposit, Skellefte District, Sweden

“…The interpretation of a tectonic origin for durchbewegt ore has been noted in many VMS deposits, among others those in the Bathurst and Flin Flon camps in Canada (van Staal and Williams, 1984;Park, 1996;de Roo and van Staal, 2003;Jonasson et al, 2009); the ABM deposit, Canada (Denisová et al, 2023); the Copperton deposit, South Africa (Bailie and Gutzmer, 2011); the Ashele VMS deposit, China (Zheng et al, 2016); Cerro Maimon, Dominican Republic (Torró et al, 2016); the Iberian Pyrite Belt and northwest Iberia (Castroviejo et al, 2011); and the Urals (Vikentyev et al, 2017). However, it is worth noting that synvolcanic transported breccias, with clasts from collapsing domes and block faulting, may be mistakenly identified as durchbewegt ore when deformed (Lafrance et al, 2020).…”

“…The formation of durchbewegt ore is largely due to ductile solid-state remobilization processes. Nevertheless, de Roo and van Staal (2003) suggested solution mass transfer as an assisting process after observing dilational jogs along major shear zones defined by sulfide mylonites at the Heath Steele and Brunswick mines, Canada. Veins and infilling of strain shadows are common textures in durchbewegung structures that suggest solution mass transfer (Lafrance et al, 2020).…”

“…Orebody morphology is also influenced by the pyrite content, which produces stacking or transposition (Lafrance et al, 2020). De Roo andvan Staal (2003) explain that strain partitioning between pyrite-rich ore and pyrite-poor ore produced tectonic layering (i.e., stacking) in the Heath Steele and Brunswick deposits, Bathurst Mining Camp, Canada. In the Iberian Pyrite Belt, stacking produced thicker orebodies, whereas in deposits in northwest Iberia, transposition produced flattened, thinner, and elongated orebodies (Castroviejo et al, 2011).…”

Great Mining Camps of Canada 7. The Bathurst Mining Camp, New Brunswick, Part 1: Geology and Exploration History

“…Tectonic remobilization of ductile sulphide occurs locally, e.g. the pyrrhotite breccia units at Heath Steele (de Roo et al 1991). Recrystallization of sulphide minerals in the contact aureoles of younger felsic intrusions increases their grain size, e.g.…”