Abstracts
Abstract
This paper deals with the structure of the region surrounding Heath Steele Mines, which is situated in the southern part of the Ordovician volcanic-sedimentary complex of the Bathurst Camp, New Brunswick. In this area, five generations of deformation structures are recognized on the basis of orientation, tectonic style, and systematic overprinting relationships.
The earliest recognizable deformation (D,) is characterized by tight to isoclinal F, folds of a compositional layering (S,). A cleavage (S,) parallel to the axial plane of these folds was locally rotated into a transposition foliation (S2) during the D2 deformation. Where gently dipping, S2 was cast into domes and basins in two events (D, and D,) of upright folding with axial plane cleavages S¥ and S}. Where steeply dipping, S2 was subjected to recumbent folding (Dk) prior to the fifth deformation (D,). Overprinting relationships between the D( and Dk events are ambiguous, so their correlation with the third and fourth deformations remains open to interpretation.
The macroscopic structure in the Heath Steele Mines area is dominated by an open fold (the North Little River Lake Fold) of a belt of metasedimentary rocks and augen schists. This belt is host to the Heath Steele sulphide orebodies and is also an F, fold zone. The age of the macroscopic fold is not well constrained, but the asymmetry of second-order F2 folds reverses across its hinge, and its southwestern limb is attenuated in a zone of high D2 strain, suggesting that it is an F2 fold. The zone of high D2 strain separates the folded belt of metasedimentary rocks and augen schists from a pod of massive porphyry and granitoid rocks.
RESUME
Cet article porte sur la structure de la region entourant les mines Heath Steele et se situant dans la partie meridionale du complexe volcano-sddimcntaire ordovicien de Bathurst Camp, au Nouveau-Brunswick. Dans cette region, l'orientation des structures, le style tectonique et le caractere systematique des superpositions permettent de reconnaitre cinq episodes de deformation.
La deformation la plus ancienne a etre reconnue (D,) se caracterise par des plis F, serres a isoclinaux affectant un rubanement de composition (S,). Une schistositi (S,), parallele a la surface axiale de ces plis, se modifia localement, par rotation, en une foliation de transposition (S2) durant la deformation D2. Li ou son pendage 6tait faible, S2 prit la forme de domes et cuvettes en deux episodes (DT et D}) de plissement vertical accompagnes de schistosit£s de surface axiale St et S?. La ou son pendage 6tait 6\ev6, S2 fut soumise a un plissement couche' (Dk) pr£c6dant la cinquieme deformation (D}). Les superpositions relatives des Episodes Dr et Dk sont ambigtles; leur correlation avec les troisieme et quatrieme deformations reste a determiner.
La structure macroscopique dans les mines Heath Steele est dominee par un pli ouveit (le pli de North Little River Lake) au sein d'une ceinture de schistes oeilles et de roches m&as&iimentaires. Cette ceinture est l'hote des gisements de sulfures de Heath Steele et elle est aussi une zone de plis F,. L'ige du pli macroscopique n'est pas bien delimited mais l'asymdtrie des pi is de deuxieme ordre F2 se renverse a travers sa charniere et son flanc sud-ouest est attenu6 dans une zone oil la contrainte D2 est elevee, ce qui porte a croire qu'il s'agit d'un pli F2. Cette zone de contrainte D2 61evee separe la ceinture plissee de roches m6tase<iimentaires et de schistes oeilles d'une intumescence de porphyre et de roches granitoi'des massifs.
Download the article in PDF to read it.
Download