The Lyon Lake – Claw Lake sulphide bearing graphitic shale is contained within a predominantly sedimentary sequence of coarse to fine clastics with minor carbonate and mafic volcanic rock.
Sulphide mineralogy consists mainly of pyrite and pyrrhotite occurring as nodules, lensoid pods and narrow bands conformable with bedding. Traces of chalcopyrite, sphalerite and arsenopyrite are present as well.
Cu, Zn, Ni, Co, Mn and As were analysed in sulphides, graphitic shale and wall rock. Results suggest: (1) Sulphides contain higher contents of Cu, Zn, Co, Ni, and As than graphitic shale or wall rock and (2) Mn, Zn, Co and Ni content decreases eastward along the formation in graphitic shale.
Analyses of a vertical section through the formation suggests: (1) Cu, Zn, and Mn are enriched in the footwall rocks as opposed to the hanging wall rocks, (2) Zn and As are concentrated in graphitic shale in comparison with hanging wall rocks and (3) Co and Ni content is relatively uniform throughout the section.
Element ratios have been used to investigate the depositional environment of sulphides and host rock. Results show: (1) Co:Ni ratios in sulphides and graphitic shale are consistent with other worker's data for a sedimentary origin and (2) Mn:Fe ratios are suggestive of volcanic contribution to the western margin of the formation.
Carbon content in the graphitic shale varies from 1.60% - 12.06%. X-Ray studies indicate carbon is either present in an amorphous form or below the detection limit of this technique.
X-Ray studies indicate the pyrrohtite present in monoclinic possibly derived by metamorphism from pyrite.
Evidence suggests that the graphitic shale is derived in a sedimentary basin in which there was volcanic activity at the western margin. This was followed by large scale mafic volcanism. Sulphides derived by sedimentary or diagenetic processes is likely, since there is no evidence for a direct volcanic exhalative source.