Native antimony and bournonite intergrowths in galena from the English Lake District

Abstract

AbstractThe Driggith vein is representative of the lead-zinc mineralization in the Caldbeck Fells area, with a primary mineral assemblage consisting of quartz, baryte, calcite, chalcedony, pyrite, arsenopyrite, galena, sphalerire, bournonite, argentian tetrahedrite, and native antimony. Broadly similar assemblages are found in Pb-Zn mineralization of Upper Devonian to Permian age else-where in the Lake District. The paragenetic sequence appears to have been early pyrite and minor arsenopyrite associated with quartz; with later baryte, calcite, sphalerite, and chalcopyrite enclosed by galena. Within the galena occur inclusions of tetrahedrite, bournonite, and native antimony. A later stage of baryte mineralization was followed by the alteration of primary sulphides to secondary minerals. Elsewhere in the Lake District, galena occurring in this association also contains inclusions of native antimony, bournonite, and other sulphosalts, and in this respect differs from galena associated with earlier veins composed dominantly of chalcopyrite, pyrite, and arsenopyrite. The inclusions make a major contribution to the high antimony values reported in trace element analyses of galena from the Lake District. The occurrence of these inclusions, which in some cases display preferred orientation within the host galena, is discussed in terms of phase relations involving PbS and AgSbS2.