Unusual sphalerite, chalcopyrite, and stannite intergrowths at tin deposits

Unusual intergrowths of sphalerite, chalcopyrite, and stannite have been described in two samples from the St. Agnes (Cornwall) and Sinancha (southern Primorye) tin deposits. Possible origins of these sulfide intergrowths and their implications for understanding the formation conditions of the deposits are discussed on the basis of ore microscopy and analytical data. At the St. Agnes deposit, the intergrowths appeared due to the breakdown of a high-temperature solid solution with formation of a Zn-stannite matrix, chalcopyrite lamellae, and rounded drop-shaped inclusions of sphalerite. At the Sinancha deposit, the rare myrmekite stannite-sphalerite intergrowths are interpreted as eutectic textures of mutual penetration that resulted from ore metamorphism at the contact of a dike.