Gold occurrences in copper-magnetite-apatite deposit at Seruwila, Sri Lanka

This study presents petrology and evidence for possible gold occurrences in Seruwila copper–iron oxide–apatite (IOA) deposit, hosted in an ultramafic intrusion which is located at the boundary between the Highland and Vijayan complexes, within the intermediate-granitic basement in north-eastern Sri Lanka. The study is complemented with petrological observations and XRD and SEM analysis, respectively, to investigate the petrology/subsurface geology of the deposit and identify possible gold occurrences in the deposit. The ore-bearing rocks are mainly composed of magnetite and apatite in various proportions, hosted in an ultramafic intrusion with cumulate features within the granitic-intermediate basement. The secondary veins contain magnetite, chalcopyrite, pyrrhotite, and pyrite together with apatite and scapolite, tremolite, diopside, and minor actinolite and calcite, serpentinite, anhydrite, or gypsum. The clinopyroxene euhedral crystals show cumulus textures including grain triple junctions and large dihedral angles (∼120°), showing magmatic origin. Texturally two types of amphiboles are identified as coarse-grained (0.5–1 mm), pale green euhedral amphibole that is free of inclusions, and fine-grained (