E. Rastad; H. Tajedin; A. Yaghubpur; M. Mohajel
Abstract
The Barika gold (and silver) rich-massive sulfide deposit is located 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesit, meta-tuffite, ...
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The Barika gold (and silver) rich-massive sulfide deposit is located 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesit, meta-tuffite, phyllite, and slate rocks. The Barika deposit is metamorphosed to greenschist facies, and underwent Barika shear zone- related deformation. The metamorphism/deformation events have superimposed on the synvolcanic stratiform ore and resulted in a variety of mineralogy and textures. Ore minerals in the deposit were originally composed of pyrite, sphalerite, galena, tetrahedrite- tenantite and stibnite which were deposited during synvolcanogenic hydrothermal activity. Gold probably was occurred as submicroscopic inclusions or invisible gold locked in pyrite and electrum in barite. Prograde metamorphism/deformation obliterated almost the sedimentary textures in the stratiform ore. the regional metamorphism have resulted in the development of granoblastic textures with triple junctions in pyrite which lead to migration of submicroscopic gold to the crystal boundary to form microscopic electrum. Shear zone - related deformation, lead to chemical remobilization of pre-existing mobilizable metallic constituents (e.g., Au, Ag, Pb, Sb, As and Hg) and eventually reconcentrated them as visible electrums associated َwith Ag, As, Sb, Pb, Hg – rich sulfosalt minerals at microfractures and open spaces which have developed during the shearing deformation. Metamorphic/deformation remobilization was important in releasing refractory Au from sulfides and locally concentrating it in a recoverable form (electrum).
