Geology, lithogeochemistry and genesis of the Murgul massive sulfide deposit, NE-Turkey


Tuysuz N.

CHEMIE DER ERDE-GEOCHEMISTRY, no.3, pp.231-250, 2000 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Publication Date: 2000
  • Journal Name: CHEMIE DER ERDE-GEOCHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.231-250
  • Karadeniz Technical University Affiliated: Yes

Abstract

The Murgul massive sulfide deposit is located in the eastern part of the Pontide island are and is associated with dacitic domes and dacitic pyroclastics located along the margin of a caldera with a diameter of approximately 35 km. In the mine area a lower sequence of mafic rocks is overlain by felsic units (host to the ore), which in turn are overlain by upper mafic rocks, arl of Upper Cretaceous age. The footwall consists of dacites and dacitic pyroclastic rocks, whereas the hanging wall consists of chemical sedimentary rocks, gypsum-bearing vitric tuffs, second- stage dacites which contain epithermal Au mineralization, accretionary lapilli tuffs, purple colored vitric tuffs, third-stage purple dacites (with no mineralization), and epiclastic rocks. The first stage dacitic domes grade from a massive core to flow brecciates and hyaloclastites towards outer portions. Geologic and petrographic features of the host rocks indicate a shallow marine environment for the formation of the massive sulfide ores. The three dacitic groups have same primary mineralogy and show similar chondrite-normalized REE patterns. The mine includes two in-situ ore bodies, Damar and Cakmakkaya, and one transported ore body, Bognari. Stockwork and disseminated ore types dominate the Cakmakkaya and Damar ore bodies: although massive ores are also found. The Bognari ore body is solely made up of massive ores which show elastic textures indicative of slumping, brecciation and transportation. Massive ores at Cakmakkaya show sedimentary textures such as lamination, graded bedding, and colloidal and framboidal textures which suggest chemical precipitation. Epithermal Cu-Au mineralization is associated with second-stage dacites, and is superimposed on the stockwork ores of the first-stage dacites, thereby increasing their Cu contents. Silicification is restricted mainly to the ore bearing dacites, whereas sericitization, argillization, and carbonatization occur widely both in dacites and overlying tuffeceous units. The REE contents vary considerably depending on mass change effects related to alteration. Fluid inclusion studies indicate homogenization temperatures of 140-170 degreesC for the epithermal Cu-Au mineralization. The massive sulfides include a black ore assemblage of framboidal and anhedral pyrite, sphalerite and galena; and a yellow ore assemblage consisting largely of chalcopyrite, pyrite and tetrahedrite. Supergene alteration has caused replacement of chalcopyrite and tetrahedrite by bornite, and replacement of bornite by covellite and digenite.