Shu-Ili gold-bearing ore belt in Kazakhstan: Systematization and evaluation of gold deposits

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Rafailovich, Mikhail۱; Los, Vladimir۲
Holding Date 08 September 2008

Shu-Ili ore belt is a linear folded structure which was formed in Late Ordovician as result of collision of Kazakhstan and Kyrgyzstan microcontinents. Gold deposits are an important raw material and basic source of gold production.
The main gold potential of ore belt is concentrated in gold-sulfide-quartz deposits. The major features of their formation, structure, material composition and commercial importance are as following.
Gold-sulfide-quartz deposits form a vertical line of ore objects. The mesothermal representatives relate to large plutons and sources of granitization, the deposits of intermediate zone – to small intrusions of diorite-granodiorite, the near-surface objects – to contrastly-differentiated volcanic constructions, subvolcanic bodies and dikes. Cumulative depth range of existence of gold bearing ore-magmatic systems is up to 3-4 km.
Attachment to various structural elements is signifcant for deposits. Shear zones are favorable for localization of gold deposits in regional plan. Mosaic systems of shear fractures and ruptures, upthrusts and upthrusts-thrusts, mylonites, ring and radial faults prevail in local scale. A variety of tectonic elements and their spatial variability have caused great number of morphological ore types (veins, stockworks, mineralized zones, lenticular, saddle-shaped, streaky impregnated bodies).
Gold deposits are accompanied by haloes of hydrothermal alterations. Beresitization (quartz, sericite, carbonate, albite, sulfides) is "throughout" type of hydrothermolites. Other alterations: in mesothermal zone - greisenization (Sarybulak) and potash feldspathization (Kogadyr); in intermediate (hypabyssal) zone - adularization (Akbakay), listvenitization (Chokpar); in near-surface zone - argillization (Aktjube, Ashiktas).
Various deep objects differ by quantity and composition of sulfide minerals. Deposits of near-surface and mesothermal zones are characterized accordingly by poorly-weakly sulphidic (0,5-5,0 %) and weakly sulphidic (2-4 %) ore. Hypabyssal objects are moderately sulphidic (10-30 %). Early high-temperature associations (gold-chalcopyrite, gold-bismuthine, gold-bismuthine-scheelite) prevail in deep deposits. Late gold-polymetallic, gold-silver, gold-telluride, gold-sulphosalt and gold-sulfoantimonite assotiations are located in ore of intermediate and shallow zonez.
According to commercial value gold deposits are subdivided into four groups. The most important first group is formed by veined ore objects of Akbakay type with middle and high gold grades. The second group is composed by middle size deposits with large stockwork morphology and low gold grades (Kogadyr, Ashiktas). The third group includes vein middle and small size objects of Au-Pb-Zn type with gold concentration 5-10 g/t (Chokpar). The fourth group unites numerous small-sized deposits with free-milling ores (Majbulak, Ushalyk, Mynaral).