Issue 3(43), 2016

DOI 10.21440/2307-2091-2016-3-29-33

Pakrut gold deposit (Central Tajikistan) and specifics of its genesis pdf

N. F. Nabiev, A. R. Fayziev

Pakrut gold deposit is located in a series of linearly elongated subparallel disjunctive disturbances among metasomatites of carbonate-quartz-albite composition. The geological structure of Pakrut gold deposit involves both plicative and disjunctive violations within a single graben-anticlinal structure. On the deposit, there are 4 stages of mineral formation: I – pre-ore quartz-albite-carbonate; II – unproductive quartz-pyrite-arsenopyrite; III – early productive gold-quartz-carbonate-sulphide;
IV – productive late quartz-carbonate-barite-fahlore with gold and silver. In the lower part of the field dominates an early high-pyrite-arsenopyrite stage, in the middle part – polymetallic stage, and in its upper part – stibnite-sulphosalt mineralization stage. The latter is more recent and less high temperature formation. Gold mineralizatio is related to the early productive and late productive mineralization stages. Native gold on the Pakrutsk deposit occurs as finely dispersed dusty disseminations, cloddy, drop-shaped, oval, tape, shapeless and plate selections. In extremely rare cases, the gold occurs in the form of octahedral crystals. The most gold bearing are vein-disseminated ores with pyrite and arsenopyrite, and gold in them is mostly finely dispersed. Gold differs by chemical purity and was formed from substantial hydrocarbon solutions at a temperature of 250–150 °C. For gold mineralization of Pakrut deposits one ought to expect subcrustal connection with a source of the substance. This is evidenced by confinement of the deposit to the regional deep foundation fault, the presence if the Pakrut fault zone of carbonaceous metasomatites of restored nature and presence on the area of the deposit of sub-alkaline gabbros and basalts. The genesis of gold mineralization of Pakrut deposit by the nature of connection with the wallrock metasomatism and other signs scientists define as hydrothermal-metasomatic, with vein-interspersed mineralization type. The main role in mineralization placing belonged to the processes of the implementation of open spaces, with the subordinate role of metasomatic replacement of wall rocks, which took place during the formation of the products of the earliest stages of mineralization. In the final stages here were nearly no near-vein rocks changes.

Keywords: gold; deposit; Pakrut; mineralization; stage; generation; impurity elements.

 

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