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Khandiza

Uzbekistan

Main commodities: Zn Pb Cu
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The Khandiza volcanic hosted Cu-Zn-Pb deposit is located in the Gissar zone of southern Uzbekistan, approximately 300 km SW of Tashkent, adjacent to the South Tien Shan Belt and is hosted by Lower Carboniferous tuffs (Smirnov, 1977). The deposit is said to constitute a large Zn-Pb and small Cu resource.

The succession at Khandiza is as follows, from the base, (Smirnov, 1977):

Precambrian to Devonian
Paragneiss and schists, containing amphibolite, quartz and marble.
Unconformity
Lower Carboniferous
Lower volcano-sedimentary unit, with two members, a). a lower conglomerate, acid tuff, quartz sandstone and siltstone, and b). an upper carbonate chert band consisting of dolomite and siliceous tuffs. The pyritic orebodies of the lower horizon of the Khandiza deposit are restricted to the dolomites of this member.
Upper volcanogenic unit, again with two members, a). vitro-clastic, lithoclastic, ashy and crystalline tuffs of acid composition, which are interstratified with siliceous tuffs - the upper, main pyritic orebodies of the deposit are confined to this member, and b). an upper unit of crystallo-clastic and agglomeratic litho- and vitro-clastic tuffs of rhyodacite porphyries, alternating with lavas of the same composition, tuffaceous sandstones and tuffs.
Limestone, calcareous and siliceous rocks and argillites which conformably overlie the previous unit.
These are unconformably followed by late lower Carboniferous terriginous sediments comprising conglomerates, polymict sandstones and argillites.
Unconformity
Mesozoic and Cenozoic
Terriginous sediments.

This sequence is cut by pre-Carboniferous leucocratic muscovite granites and lower Carboniferous sub-volcanic rhyolite and rhyodacite porphyries.

Faulting is present in a number of orientations. The two most important structures trend generally east-west, and comprise a). a thrust which separates the lower Carboniferous from the underlying older metamorphics, and b).  a parallel thrust plane separating the lower Carboniferous volcano-sedimentary and volcanogenic units. A third thrust is developed at the top of the main orebody, at its contact with the upper member of the volcanogenic unit (Smirnov, 1977).

The 'lower pyritic orebodies' are predominantly pyritic, while the 'upper pyritic orebodies' are polymetallic. These polymetallic orebodies contains the main ore reserves. They are conformable and occur as a single layer. Their upper margin is sharp, and often tectonically defined, whereas the lower contact is gradational and vague. Four ore types are recognised, i). namely massive, ii). porphyritic (fine grained ore with segregations of pyrite and sphalerite), iii). banded and iv). segregated/disseminated. The composition of the polymetallic ores generally comprises chalcopyrite:galena:sphalerite:pyrite in the ratio 0.2:1:3:4. Traces of Ag, Bi, Se, Te and Cd accompany the Cu-Pb-Zn ore. The massive sulphides contain 85 to 95% sulphides. Veinlet mineralisation is also associated with the polymetallic ores. The veinlet style contains 20 to 30% sulphides, including pyrite, sphalerite, galena and chalcopyrite with a gangue of quartz, carbonate, sericite and less frequently barite. There is a vertical zonation within the orebody from Cu-Zn at the base to Pb at the top (Smirnov, 1977).

The orebody has been interpreted to have formed in three stages, i). an early pyrite-hematite diagenetic stage, ii). a polymetallic hydrothermal phase, overprinted by iii). a tectonic/metamorphic redistribution and recrystallisation event (Smirnov, 1977).

The most recent source geological information used to prepare this summary was dated: 1996.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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