Sinyukhinskoe, Sinyukha

Altai Republic, Russia

Main commodities: Au Cu
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The Sinyukhinskoe or Sinyukha skarn gold-copper deposit is located ~700 km SSE of Novosibirsk, 40 km east of the town of Gorno-Altaisk in southwestern Sibera, Russia (#Location: 51° 54' 4"N, 86° 41' 28"E).

It is situated in the Russian Altai, part of the Central Asian Orogenic Belt (CAOB) which lies between the East European, Siberian, North China and Tarim cratons and extends from the Uralides in the west to the Pacific margin in the east. The deposit occurs in the Gorny Altai terrane, formed at an active margin of the Siberian continent that consists of i). a late Neoproterozoic to Mid Cambrian subduction-accretionary complex, ii). Ordovician to Early Devonian passive margin, iii). Devonian to Early Carboniferous active margin, and iv). Devonian to Carboniferous to Permian collisional complex (Safonova, 2014). The Sinyukhinskoe deposit is part of a north to NE-trending Devonian to Early Carboniferous volcanoplutonic belt that extends along the eastern edge of the Gorny Altai terrane, representing a back-arc to the Devonian to Early Carboniferous active continental margin (Shokalsky et al., 2000).

The volcanic rocks of the belt include contrasting basalt, andesitic basalt to basalt-rhyolite units that formed during back-arc rifting (Kruk et al., 2008). The plutonic rocks range from gabbroic through granodiorite to granite and leucogranite, which have been subdivided into two or more suites including the early Yugalin monzogabbro-monzodiorite-granodiorite suite, and the late Turochak granite-leucogranite suite (Kruk et al., 2008; Turkin et al., 2001; Gusev, 1994; Vladimirov et al., 2001; Rudnev, 2010). These suites occur as large plutons dated (U-Pb zircon) at 398±2 Ma to 406±4 Ma from the Yugalin pluton (Gusev, 2007; Gusev and Gusev, 2012) and 390±6 Ma of the Turochak pluton (Rudnev, 2010). A third younger Kyzyltash monzogranite-granite suite of the Tsagan pluton has been dated at 381±2 to 340 Ma (Turkin et al., 2001; Gusev and Lavinishnikova, 2011). Alternatively, separate nearly-coeval plutons may reflect a single, complex and extended differentiated gabbro-diorite-granodiorite-granite supersuite.

The Yugalin suite is considered to represent the parental pluton to the Sinukhinskoe Au-Cu skarn deposit. In the deposit area, this suite is represented by the Yugalin (Sinyukha) pluton (Gusev, 1994, 2007; Gusev and Gusev, 2012). Some intrusions of the Kyzyltash suite are also accompanied by Au-bearing magnetite and garnet skarns as well as by stockwork (porphyry-style) Cu-Au-Mo mineralisation (e.g., Kulbich Cu-Au-Mo occurrence; Turkin et al., 2001; Gusev et al., 2011).

The Sinyukhinskoe deposit comprises at least 18 of separate zones of Au-Cu or Au mineralisation (Turkin et al., 2001) that are associated with limestone horizons within a thick volcanic sequence of alternating Cambrian sedimentary and mafic to intermediate volcanic rocks. These rocks form a large roof pendant in the Yugalin (Sinyukha) granitoid pluton, removed from the main contact of the Yugalin (Sinyukha) gabbro-monzodiorite-granodiorite pluton. The larger mineralised zones also appear to be controlled by junctions and intersections of variously oriented steeply-dipping to flat faults marked by variously oriented swarms of mafic to granitic dykes (Soloviev, et al., 2019).

The larger dominantly garnet-pyroxene skarn zones have a stratified appearance, replacing flat-lying to gently-dipping units of alternating carbonate and mafic volcanic rocks (predominantly andesite to trachyandesite and andesite-basalt tuffs, and less frequently basalt to andesitic basalt lavas). These zones are from 1 up to several tens of metres in thickness and range from tens to hundreds of metres in width and length. In contrast, skarn assemblages that are predominantly wollastonite-garnet to wollastonite are relatively minor, appear to be possibly younger, and have a more limited extent within a much wider halo of pyroxene- and garnet-dominant zones of skarn alteration (Korotkikh and Voroshilov, 2011), and are typically found at higher levels.

Most of the significant Cu and particularly Au mineralisation post-dates intramineral mafic dykes which may constitute as much as 60 vol.% in some mineralised zones. These dykes cut skarn zones indicating they accompanied a new pulse of structural re-activation of both steep and flat faults (possibly including thrusts; Gusev, 1998). Zones of quartz-sulphide veining also intersect flat-lying skarn zones at a high angle, and were accompanied by propylitic and phyllic alteration. These are, in turn, associated with renewed pulses of structural re-activation. Mineralisation is consistently abundant in some parts of skarn zones but is generally absent in skarns distal to structural intersections. It is irregularly distributed within the skarn zones, and is not directly related to the development of skarn alteration. Larger zones of mineralisation have a complex steeply-dipping, locally columnar shape, with discontinuous high-grade pods, branching apophyses, and sub-horizontal mineralised lenses, separated by barren to weakly-mineralised domains. Large orebodies do occur in zones of wollastonite, garnet-wollastonite and garnet-pyroxene-wollastonite skarn, although conversely, large volumes of skarns are barren, whilst some mineralised intervals are even found external to skarn alteration, particularly in limestones.

Economic Au-Cu skarn mineralisation is found in skarns altered during propylitic and phyllic stages and enriched in sulphide minerals (bornite, chalcocite, chalcopyrite) and native gold. Individual orebodies vary from 1 to 20 m in thickness, 10 to 400 m in strike length, and from 5 to 150 m down dip. The vertical extent of mineralisation exceeds 2 km. Average grades in different orebodies vary from 4 to 37 g/t Au, and average from 0.5 to 1.8% Cu (Turkin et al., 2001).

Au-quartz-sulphide style Au (with minor Cu) mineralisation, separate from the skarns, occurs as quartz-sulphide and quartz-K feldspar-sulphide veining associated with phyllic alteration zones, and is related to structurally complicated, complex-shaped zones of strike-slip faults, fault junctions and intersections. These zones are lens-shaped and have limited thickness, generally <10 m, but grades of as much as 12 g/t Au, and averages of 1.8% Cu. Some zones of this mineralisation are related to the skarn type orebodies, whilst others extend into sedimentary-volcanic rocks and granitoid intrusions with no spatial association with mineralised skarns. Dense quartz-sulphide veining zones locally evolve into quartz-sulphide stockworks that vary from relatively isometric to oval and linear with areal dimensions of up to 0.25 x 1.5 km. Average Au grades in different stockworks vary from 0.5 to 7.2 g/t, but are typically ~2 g/t Au (Turkin et al., 2001). These stockworks occur both proximal to the main mineralised zones of the deposit and distal, the latter inside the Yugalin pluton and at its opposite contact zones. In many locations, this mineralisation has given rise to Au placers.

The Sinyukhinskoe (Sinyukha) deposit was discovered in 1950 and has been mined since, with annual production of 0.4 to 0.5 tonnes of gold. Currently reserves comprise ~20 t Au with resources of ~100 t. The average grade is 9.2 g/t Au (varying from 4 to 37 g/t Au for different resource blocks; Turkin et al., 2001) at 1 g/t Au cut-off. There are also substantial, although never delineated Cu resources, with average grades (for different resource blocks) from 0.5 to 1.8% Cu (Turkin et al., 2001).

The most recent source geological information used to prepare this summary was dated: 2019.    
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
   Selected References:
Soloviev, S.G., Kryazhev, S.G., Dvurechenskaya, S.S. and Uyutov, V.I.,  2019 - Geology, mineralization, fluid inclusion, and stable isotope characteristics of the Sinyukhinskoe Cu-Au skarn deposit, Russian Altai, SW Siberia: in    Ore Geology Reviews   v.112, 28p. doi.org/10.1016/j.oregeorev.2019.103039.

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, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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