Lazurnoe, Vostochnoe, Dioritovoe, Srednee
Cu Au Mo
Super Porphyry Cu and Au|
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The Lazurnoe cluster of porphyry copper-gold-molybdenum deposits and veined/stockwork Au (to Au-W) deposits and occurrences is located 200 km ENE of the city of Vladivostok, and ~520 km SSW of Khabarovskiy, in Primorskiy Kray of the Russian Far East (#Location: 44° 1' 54"N, 134° 24' 57"E).
The Lazurnoe deposit cluster comprises at least four zones of Cu-Mo-Au mineralisation associated with separate groups of intrusive stocks, likely representing different magmatic/porphyry centres. These are the main Lazurnoe Zone (deposit) and three satellites, the Vostochnoe, Dioritovoe and Srednee zones that are respectively 2 km west, 3 km NNE and 10 km NNE of Lazurnoe. As of mid 2020, these deposits were only partially evaluated with scope for increased resources and grade.
Lazurnoe is a shoshonite-related porphyry Cu-Au-Mo system. It was formed in a continental transform margin setting, deposited after the cessation of active subduction, and is interpreted to be the result of low degree partial melting of earlier subduction-modified fertilised/metasomatised lithospheric mantle (e.g., Khanchuk et al., 2016; Grebennikov et al., 2016).
For detail of the regional setting of this part of the Central Asian and Palaeo-Pacific orogenic belts see the separate Manchuria Overview record that will be available soon.
The Lazurnoe deposit cluster is situated within the Zhuravlevka Terrane, which lies in the southern part of the Mesozoic Sikhote-Alin Orogenic System that extends northward from Vladivostok for >1500 km along the coast of the Sea of Japan.
The host Early to early Late Cretaceous intrusive suites of the terrane have mixed crustal-mantle geochemical signatures, together with more distinctly mantle-related high-K calc-alkaline to shoshonitic, monzogabbro-monzodiorite suites, accompanied by trachyandesite-trachybasalt volcanic rocks (Kruk et al., 2014; Jahn et al., 2015). Tectonic activity along the major, longitudinal Central Sikhote-Alin strike-slip fault is interpreted to have initiated decompression melting in the upper mantle along a narrow deeply-penetrating zone (Khanchuk et al., 2016). This led to mantle upwelling, and partial melting of the overlying, earlier subduction-modified fertilised/metasomatised lithospheric mantle as described above. The resultant partial melt appears to have been subjected to intense amphibole fractionation during its crystallisation, facilitating water and metal saturation in the evolving magma. This partial melt formed the high-K calc-alkaline to shoshonitic intrusions of the terrane that was further differentiated to form the mineralisation and deposits found within the Sikhote-Alin Orogenic System (Soloviev et al., 2019).
The Lazurnoe deposit cluster occurs on the far SSW flank of the larger, tin mineralisation dominated Kavalerovo Mineral District that is hosted within the Cretaceous turbidite basin of the Zhuravlevka Terrane (Gonevchuk et al., 2005, Gonevchuk et al., 2010). The Sn mineralisation is related to a variety of Early to early Late Cretaceous to Late Cretaceous to Paleogene plutonic suites. The oldest of these, the 120 to 90 Ma Lower to early-Upper Cretaceous Berezovsk-Ararat suite of ilmenite-series, high-K calc-alkaline to shoshonitic intrusions, is accompanied by Sn-polymetallic mineralisation (e.g., the Arsenievskoe deposit). Associated coeval picrite-trachybasalt-trachyandesite volcanics are found locally within the area (Kovalenko et al., 1988). The 100 to 85 Ma Late Cretaceous Uglovsky plutonic suite and the 85 to 60 Ma to 70 to 60 Ma Late Cretaceous-Paleocene Shumninsky and other plutonic suites are accompanied by Sn-W and Sn-rare metal (Li, Be, Nb, Ta) mineralisation respectively (Gonevchuk et al., 2005, Gonevchuk et al., 2010).
A number of different Cretaceous to Paleogene plutonic and volcano-plutonic suites are found in the Lazurnoe deposit area, including:
• An Early Cretaceous magnetite-series, high-K calc-alkaline to shoshonitic, monzogabbro-monzodiorite-granodiorite of the Lazurnoe Plutonic Suite which hosts porphyry Cu-Au-Mo mineralisation in contrast to the almost coeval but ilmenite-series Sn-rich Berezovsk-Ararat Suite. Early monzogabbro to monzodiorite of the Lazurnoe Plutonic Suite was dated at 110.0 ± 4.0 Ma (K-Ar amphibole and biotite), whilst late granodiorite yielded an age of 103.5 ± 1.5 Ma (U-Pb zircon; Sakhno et al., 2011);
• The early Late Cretaceous, transitional magnetite- to ilmenite-series, medium-K calc-alkaline granodiorite to granite of the 95 to 80 MaSinancha suite that is accompanied by Au mineralisation, whilst the nearly coeval Uglovsky suite found elsewhere in the Kavalerovo district is accompanied by Sn mineralisation (Avilova et al., 2016, Gonevchuk et al., 2011); and
• Late Cretaceous to Paleogene suite(s) of mafic to intermediate and granitic dykes.
Gold mineralisation in the Lazurnoe deposits area occurs in auriferous quartz-sulphide veins that are found within extended linear quartz-sericite-chlorite-carbonate alteration zones. These veins contain native gold and associated pyrite, arsenopyrite and pyrrhotite, with local chalcopyrite, bismuth minerals as well as other sulphides and tellurides. Gold grades vary from fraction of a gram per tonne to >100 g/t Au (Yushmanov, 2009). These auriferous quartz-sulphide veins are probably the source of gold in the large placer deposits in the district (Soloviev et al., 2019).
The main Lazurnoe deposit occupies an ~1.5 km diameter composite stock made up of several intrusions and numerous apophyses, and persists into the adjacent sedimentary wall rocks. The stock is composed of multiple weakly to strongly porphyritic intrusive phases and accompanying dykes that include monzogabbro, monzodiorite and monzonite, with subordinate younger quartz monzonite and granodiorite. Three main intrusive stages are recognised (Soloviev et al., 2019):
• Stage 1, composed of two phases, monzogabbbro to monzodiorite and monzogabbro- to monzodiorite-porphyry, occurring as a medium- to fine-grained dark-grey to dark greenish-grey rock composed of 20 to 30 vol.% light-green pyroxene (diopside-augite, enstatite-augite), 5 to 15 vol.% yellowish-green amphibole, 10 to 15 vol.% biotite, plagioclase (35 to 45 vol.% labradorite and 15 to 20 vol.% andesine) and 3 to 7 vol.% K-feldspar (orthoclase-perthite), with sporadic 1 to 2 vol.% olivine. Both equigranular and porphyritic varieties are present, corresponding to the different intrusive phases. Up to 40% phenocrysts of pyroxene, amphibole and plagioclase may be present either together or separately, suggesting additional porphyry intrusive phases. Accessory minerals include magnetite
(locally as much as 3 to 5 vol.%), titanite, apatite and zircon.
• Stage 2, composed of another two phases, of monzonite to monzonite-porphyry, again with the separate phases represented by equigranular and porphyritic varieties. It is a medium- to fine-grained dark-grey to dark greenish-grey to pinkish-grey rock composed of 1 to 5 vol.% light-green pyroxene (augite), 15 to 20 vol.% yellowish-green amphibole, 10 to 15 vol.% biotite, 40 to 60 vol.% zoned and twinned plagioclase (andesine-labradorite), and 10 to 25 vol.% K-feldspar (orthoclase-perthite). The porphyritic phase has dominant amphibole and plagioclase phenocrysts are up to 3 mm across which are up to 50 vol.% of the rock, within a finer-grained groundmass. Accessory minerals include locally 3 to 5 vol.% magnetite with titanite, apatite and zircon.
• Stage 3, composed of another two phases corresponding to equigranular and porphyritic varieties of quartz monzonite and quartz diorite (tonalite) to granodiorite to quartz monzonite-porphyry and granodiorite-porphyry. A medium- to fine-grained grey to pinkish-grey rock composed of 0 to 5 vol.% yellowish-green amphibole, 15 to 25 vol.% biotite, zoned and twinned plagioclase (40 to 50 vol.% andesine), and 20 to 25 vol.% K-feldspar (orthoclase-perthite). The porphyritic phase is characterised by typically 25 to 40 vol,%, locally up to 70 vol.% biotite and plagioclase phenocrysts that are up to 3 mm across. Accessory minerals include magnetite, titanite, apatite and zircon.
Mineralisation and Alteration
The composite intrusive stock is overprinted by a concentric alteration halo passing outwards from a core of potassic alteration containing magnetite, chalcopyrite and minor bornite, into a peripheral propylitic zone containing dominant pyrite and chalcopyrite. Potassic alteration is represented by zones up to several hundreds of metres across of pervasive replacement, incorporating stockworks of variously-oriented veinlets and veins and their coalescing selvages. These zones of pervasive replacement are represented by fine-grained patchy to massive fine-grained quartz-biotite and quartz-K feldspar-biotite aggregates. In the igneous rocks, mafic phenocrysts are replaced by fine-grained biotite, whist plagioclase phenocrysts are progressively replaced by K feldspar. The development of local dark-green amphibole, as well as calcite and plagioclase (oligoclase) indicates sodic-potassic alteration. The siltstone wall rocks are altered to an assemblage of fine-grained quartz-biotite-K feldspar± plagioclase.
Zones of pervasive potassic alteration contain numerous A-type quartz-K feldspar and quartz-biotite veinlets from <1 to several mm thick. These veins vary from barren to containing minor bornite, chalcopyrite and magnetite. Magnetite occurs both in their cores and outer zones and contains microinclusions of bornite and chalcopyrite. Magnetite is also abundant as background fine dissemination in altered igneous rocks, particularly monzogabbro (up to several percent), where it is associated with fine-grained biotite. Pyrite is locally present in these veins. The potassic alteration assemblages are interpreted to have formed from a homogenous, high-salinity (45 to 48 wt.% NaCl and 9 to 10 wt.% CaCl2), sodic-calcic aqueous-chloride fluid (Soloviev et al., 2019).
Propylitic alteration occurs as two slightly different assemblages. An inner zone is more proximal to the porphyry stock, overprinting the outer and upper parts of the potassic zone, and occurring as both pervasive replacement and veinlets. The pervasive alteration selectively replaces mafic minerals (mainly amphibole and biotite) with chlorite (locally with magnetite and titanite), and feldspars with patchy aggregates of chlorite-plagioclase-quartz-calcite-magnetite. Veinlets are composed of quartz with chlorite to chlorite-epidote-albite selvages. Pyrite is much more abundant than in potassic alteration assemblages, occurring as fine disseminations, particularly in close association with chlorite. Chalcopyrite is also associated with veinlets but is more distinctly related to the pervasive chlorite- and particularly epidote-rich replacement. The outer propylitic zone is more distal, typically >100 m to locally >1 km from the porphyry stock, replacing metasedimentary and metavolcanic country rocks. It is generally pervasive and weaker, without associated veining, and is characterised by relatively more abundant epidote and albite and relatively rare magnetite. Propylitic
alteration assemblages are interpreted to have formed from a homogenous sodic-calcic aqueous-chloride fluid characterised by a decreasing salinity
(from 29 to 31 wt.% NaCl and 18 to 19 wt.% CaCl2 through 24 to 25 wt.% NaCl and 16 to17 wt.% CaCl2 to 12±0.5 wt.% NaCl and 12±0.5 wt.% CaCl2; Soloviev et al., 2019).
Both the potassic and propylitic zones in the northern and southern parts of the pluton are overprinted by extensive phyllic alteration.
Phyllic alteration is less constrained in its distribution by the known outlines of the intrusive stock, although 'hidden' irregularities in the latter may exert an influence. It overprints zones of both potassic and propylitic alteration, but is also superimposed on previously unaltered metasedimentary rocks. It occurs as both pervasive replacement and sets of variously oriented to sheeted veinlets. Pervasive replacement is typically represented by replacement of both mafic minerals and feldspars with aggregates of fine-grained sericite-quartz-carbonate-pyrite, whilst quartz phenocrysts remain unchanged. With increasing intensity, a sericite-quartz assemblage develops, then finally an almost monomineralic quartz, including quartz-only veinlets which resemble A- to B-type veins, but have sericite selvages. Minor chlorite is present mostly associated with carbonates (and locally albite) in zones of pervasive replacement or in the outermost selvages of the veinlets. Carbonates include both calcite and Fe-Mg carbonates (siderite, ankerite, dolomite). Trace tourmaline is locally recorded. Phyllic alteration assemblages are interpreted to have formed from a homogenous high-salinity (30 to 37 wt.% NaCl and 5±0.5 wt.% CaCl2; Soloviev et al., 2019)
The most abundant sulphide mineral in phyllic alteration assemblages is pyrite, which together with chalcopyrite and/or molybdenite, occurs as finely disseminated euhedral crystals in the pervasively altered igneous rocks and in thin, typically <5 mm thick veinlets. Chalcopyrite and molybdenite are unevenly distributed as both fine disseminations in pervasive replacement zones and as larger, 1 to 3 cm aggregates in quartz-sericite veinlets. Type-B quartz-molybdenite veinlets appear to be younger than type-A or transitional type-AB quartz-pyrite and quartz-pyrite-molybdenite veinlets. Phyllic alteration consistently overprints potassic and propylitic alteration zones, and can result in either Cu grade increases or dilution. More typically, phyllic alteration overprint results in an addition of Mo, up to 0.5% and/or Au, typically fractions of gram per tonne grade increase.
The alteration and mineralisation described above is cut locally by subvertical Au-bearing quartz-sulphide veins that are typically 1 to 2 m thick and as much as 200 to 300 m long (Soloviev et al., 2019).
These auriferous late quartz-sulphide veins crosscut both igneous and sedimentary rocks and follow steeply dipping, linear transverse fracturing zones. At least 30 large quartz-sulphide veins have been encountered in the Lazurnoe Deposit (Yushmanov, 2002, Yushmanov, 2009, Avilova et al., 2016), although the largest veins appear to be outside of porphyry-style alteration and mineralisation zones. Their central sections, which are from 1 to 2 cm, up to 1 m thick, comprise mono-mineralic quartz or quartz-carbonate aggregates, sandwiched between sericite-albite-carbonate selvages that include minor chlorite, trace tourmaline and fluorite. Quartz-carbonate aggregates locally cement zones of multiple tectonic brecciation. Sulphide minerals, other than pyrite and minor chalcopyrite, include locally abundant arsenopyrite, sphalerite and galena, with trace stibnite. Scheelite occurs locally, whilst various sulphosalts, Bi minerals, electrum and often coarse native Au (fineness 70 to 90%; Yushmanov, 2009) occur, contributing to locally high, up to 100 to 300 g/t Au and several hundreds g/t Ag grades. These quartz-sulphide veins are reported to extend for ~1.5 km along strike with thicknesses of up to 0.9 m in their central parts, containing 8.7 to 58.0 g/t Au (Yushmanov, 2009). The central parts of these veins are surrounded by a stockwork halo of thin branching, locally sheeted veinlets paralleling the central vein and contain up to 2.8 g/t Au over as much as 11.8 m (Yushmanov, 2009).
Cu-Au-Mo porphyry mineralisation forms an oval shaped annulus of disconnected ~100 to 300 m wide zones within the outer sections of the stock, coincident with the most intense potassic alteration, overprinted by propylitic and phyllic assemblages. The deposit includes at least two higher-grade zones carrying chalcopyrite and bornite that are surrounded by weak pyrite-chalcopyrite mineralisation (Soloviev et al., 2019).
Mineralisation grades are typically 0.15 to 0.30% Cu, with local intervals of 0.4 to 1% Cu, 0.2 to 0.3 g/t Au, 1 to 10 ppm and rarely up to 50 to 300 ppm Mo, with elevated 0.02 to 9.34 g/t Pt and 0.01 to 2.96 g/t Pd (Yushmanov, 2009).
The first intrusive stage rocks are overprinted by potassic alteration which is less abundant in the second stage rocks. The potassic assemblages in these two stages are overprinted by propylitic alteration, whereas phyllic alteration overprints potassic and propylitic alteration and is most distinctly related to the third intrusive stage rocks and overprints the latter. The late auriferous quartz-sulphide veins intersect all types of hydrothermal alteration related to the Early Cretaceous intrusions.
The Vostochnoe Zone is associated with a predominantly granodiorite-porphyry stock, again ~1.5 km in diameter. The dominant alteration style is phyllic, characterised by pyrite and molybdenite with minor chalcopyrite mineralisation, whilst potassic and propylitic alteration is weak. Molybdenum grades range between 40 and 180 ppm. Mineralisation is cut by en echelon zones of auriferous quartz-sulphide veining up to several tens of metres across and up to 1.5 km along strike (Yushmanov, 2001). An adjacent large gold-scheelite placer accumulation is likely related to this late Au mineralisation (Soloviev et al., 2019).
The Dioritovoe Zone is hosted within another composite stock composed of monzodiorite to dominant granodiorite to granodiorite porphyry phases. These intrusions are overprinted by a zoned hydrothermal alteration halo characterised by a weak chalcopyrite-pyrite-magnetite mineralisation in potassic and propylitic alteration zones. The latter contain low grade of 0.02 to 0.1% Cu, 0.001 to 0.05 g/t, with rare intervals up to 0.1 to 0.3 g/t Au, and trace Mo (1 to 2 ppm Mo). More intense mineralisation is found in monzodiorite near its contacts with quartz monzonite and granodiorite. Phyllic alteration forms narrow (from a few cm, up to 2 to 3 m thick), steeply dipping planar zones overprinting minor zones of potassic and propylitic alteration (Soloviev et al., 2019.
The Srednee Zone is characterised by dominant quartz monzonite-, quartz diorite (tonalite)- and granodiorite-porphyry dykes as well as by abundant breccias with magmatic or hydrothermal cement. The hydrothermal breccias are cemented by a fine-grained and cryptocrystalline quartz-albite-sericite-pyrite matrix resembling a phyllic alteration assemblage, although magmatic breccia with a quartz monzonite- to granodiorite-porphyry matrix is cut by quartz-sericite-pyrite veinlets. The breccias are composed of angular to rounded clasts of sedimentary host rocks (siltstone, sandstone, argillite, quartzite, chert and mafic volcanic rocks) and fragments of minerals (quartz, feldspars) that range from a fraction of, to several cm across. Some clasts have undergone hornfelsing and/or potassic alteration (biotite dominant ) prior to brecciation. Fragments of propylitic-altered rocks (with chlorite-magnetite-pyrite aggregates) are also observed. Local potassic and propylitic alteration, as well as wider intervals of phyllic alteration are present. Cu mineralisation, typically grades from 0.1 to 0.2% Cu, and occurs in various hydrothermal assemblages including chalcopyrite-magnetite to pyrite-magnetite-chalcopyrite and dominant pyrite-chalcopyrite. Molybdenite is present in propylitic and particularly phyllic alteration assemblages.
Reserves and Resources
The deposit remained only partially evaluated in late 2019 (when the source paper, Soloviev et al., 2019, was published).
An initial resource of 0.5 Mt of contained Cu-equiv., with average grades of 0.32% Cu, 0.19 g/t Au and 0.01% Mo was reported by Efimov, (2008).
After further testing, the resource increased to ~1 Mt of contained Cu-equiv. (Naidenko, 2013) and ~2 Mt of contained Cuequiv. (Popov et al., 2019).
Yushmanov (2009) estimated a 110 t Au endowment for auriferous quartz-sulphide veins plus 15 to 20 t Au in placers in the Lazurnoe deposit area.
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.
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Khanchuk, A.I., Kemkin, I.V. and Kruk, N.N., 2016 - The Sikhote-Alin orogenic belt, Russian South East: Terranes and the formation of continental lithosphere based on geological and isotopic data: in J. of Asian Earth Sciences v.120, pp. 117-138.|
Soloviev, S.G.,Kryazhev, S.G., Avilova, O.V., Andreev, A.V., Girfanov, M.M. and Starostin, I.A., 2019 - The Lazurnoe deposit in the Central Sikhote-Alin, Eastern Russia: Combined shoshonite-related porphyry Cu-Au-Mo and reduced intrusion-related Au mineralization in a post-subduction setting: in Ore Geology Reviews v.112, 26p. doi.org/10.1016/j.oregeorev.2019.103063|
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