Gold

PROSPECTING FOR NEW GEOLOGICAL AND ECONOMIC GOLD MINERALIZATION TYPES WITHIN THE LEBEDINSKY ORE PLACER CLUSTER, REPUBLIC OF SAKHA (YAKUTIA)

Work schedule: 2013-2015

Major work results for the project:

  • Forecasting-prospecting models of the Lebedinsky ore placer cluster (LOPC) and gold fields
  • Structural-formational, remote, geophysical and geochemical forecasting basics; 1:25 000 LOPC gold potential map, online gold deposits and occurrences catalog
  • Identification of ore fields (Orto-Sala-Verkhnekuranakhskoye, Malokuranakhskoye, Koltykon-Samodumovskoye, etc.) and prospecting sites within them hosting prospective gold deposits of new geological and economic (structural-morphological) types to be discovered; a set of 1:10 000, 1:5 000, 1:2000 – 1:500 geological maps and sections
  • Stockwork gold mineralization zones cutting Mesozoic alkaline intrusives, Archean-Proterozoic crystalline basement and its Vendian-Cambrian sedimentary cover rocks were identified and traced, their morphology and parameters, gold and associated metal distribution patterns were determined
  • Localized, estimated and approved (as of January 1, 2016) primary gold resources are: 27 t averaging 3.0 g/t (inferred) and 25 t at 4.0 g/t (potential)
  • Recommendations on further prospecting in LOPC southern side.

LOPC (Fig. 1) is located in the Central Aldan mining district of the Republic of Sakha (Yakutia), sheet 0-51-XVIII. Structurally, it is located in the northwestern side of the Verkhneyakokutskaya depression. By the early 1990s, 32 t and 42 t Au, respectively, were produced at primary gold-sulfide-quartz deposits paragenetically associated with Mesozoic essentially alkaline magmatism, and adjacent major economic LOPC placers.

High-grade (averaging 7 g/t) mined-out deposits (Lebedinskoye, Koltykonskoye, Samodumovskoye, Radostnoye) confined to uplifted thin (up to 150 m) tectonic blocks of the Aldan shield sedimentary cover were classified as “Lebedinsky type” represented by banded stratoidal gold-carbonate-sulfide, esentially oxide flat-dipping deposits at several section levels of Vendian limestone-dolomite sequence, associated high-dipping gold-sulfide-quartz veins and combined (sometimes multi-tier) bodies.

LOPC resource potential is not exhausted. Its increase may be sources from new geological and economic types of gold deposits, primarily high-dipping zones of stockwork (veinlet-disseminated and vein-stringer) gold pyrite-(arsenopyrite-chalcopyrite-galena) mineralization (with stalky pyrite-quartz gold-bearing veins) cutting monzonite-syenite-porphyry intrusives, sedimentary cover and basement rocks (deposit “mineralizing feeders”). Their economic significance (based on modern conditions) was proved by prospecting and estimation completed over the last decade in the central LOPC, at the Gora Rudnaya deposit; its reserves are currently at the State Commission on Mineral Reserves’ approval stage.

With regard to LOPC geological structure, two gold field forecasting-prospecting models were constructed; they include formational, lithological-stratigraphic, structural, morphological, metasomatic, mineralogical, geochemical and geophysical indicator elements.

The first model (Fig. 2) represents the ore cluster’s northern, central and southwestern sides where Precambrian basement rocks, Vendian overlying limestone-dolomite sequence (up to 150 m thick), and Mesozoic alkaline-earth and subalkaline intrusive complexes are eroded to day surface. Orto-Sala-Verkhnekuranakhskoye, Malokuranakhskoye, Koltykon-Samodumovskoye, Gora Rudnaya and Radostnoye ore fields, Verkhneyakokutskoye and Tayozhnoye potential ore fields were identified here.

The second model (Fig. 3) represents LOPC southeastern side; within the Verkhneyakokutskoye depression, the sedimentary cover composed of Vendian-Cambrian carbonate and Early Jurassic terrigenous deposits is at least 450 m thick. Mesozoic magmatism is represented by multiple high-dipping alkaline dikes and sills. The Yurskoye potential ore field was identified here.

Based on TsNIGRI’s prospecting, LOPC primary gold inferred resources were approved:

  • Р1 - 27 t, with ore content – 3.0 g per ton
  • Р2 - 25 t, with ore content - 4,0 g per ton

Figure 1. LOPC geological map

Figure 2. Model of central, northern and southwestern LOPC gold deposits

Figure 3. Model of southeastern LOPC gold deposits