Deposit Types Gold mineralisation of the SJG (Songjiagou) Project is hosted within the pyritic-sericitic conglomerate of the Linsishan Formation from Laiyang Group of Cretaceous-age. Gold enrichment occurs as veins, as well as in disseminated and stockwork distributions. The SJG vein-type mineralisation could be appropriately described as mesothermal genesis. The disseminated and stockwork types of mineralisation have some aspects of epithermal mineralisation but are both spatially and genetically associated with the vein-type; as such it can be considered a variant of that type. The SJG Project’s conglomerate type gold deposit is believed to be associated with mesothermal filling activities and followed by alterations and metasomatism. Property geology The SJG Project is situated in the eastern part of the Jiaobei Terrane and on the northeast margin of the Jiaolai Basin and is regarded as part of the Muping-Rushan gold belt. Paleoproterozoic metamorphic rocks of the Jingshan Group are mainly distributed to the north of the SJG Project area near Tanjia village, and are comprised of biotite granulite, graphite-bearing gneiss, leucogranite, and marble. These strata generally dip southeast with angles varying from 15° to 50°. Cretaceous-age rocks are predominately represented by the Linsishan Formation, part of the Laiyang Group and comprised of conglomerate and sandstone. The Linsishan Formation in the SJG Project area has an overall northeast strike and dips southeast wi ........

The SJG Underground Mine utilises cut-and-fill mining and shrinkage stope mining methods and relies on cemented paste fill or cemented rock fill to support the stoping operation. The development system mainly consists of a trackless access ramp, six level haulage ways, an auxiliary shaft, a surface upcast and an underground upcast.

Off-road/underground dump trucks move both ore and wastes to surface along the level haulage way and the access ramp.

The mine is scheduled to operate 8 hours per shift, 3 shifts per day, 330 days per year. Hauling of ore along the access ramp is scheduled to operate just one shift per day. The production capacity is assumed to be 90 ktpa ore.

Mining methods
The mining methods include cut-and-fill mining and shrinkage stope mining.

Cut-and-fill mining
Stope development includes: a footwall haulage drive on the main level for ventilation, hauling of ore; two cross cuts at the main level for water drainage; a raise connection in the footwall, with access drive to each slice for filling material, workers, and storage of ore; an undercut of the stope area.

The stopes are between 50 and 60 m in length and include a 5 m thick sill pillar at the bottom of the cut and fill panel that is recoverable.

Recovery of ore starts from the bottom undercut, advancing upward at 1.8 m slice interval/cut. The blastholes are 1.8 m long with a dip angle of 0 degree or slightly dipping at 0.8–1. ........

Crushing The crushing circuit includes a RoM stockpile, a coarse crushing circuit, a medium and fine crushing circuit, and a screening circuit. The crushing process is a traditional ‘‘three-stage crushing with one closed circuit’’, and the ore which is not more than 1,000 mm is crushed to achieve 80% less than 12 mm (P80 = 12 mm). The ore is transported to the RoM stockpile at the processing plant by truck and fed into the 450 m3 RoM hopper by the front-end loader. A heavy-duty ore feeder installed at the bottom of the RoM hopper feeds ore to a jaw crusher for primary crushing. The crushed product is sent to the buffer bin by the #1 belt conveyor, from where it will be fed into a cone crusher by the moving belt feeder at the lower part of the buffer bin for secondary crushing. Ore discharged from the secondary crusher is transported by the #2 belt conveyor to the two vibrating screens at the screening workshop for screening. The oversize materials are transported to the buffer bins by the #3 belt conveyor for tertiary crushing. There are two tertiary cone crushers, which are fed respectively by two moving belt feeders, and the ore produced is also transported to the screening workshop through the #2 belt conveyor. The fineness of the undersize material is P80 = 12 mm, and it is sent to two 1,800 m3 crushed ore silos by the #4 belt conveyor. Grinding The grinding circuit consists of two crushed ore silos, two grate ball mills and two double-spiral classifiers, which form two identical ‘‘one-stage closed-circuit’’ grinding series, grinding the crushed ore to 50% less than 200 meshes (P50 = 75 µm). The crushed ore in the silo is fed onto the #5 belt conveyor by two electromagnetic vibrating feeders installed in the lower part of the silo and sent to the ball mill. The floatation potential of hydrogen (the ‘‘pH’’) adjuster lime is evenly added to the material stream on the #5 belt conveyor. The ball mill and the double-spiral classifier form a closed circuit, and the ore discharged from the ball mill is fed into the spiral classifier for classification. The return sand from the classifier is sent back to the mill for re-grinding. The overflow fineness is P50 = 75 µm, which flows into the floatation circuit by itself.

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