Mineralization
The Ying Property contains multiple mesothermal silver-lead-zinc-rich quartz-carbonate veins in steeply-dipping fault-fissure zones which cut Archean gneiss and greenstone. To date, significant mineralization has been defined or developed in at least 308 discrete vein structures, and many other smaller veins have been found but not as yet well explored.

Structurally, the vein systems throughout the district are all somewhat similar in that they occur as sets of veins of generally similar orientation enclosed by fault-fissure zones which trend most commonly northeast-southwest, less commonly north-south, and rarely northwest-southeast. The structures extend for hundreds to a few thousand metres along strike. They are often filled by altered andesite or diabase dikes together with quartz-carbonate veins or as discrete zones of altered bedrock (mainly gneiss) associated with local selvages of quartz-carbonate veinlets. From one-third to one-half of the structures exposed at the surface are conspicuously mineralized as well as altered.

The vein systems consist of narrow, tabular or splayed veins, often occurring as sets of parallel and offset veins. The veins thin and thicken abruptly along the structures in classic “pinch-and-swell” fashion with widths varying from a few centimetres up to a few metres. “Swells” formed in structural dilatant zones along the veins often forming mineralized “shoots”. At the SGX mine, these shoots range from 30 m to more than 60 m in vertical and horizontal dimensions over true vein widths of 0.4 m to 3.0 m. The vertical dimension of the SGX shoots is commonly twice or more the horizontal dimension. Longitudinal sections constructed along the veins indicate that many of the shoots have a steep, non-vertical rake.

The vein systems of the various mine areas in the district are also generally similar in mineralogy, with slight differences between some of the separate mine areas and between the different vein systems within each area. These differences have been attributed to district-scale mineral zonation at different levels of exposure. This subtle zonation is thought to be perhaps analogous to the broad-scale zonation patterns observed in the Coeur d’Alene District (USA) and characteristic of many other significant mesothermal silver-lead-zinc camps in the world (Broili et al. 2008, Broili et al. 2010).

Deposit types
The deposits described in this report are epigenetic vein deposits that have mesothermal characteristics. Mesothermal vein systems typically occur in rocks associated with orogenic belts, in the case of the Ying district, the Qinling orogenic belt. Mineralization is associated with deep-seated shear zones that cut the metamorphic rocks. The veins form in a temperature range of 200 – 300°C, at pressure depths from 600 m to 5,000 m. The veins occur in sets with the major veins in the system tending to be continuous for over 1,000 m in lateral and vertical sense.

The Ying Mining District has been intermittently mined over many years by small-scale, local miners. Silvercorp commenced mining at its Ying property (SGX mine) in April 2006. Its current mining activities continue to be focused at the SGX mine, but now also include the HZG (a satellite deposit to SGX), HPG, TLP, LME, and LMW mines, and the DCG project.

Underground access to each of the mines in the steeply-sloped, mountainous district is via adits at various elevations, inclined haulageways, shaft / internal shafts (winzes), and declines (ramps).

The mines are developed using trackless equipment – 20 t trucks and single-boom jumbos; small, conventional tracked equipment – electric/diesel locomotives, rail cars, electric rocker shovels; and pneumatic hand-held drills. At most of TLP, four adits of SGX, part of LME and part of LMW mines, small tricycle trucks with a payload of up to three tonnes each are used to haul ore to surface. These tricycle trucks are being gradually replaced by rail cars in all mines except for TLP.

The global extraction sequence is top-down between levels, and generally outwards from the central shaft or main access location. The stope extraction sequence is bottom-up, with shrinkage and resuing being the main mining methods. Jacklegs are used in stope blast drilling. In-stope ore handling is by hand-carting / hand-shoveling to specially manufactured steel-lined ore passes for resuing stopes, and by gravity to draw points for shrinkage stopes. Production mucking uses mostly hand shovels or, occasionally, rocker shovels, with rail cars and battery-powered or diesel locomotives transporting ore to the main shaft, inclined haulageway or main loading points in declines. Ore transport to surface is accomplished via skip/cage hoisting (shaft), rail-cars (tracked adit and/or inclined haulageway), small tricycle trucks, or 20 t trucks on ramps. Some hand picking of high-grade ore and of waste may be carried out on surface at either ore pile or sorting belt, with transport to the centralized processing plants being via 30 t and 45 t trucks or barge and truck combination.

SGX
The SGX mine is located in the western part of the Ying district. It is accessed by eight adits and a ramp to 260 mRL with a total length of 2,955 m. An inclined-haulageway from the ramp at 260 mRL is being extended to -90 mRL. When the extension is completed by the end of 2020, the total length of the ramp will be 5,600 m. In addition, an S2 branch ramp of 1,020 m from 83 mRL to -20 mRL is being developed and is expected to be completed in 2021. In respect of the existing underground infrastructure and the distribution of Mineral Resources, the whole mining area is divided into 13 production systems. A production system is an independent mining area with an independent transport and muck-hoisting system. SGX is the largest of the Silvercorp.

HZG
The HZG mine is a satellite of the SGX mine, with portals located about 4 km to the south of the main SGX site. It is accessed by five adits and hosts five production systems. A ramp of 2,100 m from 712 mRL to 500 mRL is being developed and is expected to be completed in early 2021. There are 21 known veins. The vein widths for mining range from about 0.2 m to 3.0 m, the veins being generally similar to those found throughout the district.

HPG
The HPG mine has been operated since 2007 and is located in the central part of the Ying district, to the north-east of the SGX mine. It is accessed from six adits and mining from 36 veins is projected in the LOM plan between 100 mRL and 630 mRL. The HPG mine is divided into five production systems.

TLP
The TLP mine lies about 11 km east–southeast of SGX. There are 77 known veins, all dipping westward. The mine is serviced from eight adits and hosts seven production systems. The 3,300 m ramp from 840 mRL to 510 mRL will be completed by the end of 2020. The mining plan currently shows production occurring through to 2036 from stopes between 510 mRL and 1,070 mRL and from vein widths generally between 0.3 m and 5.0 m.

LME
The LME mine is located just south of the TLP mine and about 12 km from SGX. 23 veins with steep dips to either east or west have been identified. Access is via one adit, three shafts and two inclined haulageways. A 2,500 m ramp is being developed from 600 mRL at the TLP ramp to 350 mRL and is scheduled for completion in 2021.

LMW
The LMW mine is located just south of the TLP mine and about 12 km from SGX. To date, 72 veins with steep dips to either the north-east or north-west have been identified. Access is via four adits, two shafts, and one ramp.

DCG Project
The DCG project is located around 2.7 km north-west of TLP mine. There are three veins, C4, C4E, and C8, which strike north-east and dip north-west. The project is in the development stage and production is anticipated to commerce in late-2021.

Mining methods
Shrinkage stoping and resue stoping are the mining methods employed at the Ying mines. The LOM plan envisages the continuation of these methods.

Shrinkage stoping
A sill drive is initially driven along the vein at 1.8 m height. For typical shrinkage stopes, the lower part of the vein will be mined at 1.2 m width, while the upper part will be mined at 0.8 m width. An access drive at 2 m wide x 2 m high (conventionally a footwall drive) is also developed parallel to the vein at a stand-off distance of about 6 m. Crosscuts for ore mucking from draw- points are driven between the vein and the strike drives at approximately 5 m spacing. Each stoping block is typically 40 m to 60 m in strike length by 40 m to 50 m in height. Travelway raises that are also used for services are established between the levels at each end of the stope block. Waste packs are built on each void side of the raise as stoping proceeds upwards.

Resue stoping
Resue stoping veins are typically high-grade and generally between 0.1 m (minimum extraction 0.3 m) and 0.80 m width. Resue stoping involves separately blasting and mucking the vein and adjoining waste to achieve a minimum stope mining width.

Vein and access development preparation is essentially the same as for shrinkage stoping, other than draw points being established at approximately 15 m spacing along strike. Blasted ore is mucked into steel-lined mill holes that are carried up with the stope and feed to the draw points. The base of the mill holes is held in place with a timber set.

Half-upper lifts are drilled with jacklegs and blasted in essentially the same manner as for shrinkage stoping. Typically, after a lift in the vein is blasted and mucked, the footwall is blasted and the ensuing waste is used to fill the space mined out and to provide a working floor. This process is repeated until the stope sill (crown) pillar is reached. The entire stope is left filled with waste from the slashing of the footwall.

Backfill
Backfill such as tailings or development waste is not required for shrinkage mining, where blasted ore provides a working platform for each stope lift. The ore is removed on completion of stope mining leaving an empty void. There is potential to opportunistically dispose of development waste into these voids, but current mine plans do not make allowance for this.

The resue stoping method uses blasted waste from the footwall (to achieve the minimum mining width) as the working platform for each stope lift. The waste remains in the stope at completion of stope mining.

Mill Plant 1 (Xiayu)
Crushing
The crushing is a closed circuit, consisting of jaw-cone crushers with a vibrating screen. The primary jaw crusher (Model: PEF 500 x 750) has a closed side setting of 80 mm. Discharge from the primary jaw crusher is conveyed to the 15 mm aperture vibrating screen. Ore larger than 15 mm is conveyed to the secondary cone crusher (Model: PYH-2X cone crusher), which has a closed side setting of 15 mm. Discharge from the secondary crusher is conveyed back to the 15 mm aperture screen. Product undersize discharge from the screen feeds fine-ore bins with live storage capacity of 100 t.

Dust from the crushing and screening processes is collected under vacuum, captured in a baghouse dust filter and then transferred to a process tank, with the resulting slurry introduced to flotation.

Milling classification (two trains)
• Crushed ore from the live bins is conveyed to a closed milling circuit consisting of two trains, each with a grate-discharge ball mill (Model: MQCG 2100 x 3600) and a screw classifier (Model: FG-200).
• The ball charge is made up of Mn-steel balls, with diameters ranging from 60 mm to 120 mm.
• The target grind size is 61% to 63% passing 200 mesh and the overflow density is maintained at 40% solids by weight, when introduced to the conditioning tanks ahead of lead flotation.

Mill Plant 2 (Zhuangtou)
Crushing
The crushing is a closed circuit, consisting of two jaw-cone crushers with a vibrating screen (see Figure 17.6). The primary jaw crusher (Model: PEF 800 x 1000) has a closed side setting of 80 mm. Discharge from the primary jaw crusher is conveyed to the secondary cone (Model: PYHD-3CC), which has a closed-side setting of 15 mm. Discharge of the secondary cone is conveyed to the 15 mm aperture vibrating screen. Ore larger than 15 mm is conveyed to the tertiary cone crusher (Model: PYH-3CC), which has a closed-side setting of 15 mm. Discharge from the tertiary crusher is conveyed back to the 15 mm aperture screen. Undersize product discharge from the screen feeds ore bins with a live capacity of 1,000 t.

Milling classification
Crushed ore from the live bins is conveyed to a closed milling circuit consisting of a two trains, each of grate-discharge ball mill (Model: MQG 2.7 x 4.0) and 15” hydrocyclone / spiral classifiers (Model:2FG2.4).

Silvercorp runs two processing plants, Plant 1 (also known as No.1 Mill) and Plant 2 (also known as No.2 Mill), for the Ying operations, with a total design capacity of 1,600 tpd (prior to October 2011), and then 2,600 tpd after October 2011 when expansion phase II was completed. The two plants are situated within 2 km of each other.

Both plants were designed based on the lab tests completed by HNMRI in 2005.
• Plant 1 (Xiayu Plant, 600 tpd) has been in operation since March 2007.
• Plant 2 (Zhuangtou Plant): (1) Phase I (1,000 tpd) has been in production since December 2009; (2) Phase II (1,000 tpd) has been in production since October 2011 when expansion of another parallel flotation bank was completed. The total design processing capacity is now 2,000 tpd.
• Total processing capacity for Plants 1 and 2 in 2020 is 2,600 tpd of ore.

Ore supply
Ore from the Ying mines is shipped via barge and/or truck to the milling flotation Plants ........