Overview
The Lexindin (G Zone) mine, technically identified as the Gaocheng (GC) project, stands as a cornerstone of high-efficiency poly-metallic mineral processing in the Guangdong Province of China. Owned and operated by Silvercorp Metals Inc. through its subsidiary Guangdong Found Mining Co., Ltd., this facility represents a sophisticated integration of modern automation and traditional metallurgical excellence. Located within the Gaocun Township of the Yun’an District, the mine is strategically positioned in a region known for its rich mesothermal vein infill deposits, which provide a complex ore matrix containing silver, lead, and zinc.
Since its commercial inception in early 2014, the G Zone processing circuit has undergone significant technological evolutions to address the challenging mineralogy of the site. The project operates under a comprehensive 30-year mining permit, covering a surface area of approximately 5.52 square kilometers and extending to depths of minus 530 mRL. The significance of the Lexindin facility lies not only in its throughput capacity but also in its ability to consistently deliver high-grade concentrates despite fluctuations in head grades. As an underground operation utilizing a hybrid access method of declines and shafts, the mine feeds a processing plant designed to handle 1,600 tonnes per day (tpd), translating to an annual nominal capacity of roughly 330,000 tonnes. The project serves as a global benchmark for the application of X-ray intelligent sorting and sequential flotation in narrow-vein poly-metallic mining, making it a critical asset for the company and the broader regional economy.
Key Process Stages
The mineral processing flowsheet at the Lexindin (G Zone) facility is a multi-stage circuit designed for maximum metal recovery and waste rejection. The key stages include:
- Primary and Secondary Crushing: The circuit begins with a ROM (Run-of-Mine) bin feeding a PE600×900 jaw crusher. A critical operational strategy here involves running the crushing system during “electricity price valley” periods to optimize costs.
- X-Ray Intelligent Sorting: A relatively recent and highly innovative addition, the X-ray sorting system pre-sorts ore before it reaches the grinding stage. This system effectively identifies and discards waste rock, thereby increasing the head grade of the material entering the mill and reducing overall energy consumption.
- Grinding and Classification: The facility utilizes two parallel and independent grinding circuits, providing operational flexibility. Each circuit features ball mills in closed circuit with hydrocyclone clusters to achieve the target grind size for optimal liberation.
- Sequential Preferential Flotation: Modified from a traditional sequential process in 2013, the current flowsheet employs a lead preferential flotation stage, followed by a zinc-sulphur mixed flotation, and finally a zinc-sulphur separation stage. This sequence is vital for managing the complex interplay between galena and sphalerite.
- Gravity Separation for Tin: Tailings from the flotation circuit are treated using classified shaking tables to recover tin, achieving a recovery rate of approximately 34%.
- Dewatering and Filtration: Concentrates are thickened in central-drive thickeners and then processed through ceramic disc vacuum filters (HTG series) to reach a final moisture content of 10% to 12%.
- Tailings Management: The facility utilizes a deep-cone thickener for high-concentration underflow (over 72% solids), which is either directed to the backfill system or dry-stacked in the Tailings Storage Facility (TSF).
Critical Data
The following table outlines the technical performance metrics and design parameters of the Lexindin (G Zone) processing plant based on recent operational records.
| Parameter | Value | Unit |
|---|---|---|
| Nominal Throughput Capacity | 1,600 | tpd |
| Annual Processing Rate | 330,000 | t/a |
| Lead (Pb) Recovery Rate | 90.0 | % |
| Zinc (Zn) Recovery Rate | 89.0 | % |
| Silver (Ag) Total Recovery | 83.0 | % |
| Lead Concentrate Grade | 44 – 45 | % Pb |
| Zinc Concentrate Grade | 44.0 | % Zn |
| Silver Grade in Lead Concentrate | 1,500 | g/t |
| Silver Recovery in Lead Concentrate | 60.0 | % |
| Silver Recovery in Zinc Concentrate | 23.0 | % |
| Tin (Sn) Recovery from Tailings | 34.0 | % |
| Primary Crusher Power | 75 | kW |
| Water Consumption per Tonne | 5.0 | m³/t |
Technical Details and Sustainability
The technical sophistication of the Lexindin (G Zone) mine is most evident in its adaptable flotation circuit. Historically, the plant utilized a lead-zinc-sulphur sequential preferential flotation process. However, as the ore mineralogy shifted, engineers implemented a radical change in 2013, moving to a lead preferential flotation followed by a zinc-sulphur mixed flotation. This modification was crucial for improving the separation efficiency of zinc from sulphur minerals, which had previously caused dilution in the zinc concentrate. Today, each of the two grinding lines can process between 900 and 950 tpd, allowing the plant to exceed its nominal 1,600 tpd design capacity when mining supply permits.
Sustainability is integrated into the core engineering of the G Zone. The plant is built on a steep hillside, a design choice that leverages gravity for pulp conveyance, significantly reducing the energy required for pumping. Furthermore, the water management system is a model of circular economy principles. Approximately 5 cubic meters of water are used per tonne of ore, but the majority of this is sourced from mineral processing return water and treated mine water. New water is only drawn from the Hashui River as needed, after undergoing treatment in a dedicated purification facility on-site. This closed-loop approach minimizes the environmental footprint on the local watershed.
In terms of waste management, the move toward dry-stacking tailings has been a significant environmental milestone for the project. By filtering tailings to a high density and using bulldozers to spread them on a bench-by-bench basis, the mine reduces the risks associated with traditional wet tailings dams. Moreover, the facility is exploring the potential for copper-lead separation from the lead concentrate, which currently contains 2% to 3% copper. Successful implementation of a copper separation flotation stage could further diversify the mine’s revenue streams while improving the marketability and purity of its lead concentrates. With ongoing optimizations in the X-ray intelligent sorting systems, the Lexindin (G Zone) mine is well-positioned to maintain its status as a low-cost, high-recovery producer for decades to come.
Source: Lexindin (G Zone) / Gaocheng Silver-Lead-Zinc Technical Report
Source: NI 43-101 Technical Report
This article provides an overview of mineral processing developments based on publicly available technical reports and industry analysis.
