Mesa J

Overview

Mesa J is an open pit operation with site-based processing and train loading facilities. It started production in 1992 and has an annual production capacity of 7 million tonnes per year.

Rio Tinto's iron ore operations in the Pilbara also include a 53 per cent interest in Robe River Iron Associates' three mines: Mesa J, Mesa A/Warramboo and West Angelas. The Mesa A and J are considered part of the Robe Valley Operations.  Robe River primarily exports under medium and long term supply contracts  with major integrated steel mill customers in Japan, China, Europe, South Korea and Taiwan.

In 2011, the Robe Valley Operations (Mesa A and J) produced 57.5 million tonnes of iron ore.

Rio Tinto iron ore operations in the Pilbara have an annual capacity of 220 million tonnes, with advanced plans to increase capacity to 283 million tonnes by 2013, on a pathway to 333 million tonnes. With a network of 14 mines, three shipping terminals and the largest privately owned heavy freight rail network in Australia, Rio Tinto's Pilbara operations make up a major part of Rio Tinot's iron ore activities globally. Rio Tinto's operations began in 1966 and are well positioned to meet the growing needs of the world's iron and steel industry.

In the Pilbara, Rio Tinto wholly own Hamersley Iron's eight mines and also operate the Hope Downs mine (50:50 joint venture between Rio Tinto and Hancock Prospecting Pty Limited), the Channar mine (Rio Tinto: 60 per cent) and the Eastern Range mine (Rio Tinto: 54 per cent). 

Location

The Mesa J iron ore mining operation is located 200 kilometres south west of Karratha in Western australia.

Western Australia occupies the whole western part of the continent. Its economy is largely driven by extraction and processing of a diverse range of mineral and petroleum commodities. The state contributes an estimated 58 percent of Australia's Mineral and Energy Exports.

Geology & Mineralization

The Pilbara region is located in the northwest of Western Australia, approximately 1,100km north of Perth. The region contains the 80,000 square km Hamersley Iron Province. The geology of the Province is characterized by a 2,500 million years old group of late Archaean and early Proterozoic rock formations known as the “Hamersley Group”.

The Hamersley Group was formed by chemical sedimentation of minerals in a marine (ocean) environment. The processes which formed the Hamersley Group occurred after volcanic activity introduced basalt rocks in the area. Sedimentary rocks like sandstones also occur in the group due to weathering and transportation of rocks which occurred during the period when the Hamersley Group was formed.

The Hamersley Group is approximately 2.5km thick. It contains several large units of Banded Iron Formation (BIF): rock with bands of iron minerals (magnetite and hematite) and gangue minerals (mostly carbonates, silicates and chert). Typically, unenriched BIF contains about 30 per cent iron by weight.

The BIF layers have been deformed by geological processes, and eroded by weathering resulting in the geological formations that we see today.

In the Pilbara, other types of ore deposit exist, notably channel iron deposits, but these are derived from the original bedded iron formations.

Channel Iron Deposits
The Channel Iron Deposits (CIDs) were formed in ancient meandering river channels. As bedded iron deposits were eroded by weathering, iron particles were concentrated in these river channels.  Over time these particles were rimmed with goethite deposited by percolating iron-enriched ground water approximately 15-30 million years ago, which also fused the particles together.

Channel Iron Deposits appear as low flat-topped hills called mesas and have also been located concealed under the cover of more recent rocks.  These deposits range in thickness between 5m and 40m thick.  This type of deposit is believed to be unique to Western Australia.

CIDs are quite different from bedded ores. Their chief characteristic is their pisolitic 'texture': rounded hematitic 'pea-stones', 0.1mm to 5mm in diameter, rimmed and cemented by a goethitic matrix. The ore is brown-yellow in colour.  They typically contain minor amounts of clay in discrete lenses.

Mining & Operation

Rio Tinto is a world-class asset manager, operating and maintaining all mining, rail, power and port facilities in the Pilbara on behalf of asset owners Hamersley Iron (Rio Tinto: 100 per cent) and Robe River (Rio Tinto: 53 per cent).

Mesa J is an open pit operation with site-based processing facilities.

Mining equipment include:
Dozers: â€¢ Komatsu WD900 â€¢ D10R, D10T
Dump Trucks: â€¢ Cat 785C, 789C 
Excavators: â€¢ Hitachi, EX450, EX1900, EX3600
Graders:ʉۢ Cat 16H, 24H
Loaders: ʉۢ Komatsu WA500, WA900, WA1200ʉۢ Cat 926, 928, 950, 992G
Water Truck: â€¢ Cat 777
Drills:ʉۢ DM-M3, Pit Viper

Areas for open-pit mining are selected using the mine plan. Identified areas are tagged, and then holes are drilled in an appropriate pattern by rigs. The drill holes are filled with an explosive, most often ANFO (Ammonium Nitrate/Fuel Oil) and then charged. The resulting blast breaks the material to a size required for digging. The broken material is loaded for transport by face shovels, excavators or front-end loaders into haul trucks. Haul trucks at Rio Tinto Iron Ore operations are typically in the 190 tonne and 240 tonne class. 

Processing

Overland conveyors are used to transport partially crushed feed at sites where there are long distances between the pits and process plants. 

Processing of the ore ranges from simple crushing and screening to a standard size, through to processes that beneficiate or upgrade the quality of the iron ore products. This is done by physical processes, which remove impurities by differences in particle density or size gravity or size separation. Processing may be wet or dry.

The processed ore is stockpiled and blended to meet product quality requirements, before being reclaimed and conveyed to rail load-out. The ore is loaded into ore for transport to the port facilities.

Environment & Community

Rio Tinto's Iron Ore group seeks to balance economic, social and environmental considerations across all parts of its business. This is achieved by making sustainable development considerations an integral part of our business plans and decision-making processes. 

Rio Tinto's Sustainable Development and Climate Change Panel supports senior leadership to embed sustainable development into the way we work. The group oversees the organisation's identification and management of economic, environmental and social risks, and opportunities. 

In addition to Rio Tinto's statement of business practice, The way we work, Rio Tinto define its commitment to sustainable development with nine principles. Together, these principles guide the way we plan for the future.

Closure

The closure of a mine or other operating sites requires planning beyond simply rehabilitating the site. Rio Tinto consider the management of social issues resulting from closure, especially in remote areas where communities are dependent on the socio-economic benefits of the mine.

Rio Tinto plans for closure from the earliest stages of project development to decommissioning activities and are guided by the Rio Tinto Closure Standard. 

The intent of the standard is to ensure that Rio Tinto managed activities are left in a condition which minimises adverse impacts on the human and natural environment.

Rio Tinto experiences with closure planning have helped the business understand that the environmental and social legacy is possibly the most tangible indicator of an operations contribution to sustainable development in the areas where we operate. Consequently, we have adopted a multi-disciplinary approach to closure planning, requiring a wide range of technical and business disciplines. 

These activities allow Rio Tinto to influence the design, development, operation and closure of all managed operations to ensure post-closure outcomes that meet needs and expectations outside of the business.

Product stewardship

Product stewardship means understanding the life cycle of the metals and minerals we produce, including the safe production, use and disposal of metal and mineral products as the need for them continues in society.

Increasingly, producers have both individual and joint responsibility with other stakeholders to ensure that products are managed safely across their life cycles. Our product stewardship work allows us to improve our understanding of the health, safety and environmental implications of the use of our products. Rio Tinto's product stewardship strategy emphasises the importance of understanding threats and opportunities in the market, and the importance of engagement with key stakeholders including customers, suppliers, regulators and communities. 

Rio Tinto is in the process of implementing a formal material-stewardship programme, as well as completing life cycle assessments on key products. Material stewardship is a collective term for resource, process and product stewardship. It means better understanding and taking responsibility for our iron ore products, from their discovery and mining, production, use and management at end of life.