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University of Canterbury (2008)

The Hydrogeology and Hydrochemistry of the Mt. Tom Price Mine, Pilbara, Western Australia – A Groundwater Flow Model

Manewell, Neil

Titre : The Hydrogeology and Hydrochemistry of the Mt. Tom Price Mine, Pilbara, Western Australia – A Groundwater Flow Model

Auteur : Manewell, Neil

Université de soutenance : University of Canterbury

Grade : Master of Science 2008

Résumé partiel
The Mt. Tom Price Mine, located in the Pilbara region of Western Australia, has been the site of major iron ore mining since the 1960s by Rio Tinto Iron Ore/Pilbara Iron. The thesis project area covers approximately 121 km², covering the Mt. Tom Price Mining area and the surrounding catchment boundary. The climate in the Pilbara region is arid, with rainfall driven by seasonal cyclonic events, producing 300 mm/year net rainfall on average. The geology of the Mt. Tom Price area consists of a series of banded iron formations (BIF) and shales that are generally low in hydraulic conductivity values. Iron ore in the region is produced through the process of supergene enrichment whereby gangue minerals are dissolved and replaced with haematite and goethite. Mining is focused in a series of open cast pits including, North Deposit, West Pits, Centre Pits, Southern Ridge, South East Prongs, Section Six, Section Seven, and the proposed Marra Mamba Pits. Due to the impermeable nature and complex geology of the BIF sequence, groundwater flow is dominated by bedrock aquifer flow, with compartmentalization occurring in several areas of the mine. Highly faulted and folded units can also have increased hydraulic conductivity values. Pit floor lowering began to encounter the regional water table in early 1994. A series of dewatering bores and depressurization measurements have been utilized to ensure dry mining practice. This data was used to help understand regional groundwater flow and create the Mt. Tom Price Groundwater Model (MTPGM). A 3D geological model of the project area was created to aid visualisation of semi-regional hydrogeology. From this model, accurate template files were created so that geological detail loss is kept to a minimal when entering hydrogeological parameters into the MTPGM. The MTPGM was setup using PMWIN Pro, a graphical user interface for use with MODFLOW. Stresses such as recharge and pumping were entered via software packages within MODFLOW. The model was run to simulate measured 1994-2007 responses to dewatering and high rainfall events. A Parameter Estimation (PEST) software package and trial and error calibration was used to lower stress response variances that were observed in the model output files.

Mots clés : Tom Price ; Hydrogeology ; Hydrochemistry ; Pilbara ; Australia ; Groundwater Modelling ; MODFLOW

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