Long term mine site rehabilitation studies at Stockton open cast coal-mine

• Main Author: Alarcon Leon, Edgardo
• Format: Other/Unknown Material
• Language: English
• Published: University of Canterbury 1997
• Subjects: Greenland; Rata
• Online Access: http://hdl.handle.net/10092/16797; https://doi.org/10.26021/9060

Rehabilitation of mine sites normally requires restoration of or even improving land use and environmental factors in the affected region. The present studies have assessed environmental parameters that are the principal constraints for mine development in the Stockton Plateau, including in particular surface water and underflow leachate quality. Gently dipping quartzose sandstone and grits, localised siltstones, and carbonaceous mudstones of early Tertiary age comprise the Buller Coalfield. The Brunner Coal Measures (BCM) unconformably overlie rocks of early Cretaceous Berlins Porphyry and Greenland Group of Ordovician age. These sequences, in turn, are underlie the recently nominated Millerton sandstones and mudstones of the Kaiata Formation, which were almost entirely eroded from the area investigated. This geological setting in combination with the harsh climatic conditions of the area inhibits any significant ecosystem development. However, dominant medium size vegetation such .as manuka, hebe and rata develop mainly in shaded areas. Chemical, physical and mechanical evaluation of the overburden waste rock materials has identified three principal lithotypes. The coarse to very coarse massive sandstone and grit and granule conglomerates were grouped into LIT I (A-B).The fine to coarsely laminated micaceous siltstone and fine to medium sandstones compose LIT II, and the carbonaceous mudstone and the fine muddy siltstones are grouped in LIT III. The carbonaceous mudstones, which are a subordinate unit in the Brunner Coal Measures, contains substantial disseminated pyrite concentrations; whilst the other assessed mudstone of the Kaiata Forn1ation, is the most reactive with framboidal pyrites present in various micromorphologies. These sulphide bearing minerals in contact with water and oxygen trigger acid rock drainage (ARD). The liquid solutions are being released from the mined areas as underflows from overburden stockpiles, and contribute significantly to the surface water chemistry. Acid mine drainage (AMD) ...