Structural setting of the Globe‐Progress and Blackwater gold mines, Reefton goldfield, New Zealand

Abstract

Globe-Progress and Blackwater mines, the two largest mines in the Reefton goldfield of North Westland, have been placed into a regional structural context dominated by upright, tight folding of the host-rock Ordovician Greenland Group turbidites. The Greenland Group lacks distinctive lithostratigraphic marker horizons or biostratigraphic control, but mapping out areas of common structural facing from the determination of bedding-cleavage vergence along two transects has revealed a series of northtrending, generally shallow plunging folds. Undisrupted fold hinge closure is rarely seen, but the bedding-cleavage vergence boundaries are inferred to be fold hinge regions or in some instances post-folding faults. Vergence boundaries are often accompanied by changes in sedimentological younging. The technique defines the location of fold hinges, faults and, potentially, because of the structural control on mineralisation, gold-bearing quartz veins.The Globe-Progress gold-bearing quartz vein system occurs in a zone of relatively tight and shorter wavelength folds within a wider framework of more open, longer wavelength, east-verging folds. On the western flanks of Globe Hill, the Globe-Progress shear separates east-verging folded strata in the hanging wall from more symmetrically folded, commonly overturned strata in the footwall. The shear curves from an easterly strike to a southerly strike and steepens from 30-40° dips at depth to near-surface dips of 70-80°. Minor structures in the hanging wall indicate west over east-directed movement of the Globe-Progress shear. The Blackwater quartz vein system occurs parallel to steeply west-dipping, west-facing strata in a section of tight upright folds. The folds occur within the hinge area of a regional synclinal structure, which in turn is one of a series of 4-5 km long wavelength folds. G99033

Hydrothermal alteration in metasedimentary rock-hosted orogenic gold deposits, Reefton goldfield, South Island, New Zealand

“…Adams et al (1975) inferred that metamorphism was Silurian to Devonian, based on K-Ar dates of 438 to 395 Ma. Regional structural mapping by Rattenbury and Stewart (2000) showed that most of the gold-bearing quartz lodes are confined to a NNE-trending corridor about 5 km in width, which has shorter wavelength and tighter folds than in the adjoining areas.…”

“…The wide alteration halo at Globe-Progress is interpreted to be a result of repeated deformation, including reverse and strike slip movements, along the GlobeProgress shear, a major shear zone which is markedly discordant to the northerly trending regional fold pattern (Rattenbury and Stewart 2000). This deformation has produced fracture permeability for the hydrothermal fluids to flow out from the main lodes (Christie et al 2000).…”

“…These results are interpreted in concert with drill hole geochemical and lithological data supplied by GRD Macraes Ltd. for the Globe-Progress, General Gordon, Merrijigs and Blackwater deposits. This study is part of a larger ongoing project at the Institute of Geological and Nuclear Sciences that is examining the geology, structure, hydrothermal alteration, and style and age of mineralisation in the Reefton goldfield (Goldfarb et al 1995;Christie and Brathwaite 1998;Christie et al 1999aChristie et al , 1999bChristie et al , 2000Cox 2000;Rattenbury and Stewart 2000).…”

Structure of the Buller and Takaka Terrane rocks adjacent to the Anatoki Fault, northwest Nelson, New Zealand

“…2 cross-section C). (Grindley 1971(Grindley , 1980Laird 1972;Coleman 1977Coleman ,1981Nathan 1978;Cooper 1979b;Roder & Suggate 1990;Harrison 1993;Rattenbury & Stewart 2000).…”

Experimental Metalloid Mobilisation from a New Zealand Orogenic Gold Deposit

“…The mine was worked underground from 1876 to 1920 and was reopened as an open pit in 2007 (Christie and Brathwaite 2003;Druzbicka and Craw 2013). The host rocks are Ordovician quartz-rich clastic metasediments (Cooper 1974;Rattenbury and Stewart 2000). Greenschist facies metamorphism and associated deformation resulted in partial recrystallisation of the rocks, mainly to quartz, albite, muscovite, and chlorite.…”