Please use this identifier to cite or link to this item: https://hdl.handle.net/1959.11/7290
Title: Shear-hosted base metal mineralisation at the Dana Peaks, Murchison Mountains, Fiordland, New Zealand
Contributor(s): Allibone, Andrew (author); Ashley, Paul  (author); Mackenzie, Doug (author); Craw, Dave (author)
Publication Date: 2010
DOI: 10.1080/00288306.2010.498406
Handle Link: https://hdl.handle.net/1959.11/7290
Abstract: Darran Suite dioritic, tonalitic and granodioritic plutonic rocks and schistose Loch Burn Formation volcaniclastic rocks in the central Murchison Mountains at the Dana Peaks have been affected by widespread biotite-sericite-chlorite-albite-quartz-pyrite±carbonate±epidote/clinozoisite±titanite/rutile±actinolite alteration. More intense, paler coloured sericite-albite-quartz-pyrite±carbonate alteration is concentrated along orange weathered shear zones. Alteration assemblages are transitional between those commonly referred to as propylitic, potassic and phyllic. Altered rocks contain anomalous concentrations of copper, lead, zinc and silver over an area of c. 2.56 km. Metal concentrations 2-5 times those typical of Darran Suite plutonic rocks and the Loch Burn Formation are commonly associated with more extensive weak to moderate intensity alteration. Higher metal grades up to c. 0.5% copper, 1% zinc, 1.3% lead and 30 ppm silver are concentrated in or adjacent to the 1-5 m wide, more intensely altered shear zones which contain entrained lenses of pyritised country rock, breccias and quartz±K-feldspar±chlorite±carbonate±hematite±tourmaline veins. Some mineralised rocks also contain traces of tungsten (2-7 ppm), arsenic (<5-35 ppm) and tellurium (0.2-5.4 ppm). Most samples lack detectable molybdenum (<3 ppm), gold (<0.004 ppm) or bismuth (<0.2 ppm), with atypical higher values (40, 0.03 and 50 ppm, respectively) generally restricted to the most intensely altered and/or deformed rocks. The mineralised rocks show a close spatial and temporal relationship with several narrow ductile shear zones that probably developed in the Early Cretaceous between c. 128 and 110 Ma. Mineralised shear zones form minor splays off larger shear zones that are part of a major intra-arc fault system, active along or near the boundary between inboard and outboard parts of the Median Batholith at this time. Traces of similar lead mineralisation are present at the head of the Mid Burn c. 8 km to the northeast along strike on the same regional-scale fault system as the Dana Peaks locality. Fluids and metals are likely to have been derived from metamorphism of the Loch Burn Formation and/or adjacent plutonic rocks. A magmatic hydrothermal origin is considered unlikely as the metal assemblage lacks Mo, Bi, Au, Sn and W and the adjacent plutonic rocks probably crystallised several million years or more before alteration and mineralisation.
Publication Type: Journal Article
Source of Publication: New Zealand Journal of Geology and Geophysics, 53(4), p. 271-294
Publisher: Taylor & Francis Asia Pacific
Place of Publication: Singapore
ISSN: 1175-8791
0028-8306
Fields of Research (FoR) 2008: 040307 Ore Deposit Petrology
Socio-Economic Objective (SEO) 2008: 840199 Mineral Exploration not elsewhere classified
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article

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