Geochemical signatures of mesothermal Au-mineralized late-metamorphic deformation zones, Otago Schist, New Zealand

Craw, Dave (författare): Geology Department, University of Otago, Dunedin, New Zealand

MacKenzie, Doug (författare): Geology Department, University of Otago, Dunedin, New Zealand

Pitcairn, Iain (författare): Stockholms universitet,Institutionen för geologi och geokemi

Teagle, Damon (författare): National Oceanography Centre, University of Southampton, Southampton, UK

Norris, Richard (författare): Geology Department, University of Otago, Dunedin, New Zealand

(creator_code:org_t)

2007
2007
Engelska.
Ingår i: Geochemistry: Exploration, Environment, Analysis. ; 7, s. 225–232-

Abstract Ämnesord

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Hydrothermal processes along two regional-scale shear zones in theOtago Schist were dominated by structurally controlled fluid flow and mineralization in the host schist, with relatively minor quartz vein formation, and mineralized rocks are only subtly different from unmineralized rocks. Most Au in the shear zones is associated with sulphide minerals (pyrite and arsenopyrite) disseminated through the host schist or along microshears. Minor enrichment of Sb, Mo and Bi (ppm level) is detectable in the Hyde-Macraes Shear Zone (HMSZ). Hydrothermal muscovite is slightly more aluminous (1–2 wt%) than metamorphic muscovite in both shear zones. HMSZ muscovite averages >900 ppm N, in contrast to metamorphic muscovite that averages c. 200 ppm N. In both shear zones, rutile has replaced metamorphic titanite and epidote has altered to carbonate and phyllosilicates, but these reactions were nearly isochemical. Structurally controlled hydrothermal graphite in the HMSZ occurs in microshears (up to 3 wt%, above background <0.2 wt%). Alteration in the Rise & Shine Shear Zone (RSSZ) was accompanied by addition of abundant ankerite. The two shear zones have subtly different geochemical signatures and are not directly genetically related. However, As enrichment is a key exploration target for both shear zones.

Av författaren/redakt...: Craw, Dave; MacKenzie, Doug; Pitcairn, Iain; Teagle, Damon; Norris, Richard

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