Cocker, Helen A., Mauk, Jeffrey L., and Rabone, Stuart D.C. (2013) The origin of Ag–Au–S–Se minerals in adularia-sericite epithermal deposits: constraints from the Broken Hills deposit, Hauraki Goldfield, New Zealand. Mineralium Deposita, 48. pp. 249-266.

PDF (Published Version) - Published Version Restricted to Repository staff only

Abstract

The 7.1 Ma Broken Hills adularia-sericite Au–Ag deposit is currently the only producing rhyolite-hosted epithermal deposit in the Hauraki Goldfield of New Zealand. The opaque minerals include pyrite, electrum, acanthite (Ag2S), sphalerite, and galena, which are common in other adularia-sericite epithermal deposits in the Hauraki Goldfield and elsewhere worldwide. Broken Hills ores also contain the less common minerals aguilarite (Ag4SeS), naumannite (Ag2Se), petrovskaite (AuAgS), uytenbogaardtite (Ag3AuS2), fischesserite (Ag3AuSe2), an unnamed silver chloride (Ag2Cl), and unnamed Ag ± Au minerals. Uytenbogaardtite and petrovskaite occur with high-fineness electrum. Broken Hills is the only deposit in the Hauraki Goldfield where uytenbogaardtite and petrovskaite have been identified, and these phases appear to have formed predominantly from unmixing of a precursor high-temperature phase under hypogene conditions. Supergene minerals include covellite, chalcocite, Au-rich electrum, barite, and a variety of iron oxyhydroxide minerals. Uytenbogaardtite can form under supergene and hypogene conditions, and textural relationships between uytenbogaardtite and associated high-fineness electrum may be similar in both conditions. Distinguishing the likely environment of formation rests principally on identification of other supergene minerals and documenting their relationships with uytenbogaardtite. The presence of aguilarite, naumannite, petrovskaite, and fischesserite at Broken Hills reflects a Se-rich mineral assemblage. In the Hauraki Goldfield and the western Great Basin, USA, Se-rich minerals are more abundant in provinces that are characterized by bimodal rhyolite–andesite volcanism, but in other epithermal provinces worldwide, the controls on the occurrences of Se-bearing minerals remain poorly constrained, in spite of the unusually high grades associated with many Se-rich epithermal deposits.

Item ID:	64317
Item Type:	Article (Research - C1)
ISSN:	1432-1866
Keywords:	Hauraki goldfield; New Zealand; Epithermal; Electrum; Uytenbogaardtite; Petrovskaite
Copyright Information:	© Springer-Verlag 2012
Funders:	New Zealand Ministry of Science and Innovation, Education Endowment Trust of the New Zealand Branch of the Australasian Institute of Mining and Metallurgy, The University of Auckland Faculty of Science, Geological Society of New Zealand, Broken Hills Gold Co.
Date Deposited:	08 Sep 2020 21:51
FoR Codes:	04 EARTH SCIENCES > 0403 Geology > 040307 Ore Deposit Petrology @ 50% 04 EARTH SCIENCES > 0403 Geology > 040306 Mineralogy and Crystallography @ 50%
SEO Codes:	97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 80% 84 MINERAL RESOURCES (excl. Energy Resources) > 8499 Other Mineral Resources (excl. Energy Resources) > 849999 Mineral Resources (excl. Energy Resources) not elsewhere classified @ 20%
Downloads:	Total: 1
	More Statistics