The GRE46 gold deposit is one of several structurally controlled intrusion-related epithermal gold deposits that are hosted by the Lake Cowal Volcanic Complex at the southern end of the Junee–Narromine Volcanic Belt, which forms part of the Ordovician to early-Silurian Macquarie Arc. The GRE46 mineralisation is hosted within a sequence of calc-alkalic subaqueous volcanic and volcaniclastic rocks, including polymict volcanic breccias, mud- to sandstones, coherent andesite to dacite flows with common hyaloclastite and peperite textures, and diorite to granodiorite dykes and sills. Gold mineralisation has both strong structural and lithological controls and is associated with quartz–carbonate–pyrite veins, containing variable chalcopyrite, galena, sphalerite and minor tellurides. The style and intensity of host-rock alteration is highly variable and is strongly influenced by the protolith. Generally consisting of a background chlorite + albite + calcite ± epidote dominant propylitic alteration, which is overprinted by white mica + quartz + pyrite ± albite ± ankerite phyllic alteration that is spatially associated with gold mineralisation. Reflectance spectroscopy data has been obtained from several drill holes using the continuous core scanning HyLogger-3 system. These hyperspectral reflectance spectra have been used to characterise the nature of both primary and alteration mineralogy and compare host-rock controls and hydrothermal alteration processes associated with gold mineralisation. The HyLogger-3 data show systematic changes in the dominant phyllosilicate mineral assemblage associated with background propylitic and proximal phyllic alteration. Moreover, these data highlight compositional variation in alteration minerals, which defines a broad-scale geochemical gradient associated with the gold mineralisation. Spectrally, this geochemical gradient is characterised by: (1) a trend towards more muscovite-dominant mica compositions, observed via a change from long- to short-wavelength 2200 nm absorption features; (2) an increase in the chlorite AlVI content, inferred from the 2250d/2340d ratio; and (3) an increase in the abundance of Fe–Mg carbonates compared with Ca carbonate with consistently shorter wavelength 6500 nm carbonate feature readings.
Read full abstract- All Solutions
Editage
One platform for all researcher needs
Paperpal
AI-powered academic writing assistant
R Discovery
Your #1 AI companion for literature search
Mind the Graph
AI tool for graphics, illustrations, and artwork
Journal finder
AI-powered journal recommender
Unlock unlimited use of all AI tools with the Editage Plus membership.
Explore Editage Plus - Support
Overview
386 Articles
Published in last 50 years
Articles published on Phyllic Alteration
Authors
Select Authors
Journals
Select Journals
Duration
Select Duration
381 Search results
Sort by Recency