Post on 12-Sep-2018
Application of hyperspectral data for assessing 3D lithological and alteration architecture of porphyry Cu-Au systems
Jamie Robinson David Tilley, Charlotte Barry, Peter Downes, John Greenfield, Joel Fitzherbert and Phil Blevin
This work is part of the surveys efforts to develop training or system type characterisation datasets
We want to get to a point where we can develop spatial vectors into systems • To do this, how we collect and process our data is very important • Need to break-up/domain data to isolate variables
Need to be able to identify ‘anomaly’ from ‘background’ • Nymagee type system the transition from background into the alteration system
is over scales of tens of metres • For Cargo, we are not seeing the edge of the system. The transition is likely to be
over kilometres or tens of kilometres
Need broader-regional scale datasets. How? • As well as drill core/chips, hyloggerTM can scan slabs/rock samples
We need to move from looking at hyperspectral logged drill holes in isolation, and start to look at mineralogical variability over mineral system scale, rather than the drill hole scale
Even in simple systems you cannot directly plot
meaningful system scale spatial mineralogy
Projects aim to fill the gap between hyperspectral data collection and exploration outcomes
?
How do we take the raw data, process, validate and provide an outcome which has significant
system vectoring application?
Limitations of Hylogger that need to be recognised to examine the data: • The hylogger outputs mineral point count data • Recognition of minerals within the core can be
affected by: • Grain size • Grain orientation • Mineral colour/reflectivity
• The output point count data is based on matching spectral signatures of scanned points against signatures in the TSG library
• Current work only based on shortwave infrared (clays, phyllosilicates, amphiboles, sulphates, carbonates).
Downes et al in review
Strongly shoot controlled Cu within a NNW trending fault zone
Metamorphosed clay-rich • Quartz–muscovite/illite • Minor scattered plagioclase
& chlorite • Trace K-feldspar
Quartzo-feldspathic • quartz–muscovite-
plagioclase • minor chlorite • trace K-feldspar
white mica
feldspar
Fe-chlorite
Mg-chlorite
sulfides (aspectral) & Fe-oxide
quartz The margins of the alteration system are clearly observed across strike
Melrose Melrose Melrose Melrose Melrose Melrose Melrose Melrose Melrose TroughTroughTroughTroughTroughTroughTroughTroughTrough
Rast Rast Rast Rast Rast Rast Rast Rast Rast TroughTroughTroughTroughTroughTroughTroughTroughTrough
Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Canbelego - Mineral Hill Rift Zone Hill Rift Zone Hill Rift Zone Hill Rift Zone Hill Rift Zone Hill Rift Zone Hill Rift Zone Hill Rift Zone Hill Rift Zone
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Beloura Tank
Boomerang Tank
Kilparney
Mountain dam
White Tank
Rookery
Booth
Blue Mountain
Stoney Tank
Elura
Lerrida
McKinnons Tank
Kirry
Wiralong
Lillvale
Mineral HillMineral HillMineral HillMineral HillMineral HillMineral HillMineral HillMineral HillMineral Hill
Tallebung MineTallebung MineTallebung MineTallebung MineTallebung MineTallebung MineTallebung MineTallebung MineTallebung Mine
Girilambone MineGirilambone MineGirilambone MineGirilambone MineGirilambone MineGirilambone MineGirilambone MineGirilambone MineGirilambone Mine
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Mt Boppy MineMt Boppy MineMt Boppy MineMt Boppy MineMt Boppy MineMt Boppy MineMt Boppy MineMt Boppy MineMt Boppy Mine
Nymagee - HeraNymagee - HeraNymagee - HeraNymagee - HeraNymagee - HeraNymagee - HeraNymagee - HeraNymagee - HeraNymagee - Hera
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Peak Mine Peak Mine Peak Mine Peak Mine Peak Mine Peak Mine Peak Mine Peak Mine Peak Mine PerseverancePerseverancePerseverancePerseverancePerseverancePerseverancePerseverancePerseverancePerseverance
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Mt Allen MineMt Allen MineMt Allen MineMt Allen MineMt Allen MineMt Allen MineMt Allen MineMt Allen MineMt Allen MineWagga TankWagga TankWagga TankWagga TankWagga TankWagga TankWagga TankWagga TankWagga Tank
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Mc Kinnons Mc Kinnons Mc Kinnons Mc Kinnons Mc Kinnons Mc Kinnons Mc Kinnons Mc Kinnons Mc Kinnons TankTankTankTankTankTankTankTankTank
COBARCOBARCOBARCOBARCOBARCOBARCOBARCOBARCOBAR
0km 50km
Rookery Fault
Nymage Fault
Sandy Creek Fault
Gilm
ore linamentW
agga
- Nym
agee
Stru
cture
Woonarra Fault
Rookery Fault
Plug Tank F
Amphitheatre Fault
Jackermaroo F
ault
Buck
war
oon
Faul
t
Coonara Fault
COBAR SUPERBASIN
Simplified Geology and Mineral Deposits
David 2007 Cobar
Sydney
= mineralised zone
Fe-chlorite
Mg-chlorite
NMD053W1 NMD047
Transition from Fe to Mg chlorite proximal to mineralised zone
Consistent finding of broader Cobar-Nymagee Alteration study
Spatial plotting Fe and Mg chlorite should recognise a gradient within the plane of the host structural zone. Potential vector towards mineralisation within the plane of the
host structural zone
Downes et al. in review
Downes et al in review
Much greater alteration complexity associated with Porphyry Cu-Au systems: • Alteration over broader scales • Superposition of assemblages • Prograde and retrograde assemblages • Broader range of pre-, syn and post
mineralisation lithologies
Holliday & Cooke 2007
Cadia
Orange
Bathurst Cargo
Cadia
Bathurst 250k Metalogenic Simplified geology – Downes et al 2013
Orange
Bathurst
Orange Sydney
Stage 1: Translating and simplifying logging code system Stage 2: Data domained by lithology and spatial variability of mineralogy examined between holes evaluated Stage 3: 1st pass point data interpolation
16 holes scanned with Hylogger
Translating and simplifying logging code system
Combination of translating codes to GSNSW system where
textural qualifiers separated from basic lithology code &
checking the logged lithology against spectral signature
e.g. 4 textural variations of andesite merged to one (with textural qualifier)
Numeric data domained by lithology and drillhole
Data does not extend to or beyond the edge of the system to estimate background but clear trends exist in the data
Part of argillic or phyllic assemblage as per Leach 2008 Part of Potassic assemblage as per Leach 2008 Part of propylitic assemblage as per Leach 2008
Why the difference? • Hylogger data needs validation using petrography
and xrd • Possible some biotite variants not
recognised in hylogger data & spectral library needs update
• Biotite may be fine grained or misoriented relative to the scanner
• Biotite may be overestimated in logs
• Biotite may be retrogressing (to Mg Chlorite?)
Note: All current interpolation given identical elipsoid constrains for first pass comparison
First pass anisotropic interpolations Visually Logged biotite within holes scanned
Hylogged data Interpolated biotite-phlogopite
Example: Spatial variation in Fe and Mg Chlorite • As observed in 2D plots of
domained data, Fe and Mg chlorite
• Mg chlorite appears spatially
related to copper, Fe chlorite occurs on margins
• Margins of system are not
constrained by current scanned drillholes
The Nymagee study demonstrated in a relatively simple system that the background metamorphic mineralogy can be separated
from alteration mineralogy
Increased Mg chlorite relative to Fe chlorite could be used as an indicator of proximity to mineralisation
In the more complex porphyry systems we need to domain data to better isolate mineral gradients
However, there are trends in the hylogger data that can be
recognised at this early stage
Validation of observations in first pass analysis (petrography & XRD)
Use thermal Infrared data
Characterisation of plagioclase
Determination of alteration vs magmatic K feldspar
How does the observed alteration relationship compare to magnetic susceptibility?
Re-evaluate methods and relationships in other systems