| Title | Compositional data analysis to constrain the geochemical footprint of iron oxide copper-gold deposits, Great Bear Magmatic Zone, Northwest Territories, Canada |
| Author | Montreuil, J -F; Corriveau, L |
| Source | Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 36, 2011 p. 144-145; 1 CD-ROM |
| Year | 2011 |
| Alt Series | Earth Sciences Sector, Contribution Series 20120009 |
| Meeting | GAC/AGC - MAC/AMC - SEG - SGA; Ottawa; CA; May 25-27, 2011 |
| Document | serial |
| Lang. | English |
| Media | paper; CD-ROM |
| Province | Northwest Territories |
| NTS | 85N/10 |
| Area | Lou Lake; Cole Lake; Fab Lake |
| Lat/Long WENS | -117.0000 -116.5000 63.7500 63.5000 |
| Subjects | economic geology; geochemistry; geochemical analyses; geochemical interpretations; hydrothermal alteration; alteration; mineral occurrences; mineral deposits; iron oxides; copper; gold; uranium; Great
Bear Magmatic Zone |
| Program | Uranium, GEM: Geo-mapping for Energy
and Minerals |
| Abstract | Iron oxide copper-gold (IOCG) systems are characterized by a wide range of hydrothermal alteration types that indiscriminately and intensively replace their host rocks over several kilometres. The
resulting alteration imprint can be reproduced irrespective of the nature of the original host and intense alteration is usually the norm over areas of >100 km2. Consequently, mass-balance systems analysis (e.g. Gresen's equations) cannot be used
systematically for lithogeochemical characterization of geochemical zonation and partitioning within the alteration zones of IOCG systems. For effective geochemical evaluation of these rocks, the use of log-ratio transforms has been applied as they
overcomes the closure constraint inherent with geochemical data and permits the use of multivariate statistical tools for geochemical process identification. To provide robust discrimination parameters for IOCG hydrothermal alteration with
multivariate statistical methods, the geochemical data must have accompanying reliable and carefully documented field observations. Cataloguing this additional information provides useful qualifications for understanding the para-genesis of the host
hydrothermal system and associated mineralization. The numerous IOCG hydrothermal systems of the Great Bear magmatic zone in the north-western Canadian Shield are good candidates to undertake such multivariate statistical studies using the log-ratio
approach. These systems encompass a wide range of hydrothermal alteration emplaced in different protoliths and are sufficiently intense to have completely replaced the original rock. Their evolution history is well constrained within an alteration to
mineralization zoning model. A database of fully documented geochemical analysis is available. Principal component analysis (PCA) was done on the lithogeochemistry of 458 hydrothermally altered and mineralized rocks from the Port Radium-Echo Bay IOCG
district and various IOCG systems within the Southern Great Bear magmatic zone (including the NICO and Sue Diane deposits). PCA analysis records strong partitioning between LREE and HREE in most alteration zones. Decoupling of typical element
association (e.g. Ca and Sr) is commonly observed. Calcium and K-Na are either decoupled or negatively correlated, whereas K and Na are sometime positively correlated. PCA analysis also indicates that the influence of protolith
composition on
resulting alteration signature is only weak to moderate as very distinctive signatures are not observed, indicating that the alteration signature dominates over the protolith signature. A linear discriminant analysis confirms the difference between
the various alteration types of the IOCG model. Current modelling is unable to retrace significant chemical modification of high-temperature alteration from the low temperature alteration overprints in the IOCG systems that have been
studied. |
| GEOSCAN ID | 291359 |
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