GEOSCAN, résultats de la recherche


TitreCompositional data analysis to constrain the geochemical footprint of iron oxide copper-gold deposits
AuteurMontreuil, J -F; Corriveau, L; Grunsky, E
SourceGoldschmidt 2012, abstracts; 2012 p. 1
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120247
RéunionGoldschmidt 2012; Montreal; CA; JUNE 24-29, 2012
Medianumérique; en ligne
ProvinceTerritoires du Nord-Ouest
Lat/Long OENS-117.0000 -116.5000 63.7500 63.5000
Sujetsanalyses géochimiques; interprétations géochimiques; altération hydrothermale; altération; gîtes minéralogiques; gisements minéraux; oxydes de fer; cuivre; or; uranium; Zone de Great Bear Magmatic ; géologie économique; géochimie
ProgrammeGisements polymétalliques - Zone magmatique du Grand lac de l'Ours (T.N-O.), GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
Lithogeochemical analysis of alteration haloes is an important exploration vector towards hydrothermal ore deposits. Iron oxide copper-gold (IOCG) systems display a systemic development of hydrothermal alteration types from sodic, to calcic-iron, and high to low temperature potassic-iron and potassic alteration paragenesis that indiscriminately replace host rocks at local and regional scales. Where intense and pervasive, alteration leads to complete and systemic mineralogical, chemical and textural transformation of precursor rocks, resulting geochemical composition for each alteration type is reproducible irrespective of the nature of the original host. However the zoning in the alteration haloes and the types of deposits formed vary as a function of unidirectional, cyclical or non unidirectional evolution of the hydrothermal system [1]. To further the development of geochemical vectors to IOCG and affiliated deposits and orient exploration campaign in under-explored settings, we document the geochemical signature of hydrothermal alteration from the Great Bear magmatic zone (GBmz) IOCG systems through the application of compositional data analysis based on the log-ratio approach and principal component analysis (PCA).
Results and Conclusions
PCA has enabled the characterisation of the geochemical signature of the diagnostic alteration types. When compared to the other IOCG alteration types defined in the preceding section, potassic and potassic-iron alteration show relative enrichment in K, Al, Ba, Si, Rb, Zr, Ta, Nb, Th and U. In contrast, when compared with the other alteration types, calcic-iron alteration exhibit relative enrichment in Ca, Fe, Mn, Mg, Zn, Ni and Co. Sodic alteration is relatively enriched in in Na, Sr and Zr compared to the other alteration signatures.
The observed compositional variations established for each alteration type were thereafter portrayed in IOCG alteration indexes.
Combined with the IOCG alteration vector to mineralization model, the resulting IOCG alteration indexes led to the development of an IOCG alteration discrimination diagram that provides a useful tool to quickly evaluate if a geochemical composition is related to IOCG -associated hydrothermal alteration. Plotting the alteration indexes on the GBmz regional geology map further demonstrates that the IOCG alteration indexes can provide a framework for field evaluation of the potential fertility and maturity of the GBmz IOCG systems and ultimately vector to ore during exploration.