首页|A novel approach using detrital apatite and till geochemistry to identify covered mineralization in the TREK area of the Nechako Plateau,British Columbia
A novel approach using detrital apatite and till geochemistry to identify covered mineralization in the TREK area of the Nechako Plateau,British Columbia
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Resistant indicator minerals (RIM) have been used in mineral exploration in recent years to help identify and locate buried deposits because their compositions reflect their source rocks and,in some cases,specific types of mineral deposits. Apatite is a potential RIM because,in addition to its resistance to physical and chemical weathering,it is widespread in most rocks and mineral deposits. Our previous work discriminated the major types of mainly magmatic-hydrothermal mineral deposits in terms of linear discriminant functions using the Mg,V,Mn,Sr,Y,La,Ce,Eu,Dy,Tb,Pb,Th and U contents of apatites. Step-wise discrimination diagrams permit subdividing apatites by origin. We have analyzed detrital apatite grains recovered from till in ten study areas from the glaciated and underexplored Nechako Plateau of central British Columbia by electron probe microanalysis and laser ablation-inductively coupled plasma maB spectrometry. To aid interpreting these apatite data,we also used till geochemistry,and detrital chalcopyrite and gold grain counts. A total of 342 apatite grains (344 analyses) were claBified as aBociated with mineralization,whereas 41 apatite grains were claBified as derived from barren rocks,and two grains were claBified as 'unknown'. Mineralization-related apatite grains were claBified as alkalic porphyry Cu-Au (80),porphyry Cu-Mo-Au (28),porphyry Mo (72),porphyry-related Cu-Au breccia (16),W skarn (112),orogenic Au (26),orogenic Ni-Cu (7),and Kiruna-type 10A (3) deposit-types. Detrital apatite grains in till down-ice from developed mineral prospects in brownfield areas were correctly identified by the discriminant method. Detrital apatites also helped to generate many new exploration targets in greenfield areas lacking known mineralization or hosting only minor mineral occurrences. These findings validate the apatite discriminant method and demonstrate its usefulneB as a practical exploration tool in graBroots programs.
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