Final Report - Geoscience BC

4 1 9 . 7 12 55 07 51 0 01 2 51 5 01 7 52 0 02 2 52 5 02 7 53 0 03 2 53 5 03 7 54 0 00R O C KA L T N0M A G S U S2 6 60 5m g0cp20 2 0p y02 55 07 51 0 01 2 51 5 01 7 52 0 02 2 52 5 02 7 53 0 03 2 53 5 03 7 54 0 04 1 9 . 7 1Trends in magnetic susceptibility at MilliganMonzonite Hybrid AndesiteAndesite0m420mLow magnetiteabundance, lowsusceptibility, ingenerally unalteredandesitic rocks.Increased pyrite withcarbonate/epidotealteration.Potassic alterationPropylitic alterationCarbonate alterationPropylitic overprintingpotassic alterationCarbonate overprintingpotassic alterationPotassic alteration in andesite yields magnetite.Overprinting by other alteration assemblagescauses irregular susceptibilityWhere unaltered – a drop in susceptibilityWhere potassic alteration occurs in monzonite,K-spar/biotite forms preferentially (less Fe formagnetite) thus slightly lower susceptibilities?GeolAltnMagSusMagCpyPyFigure 8. Trends in magnetic susceptibility at Mt. Milligan18