Helicopter ZTEM-Magnetic-Radiometric Surveys FOR EPITHERMAL SULPHIDATION GOLD over BAKER-SHASTA PROPERTY, Toodoggone Region, North-Central BC. By J.M. Legault (Geotech) and Bill Yeomans (Sables Resources Ltd.) Presented at Geotech Roundup Mini-Symposium, BCIT, Vancouver BC, 26-January, 2018
OUTLINE Baker-Shasta ZTEM Survey Introduction ZTEM Basics Geophysics of Epithermal Gold Systems Geology and Mineralization at Baker-Shasta. Baker-Shasta ZTEM, Magnetic & Radiometric results. Multi-parameter Geophysics vs Stream Sediment Geochemistry Results Conclusions & Recommendations
AEM OVERVIEW Baker-Shasta ZTEM Survey AIRBORNE ELECTROMAGNETICS VTEM TIME-DOMAIN EM Helicopter AEM Systems ZTEM NATURAL FIELD (PASSIVE) EM Impulse FREQUENCY DOMAIN EM Highlighting Three Main Airborne Electromagnetic Systems and Platforms available for Mineral Exploration.
ZTEM is a Passive EM system Measures EM fields in audio-frequency range (22-720Hz) from distant thunderstorms for deep (>1km) Resistivity Mapping. ZTEM BASICS Baker-Shasta ZTEM Survey Parameters Transmitter Receivers ZTEM Not required (Passive) Airborne: Hz (Horizontal) Rx coil diameter Mobile = 7.2m Base (Ground): Hx & Hy (Vertical) Nominal Rx Height Sampling Rate Frequencies (Hz) EM Skin Depth Penetration Base = 3.5m 50-100m (Relatively unnaffected by Receiver height) A/D = 2000 Hz Output = 2.5Hz (~10m/sample) 18, 25, 37, 75, 150, 300 Hz (+/-600) 22, 30, 45, 90, 180, 360 Hz (+/-720) ~1km-5km for 1k Ω-m Host rocks ~300m-1.5km for 100 Ω-m ~100m-500m for 10 Ω-m C) ZTEM Base Station Receivers
ZTEM BASICS ZTEM Tipper Equation Baker-Shasta ZTEM Survey MagnetoVariational (MV) Dataset along North (X), East (Y) & Vertical (Z) ZTEM Measures 3 components (xy-z) of EM fields from Plane wave current flow in/around Conductive and Resistive geology, detects anomalous Vertical fields (Tipper). ( Arora et al, 1998)
ZTEM Basics Baker-Shasta ZTEM Survey ZTEM (modified after Castels, 2006) In Phase (IP) In Phase (IP) Quadrature (QD) Showing ZTEM frequency range in AMT natural field spectrum and Typical ZTEM response over Strong (left) and Weak (right) Conductive Tabular Bodies. Quadrature (QD) (after Sattel and Witherly, 2012)
ZTEM Basics ZTEM Data XIP-075Hz YIP-075Hz Baker-Shasta ZTEM SURVEY ZTEM 2D Inversion Results IP_DT-075Hz IP_TPR-075Hz ZTEM 3D Inversion Results 3D Resistivity Voxel 2D Resistivity Section Showing typical ZTEM data types and Resistivity sections and volumes obtained from 2D & 3D Inversion Modeling over Copaquire Porphyry Copper deposit, Chile
Baker-Shasta ZTEM Survey EPITHERMAL GOLD DEPOSIT DISTRIBUTION Baker-Shasta LS Showing Location of Baker Shasta Deposits and Distribution of Selected Epithermal and Intrusionrelated Au Deposits in North & Central America. (After Taylor, 2007)
Baker-Shasta ZTEM Survey Geophysics of Epithermal Gold Systems Hot Spring Silicification Mushroom At Surface Epithermal Illite-Sericite Deposits Below Mushroom Cap at surface Propyllitic Alteration Porphyry Deposits Silicification in Center of Vein System Very High Resistivity Mushroom at Surface Very Low Resistivities below Mushroom cap Lower Resistivities in Surrounding Rocks Very High Resistivities Mesothermal Deposits in Center of System Epithermal gold deposits are fossils of geothermal (hot springs) systems and occur above intrusions and/or porphyry copper deposits that form at greater depth. Low and High sulfidation (LS) epithermal systems host mix of alteration minerals that create favourable Resistivity Contrasts (Silica=Resistive / Clays=Conductive) with Host rocks. Epithermal deposits sometimes lack sufficient sulfides for detection with induced polarization, which makes Resistivity & EM methods favourable tools for their exploration. (After Williams, Towards a multidisciplinary integrated exploration process for gold discovery, In Proceedings of Exploration 97 )
Baker-Shasta ZTEM Survey Geophysics of Epithermal Gold Systems TECHNIQUE EM/Resistivity Magnetics Radiometrics HIGH SULFIDATION EPITHERMAL Resistivity High from Silica Alteration (Typical) Resistivity Low Also Possible (Deep Erosion or Strong Clay Alteration) Magnetic Low (Typical for Magnetite-Depletion) Mag-High at Depth also Possible (Intrusive source) Radiometric Low (Acid Leaching) LOW SULFIDATION EPITHERMAL Resistivity Low from Clay Alteration (Typical) Resistivity High also Possible (Deep Erosion or Silica Flooding into Permeable Units) Magnetic Low (Typical for Magnetite-Depletion) Mag-High at Depth also Possible (Intrusive source) Potassium High (Adularia- Illite alteration) (After Hoschke (2011), Geophysical Signatures of Copper-Gold Porphyry and Epithermal Gold Deposits Implications for Exploration ) Resistivity Signatures over Porphyry & Epithermal Au systems will vary according to the Erosional Level.
Epithermal Gold Examples Martabe HS North Sumatra Pajingo LS Queensland AUS Baker-Shasta ZTEM Survey Resistivity highs Waihi LS New Zealand Yanococha HS Peru Resistivity high Trend Resistivity highs(mainly) Resistivity Lows(also) (After Hoschke (2011), Geophysical Signatures of Copper-Gold Porphyry and Epithermal Gold Deposits Implications for Exploration ) Resistivity high Resistivity Low The resistivity response in LS epithermal systems will vary greatly depending on the level of exposure/erosion. High in the system will be complex (i.e., conductive or resistive). Lower in the system, veins and alteration will be easier to identify with resistivity (Hoschke, Newmont/Newcrest, 2011).
Baker-Shasta ZTEM SURVEY ZTEM AT DOLLY VARDEN LS EPITHERMAL Ag RADIOMETRICS EQ POTASSIUM TOTAL MAGNETIC INTENSITY (TMI) ZTEM IN-PHASE TPR (180Hz) MAG-HIGH K-HIGH LOCAL MAG-LOW RESISTIVITY HIGH (after Walker et al., 2017) Radiometric High due K-alteration at Dolly Varden (but Felsic Volcanics too). Local Magnetic Lows due to Depletion with Larger Mag High over DV deposits (Deeper Intrusives) ZTEM Resistivity High due to K-alteration (but Felsic volcanics too) NW & NE Structures also visible
TOODOGGONE DISTRICT REGIONAL GEOLOGY Mesozoic Toodoggone district is located in north-central BC along the eastern margin of the Intermontane Belt Baker-Shasta ZTEM SURVEY The Intermontane Belt represents a succession of volcanic arcs and accretionary complexes formed by subduction of oceanic plates under the North American plate. The Stikinia Terrane is part of the eastern Intermontane Belt The Toodoggone district comprises Upper Triassic to Lower Jurassic Hazelton Group Toodoggone Formation volcanic and sedimentary rocks which unconformably overlie island-arc volcanic/sedimentary rocks of the Lower Permian Asitka Group and Middle Triassic Takla Group Major structures are oriented northwest to N-S and are offset by northeast structures. Most faults are steeply dipping normal faults. Strike slip and thrust faults are less common Mesozoic Toodoggone district of the Stikinia Terrane hosts Au-Cu-Mo porphyry and Au-Ag HS -LS epithermal deposits Toodoggone District Kemess
SOUTH TOODOGGONE DISTRICT GEOLOGY Regional Geology The Toodoggone District is comprised of 4 Groups: Early Permian Asitka marine sedimentary and volcanic rocks Mid Triassic Takla basalt Late Triassic to Early Jurassic Hazelton volcanic and volcaniclastic rocks include Lower and Upper Members Cretaceous Sustut conglomerates and interlayered mudstones, sandstones and ashtuff Upper Triassic to Lower Jurassic mineralization associated with plutonism Black Lake calc-alkaline plutons and dykes intrude the Asitka, Takla, and Hazelton Groups North Kemess and South Kemess Au-Cu porphyry deposits intrude into the Takla basalt Geotech VTEM survey outlined in red Baker-Shasta ZTEM SURVEY
Baker-Shasta Property Geology Baker Deposit Geology Past producers Baker and Shasta Mines are low sulphidation epithermal Au-Ag deposits which formed in the Toodoggone district between (ca. 192 to 162 Ma.) Baker veins occupy ENE striking,steeply dipping structures that cut the Takla Group volcanic rocks (basalt / andesite / rhyodacite); alteration includes epidote-chlorite-calcite+/-pyrite Felsic dikes and porphyritic stocks intrude Takla Group Skarn alteration occurs in Asitka limestones(blue) proximal to Duncan Granodiorite located 200m SW of the Baker deposit The Baker deposit demonstrates a strong genetic link between epithermal and magmatic ore fluids Total production A and B veins 77,500 tonnes yielding 1,168 kg Au and 23,085 kg Ag, with reserves of 50,000 metric tonnes containing 20.1 g/t Au and 177 g/t Ag Baker-Shasta ZTEM SURVEY
Baker-Shasta Property Geology Shasta Deposit Geology Shasta deposit is an adularia-sericite type epithermal deposit in which deposition of metals coincided with the transition from quartz to calcite dominant gangue N-S oriented stockwork breccia zones dip 60 degrees west while SSE oriented veins dip 70 degrees NE Mineralization is associated with stockwork breccia zones associated with strong, hydrothermal potassic alteration of dacitic lapilli tuffs and flows of the Saunders Member of the Lower Toodoggone Formation. Hydrothermal alteration envelopes are <50m wide Mineralization includes pyrite, sphalerite, chalcopyrite, galena, acanthite, electrum and native silver WNW and NNE striking brittle-ductile faults cut and offset the veins at Shasta Total reserves estimated at 1,600,000 metric tonnes grading 2.84 g/t Au and 132.2 g/t Ag Baker-Shasta ZTEM SURVEY
ZTEM SURVEY RESULTS BAKER-SHASTA GEOLOGY & ZTEM LOCATION Baker-Shasta ZTEM SURVEY ZTEM FLIGHT LINES AND DIGITAL ELEVATION MODEL (DEM) BAKER MINE BAKER MINE SHASTA MINE SHASTA MINE 982 line-km at 150m + 1.5km ties ZTEM-Magnetics-Radiometrics August 17-23, 2017. Showing Location of Baker-Shasta Claims over Regional Geology and Flight lines over DEM Baker Mine in northwest corner (topo high), Shasta Mine in southeast (topo low).
ZTEM SURVEY RESULTS REDUCED TO POLE (RTP) MAGNETICS (Corrects for Mag Inclination/Declination) Baker-Shasta ZTEM SURVEY ANALYTIC SIGNAL OF MAGNETIC FIELD (Corrects for Magnetic Remanence Effects) BAKER MINE BAKER MINE SHASTA MINE SHASTA MINE Showing Regional and Local Magnetic Signatures across the property. Baker and Shasta Deposits are located in well defined, local magnetic lows.
ZTEM SURVEY RESULTS RADIOMETRICS EQ POTASSIUM % (Maps K-Mineral Distribution & Alteration) Baker-Shasta ZTEM SURVEY RADIOMETRICS Th/K RATIO (Corrects for Overburden/Bedrock Effects) BAKER MINE BAKER MINE SHASTA MINE SHASTA MINE Showing Regional and Local Radiometric Signatures across the property. Baker and Shasta lie in local Potassium highs that lie along by NE-trending K-lows
ZTEM SURVEY RESULTS Baker-Shasta ZTEM SURVEY IN-PHASE 180Hz TOTAL PHASE ROTATION (TPR) IN-PHASE 180Hz TOTAL DIVERGENCE (DT) BAKER MINE BAKER MINE SHASTA MINE SHASTA MINE Showing Both Types of ZTEM Data Representations both Map Apparent Conductivity: TPR (left) highlights Regional Geology; DT (right) shows more Structure & Local Geology Both images enhance Major NW-SE conductive trend, cross-cut by NE-SW trends.
ZTEM SURVEY RESULTS ZTEM IN-PHASE DT (720Hz) (Shallow Depth Penetration) Baker-Shasta ZTEM SURVEY ZTEM IN-PHASE DT (30Hz) (Greater Depth Penetration) BAKER MINE BAKER MINE SHASTA MINE SHASTA MINE Showing ZTEM Results for Shallow (high frequency DT) and Deep (Low frequency): Shallow Data (left) enhance NW & NE trends, these extend to depth (right). Baker & Shasta Occur along NE trending splays away from Main NW trend.
ZTEM SURVEY RESULTS ZTEM 2D RESISTIVITY (-100m) (Shallow Depth ) Baker-Shasta ZTEM Survey ZTEM 2D RESISTIVITY (-500m) (Greater Depth) BAKER MINE BAKER MINE SHASTA MINE SHASTA MINE Showing ZTEM 2D Inversion Results at Shallow (left) and Deep (right) Levels: Baker & Shasta lie in NE conductive trends away from main NW conductive Structure Other NW and NE conductive trends are also visible.
Baker-Shasta ZTEM Survey RESULTS AT BAKER MINE RADIOMETRICS EQ POTASSIUM % MAGNETIC ANALYTIC SIGNAL (ANSIG) ZTEM IN-PHASE DT (180Hz) NW-SE STRUCTURES WEAK K-HIGH IN K-LOW REGION WEAK MAGNETIC LOW 0 CONDUCTIVITY HIGH 1km NE-SW STRUCTURES Baker is characterized by : Weak Potassium high (K-alteration), in larger NE trending K-low structure; Weak Local Magnetic Low (depletion), at Intersection between NW and NE Conductive structures. Consistent with LS Epithermal Au-Ag signatures at shallow-erosional levels (Waihi LS, NZ).
Baker-Shasta ZTEM Survey RESULTS AT SHASTA MINE RADIOMETRICS EQ POTASSIUM % MAGNETIC ANALYTIC SIGNAL (ANSIG) ZTEM IN-PHASE DT (180Hz) NW-SE STRUCTURES NE-SW STRUCTURES NE-SW STRUCTURES NW-SE STRUCTURES K-HIGH RESISTIVITY HIGH WEAK MAGNETIC LOW 0 1km Shasta is characterized by : Strong Potassium high (K-alteration) in larger NE trending K-low structure Weak Magnetic Low (depletion) and Resistivity high at Intersection between NW and NE structures. Consistent with LS Epithermal Au-Ag signatures at Deep erosional level (like Dolly Varden)
Baker-Shasta ZTEM Survey ZTEM TARGETING ZTEM CONDUCTIVE ANOMALIES (from 360Hz DT Image) ZTEM RESISTIVE ANOMALIES (from 360Hz DT Image) 0 2km 0 2km BAKER-STYLE CONDUCTIVE SIGNATURES SHASTA-STYLE RESISTIVE SIGNATURES Showing ZTEM anomalies over 30Hz In-phase DT
Baker-Shasta ZTEM Survey ZTEM TARGETING ZTEM CONDUCTIVE ANOMALIES Over Magnetic Lows ZTEM RESISTIVE ANOMALIES Over Magnetic Lows 0 2km 0 2km BAKER-STYLE ZTEM+MAG SIGNATURES SHASTA-STYLE ZTEM+MAG SIGNATURES Showing ZTEM anomalies over Magnetic Analytic Signal
Baker-Shasta ZTEM Survey ZTEM TARGETING ZTEM CONDUCTIVE ANOMALIES Over Magnetic Lows + Radiometric K-Lows ZTEM RESISTIVE ANOMALIES Over Magnetic Lows + Radiometric K-Highs 0 2km 0 2km BAKER-STYLE ZTEM+MAG SIGNATURES SHASTA-STYLE ZTEM+MAG SIGNATURES Showing ZTEM anomalies over Radiometric Eq Potassium
Vectoring VTEM Targets with Stream Sediment Geochemistry Baker-Shasta ZTEM Survey BAKER-STYLE ZTEM+MAG SIGNATURES with Stream Sed Anomaly SHASTA-STYLE ZTEM+MAG SIGNATURES with Stream Sed Anomaly Dec-2017 Showing Cu (ppm) and Au (ppb) Ultra-Trace ICP-MS
Baker-Shasta ZTEM Survey CONCLUSIONS & RECOMMENTATIONS ZTEM results have identified Conductive signatures that correlate with Magnetic Low and Potassium Radiometric signatures that coincide with those observed over the Baker Mine and are consistent with shallow eroded LS Epithermal Au deposits. At least 10 correlate with Stream Sediment Geochemistry anomalies that represent follow-up targets for Baker-type LS epithermal mineralization ZTEM results have also identified Resistive signatures that correlate with Magnetic Lows and Potassium Radiometric signatures that coincide with those observed over the Shasta Mine & are consistent with deeply eroded LS Epithermal Au deposits At least 3 correlate with Stream Sediment Geochemistry anomalies that represent follow-up targets for Shasta-type LS epithermal mineralization Our analyses of ZTEM+Mag+Radiometrics and Stream Sed Geochem have identified prospective targets but solely based on Visual correlation of data-based multicomponent evidence. Additional 3D ZTEM & 3D Magnetic inversions, and more Rigorous 3D Predictive Classification/Neural Network type targeting are recommended in future follow-up.
Helicopter ZTEM-Magnetic-Radiometric Surveys for Epithermal Low Sulphidation Gold over the Baker-Shasta Property, Toodoggone Region of North-Central BC ACKNOWLEDGEMENTS Our sincerest thanks to the SABLE RESOURCES INC. for allowing us to present these results. Presented at Geotech Roundup Mini-Symposium, BCIT, Vancouver BC, 26-January, 2018