ZTEM 2D Synthetic Modelling - Pecors Magmatic Massive Sulphide Target - Powerpoint
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ZTEM 2D Synthetic Modelling - Pecors Magmatic Massive Sulphide Target - Powerpoint
![From: hawke@cogeco.ca [mailto:hawke@cogeco.ca]
Sent: Sunday, November 27, 2016 10:19 AM
To: Jean M. Legault
Subject: RE: ZTEM information
Jean
I made up three hypothetical orebodies that I believe might be achievable for the project in question and
I calculated an average conductivity for the body based on a mix of 35% pyrrhotite, 20% chalcopyrite, 15
% pyrite and 30% rock. This would work out to a conductivity of 3.6 mSm. You may have better numbers
than I and if so feel free to substitute your own. The three hypothetical orebodies are as follows
30 Mt - 600m length 110m wide and 300 m thick
15Mt – 600m length 50m wide and 150 m thick
7.5 Mt – 600m length 25m wide and 50m thick
If we were to bury each one at depths of 700m, 1400m and 2100m which one if any or what combination
would produce a response(s) on the ZTEM.
Any help you could provide would be much appreciated
Sincerely
Don Hawke
Modeling Objectives
Pecors ZTEM 2D Synthetic Model
Objective: Using Geologic Model from Magnetic inversion Create Conceptual Model and
Determine detectability of buried ~7.5Mt Magmatic massive sulphide body buried at
700m, 1400m & 2100m using ZTEM airborne EM.
Method: Use 2D MT forward modeling code of Wannamaker et al. (1985) in GeotoolsTM to
obtain ZTEM synthetic fwd model Tipper data and then invert using Geotech Av2dtopoTM
2D ZTEM inversion code. Test for 200m, 300 and 500m minimum depth.
Pecors Magnetic Anomaly
Pecors 3D Magnetic Inversion
~3km
Volume = Mass = 7,500,5000 tonnes x 1000 kg/t x 1000 g/kg = 2,142,857 m3
Density 3.5 g/cc x (100 cm/m)3
Approx. Size = 2,142,857 m3 = Approx. 300m wide x 10m thick x 700m long
(after Reed, 2014)
(after Reed, 2014)
6000 m](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
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ZTEM 2D Synthetic Modelling - Pecors Magmatic Massive Sulphide Target - Powerpoint
- 1. INTERNATIONAL MONTORO RESOURCES LTD. ZTEM 2D Synthetic Modeling Pecors/Serpent River Project, Elliot Lake ON Buried Magmatic Massive Sulphide Target BY JM Legault, M.Sc.A., P.Eng, P.Geo Chief Geophysicist – Geotech Ltd. 6-Jan-2017
- 2. From: hawke@cogeco.ca [mailto:hawke@cogeco.ca] Sent: Sunday, November 27, 2016 10:19 AM To: Jean M. Legault Subject: RE: ZTEM information Jean I made up three hypothetical orebodies that I believe might be achievable for the project in question and I calculated an average conductivity for the body based on a mix of 35% pyrrhotite, 20% chalcopyrite, 15 % pyrite and 30% rock. This would work out to a conductivity of 3.6 mSm. You may have better numbers than I and if so feel free to substitute your own. The three hypothetical orebodies are as follows 30 Mt - 600m length 110m wide and 300 m thick 15Mt – 600m length 50m wide and 150 m thick 7.5 Mt – 600m length 25m wide and 50m thick If we were to bury each one at depths of 700m, 1400m and 2100m which one if any or what combination would produce a response(s) on the ZTEM. Any help you could provide would be much appreciated Sincerely Don Hawke Modeling Objectives Pecors ZTEM 2D Synthetic Model Objective: Using Geologic Model from Magnetic inversion Create Conceptual Model and Determine detectability of buried ~7.5Mt Magmatic massive sulphide body buried at 700m, 1400m & 2100m using ZTEM airborne EM. Method: Use 2D MT forward modeling code of Wannamaker et al. (1985) in GeotoolsTM to obtain ZTEM synthetic fwd model Tipper data and then invert using Geotech Av2dtopoTM 2D ZTEM inversion code. Test for 200m, 300 and 500m minimum depth. Pecors Magnetic Anomaly Pecors 3D Magnetic Inversion ~3km Volume = Mass = 7,500,5000 tonnes x 1000 kg/t x 1000 g/kg = 2,142,857 m3 Density 3.5 g/cc x (100 cm/m)3 Approx. Size = 2,142,857 m3 = Approx. 300m wide x 10m thick x 700m long (after Reed, 2014) (after Reed, 2014) 6000 m
- 3. 1) Model 1 (100 S Body at 700m) – 2D Forward Model) Tzx(In-line)In-Phase(%)Tzx(In-line)Quadrature(%) +25% -25% +25% -25% X Z Air Layer below helicopter 10k ohm-m x 50m thick Archean Basement 1000 Ω-m In Phase Tzx Tipper from 2D ZTEM Fwd Model Quadrature Tzx Tipper from 2D ZTEM Fwd Model X Z +/- 0.01 approx. ZTEM noise floor Comments: All Quadrature responses are well above Expected Threshold Noise levels. Comments: In-Phase responses are well above Expected Threshold Noise levels. +/- 0.01 approx. ZTEM noise floor 0% MS Body 0.1 ohm-m 10m Thick (100 Siemens) 300m Wide Reverse Cross-Overs (180-720Hz) = Resistor 720Hz0% Pecors Model 1 – ZTEM 2D Inversion Model Tzx In Phase - Calculated Tzx Quadrature - Calculated (Comments: XQD Profile reversals due to Different Quadrature Polarity Convention Used in ZTEM Av2dinv code (exp(-iwt) versus Geotools (exp(+iwt)). ZTEM 2D Resistivity Comments: The expected ZTEM response is moderate-strong In-phase response and Quadrature response. The 2D inversion returned a Resistivity model that appears to resolve the Targeted MS bodies at 700m depth and is easily detectible above S/N levels. However the 2D does not recover the Layered Cover or the Mafic Intrusive. Resistive Host ~1000 Ωm ~700 m 6000 m Conductor ~3 Ωm ~300-500m Wide At ~750m Depth +/- 0.01 approx. ZTEM noise floorTzx In Phase - Synthetic/Observed +/- 0.01 approx. ZTEM noise floor Tzx Quadrature - Synthetic/Observed Reverse Cross-Overs (22H-360z) = Conductor 2D Fwd Modeling using Wannamaker et al. (1985) PW2dfwd code in Geotools MODEL 1 Huronian Cover Rocks 500 Ω-m x 300m thick Mafic Intrusive 5000 Ω-m 700m 300m Normal Cross-Over (720z) = Resistor Normal Cross-Overs (22-90Hz) = Conductor 6000 m
- 4. 1) Model 2 (100 S Body at 1400m) – 2D Forward Model) Tzx(In-line)In-Phase(%)Tzx(In-line)Quadrature(%) +25% -25% +25% -25% X Z Air Layer below helicopter 10k ohm-m x 50m thick Archean Basement 1000 Ω-m In Phase Tzx Tipper from 2D ZTEM Fwd Model Quadrature Tzx Tipper from 2D ZTEM Fwd Model X Z +/- 0.01 approx. ZTEM noise floor Comments: All Quadrature responses are above Expected Threshold Noise levels. Comments: In-Phase responses are above Expected Threshold Noise levels. +/- 0.01 approx. ZTEM noise floor 0% MS Body 0.1 ohm-m 10m Thick (100 Siemens) 300m Wide Reverse Cross-Overs (45-720Hz) = Resistor 720Hz0% 720Hz Pecors Model 2 – ZTEM 2D Inversion Model Tzx In Phase - Calculated Tzx Quadrature - Calculated (Comments: XQD Profile reversals due to Different Quadrature Polarity Convention Used in ZTEM Av2dinv code (exp(-iwt) versus Geotools (exp(+iwt)). ZTEM 2D Resistivity Resistive Host ~1000 Ωm ~1300 m 6000 m Conductor ~18 Ωm ~500-100m Wide At ~1300m Depth +/- 0.01 approx. ZTEM noise floorTzx In Phase - Synthetic/Observed +/- 0.01 approx. ZTEM noise floor Tzx Quadrature - Synthetic/Observed Reverse Cross-Overs (22-90z) = Conductor 2D Fwd Modeling using Wannamaker et al. (1985) PW2dfwd code in Geotools MODEL 2 Huronian Cover Rocks 500 Ω-m x 300m thick Mafic Intrusive 5000 Ω-m 1400m 300m Normal Cross-Overs (180-720z) = Resistor Normal Cross-Over (22Hz) = Conductor Comments: The expected ZTEM response is moderate In-phase response and Quadrature response. The 2D inversion returned a Resistivity model that appears to resolve the Targeted MS bodies at ~1300m depth and is easily detectible above S/N levels. However the 2D does not recover the Layered Cover but maybe Resistive Intrusive. 6000 m
- 5. 1) Model 3 (100 S Body at 2100m) – 2D Forward Model) Tzx(In-line)In-Phase(%)Tzx(In-line)Quadrature(%) +25% -25% +25% -25% X Z Air Layer below helicopter 10k ohm-m x 50m thick Archean Basement 1000 Ω-m In Phase Tzx Tipper from 2D ZTEM Fwd Model Quadrature Tzx Tipper from 2D ZTEM Fwd Model X Z +/- 0.01 approx. ZTEM noise floor Comments: All Quadrature responses are above Expected Threshold Noise levels. Comments: In-Phase responses are above Expected Threshold Noise levels. +/- 0.01 approx. ZTEM noise floor 0% MS Body 0.1 ohm-m 10m Thick (100 Siemens) 300m Wide Reverse Cross-Overs (45-720Hz) = Resistor 720Hz0% 720Hz Pecors Model 3 – ZTEM 2D Inversion Model Tzx In Phase - Calculated Tzx Quadrature - Calculated (Comments: XQD Profile reversals due to Different Quadrature Polarity Convention Used in ZTEM Av2dinv code (exp(-iwt) versus Geotools (exp(+iwt)). ZTEM 2D Resistivity Resistive Host ~1000 Ωm ~1800 m 6000 m Conductor ~26Ωm ~750-1000m Wide At ~1800m Depth +/- 0.01 approx. ZTEM noise floorTzx In Phase - Synthetic/Observed +/- 0.01 approx. ZTEM noise floor Tzx Quadrature - Synthetic/Observed Reverse Cross-Overs (22-90z) = Conductor 2D Fwd Modeling using Wannamaker et al. (1985) PW2dfwd code in Geotools MODEL 3 Huronian Cover Rocks 500 Ω-m x 300m thick Mafic Intrusive 5000 Ω-m 2100m 300m Normal Cross-Overs (180-720z) = Resistor Normal Cross-Over (22Hz) = Conductor Comments: The expected ZTEM response is moderate In-phase response and Quadrature response. The 2D inversion returned a Resistivity model that appears to resolve the Targeted MS bodies at ~1800m depth and is easily detectible above S/N levels. However the 2D does not recover the Layered Cover but maybe resistive Intrusive. 6000 m
- 6. CONCLUSIONS & RECOMMENDATIONS • Synthetic 2D modeling was performed to test the applicability / suitability of ZTEM for exploring for buried magmatic massive sulphides in the Pecors/Serpent River project near Elliot Lake, Ontario. • 7.5 Mt body was estimated for 3.5gm/cc density to be 10m thick x 300m wide x 700m long. But 2D model ignores strike length so infinite strike was assumed for 10m x 300m wide conductor. Conductivity fixed at 0.1 ohm-m for Nickel Sulphides for modeling. • Three different model scenarios were studied: 100 Siemens (0.1 Ω-m x 10m thick (5 siemens) conductors at +700m, +1400m and +2100m depths of burial, associated with massive-sulphide bodies below thick Huronian cover and inside Archean mafic intrusive. • The synthetic 2D ZTEM response was calculated using the Wannamaker et al. (1985) 2D MT forward modeling code in Geotools. • These synthetic data were then used as input for the 2D ZTEM inversion using the Geotech Av2Dtopo code by Wannamaker (Uof Utah). • The 2D synthetic results suggest that all these 700-2100m deep targets will be easily detected as anomalies; however it will not be possible to recover the layered cover or to differentiate/discriminate individual mafic intrusive bodies in Archean basement. • Note, 15Mt and 30Mt sulphide bodies were not tested in ZTEM modeling, but given the success for 7.5 Mt, larger, more highly conductive bodies should also be detectible, provided they area reasonably 2-dimensional (i.e., approx. >1-3km long). • We expect that the ZTEM tipper amplitudes will weaken for shorter strike length 3D bodies. Respectfully submitted JM Legault, M.Sc.A., P.Eng, P.Geo Chief Geophysicist – Geotech Ltd. 6-Jan-2017