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Geophysical Exploration for Geothermal Pre-Feasibility Studies in Nevis

Geophysical Exploration for Geothermal Pre-Feasibility Studies in Nevis. Gravity and Self Potential Geophysics. By Frank Dale Morgan Geo-Caribes Technical Team & Massachusetts Institute of Technology. March 2006. Gravity and Self Potential Results In the OAS Report. Craddocks.

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Geophysical Exploration for Geothermal Pre-Feasibility Studies in Nevis

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  1. Geophysical Exploration for Geothermal Pre-Feasibility Studies in Nevis Gravity and Self Potential Geophysics By Frank Dale Morgan Geo-Caribes Technical Team & Massachusetts Institute of Technology March 2006

  2. Gravity and Self Potential Results In the OAS Report

  3. Craddocks Government Road Church Ground Bath Stony Grove Farms Ocean Road Brown Hill Deep Harbor Figure 1:Map of Study Area with Data Stations.

  4. Figure 2:SP Map (mV) from “Network Method”.

  5. Figure 3:Normalized 2D SP Current Source Locations.

  6. Faults Cones Soufrieres 50 Temp (C) 41 38 36 40 41 47 53 46 49 54 56 54 100 Figure 4: Normalized SP Current Sources. Faults and Cones from Huttrer (1998) and Temperatures from GeothermEx (2004).

  7. Figure 5:SP Inversion Current Sources in 3D Using Homogeneous Resistivity Assumption (10x vertical exaggeration)

  8. Bath Figure 6:Vertical W-E Section of 3D Current Sources. Bath Springs at ~1500m.

  9. Farm Estate ~Deep Harbor Figure 7:Vertical S-N Section of 3D Current Sources. Farms Soufriere ~2500m.

  10. mgal Figure 8: Bouguer Anomaly Map (mGal). (2.6 g/cc background)

  11. Figure 9: Polynomial Residual Gravity Map (mGal).

  12. Fault Cone Figure 10: Bouguer Gravity Map with Faults and Cones from Huttrer (1998).

  13. Fault Cone Figure 11: Polynomial Gravity Map with Faults and Cones from Huttrer (1998).

  14. Gravity Body Figure 12: Possible Extent of Gravity Body From BouguerMap.

  15. Gravity Body Figure 13: Possible Extent of Gravity Body From Polynomial Gravity Map.

  16. V. High Low High V. High V. High Low Figure 14: Tertiary Map of Bouguer Gravity.

  17. V. High Low V. High High Low Figure 15: Tertiary Map of Polynomial Gravity.

  18. N N N N Figure 16: Bouguer 3D Surface.

  19. NE SW Figure 17: Data Line for Gravity Modeling From Bouguer Map.

  20. Depth = 1250 m Width = 600 m Thickness = 2300 m 3.0 g/cc 2.2 g/cc 3.0 g/cc 2.2 g/cc 2.2 g/cc Depth = 200 m Width = 3000 m Thickness = 300 m (1) (2) Figure 18: Data and Model Fits. (1) Shallow Limit and (2) Deep Limit.

  21. 1 Km Data 2.25 Km Model r 0.4 Km ro ro 3 Km 0.2 Km r – ro = 0.6 g/cc Figure 19: Data and Model Fit for Realistic Gravity Body.

  22. 38 36 Low Gravity 40 41 47 53 46 49 High Gravity 54 56 54 100 Low Gravity Figure : Possible Extent of Bouguer Gravity Body with SP Current Sources.

  23. Medium Gravity 38 36 40 41 High Gravity 47 46 53 49 54 Low Gravity 56 100 54 Figure : Possible Extent of Polynomial Bouguer Body with SP Current Sources

  24. Self Potentials: Further Analysis

  25. Bath Springs Farm Estate 3D SP Source Inversion Using Homogeneous Resistivity Assumption (5x vertical exaggeration)

  26. Bath Springs Farm Estate 3D SP Source Inversion Using 2D Resistances Over a Homogeneous Halfspace (5x vertical exaggeration)

  27. Interpolated Resistance Data (log10 Ohms) Interpolated SP Data (mV)

  28. “3D” SP Source Inversion Using Interpolated SP Data and Interpolated Resistances in a Single Layer Model

  29. Gravity: Further Analysis

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