Geophysics Flashcards
Changes in strength of earth’s gravitational field.
Gravity method
Physical property is Density
Gravity method
Depth of investigation is: All
Gravity method
Changes in strength of geomagnetic field
Magnetic method
Physical property is magnetic susceptibility
Magnetic method
Depth of investigation is from surface to curie isotherm
Magnetic method
Travel times of reflected or refracted seismic waves
Seismic method
Physical property is density and elastic moduli
Seismic method
Depth of investigation is from <50m to ~2km (for multi-channel surveys)
Seismic method
Resistance, potential differences
Electrical method
Physical property is conductivity or resistivity
Electrical method
Depth of investigation is up to ~2km
Electrical method
Reflection of electromagnetic waves
Ground penetrating radar method
Physical property is relative dielectric permittivity
Ground penetrating radar method
Depth of investigation is <50km
Ground penetrating radar method
Chargeability is 13.4
pyrite
Chargeability is 13.2
Chalcocite
Chargeability is 12.3
Copper
Chargeability is 11.2
Graphite
Chargeability is 9.4
Chalcopyrite
Chargeability is 3.7
Galena
Chargeability is 2.2
Magnetite
Chargeability is 2000-3000
20% sulfides
Chargeability is 1000-2000
8-20% sulfides
Chargeability is 500-1000
2-8% sulfides
Chargeability is 100-500
Volcanic rocks/ Sandstone
Chargeability is 10-50
Granite
Chargeability is 10-20
Limestone
Physical property is 1.5 Vp (km/s)
Water
Physical property is 5.8 Vp (km/s)
Iron
Physical property is 5.5 - 6.0 Vp (km/s)
Granite
Physical property is 6.5-7.0 Vp (km/s)
Gabbro
Physical property is 2.0-6.0 Vp (km/s)
Sandstone/ Limestone
Physical property is 4.0-5.5 Vp (km/s)
Gneiss
Physical property is 2.3 - 4.7 Vp (km/s)
Slate
Degree to which substance may be magnetized.
Magnetic susceptibility
Mass per unit volume
Density
Amount of deformation of a material upon removal of the stresses; elastic moduli.
Elasticity
Ability of a material to conduct electrical current (resistivity is the inverse of _________)
Conductivity
Ability of a material to transmit radar energy to depth.
Relative dielectric permittivity
Unit of magnetic field strength is _________
Gauss = 10^-4T; Gamma = nT
Unit of gravity density is ___________.
kg/m3; g/cm3
Unit of seismic is __________.
m/sec; km/sec; m/msec
The unit of electric resistivity is ________ and conductivity is ___________.
resistivity: ohm-meters
conductivity: mho/m = seismens/m (S/m)
Vertical contrasts in physical property vis-a-vis lateral physical property contrast.
Geophysical anomaly
Magnetic low is an indicator of __________.
hydrothermal alteration
Magnetic high is an indicator of ____________.
potassic alteration
Why would you conduct magnetic survey for a porphyry copper deposit?
Magnetic high - presence of magnetite
Magnetic low - alteration destroyed magnetite
Magnetic susceptibility is -0.01.
Quartz/ Rocksalt
Magnetic susceptibility is -0.001 - 0.01
Calcite
Magnetic susceptibility is 0.4
Sphalerite/ Chalcopyrite
Magnetic susceptibility is 0.05 - 5.
Pyrite
Magnetic susceptibility is 0.5 - 35
Hematite
Magnetic susceptibility is 300 - 3500
Ilmenite
Magnetic susceptibility is 1200 - 19,200
Magnetite
Magnetic susceptibility is 0 - 3
Limestone
Magnetic susceptibility is 0 - 20
Sandstone
Magnetic susceptibility is 0.3 - 3
Schist
Magnetic susceptibility is 0.1 - 25
Gneiss
Magnetic susceptibility is 0 - 35
Slate
Magnetic susceptibility is 0 - 50
Granite
Magnetic susceptibility is 1-90
Gabbro
Magnetic susceptibility is 0.2 - 175
Basalt
Magnetic susceptibility is 90 - 200
Peridotite