EXPLORATION TECHNIQUES

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EXPLORATION TECHNIQUES

• Virginia McLemore

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WHAT ARE THE OBJECTIVES IN EXPLORATION?
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WHAT ARE THE OBJECTIVES IN EXPLORATION?

• Establish baseline/background conditions
• Find alteration zones
• Find ore body
• Determine if ore can be mined or leached
• Determine if ore can be processed
• Determine ore reserves
• Locate areas for infrastructure/operations
• Environmental assessment
• Further understand uranium deposits
• Refine exploration models

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STEPS

• Define uranium deposit model
• Select area
• Collect and interpret regional data
• Define local target area
• Field reconnaissance
• Reconnaissance drilling
• Bracket drilling
• Ore discovery

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(No Transcript)
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Select Area

• How do we select an area to look for uranium?

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Select Area

• How do we select an area to look for uranium?
• Areas of known production
• Areas of known uranium occurrences
• Favorable conditions for uranium

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COLLECT DATA

• Historical data
• State, federal surveys
• University research programs
• Archives
• Company reports
• Web sites
• Published literature
• Prospectors

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Methods

• Magnetic surveys
• Electromagnetic (EM, EMI), electromagnetic
  sounding
• Direct current (DC)
• GPR (Ground penetrating radar potential)
• Seismic
• Time-domain electromagnetic (TEM)
• Controlled source audio-magnetotellurics (CSAMT)
• Radiometric surveys
• Induced polarization (IP)

• Spontaneous potential (SP)
• Borehole geophysics
• Satellite imagery
• Imagery spectrometry
• ASTER (Advanced space-borne thermal emissions
  reflection radiometer)
• AVIRIS
• PIMA
• SFSI
• LIBS
• SWIR
• Multispectral

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REMOTE SENSING
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Remote Sensing Techniques

• Digital elevation model (DEM)
• Landsat Thematic Mapper (TM)
• ASTER (Advanced Spaceborne Thermal Emission and
  Reflection Radiometer)
• Hyperspectral remote sensing (spectral bands, 14
  and gt100 bands)
• NOAA-AVHRR (National Oceanic and Atmospheric
  Administration - Advanced Very High Resolution
  Radiometer

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Remote sensing is the science of remotely
acquiring, processing and interpreting spectral
information about the earths surface and
recording interactions between matter and
electromagnetic energy.
SATELLITE
LANDSAT
AIRBORNE
HYPERSPECTRAL
GROUND
Field Spectrometer
Alumbrera, Ar
Data is collected from satellite and airborne
sensors. It is then calibrated and verified
using a field spectrometer.
CUPRITE, NV
Goldfield, NV
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Sunlight Interaction with the Atmosphere and the
Earths Surface
Data is collected in contiguous channels by
special detector arrays. Collection is done at
different spectral and spatial resolutions
depending on the type of sensor. Each
spatial element is called a pixel. Pixel size
varies from 1/2 meters in some hyperspectral
sensors to 30 meters in Landsat and ASTER, which
are multispectral. Sensor spatial differences
and band configurations are shown below.
ELECTROMAGNETIC SPECTRUM
The electromagnetic spectrum is a distribution of
energy over specific wavelengths. When this
energy is emitted by a luminous object, it can be
detected over great distances. Through the use of
instrumentation, the technique detects this
energy reflected and emitted from the earths
surface materials such as minerals, vegetation,
soils, ice, water and rocks, in selected
wavelengths. A proportion of the energy is
reflected directly from the earths surface.
Natural objects are generally not perfect
reflectors, and therefore the intensity of the
reflection varies as some of the energy is
absorbed by the earth and not reflected back to
the sensor. These interactions of absorption and
reflection form the basis of spectroscopy and
hyperspectral analysis.
Source Bob Agars
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HYPERSPECTRAL IMAGING SPECTROSCOPY
Imaging spectroscopy is a technique for obtaining
a spectrum in each position of a large array of
spatial positions so that any one spectral
wavelength can be used to make a coherent image
(data cube). Imaging spectroscopy for remote
sensing involves the acquisition of image data in
many contiguous spectral bands with an ultimate
goal of producing laboratory quality reflectance
spectra for each pixel in an image (Goetz,
1992b). The latter part of this goal has not yet
been reached. The major difference from Landsat
is the ability to detect individual mineral
species and differentiate vegetation species.
Source CSIRO
This "image cube" from JPL's Airborne
Visible/Infrared Imaging Spectrometer (AVIRIS)
shows the volume of data returned by the
instrument. AVIRIS acquired the data on August
20, 1992 when it was flown on a NASA ER-2 plane
at an altitude of 20,000 meters (65,000 feet)
over Moffett Field, California, at the southern
end of the San Francisco Bay. The top of the
cube is a false-color image made to accentuate
the structure in the water and evaporation ponds
on the right. Also visible on the top of the
cube is the Moffett Field airport. The sides of
the cube are slices showing the edges of the top
in all 224 of the AVIRIS spectral channels. The
tops of the sides are in the visible part of the
spectrum (wavelength of 400 nanometers), and the
bottoms are in the infrared (2,500 nanometers).
The sides are pseudo-color, ranging from black
and blue (low response) to red (high response).
Of particular interest is the small region of
high response in the upper right corner of the
larger side. This response is in the red part of
the visible spectrum (about 700 nanometers), and
is due to the presence of 1-centimeter-long
(half-inch) red brine shrimp in the evaporation
pond.
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Exploration Techniques

• Geologic Mapping
• Leann M. Giese
• February 7, 2008

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Mining Life Cycle (Spiral?)

• In the mine life cycle, geologic mapping falls
  under Exploration, but it effects all of the life
  cycles

Closure
Ongoing Operations
Post-Closure
Temporary Closure
Exploration
Future Land Use
Mine Development
Operations
?????
(McLemore, 2008)
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What is geologic mapping?

• A way to gather present geologic data. (Peters,
  1978)
• Shows how rock soil on the earths surface is
  distributed. (USGS)
• Are used to make decisions on how to use our
  water, land, and resources. (USGS)
• Help to come up with a model for an ore body.
  (Peters, 1978)

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What is Geologic Mapping? (continued)

• To better understand the geological features of
  an area
• Predict what is below the earths surface
• Show other features such as faults and strike and
  dips.
• (USGS (a))

Figure 1. Graphic representation of typical
information in a general purpose geologic map
that can be used to identify geologic hazards,
locate natural resources, and facilitate land-use
planning. (After R. L. Bernknopf et al., 1993)
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Simplified Geologic Map of New Mexico
Topographic Map of the Valle Grande in the Jamez
Mountains
(from NMBGMR).
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Geologic Mapping Equipment

• Field notebooks
• Rock hammer
• Hand Lens (10x or Hastings triplet)
• Pocket knife
• Magnet
• Clip board
• Pencils (2H-4H) and Colored Pencils
• Rapidograph-type pens and Markers
• Scale-protractor (10 and 50 or 11000 and 14000)
• Belt pouches or field vest
• 30 meter tape measurer
• Brunton pocket transit
• GPS/Altimeters
• Camera
• (Compton,1985)

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Mapping types

• Aerial photographs
• Topographical bases
• Pace and Compass
• Chains

(Compton, 1985)
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Map scales

• A ratio that relates a unit of measure on a map
  to some number of the same units of measure on
  the earth's surface.
• A map scale of 125,000 tells us that 1 unit of
  measure represents 25,000 of the same units on
  the earth's surface. One inch on the map
  represents 25,000 inches on the earth's surface.
• One meter or one yard or one kilometer or one
  mile on a map would represent 25,000 meters or
  yards or kilometers or miles, respectively, on
  the earth's surface.

(from USGS (b))
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Map scales (continued)
(from USGS (b))
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What to do first?

• Most mineral deposits are found in districts
  where there has been mining before, an earlier
  geologist has noticed something of importance
  there, or a prospector has filed a mineral claim
• Literature Search
• Library (University, Government, Engineering, or
  Interlibrary loans)
• State and National bureaus of mines and
  geological surveys (may have drill core, well
  cuttings, or rock samples available to inspect)
• Mining company information
• Maps and aerial photographs
• Is the information creditable? Is it worth
  exploring?

(Peters, 1978)
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Where to go from here?

• Mapping is costly and time consuming, so an area
  of interest needs to be defined
• Reconnaissance helps narrows a region to a
  smaller area of specific interest
• Reconnaissace in the U.S. usually begins at
  1250,000-scale
• This large scale mapping can zone-in on areas of
  interest that can then be geologically mapped in
  detail (this is usually done on a 110,000 or
  112,000-scale).
• Individual mineral deposits can be mapped at a
  12,000 or 12,400-scale to catch its smaller
  significant features.
• (Peters, 1978)

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Detailed Geological Mapping

• When mapping, we want to be quick, because time
  is money, but not too quick as to make a mistake
  or miss something.
• Along with mapping occurs drilling, trenching,
  geophysics, and geochemistry
• Samples can be analyzed for Uranium
  concentrations. This gives a better idea of where
  to explore more or drill in an area.

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Uranium Deposit Types

• Unconformity-related deposits
• Metasedimentary rocks (mineralisation, fauletd,
  and brecciated) below and Proterozoic SS. Above
  (pitchblende)
• Breccia complex deposits
• Hematite-rich breccia complex (iron, copper,
  gold, silver, REE)
• Sandstone deposits
• Rollfront deposits, tabular deposits,
  tectonic/lithologic deposits
• Surficial deposits
• Young, near-surface uranium concentrations in
  sediments or soils (calcite, gypsum, dolomite,
  ferric oxide, and halite)
• Volcanic deposits
• Acid volcanic rocks and related to faults and
  shear zones within the volcanics (molybdenum
  fluorine)
• Intrusive deposits
• Associated with intrusive rocks (alaskite,
  granite, pegmatite, and monzonites)
• Metasomatite deposits
• In structurally-deformed rocks altered by
  metasomatic processes (sodium, potassium or
  calcium introduction)

(Lambert et al., 1996)
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Uranium Deposit Types (continued)

• Metamorphic deposits
• Ore body occurs in a calcium-rich alteration zone
  within Proterozoic metamoprphic rocks
• Quartz-pebble conglomerate deposits
• Uranium recovered as a by-product of gold mining
• Vein deposits
• Spatially related to granite, crosscuts
  metamorphic or sedimentary rocks (coffinite,
  pitchblende)
• Phosphorite deposits
• Fine-grained apatie in phosphorite horizons mud,
  shale, carbonates and SS. interbedded
• Collapse breccia deposits
• Vertical tubular-like deposits filled with coarse
  and fine fragments
• Lignite
• Black shale deposits
• Calcrete deposits
• Uranium-rich granites deeply weathered,
  valley-type
• Other

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Some Minerals Associated with Uranium

• Uraninite (UO2)
• Pitchblende (U2O5.UO3 or U3O8)
• Carnotite (uranium potassium vanadate)
• Davidite-brannerite-absite type uranium titanates
• Euxenite-fergusonite-smarskite group
• Secondary Minerals
• Gummite
• Autunite
• Saleeite
• Torbernite
• Coffinite
• Uranophane
• Sklodowskite

(Lambert et al., 1996)
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Example of exploring a sandstone Uranium deposit

• When looking for a sandstone-type uranium deposit
  in an area that has had a radiometric survey, our
  first place to focus in on the areas where
  radioactivity appears to be associated with SS.
  Beds. (We will disregard potassium anomalies,
  below-threshold readings, unexplained areas, and
  radioactive noise.)
• We will then map the radioactive SS. units and
  other associations with our model of a SS.
  uranium deposit.
• We will look for poorly sorted, medium to coarse
  grained SS. beds that are associated with
  mudstones or shales.
• Detailed mapping of outcrops on a smaller scale
  is now appropriate. Stratigraphic sections can
  be measured and projected to covered areas.
• Other radioactive areas that were disregarded may
  be given a second look for other possibilities
  for further investigations.

(Peters, 1978)
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References

• Compton, R. R. (1985). Geology in the Field.
  United States of America and Canada John Wiley
  Sons, Inc.
• Bernknopf, R. L., et al., 1993Societal Value of
  Geologic Maps, USGS Circular 1111.
• Lambert,I., McKay, A., and Miezitis, Y. (1996)
  Australia's uranium resources trends, global
  comparisons and new developments, Bureau of
  Resource Sciences, Canberra, with their later
  paper Australia's Uranium Resources and
  Production in a World Context, ANA Conference
  October 2001. http//www.uic.com.au/nip34.htm
  (accessed February 6, 2008).
• McLemore, V. T. Geology and Mining of
  Sediment-Hosted Uranium Deposits What is
  Uranium?. Lecture, January 30, 2008 pp. 1-26.
• New Mexico Bureau of Geology and Mineral
  Resources. http//geoinfo.nmt.edu/publications/map
  s/home.html (accessed February 1, 2008).
• Peters, W. C. (1978). Exploration and Mining
  Geology. United States of America and Canada
  John Wiley Sons, Inc.
• U.S. Geological Survey (a).
• http//ncgmp.usgs.gov/ncgmpgeomaps (accessed
  February 1, 2008).
• U.S. Geological Survey (b). http//id.water.usgs.g
  ov/reference/map_scales.html (accessed February
  6, 2008).

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GEOPHYSICAL TECHNIQUES
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Gravity and magnetic exploration

• Pedram Rostami

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Gravity TechniquesIntroduction

• Lateral density changes in the subsurface cause a
  change
• in the force of gravity at the surface.
• The intensity of the force of gravity due to a
  buried mass difference (concentration or void) is
  superimposed on the larger force of gravity due
  to the total mass of the earth.
• Thus, two components of gravity forces are
  measured at the earths surface first, a general
  and relatively uniform component due to the total
  earth, and second, a component of much smaller
  size which varies due to lateral density changes
  (the gravity anomaly).

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Applications

• By very precise measurement of gravity and by
  careful correction for variations in the larger
  component due to the whole earth, a gravity
  survey can sometimes detect natural or man-made
  voids, variations in the depth to bedrock, and
  geologic structures of engineering interest.
• For engineering and environmental applications,
  the scale of the problem is generally small
  (targets are often from 1-10 m in size)
• Station spacings are typically in the range of
  1-10 m
• Even a new name, microgravity, was invented to
  describe the work.

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• Gravity surveys are limited by ambiguity and the
  assumption of homogeneity
• A distribution of small masses at a shallow depth
  can produce the same effect as a large mass at
  depth.
• External control of the density contrast or the
  specific geometry is required to resolve
  ambiguity questions.
• This external control may be in the form of
  geologic plausibility, drill-hole information, or
  measured densities.
• The first question to ask when considering a
  gravity survey is For the current subsurface
  model, can the resultant gravity anomaly be
  detected?.
• Inputs required are the probable geometry of the
  anomalous region, its depth of burial, and its
  density contrast.
• A generalized rule of thumb is that a body must
  be almost as big as it is deep.

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Rock Properties

• Values for the density of shallow materials are
  determined from laboratory tests of boring and
  bag samples. Density estimates may also be
  obtained from geophysical well logging
• Table 5-1 lists the densities of representative
  rocks.
• Densities of a specific rock type on a specific
  site will not have more than a few percent
  variability as a rule (vuggy limestones being one
  exception). However, unconsolidated materials
  such as alluvium and stream channel materials may
  have significant variation in density.

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Field Work General

• Up to 50 percent of the work in a microgravity
  survey is consumed in the surveying.
• relative elevations for all stations need to be
  stablished to 1 to 2 cm. A firmly fixed stake or
  mark should be used to allow the gravity meter
  reader to recover the exact elevation.
• Satellite surveying, GPS, can achieve the
  required accuracy, especially the vertical
  accuracy, only with the best equipment under
  ideal conditions.
• High station densities are often required. It is
  not unusual for intervals of 1-3 m to be required
  to map anomalous masses whose maximum dimension
  is 10 m.

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Field Work General

• After elevation and position surveying, actual
  measurement of the gravity readings is often
  accomplished by one person in areas where solo
  work is allowed.
• t is necessary to improve the precision of the
  station readings by repetition.
• The most commonly used survey technique is to
  choose one of the stations as a base and to
  reoccupy that base periodically throughout the
  working day.
• The observed base station gravity readings are
  then plotted versus time, and a line is fitted to
  them to provide time rates of drift for the
  correction of the remainder of the observations.

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Interpretation

• Software packages for the interpretation of
  gravity data are plentiful and powerful.
• The geophysicist can then begin varying
  parameters in order to bring the calculated and
  observed values closer together.
• Parameters usually available for variation are
  the vertices of the polygon, the length of the
  body perpendicular to the traverse, and the
  density contrast. Most programs also allow
  multiple bodies.

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Magnetic MethodsIntroduction

• The earth possesses a magnetic field caused
  primarily by sources in the core.
• The form of the field is roughly the same, as
  would be caused by a dipole or bar magnet located
  near the earths center and aligned sub parallel
  to the geographic axis.
• The intensity of the earths field is customarily
  expressed in S.I. units as nanoteslas (nT) or in
  an older unit, gamma (g) 1 g 1 nT 10-3 µT.
  Except for local perturbations, the intensity of
  the earths field varies between about 25 and 80
  µT over the coterminous United States

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• Many rocks and minerals are weakly magnetic or
  are magnetized by induction in the earths field,
  and cause spatial perturbations or anomalies in
  the earths main field.
• Man-made objects containing iron or steel are
  often highly magnetized and locally can cause
  large anomalies up to several thousands of nT.
• Magnetic methods are generally used to map the
  location and size of ferrous objects.
  Determination of the applicability of the
  magnetics method should be done by an experienced
  engineering geophysicist.
• Modeling and incorporation of auxiliary
  information may be necessary to produce an
  adequate work plan.

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Theory

• The earths magnetic field dominates most
  measurementsz on the surface of the earth.
• Most materials except for permanent magnets,
  exhibit an induced magnetic field due to the
  behavior of the material when the material is in
  a strong field such as the earths.
• Induced magnetization (sometimes called magnetic
  polarization) refers to the action of the field
  on the material wherein the ambient field is
  enhanced causing the material itself to act as a
  magnet.
• The field caused by such a material is directly
  proportional to the intensity of the ambient
  field and to the ability of the material to
  enhance the local field, a property called
  magnetic susceptibility. The induced
  magnetization is equal to the product of the
  volume magnetic susceptibility and the inducing
  field of the earth

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Theory(continue)

• I k F
• k volume magnetic susceptibility (unitless)
• I induced magnetization per unit volume
• F field intensity in tesla (T)
• For most materials k is much less than 1 and, in
  fact, is usually of the order of 10-6 for most
  rock materials.
• The most important exception is magnetite whose
  susceptibility is about 0.3. From a geologic
  standpoint, magnetite and its distribution
  determine the magnetic properties of most rocks.
• There are other important magnetic minerals in
  mining prospecting, but the amount and form of
  magnetite within a rock determines how most rocks
  respond to an inducing field.
• Iron, steel, and other ferromagnetic alloys have
  susceptibilities one to several orders of
  magnitude larger than magnetite. The exception is
  stainless steel, which has a small susceptibility.

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• The importance of magnetite cannot be
  exaggerated. Some tests on rock materials have
  shown that a rock containing 1 percent magnetite
  may have a susceptibility as large as 10-3, or
  1,000 times larger than most rock materials.
• Table 6-1 provides some typical values for rock
  materials.
• Note that the range of values given for each
  sample generally depends on the amount of
  magnetite in the rock

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Theory(continue)

• Thus it can be seen that in most engineering and
  environmental scale investigations, the
  sedimentary and alluvial sections will not show
  sufficient contrast such that magnetic
  measurements will be of use in mapping the
  geology.
• However, the presence of ferrous materials in
  ordinary municipal trash and in most industrial
  waste does allow the magnetometer to be effective
  in direct detection of landfills.
• Other ferrous objects which may be detected
  include pipelines, underground storage tanks, and
  some ordnance.

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Field Work

• Ground magnetic measurements are usually made
  with portable instruments at regular intervals
  along more or less straight and parallel lines
  which cover the survey area.
• Often the interval between measurement locations
  (stations) along the lines is less than the
  spacing between lines.

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• The magnetometer is a sensitive instrument which
  is used to map spatial variations in the earths
  magnetic field.
• In the proton magnetometer, a magnetic field
  which is not parallel to the earths field is
  applied to a fluid rich in protons causing them
  to partly align with this artificial field.
• When the controlled field is removed, the
  protons precess toward realignment with the
  earths field at a frequency which depends on the
  intensity of the earths field. By measuring this
  precession frequency, the total intensity of the
  field can be determined.
• The physical basis for several other
  magnetometers, such as the cesium or
  rubidium-vapor magnetometers, is similarly
  founded in a fundamental physical constant. The
  optically pumped magnetometers have increased
  sensitivity and shorter cycle times (as small as
  0.04 s) making them particularly useful in
  airborne applications.

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• The incorporation of computers and non-volatile
  memory in magnetometers has greatly increased the
  ease of use and data handling capability of
  magnetometers.
• The instruments typically will keep track of
  position, prompt for inputs, and internally store
  the data for an entire day of work.
• Downloading the information to a personal
  computer is straightforward and plots of the
  days work can be prepared each night.

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• To make accurate anomaly maps, temporal changes
  in the earths field during the period of the
  survey must be considered. Normal changes during
  a day, sometimes called diurnal drift, are a few
  tens of nT but changes of hundreds or thousands
  of nT may occur over a few hours during magnetic
  storms.
• During severe magnetic storms, which occur
  infrequently, magnetic surveys should not be
  made. The correction for diurnal drift can be
  made by repeat measurements of a base station at
  frequent intervals.
• The measurements at field stations are then
  corrected for temporal variations by assuming a
  linear change of the field between repeat base
  station readings.

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• The base-station memory magnetometer, when used,
  is set up every day prior to collection of the
  magnetic data.
• The base station ideally is placed at least 100 m
  from any large metal objects or travelled roads
  and at least 500 m from any power lines when
  feasible.
• The base station location must be very well
  described in the field book as others may have to
  locate it based on the written description.

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• The value of the magnetic field at the base
  station must be asserted (usually a value close
  to its reading on the first day) and each days
  data corrected for the difference between the
  asserted value and the base value read at the
  beginning of the day.
• As the base may vary by 10-25 nT or more from day
  to day, this correction ensures that another
  person using the SAME base station and the SAME
  asserted value will get the same readings at a
  field point to within the accuracy of the
  instrument.

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Interpretation.

• Total magnetic disturbances or anomalies are
  highly variable in shape and amplitude they are
  almost always asymmetrical, sometimes appear
  complex even from simple sources
• One confusing issue is the fact that most
  magnetometers measure the total field of the
  earth no oriented system is recorded for the
  total field amplitude.
• The consequence of this fact is that only the
  component of an anomalous field in the direction
  of earths main field is measured.
• Figure 6-1 illustrates this consequence of the
  measurement system
• Anomalous fields that are nearly perpendicular to
  the earths field are undetectable

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• Additionally, the induced nature of the measured
  field makes even large bodies act as dipoles
  that is, like a large bar magnet.
• If the (usual) dipolar nature of the anomalous
  field is combined with the measurement system
  that measures only the component in the direction
  of the earths field, the confusing nature of
  most magnetic interpretations can be appreciated

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• To achieve a qualitative understanding of what is
  occurring, consider Figure in the next page.
• Within the contiguous United States, the
  magnetic inclination, that is the angle the main
  field makes with the surface, varies from 55- 70
  deg.
• The figure illustrates the field associated with
  the main field, the anomalous field induced in a
  narrow body oriented parallel to that field, and
  the combined field that will be measured by the
  total-field magnetometer.
• The scalar values which would be measured on the
  surface above the body are listed.
• From this figure, one can see how the total-field
  magnetometer records only the components of the
  anomalous field.

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Uranium Exploration
59
Magnetic

• Magnetic. Palaeochannel magnetic (either positive
  or negative) anomalies may be defined if
  high-resolution surveys are used and if there are
  sufficient magnetic minerals in the channels or
  measurable magnetic contrast between the channel
  sediments and bedrock.
• Cainozoic palaeochannels are not usually visible
  on regional magnetic data, as they are relatively
  shallow features, but careful use of detailed
  surveys may assist in locating channel deposits.

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Gravity

• Gravity anomalies in the earths gravitational
  field can in some cases be used to define the
  thickness and extent of the fluvial sediments,
  and hence palaeochannels, due to the contrast in
  density between the sediments and fresh bedrock.
  For example, the density of sand and clay is
  1.8g/cc and granitic basement is 2.7 g/cc
  (Berkman 1995).

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Hoover et al. (1992)
62
Hoover et al. (1992)
63
GEOCHEMICAL SAMPLING

• Ground water
• Surface water
• Stream sediments
• Soils
• Biological
• Ore samples
• Radon
• Track etch (identify radiaoactivity)

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Surface Sampling in Exploration

• Introduction
• Sample? Sampling?
• Sampling Programs
• Bias and Error in Sampling
• Quality Control
• Surface Sampling Methods
• Sample Handling
• Documentation Requirements
• Conclusion
• References

65
Introduction

• Sampling methods vary from simple grab samples on
  existing exposures to sophisticated drilling
  methods.
• As a rule, the surface of the mineralization is
  obscured by various types of overburden, or it is
  weathered and leached to some depth, thereby
  obscuring the nature of the mineralization."

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What is a sample? What is sampling?

• A sample is a finite part of a statistical
  population whose properties are studied to gain
  information about the whole (Webster, 1985).
• Sampling is the act, process, or technique of
  selecting a suitable sample,
• or
• a representative part of a population for the
  purpose of determining parameters or
  characteristics of the whole population.
• Why Sample?

67
Sampling Programs

• Reconnaissance
• (1) check status of land ownership, (2)
  physical characteristics of area, (3) mining
  history of the area.
• Field inspection
• surface grab sampling over all exposures of
  gravel, few seismic cross section, geobotanical
  study, and survey for old workings.
• Sampling Plan
• Special Problems Associated with Sampling
• Sample Processing or Washing
• Data Processing
• Data processing consists of record keeping,
  reporting values, and assay procedures.

68
Sampling Plan

• Defining the population of concern
• Specifying a sampling frame, a set of items or
  events possible to measure
• Specifying a sampling method for selecting items
  or events from the frame
• Determining the sample size
• Implementing the sampling plan
• Sampling and data collecting
• Reviewing the sampling process

69
Sample Size

• The question of how large a sample should be is a
  difficult one. Sample size can be determined by
  various constraints such as
• Cost.
• nature of the analysis to be performed
• the desired precision of the estimates one wishes
  to achieve
• the kind and number of comparisons that will be
  made,
• the number of variables that have to be examined
  simultaneously

70
Bias and Error in Sampling

• A sample is expected to mirror the population
  from which it comes, however, there is no
  guarantee that any sample will be precisely
  representative of the population from which it
  comes.
• biased
• when the selected sample is systematically
  different to the population.
• The sample must be a fair representation of the
  population we are interested in.
• Random errors
• The sample size may be too small to produce a
  reliable estimate.
• There may be variability in the population,
  the greater the variability the larger the sample
  size needed.

71
Quality Control

• Responsibility for maintaining consistency and
  ensuring collection of data of acceptable and
  verifiable quality through the implementation of
  a QA/QC program.
• All personnel involved in data collection
  activities must have the necessary education,
  experience, and skills to perform their duties.

72
Selecting Methods and Equipment

• Soil and sediment samples may be collected
  using a variety of methods and equipment
  depending on the following
• type of sample required
• site accessibility,
• nature of the material,
• depth of sampling,
• budget for the project,
• sample size/volume requirement,
• project objectives

73
Surface Sampling Methods

• Near-surface samples can be collected with a
  spade, scoop, or trowel.
• Sampling at greater depths or below a water
  column may require a hand auger, coring device,
  or dredge.
• As the sampling depth increases, the use of a
  powered device may be necessary to push the
  sampler into the soil or sediment layers.

74
Sampling Equipments

• Tube Sampler
• Churn Drills
• Tube Corers
• Hand Driven Split-Spoon Core Sampler
• Hand-Dug Excavations
• Backhoe Trenches Bulldozer Trenches
• Other Machine-Dug Excavations
• Augers
• Bucket or Clamshell Type Excavators

75
Surface Sampling
Floodplain sampling in southwestern Finland
(Photo Reijo Salminen, GTK).
Figure 13. Wet sieving of a stream sediment
sample in the UK (Photo Fiona Fordyce, BGS from
Salminen and Tarvainen et al. 1998,
76
Surface Sampling
Figure 16. Humus sampling in Finland using
cylindrical sampler, and the final humus sample.
(Photographs Timo Tarvainen, GTK).
77
Surface Sampling
The alluvial horizons at the floodplain sediment
sampling site 29E05F3, France.
The soil sample pit at the site 41E10T3, Finland.
78
Sample Handling

• Samples should be preserved to minimize chemical
  or biological changes from the time of collection
  to the time of analysis. Keep samples in air
  tight containers. Sediment samples should also be
  stored in such a way that the anaerobic condition
  is preserved by minimizing headspace.
• If several sub samples are collected, soil and
  sediment samples should be placed in a clean
  stainless steel mixing pan or bowl and thoroughly
  homogenized to obtain a representative composite
  sample.

79
Sample Handling

• Sample Label Information
• Label or tag each sample container with a unique
  field identification code. If the samples are
  core sections, include the sample depth in the
  identification.
• Write the project name or project identification
  number on the label.
• Write the collection date and time on the label.
• Attach the label or tag so that it does not
  contact any portion of the sample that will be
  removed or poured from the container.
• Record the unique field identification code on
  all other documentation associated with the
  specific sample container.
• Ensure all necessary information is transmitted
  to the laboratory.

80
Documentation

• Thorough documentation of all field sample
  collection and processing activities is necessary
  for proper interpretation of results. All sample
  identification, chain-of-custody records,
  receipts for sample forms, and field records
  should be recorded using waterproof, non-erasable
  ink in a bound waterproof notebook.
• All Procedures must be documented.

81
Sample Data

• From Sampling to Production Pyramid

3RD FLOOR
2ND FLOOR
1ST FLOOR
FOUNDATION
82
Conclusion

• There are many ways to sample and many methods to
  calculate the value of a deposit. It is important
  to remember to use care in sampling and to select
  the method that best suits the type of occurrence
  that is being sampled.

83
References

• Journal of the Mississippi Academy of Sciences,
  v. 47, no. 1, p. 42.
• http//www.evergladesplan.org/pm/pm_docs/qasr/qasr
  _ch_07.pdf
• http//www.gtk.fi/publ/foregsatlas/article.php?id
  10
• http//www.socialresearchmethods.net/tutorial/Mugo
  /tutorial.htm
• http//www.policyhub.gov.uk/evaluating_policy/mage
  nta_book/chapter5.asp

84

• Thank you

85
Radiometric Survey
Shantanu Tiwari Mineral Engineering Feb 07, 2008
86
Outline

• Introduction to Radiometric Survey
• Radioactivity
• Use of Radiometric Survey
• Process
• Case Study
• Conclusion
• Refrences

87
Introduction

• Radiometrics Measure of natural radiation in
  the Earths surface.
• 2. Also Known as Gamma- Ray Spectrometry (why?).
• 3. Who uses it?- Geologists and Geophysicists.
• 4. Also useful for studying geomorphology and
  soils.

88
Radioactivity

• 1. Process in which, unstable atom becomes
  stable through the process of decay of its
  nucleus.
• Energy is released in the form of radiation
• (a) Alpha Particle (or helium nuclei) - Least
  Energy- Travels few cm of air.
• (b) Beta Particle (or electrons)- Higher Energy-
  Travels upto a meter in air
• (c) Gamma Rays- Highest Energy- Travels upto 300
  meters in air.

89
Radioactivity (Contd.)

• Energy of Gamma Ray is characteristic of the
  radioactive element it came from.
• Gamma Rays are stopped by water and other
  molecules (soil Rock).
• A radiometric survey measures the spatial
  distribution of three radioactive elements
• (a) Potassium
• (b)Thorium
• (c) Uranium
• 6. The abundance of these elements are measured
  by gamma ray detection.

90
Use of Radiometric Survey

• Radioactive elements occur naturally in some
  minerals.
• Energy of Gamma Rays is the characteristic of the
  element.
• Measure the energy of Gamma Ray- Abundance.

91
Process

• How we do radiometric survey?- By measuring the
  energy of Gamma Rays.
• Can be measure on the ground or by a low flying
  aircraft.
• Gamma Rays are detected by Spectrometer.
• Spectrometer- Counts the number of times each
  Gamma Ray of particular energy intersects it.

92
Process
93
Process

• The energy spectrum measured by a spectrometer is
  in MeV.
• Range- 0 to 3 MeV.
• The number of Gamma Ray counts across the whole
  spectrum is referred as the total count (TC).

94
Process
Number of Gamma Rays (per second)
Energy of Gamma Rays
95
Process
High
Low
96
Case Study
Gold Canyon Inc. (USA)- Bear Head Uranium
Project Bear Head Uranium Project- Red Lake
Mining Camp(north-west Ontario) Covers a 23 km
strike-length of Bear Head Fault Zone 0.05 U3O8
97
Conclusion

• Good Technique
• Large Area.
• Better for plane areas.

98
References

• http//www.goldcanyon.ca/
• Suzanne Haydon from the Geological Survey of
  Victoria (Aus).

99
Thank you
100
GROUND GEOPHYSICS
101
EXPLORATION TECHNIQUES BY METALLURGICAL SAMPLING

• GERTRUDE AYAKWAH
• MINERAL ENGINEERING DEPARTMENT
• NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY
• LEROY PLACE
• SOCORRO NM
• February, 7th, 2008

102
Outline

• Introduction
• Purpose
• Sampling
• Sample Preparation
• Types of Metallurgical Sampling
• Geochemical Analysis
• Assay Techniques
• Conclusion
• References

103
Introduction

• Exploration geology is the process and science of
  locating valuable mineral or petroleum which has
  a commercial value. Mineral deposits of
  commercial value are called ore bodies
• The goal of exploration is to prove the existence
  of an ore body which can be mined at a profit
• This process occurs in stages, with early stages
  focusing on gathering surface data which is
  easier to acquire and later stages focusing on
  gathering subsurface data which includes drilling
  data, detailed geophysical survey data and
  metallurgical analysis

104
Purpose

• The purpose of this presentation is to discuss
  metallurgical sampling in exploration geology

105
Soil and Stream Sample Preparation

• Samples are reduced and homogenized into a form
  which can easily be handled by analytical
  personnel
• Soil and stream sediment samples are usually
  sieved so that particles larger than fine sand
  are removed.
• The fine particles are mixed and a portion is
  removed for chemical analysis

106
Rock Sample Preparation

• Rock samples are treated in a multi-step
  procedure
• Rocks, cuttings, or core are first crushed to
  about pea-size in a jaw crusher, then passed
  through a secondary crusher to reduce the size
  further - usually 1/10 inch
• This crushed sample is mixed, split in a riffle
  splitter and reduced to about one-half pound or
  250 grams. This 250 grams is placed in a
  pulverizer where it is reduced further to -150
  mesh for analysis

107
Metallurgical Sampling

• Types
• Geochemical Analysis
• Assay Techniques

108
Geochemical Analysis

• Involves dissolution of approximately one gram of
  sample by a strong acid
• The solution which contains most of the base
  metals is aspirated into a flame as in atomic
  absorption spectroscopy (AAS) or into an
  inductively coupled (ICP)
• AAS measures one element at a time to a normal
  sensitivity of about 1 ppm

109
Geochemical Analysis (Contd)

• Whilst ICP 20 measure more elements at a time
  to ppm levels
• The technique is low-cost, rapid, reasonably
  precise and can be more accurate if the method is
  controlled by standards.
• However accuracy is minor importance in
  geochemistry as the exploration geologist seeks
  patterns rather than absolute concentration
• Hence making geochemical analysis methods are
  considered to be indicators of mineralization
  rather than absolute measurement of
  mineralization.

110
Assay Techniques

• Wet Chemistry
• Fire Assay
• Aqua Regia Acid Digestion

111
Assay Techniques

• Assay procedures uses accurate representation of
  the mass of the sample being analyzed than in
  geochemical analytical techniques.

112
Wet Chemistry

• It's just an informal term referring to
  chemistry done in a liquid phase. When chemists
  talk about doing "wet chemistry," they mean stuff
  in a lab with solvents, test tubes, beakers, and
  flasks (Richard E. Barrans Jr., Ph.D)
• It utilizes a physical measurement, either the
  color of a solution, the weight or volume of a
  reagent, or the conductivity of a solution after
  a specific reaction
• It is a preferred technique to determine element
  concentration in ore samples

113
Fire Assay

• It is used to analyzed precious metals in rock
  or soil
• Assay ton portion of the sample is put into a
  crucible and mixed with variety of chemical (lead
  oxide)
• The mixture is fused at high temperature
• During fusion, beads of metallic lead are
  released into the molten mixture

114
Fire Assay

• The lead particles scavenge the precious metals
  and sink to the bottom of the crucible due to the
  difference in density between lead and the
  siliceous component of the sample known as slag.
• On completion, the molten mixture is poured into
  a mold and left to solidify
• After cooling, the slag is removed from the lead
  and the lead bottom is transferred into a small
  crucible known as cupel and placed back into a
  furnace

115
Fire Assay

• The lead is absorbed by the cupel leaving a bead
  of the precious metals at the bottom of the cupel
• Gold and silver is measured by weighing the bead
  on a balance
• Silver is dissolved in nitric acid and the bead
  is weighed again to determine the undissolved
  gold
• Silver is calculated by the difference

116
Aqua Regia Acid Digestion

• The same procedure is used as in fire assay but
  different method of measuring gold and silver
• Atomic absorption is used to measure gold and
  silver
• Other forms of measurement include neutron
  activation analysis and flameless atomic
  absorption

117
Conclusion

• Geochemical analysis is considered to be
  indicators of mineralization during the earlier
  stages of exploration
• Assay techniques is used to determine absolute
  measurement of mineralization
• It also determines if the ore deposit can be
  processed by conventional milling or in situ
  leaching or some other way

118
References

• http//www.alsglobal.com/Mineral/ALSContent.aspx?k
  ey31metallics
• http//www.amebc.ca/primer3.htmsampling
• http//www.newton.dep.anl.gov/askasci/chem00/chem0
  0868.htm

119
DRILLING
120
DRILLING
Samuel Nunoo New Mexico Bureau of Geology and
Mineral Resources New Mexico Institute of Mining
and Technology, Socorro, NM 7TH FEBRUARY 2008
121
Outline

• Introduction
• Purpose
• Types

122
Introduction
123

• Drilling is the process whereby rigs or hand
  operated tools are used to make holes to
  intercept an ore body.

• Drilling is the ultimate stage in exploration.

124
Purpose
125

• The purpose of drilling is
• To define ore body at depth
• To access ground stability (geotechnical)
• To estimate the tonnage and grade of a discovered
  mineral deposit
• To determine absence or presence of ore bodies,
  veins or other type of mineral deposit

126
Types
127

• Drilling is generally categorized into 2 types
• Percussion Drilling
• This type of drilling is whereby a hammer
• beats the surface of the rock, breaks it into
  chips.
• -Reverse Circulation Drilling (RC)
• Rotary Drilling
• This is the type of drilling where samples are
  recovered by rotation of the drill rod without
  percussion of a hammer.
• - Diamond Drilling
• - Rotary Air Blast (RAB)
• - Auger Drilling

128

• Percussion Drilling
• Reverse Circulation Drilling (RC)
• This type of drilling involves the use of high
  pressure compressors, percussion hammers that
  recover samples even after the water table.
• The end of the hammer is a tungsten carbide bit
  that breaks the rock with both percussion and
  rotary movement .This mostly follows a RAB
  intercept of an ore body.
• The air pressure of a RC rig can be increased by
  the use of a booster. This allows for deeper
  drilling.
• Samples are split by special sample splitter that
  is believed to pulverize the samples. This is
  done to avoid metal concentrations at only
  section of the sample. Contamination is checked
  by cleaning the splitter after every rod change
  either by brush or high air pressure from rigs
  air hose.
• RC drilling is mostly followed by diamond
  drilling to confirm some of the RC drilling ore
  intercept.
• This type of drilling is faster and cheaper than
  diamond drilling

129
http//www.midnightsundrilling.com/ reverse_circul
ation.html
130

• Rotary Drilling
• Rotary Air Blast Drilling (RAB)
• This type of drilling is common in green-field
  exploration and in mining pits.
• This drilling mostly confirms soil, trench or pit
  anomalies.
• It involves an air pressure drilling and ends as
  soon as it comes into contact with the water
  table because the hydrostatic pressure is more
  than the air pressure.
• Samples cannot be recovered after the water
  table is reached.
• Mostly a 4meter composite sampling is conducted.
  Every 25th sample is replicated to check accuracy
  of the laboratory analysis.
• RAB drilling in the mine is mostly done for blast
  holes.

131

• Rotary Drilling (Contd)
• Diamond Drilling
• This type of drilling uses a diamond impregnated
  bit that cuts the rock by rotation with the aid
  of slimy chemicals in solution such as
• - DD200, expan-coarse, expan-fine, betonite and
  sometimes mapac A and B for holes stability.
• Drill sample are recovered as cores sometimes
  oriented for the purpose of attitude measurement
  such as dip and dip directions of joints,
  foliation, lineation, veins.
• Sampling involves splitting the core into 2
  equal halves along the point of curvature of
  foliations or along orientation lines. One half
  is submitted to the lab for analysis and the
  other left in the core yard for future sampling
  if necessary.
• Standards of known assay values are inserted in
  the samples to check laboratory accuracy. Mostly
  high grade standards are inserted at portions of
  low mineralization and low grade standards into
  portions of high mineralization.
• Diamond drilling is usually the last stage of
  exploration or when the structural behavior of an
  ore body is to be properly understood.

http//en.gtk.fi/ExplorationFinland/images/ritakal
lio_diamond_drilling.jpg
http//www.almadenminerals.com/geoskool/drilling.h
tml
http//www.istockphoto.com/file_closeup/
132

• Rotary Drilling (Contd)
• Auger Drilling
• This is a type of superficial drilling in soils
  and sediments. It could machine powered auger or
  hand powered (manual).
• It is mostly conducted at the very initial stage
  of exploration. That is after streams sediments,
  soils or laterite sampling.

http//www.geology.sdsu.edu/classes/geol552/sedsam
pling.htm
133
Thank You !!!!
134
GEOPHYSICAL LOGGING

• Frederick Ennin
• Department of Environmental
• Engineering

135
INTRODUCTION

• Geophysical logging is the use of physical,
  radiogenic or electromagnetic instruments lowered
  into a borehole to gather information about the
  borehole, and about the physical and chemical
  properties of rock, sediment, and fluids in and
  near the borehole
• Logging make record of something
• First developed for the petroleum industry by
  Marcel and Conrad Schlumberger in 1972.
• Schlumberger brothers first developed a
  resistivity tool to detect differences in the
  porosity of sandstones of the oilfield at
  Merkwiller-Perchelbrom, eastern France.
• Following the first electrical logging tools
  designed for basic permeability and porosity
  analysis other logging methods were developed to
  obtain accurate porosity and permeability
  calculations and estimations (sonic, density and
  neutron logs) and also basic geological
  characterization (natural radioactivity)

136
THE BOREHOLE ENVIRONMENT

• Different physical properties used to
  characterized the geology surrounding a
  borehole-drilling
• Physical properties porosity of gravel bed,
  density, sonic velocity and natural gamma signal
• Drilling can perturb the physical properties of
  the rock
• Factors influencing properties of rocks
• Porosity and water content
• Water chemistry
• Rock chemistry and minerology
• Degree of rock alteration and mineralisation
• Amount of evaporites
• Amount of humic acid
• Temperature

137
APPLICATIONS

• Became and is a key technology in the petroleum
  industry.
• In Mineral industry
• Exploration and monitoring grade control in
  working mines.
• Ground water exploration
• delineation of aquifers and producing zones
• In regolith studies
• provides unique insights into the
  composition, structure and variability of the
  subsurface
• Airborne electromagnetics
• used for ground truthing airborne
  geophysical data sets.

138
GEOPHYSICAL LOGGING METHODS

• MECHANICAL METHODS
• caliper logging
• sonic logging
• ELECTRICAL METHODS
• resistivity logging
• conductivity logging
• spontaneous potential logging
• induced polarisation
• RADIOATIVE METHODS
• natural gamma rays logging
• neutron porosity logging

139
MECHANICAL METHODS

• Caliper logging
• caliper used to measure the diameter of a
  borehole and its variability with depth.
• motion in and out from the borehole wall is
  recorded electrically and transmitted to surface
  recording equipment
• Sonic logging
• works by transmitting a sound through the rocks
  of the borehole wall
• Consists of two parts
• transmitter and receivers separated by
  rubber connector to reduce the amount of direct
  transmission of acoustic energy along the tool
  from transmitter to receiver

Crosshole Sonic Logging method with various kinds
of defects.  (Blackhawk GeoServices, Inc.)
140
ELECTRICAL METHODS

• Used in hard rock drilling
• Resistivity
• probes measure voltage drop by passing current
  through rocks
• Conductivity
• measurements induction probes via
  electromagnetic induction
• either in filled or dry holes
• Spontaneous potential (SP) - oldest E-method
• Measures small potential differences between down
  
• hole movable electrode and the surface earth
  connection
• Uses wide range of electrochemical and
  electrokinetic processes
• Induced polarisation (IP)
• Commonly used in surface prospecting for minerals
  and downhole applications.
• Uses transmitter loop to charge the ground with
  high current
• Transmitter loop turned off and voltage change
  with time is recorded.

141
(No Transcript)
142
RADIOATIVE METHODS

• Natural Gamma logging
• simplest, high penetration distance through
  rocks (1-2 m)
• Depends on initial energy level and rock density
• Records levels of naturally occurring gamma rays
  from rocks around borehole
• Signals from isotopes K-40, Th-232, U-238
• and daughter products-
• provides geologic information
• Sophisticated tools records emission from Bi-214
  and
• Tl-208 instead of U-238 and Th-232
• provides detailed chemistry of rocks in
  borehole
• Successfully used to search for roll front
  uranium deposit in regolith

Secondary uranium minerals associated with
Gulcheru quartzite from Gandi area, Andhra
Gamma-ray Borehoole Logging Probe (Lead
Shielded)/System for measurement of high-grade
ore in borehole
143
RADIOATIVE METHODS

• Neutron Porosity Logging
• Measures properties of the rock close to the
  borehole
• Very useful tool for measuring porosity
• free neutrons almost unknown in the Earth
• Neutron emission source
• Active source emits into rocks around a borehole
• Flux of neutrons recorded at the detector is used
  as indicator of conditions around surrounding
  rocks.
• Neutron logging provides data under a variety of
  conditions in cased and uncased boreholes. .

144
RADIOATIVE METHODS

• Effects
• Hydrogen Exception
• neutrons rapidly loose energy due to
  collision with hydrogen nuclei
• (thermal neutron-like diffusing gas)
• Changes in Diameter of boreholes affects results
• Calibrated with limestone samples of differing
  water-filled porosities (equivalent limestone
  porosities)
• Used in conjunction with other logging
• methods in mineral geophysical logging in
  hard rock (lower porosities)

145
PROBLEMS AND LIMITATION

• Problems
• Biggest is the need for a well (ie. a borehole)
  to operate
• High cost of drilling meaning boreholes are
  always
• not available hence GWL will not be possible for
  a particular study.
• Colapse of holes in regolith systems
• while wireline logs are running solved with foam
  drilling
• or plastic casing insertion.
• Limitations
• Recognition that each method has weaknesses and
  strengths.
• PVC casing- prevents electrical logging neutron
  logging (hydrogen)

146
CONCLUSIONS

• Geophysical well logging provides many different
  opportunities to investigate the material making
  up the wall of a borehole, be it regolith or
  crystalline rock.
• A widen range of different sensors provide
  information which complementary in nature. Best
  results are obtained by running a suite of logs
  and analyzing their similarities and differences.

147
REFERENCES

• Hallenburg, J.K., 1984. Geophysical logging for
  mineral and engineering applications. PennWell
  Books, Tulsa, Oklahoma, 254 pp.
• Keys, W.S., 1988. Borehole geophysics applied
  groundwater investigations. U.S Geol. Surv. Open
  File Report 87-539, Denver.
• McNeill, J.D., Hunter, J.A and Bosnar, M., 1996.
  Application of a borehole induction magnetic
  susceptibility logger to shallow lithological
  mapping. Journal of Environmental and Engineering
  Geophysics 2 77-90
• Schlumberger, 2000. Beginnings. A brief history
  of Schlumber