TECHNICAL MEETING-13-14 DEC.2010 DEVELOPMENT OF MINERAL RESOURCES ACP HOUSE, BRUSSELS, BELGIUM - PowerPoint PPT Presentation

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TECHNICAL MEETING-13-14 DEC.2010 DEVELOPMENT OF MINERAL RESOURCES ACP HOUSE, BRUSSELS, BELGIUM

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Geology A simplified geological map of Eastern Ghana including Nkwanta map sheet area The area is underlain by upper Voltaian sediments along the western margin of ... – PowerPoint PPT presentation

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Title: TECHNICAL MEETING-13-14 DEC.2010 DEVELOPMENT OF MINERAL RESOURCES ACP HOUSE, BRUSSELS, BELGIUM


1
TECHNICAL MEETING-13-14 DEC.2010 DEVELOPMENT OF
MINERAL RESOURCES ACP HOUSE, BRUSSELS, BELGIUM
2
Exploration Of New Mineral Resources By
Geological Mapping, Geochemistry And Geophysics.
  • A Case Study In Ghana

Yakubu Iddirisu CEO, Geological Management
Consultancy Ltd(GEOMAN CONSULT.)
3
  • The African, Caribbean and Pacific (ACP) states
    constitute a significant proportion of the
    global landscape they account for
    approximately 19 of the earths surface area.
  • The geology of the region is favourable and
    its largely unknown potential calls for a
    sustainable mining cooperation among member
    states.

4
  • Nearly two-thirds of the ACP states are
    either mining countries or have a mining
    potential that if exploited rationally would
    contribute to their social and economic
    development. For instance mining in the
    sub-Saharan Africa excluding South Africa
    accounts for 8 of the world mining production.

5
  • It generates almost 50 of the exports and 30 of
    the fiscal resources of the major mining
    countries. 80 of the surface area of this
    region has never been represented on any
    detailed geological map (of a scale of
    1/200,000 or more) . Source ACP Group Website

6
  • The need therefore for the ACP countries to
    take inventory of their resources through
    exploration cannot be overemphasized.
  • Mineral deposits in the ground are worthless
    unless they are explored and tapped for the
    economic development of their beneficiaries.

7
  • In 2005 Ghana was a beneficiary of an
    European Funded reconnaissance exploration
    which covered 8 map sheets totaling 25,646
    square kilometers.
  • The project was under the Mining Sector
    Support Programme which lasted for 5years.

8
  • It included Geological Data Provision which
    comprised two components
  • Geological investigation of eight 1100,000
    scale map sheets in selected parts
    of the country to produce geological
    data for investment promotion.
  • The investigation comprised geological
    mapping, soil
  • geochemistry and hydrocensuses.

9
  • The Geological Investigation was undertaken by a
    Consortium comprising Council for Geoscience of
    South Africa (CGS), Bureau de Recherches
    Géologiques et Minières (BRGM) of France and
    Geological Management Consultancy Limited
    (GEOMAN) of Ghana.

10
Showing 8 mapped field sheets
11
  • An airborne geophysical survey of the entire
    Voltaian and Keta Basins was undertaken by Fugro
    Airborne Surveys (UK) with the British Geological
    Survey.
  • The survey included the following
  • Satellite imaginary interpretation
  • Magnetic and spectrometric surveys
  • Gravity surveys and EM surveys
  • Integrated Interpretation of Geological and
    Geophysical Data

12
  • AREAS SURVEYED
  • The GEOTEM regional survey included the area
    between the Volta River and Keta Basins.
  • In addition to these regional surveys, Fugro
    Airborne Surveys conducted combined GEOTEM and
    magnetic surveys in eight detailed areas, of
    which six (A1-A6) are within the Voltaian Basin,
    one (A7) partly in the Keta Basin and one (A8)
    over the Winneba Belt (light red area and red
    polygon).
  • Geotech Airborne Ltd. covered four areas with
    combined VTEM and magnetic measurements (light
    blue area and blue polygon).

By Courtesy of GGSD
13
  • Moreover, some mountainous areas outside the
    basins like Nkwanta were covered by
    helicopter-borne EM surveys undertaken by
    Geotech.

14
The Terms Of Reference (TOR) for the mapping
project were as follows
15
  • Review all existing topographic and geological
    maps and publications concerning the map areas
    and their surroundings
  • Acquire, process and interpret satellite
    imaginery to define structural and
    lithological groups

16
  • Acquire and geologically interpret airborne
    geophysical maps
  • Define a lithostratigraphic classification to be
    used during field mapping in accordance with
    Guidelines of the Sub-Commission for
    Stratigraphic Classification of IUGS Commission
    for stratigraphy

17
  • Compile all mineral occurrences located
    within the map areas
  • Compile data available on water boreholes
    (location, depth, water level and yield)
  • Prepare a GIS map to reference the outcrops
    and structures identified above (synthesis map)
  • Produce field base maps

18
Methodology
19
  • As has been pointed out earlier the investigation
    covered eight map sheets at a scale 1100,000.
    Because of time constraint, it will not be
    possible to describe the work carried in each
    map sheet. Instead Nkwanta area would be used as
    the test case area. The study area is situated
    between Hohoe and Yendi with the eastern limits
    on the Ghana Togo border.

20
Map showing the location of Nkwanta map sheet
21
Mapping
22
  • Each field team generally comprised a consortium
    geologist and a trainee with a vehicle. Vehicles
    were used mainly for transportation between camp
    and field work areas and mapping was carried out
    mainly by foot.
  • Intensive coverage with a regular grid of field
    observation and sampling was not possible due the
    pronounced relief and logistical difficulties.

23
  • Several major traverses were carried out in the
    western range and towards the Togo range at an
    interval of 8kms.
  • During the mapping process field outcrop
    coordinates were systematically acquired using a
    GPS and stored in a dataset.
  • Samples were taken and used to make thin
    sections, for geochemical and geochronological
    analyses, and for magnetic susceptibility
    measurements.

24
This picture depicts a typical rainforest terrain
where mapping was undertaken
25
An outcrop within the forest
26
Sampling
27
  • Due to difficult terrain in the Nkwanta area, a
    helicopter was used in gaining access to
    predetermined sampling points.
  • In total 3344 samples were collected in the field
    at an average sample density of one sample per
    square kilometer. Sample position coordinates
    were saved at the sampling positions on GPS.

28
This is the helicopter used to facilitate
sampling in difficult areas South of Nkwanta
29
  • Samples were screened out in Accra and Pretoria
    tolt106um fractions. These size fractions were
    analysed for 28 elements Ag, Al2O3, As, Au, Ba,
    Bi, CaO, Cd, Co, Cr, Cu, Fe2O3, K2O, MgO, Mn, Mo,
    Na2O, Ni, Pb, Sb, SiO2, Sr, Rb, ThO2, TiO2, U3O8,
    V and Zn.

30
The helicopter lands at a pre-designed spot for a
sample to be taken
31
Hydrocensus Investigation
32
  • The fieldwork consisted of geological mapping and
    hydrocensus of all existing boreholes. Water
    samples were collected and water levels, recovery
    and permeability tests conducted on the
    boreholes.
  • Thereafter, all field data were compiled and
    coded according to their lithological units into
    a computerized data base from which a 1100 000
    scale hydrogeological map was produced.

33
A hydrogeologist taking measurement in a borehole
fitted with a hand pump
34
Geology
35
A simplified geological map of Eastern Ghana
including Nkwanta map sheet area
36
  • The area is underlain by upper Voltaian sediments
    along the western margin of the combined map
    sheet with the Togo metasediments along the
    eastern margin on the Ghana- Togo border.
  • Sandwiched between these units is the Buem
    running N-S along the central parts of the mapped
    area. U-Pb analysis carried out on samples from
    the Buem yielded ages of 4617Ma, a Variscan age.

37
  • From a geochronological perspective, the Buem
    Group can no longer be associated with the
    Precambrian history of the Volta Basin. The
    evidence points to an Ordovician.

38
A gossan was identified in the southwestern
mapping area associated with ultra-mafics hosted
in quartzites.
39
EM Time Domain geophysical map showing
concurrence with geology (courtesy of GSD)
40
Mineral Potential In Nkwanta Map Sheet
41
Old map indicating the occurrence of Fe only
42
Current map indicating the occurrences of Ni
43
  • Nickel anomalies mostly occur in the western
    portion of the Buem Group where they follow the
    same N-S trend defined by other elements
    including Fe, Mg, Cr, Cu and Ag.
  • The prominent anomaly on the Ghana Togo border
    is also repeated. High Ni probably delineates
    massive sulphide type deposits within the Buem
    Group and possibly ultramafic sequences in
    the Ghana -Togo border.

44
Current map showing the distribution of Cu
45
  • Copper The most significant copper anomalies
    occur towards the western portion of the Buem
    Group and follow the same general trend as
    silver, cadmium and chromium. The Voltaian
    sediments seem to be devoid of anomalous copper.

46
Current map showing the distribution of Mn
47
  • Manganese Most of the anomalous populations
    occur on the Buem Group where they define two
    prominent N-S aligned zones in the southern parts
    of the map.

48
(No Transcript)
49
  • Environmental implications, as far as
    deficiencies and toxicities of the elements in
    particular areas are concerned, are also
    addressed. A map showing areas that could be of
    concern is included.

50
Conclusion
51
  • The EU funded regional mapping component of the
    MSSP at a scale of 1100,000 has improved the
    status of geology and ensured a better
    understanding of the subject in the eight
    selected areas and in particular the Nkwanta Map
    Sheet.

52
  • Geochronological dating as well revealed that the
    Buem group is younger than the Voltaian which has
    implications for mineral exploration.
  • Nkwanta area that was only known to host iron and
    jasper deposits had interesting and far reaching
    outcomes which are presented as a lesson and a
    way forward for the future.

53
  • The geochemistry mapping of soil data in
    particular allowed the identification of an
    apparent mineralized zones (metallogenic
    province) that may host specific types of
    mineralization.
  • The provinces and anomalies that are of
    particular interest are those identified for
    Nickel, Cobalt, Copper, Zinc and Manganese.

54
Recommendation
55
  • Coming from Ghanas experience it can be said
    without a doubt that a regional mapping program
    when properly executed associated with
    geochemistry and geophysics opens up new
    possibilities for the mineral exploration sector.

56
  • What private Exploration and Mining companies
    need are good geological maps and indicators and
    these can be made available by carrying out
  • Systematic Regional Geological mapping of the
    country on a scale of 1200 000 to 1100 000
    including dating of main units.
  • Conducting a regional soil sampling programme

57
  • Airborne regional geophysical surveys
    (Magnetics, Radiometric and Electromagnetic
    methods) to provide information for the
    integrated interpretation of the field sheets and
    in helping Mining and Mineral Exploration
    companies in their target generation.
  • Creation of good data bases and an Information
    Management System through which investors could
    have access to the data so generated.

58
End THANK YOU
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