November 2002
 


The MPMPS, a leading-edge technique to develop Québec’s territory
Daniel Lamothe
(Géologie Québec)

Two new products derived from the Mineral Potential Map Production System (MPMPS) will be released at the Geological Research Information Seminar, to be held next November 27 and 28 in Québec. A new map showing the potential for volcanogenic massive sulphide deposits in the Senneterre area (NTS 32C) will be presented. A compilation map showing the potential for Olympic Dam-Kiruna type deposits in the Manitou-Wakeham area (NTS 22I, 22P, 12K, 12L, 12M and 12N) will also be on display. Moreover, during the Seminar, a workshop on the MPMPS will be hosted by the author.

The MPMPS, a knowledge-driven approach suitable for Québec

The Système de production des cartes de potentiel minéral (SPCPM) is a mineral potential assessment tool, which makes it possible to produce maps based on an ore deposit model that show zones favourable to the presence of mineralization.





November 2002
 


A new worldwide trend

Mineral potential assessment via integration of spatially georeferenced data is an approach that is now used on a global scale, and it keeps generating more and more interest. The growing number of articles dealing with this technique confirms this. This new trend was strongly influenced by the development of new software making the process possible on a personal computer, and by the availability of new digital databases.

Formerly, zones favourable to the discovery of new deposits were generally identified by overlapping several layers of polyester, each illustrating a geological feature potentially indicating the presence of a given type of ore deposit (fault, geophysical anomaly, geochemical anomaly, etc.). Target areas were selected among those showing the largest number of overlapping features. The digital integration of georeferenced data revolutionized this approach, by making it possible to target, with pinpoint accuracy, the type of data (or theme) to process, to adapt the processing based on data-driven or knowledge-driven methods, and finally, to combine the results according to the relative importance of each theme.

The various methods used to process the data are grouped into two categories: first, data-driven methods that rely on statistical analysis to determine relevant spatial associations of various geological, geophysical or geochemical elements with known ore deposits; second, knowledge-driven methods which, based on the expert assessment of the processing geologist, rely on the definition and spatial processing of relevant metallogenic parameters for a selected model.

Data-driven methods use a training set generally derived from a digital map where a sufficient number of known deposits corresponding to the selected ore deposit model are located in the study area. The processing consists in calculating the statistical correlation between this training set and a certain number of digital maps each representing a parameter (or theme) relevant to the model (map of felsic intrusions, iron alteration, synvolcanic dykes, etc.). Data-driven methods essentially use three techniques: regression analysis, neural networks and weight of evidence.

Knowledge-driven methods (used to produce MPMPS maps) are based on an ore deposit model that is relevant for the study area. This model is based on geological parameters (heat source, favourable lithologies, faults allowing fluid circulation, etc.) which are considered as essential or favourable elements for the formation of deposits. To these parameters are also added discrete indicators (mineral occurrences, alteration indicator minerals, geochemical anomalies, etc.) signalling the presence of mineralization. In each case, these elements constitute a modelling theme. Data processing is guided by the expert’s evaluation of the role and importance of each theme in the emplacement of potential deposits. The weight attributed to the various themes and their combination may be derived either from the arbitrary assessment of an ore deposit expert, or from combination methods based on concepts such as fuzzy logic, or the Dempster-Shafer belief theory.

Data-driven methods that require a significant number of occurrences related to the selected model can only be used in areas that have already been extensively explored. The advantage of these methods lies in the fact that they are based on a factual approach that may be demonstrated and verified. However, they are based on occasionally complex statistical correlations which, from a geological standpoint, are not always meaningful. Knowledge-driven methods are more suitable in poorly explored areas where little or no favourable mineralization has been recognized to date. Since the evolution of the product is guided by the expert judgment of a metallogenist, this method yields a product that closely resembles ore deposit models already known and studied by exploration companies. On the other hand, the arbitrary weight attributed to parameters in this approach is determined by the expert preferences of the metallogenist, which may vary from one expert to another.






November 2002
 

Triennial Plan of Appalachian Exploration: Implementation in the Gaspésie Region
Serge Chevé, Pierre Verpaelst, Daniel Brisebois, André Gobeil, Serge Lachance and Pierre Pilote (Géologie Québec

Through Géologie Québec, the ministère des Ressources naturelles has long been conducting ongoing acquisition and updating of geological data on the Appalachians. Up to 2001 these activities consisted of inventories of aggregates and studies of industrial minerals in addition to geological surveys. However, a comprehensive view of exploration needs for the Appalachians as a whole had been lacking.

Consequently, during the autumn of 2000, the Service géologique de Québec (SGQ) conducted a consultation on need for geoscientific information on the Appalachians with a view to encouraging and facilitating exploration for minerals. In order to carry this out, the principal agents of exploration in the Appalachians, namely the exploration companies, mining funds and university researchers, were first asked to answer a questionnaire on the general approach Géologie Québec should take and on the areas or topics that should be given priority. Through this consultation, the main needs were identified and six regions where intervention by the SGQ was deemed advisable were consequently targeted:

Click on the map to see a larger version in GIF format.

  • Estrie - Centre du Québec (Region 1 on the map)
  • Chaudière-Appalaches (Region 2)
  • Témiscouata (Region 3), Sud de la Gaspésie (Region 4)
  • “Corridor” Pilote - Mont-Louis (Region 5)
  • Couronne nord du Bas-Saint-Laurent (Region 6A) and Gaspésie (Region 6B).

Prioritization of these intervention areas appeared necessary inasmuch as Géologie Québec wished to focus its human and budgetary resources and its strategies on regional targets rather than on topics relating to the Appalachians as a whole. On the basis of the presence of likely geological environments (metallotects), diversity of potential minerals, availability of information, and newness (metallogenic models or sectors), Géologie Québec proposed focusing on Region 4 (Sud de la Gaspésie). Further to this, a meeting was held on October 31, 2001, bringing together the principal agents involved in the field of mining exploration in the Appalachians. The meeting resulted in improvement of the triennial action plan and verification of the degree to which it met the needs expressed during the consultation. For the period 2002-2005, this plan calls for:

  1. updating the geological map;
  2. conducting integrated metallogenic and lithogeochemical studies;
  3. a new analysis of stream samples; and
  4. updating geophysical data coverage.

In the light of initial information yielded by the consultation, and despite the fact that the triennial action plan covers the period from 2002 to 2005, Géologie Québec decided to add a project to re-examine the Unité des Pics and Dôme de Lemieux gitology contexts to its program for 2001-2002. During the summer of 2002, as part of the first year of the triennial plan, the work focused on the western sector of the Sud de la Gaspésie region. This work consisted of: 1) reviewing the geological maps of the Oak Bay (22B/02) and Ruisseau Jérôme (22B/07) areas, with an emphasis on the internal structuring (organization and facies) of Dalhousie Formation volcanites; 2) re-examining gold mineralizations and their gitology context; 3) initiating lithogeochemical characterization of the Arsenault and Garin Formations; 4) completing a pilot project aimed at re-analysing stream sediment samples from the area of the Saint-André de Restigouche and Reboul showings; and 5) conducting a gravimetric survey.

Although the consultation exercise led to selecting Sud de la Gaspésie (Region 4) for action in the short term, Géologie Québec may include work proposed in the other priority regions of the Appalachians in its mid- and long-term programming.

You may obtain a copy of the triennial plan together with a description of the various target regions by contacting Mr. Pierre Verpaelst, Department Head of the Service géologique de Québec (tel.:1 (418) 627-6276, ext. 5059; fax:1 (418) 643-2816; e-mail: pierre.verpaelst@mrn.gouv.qc.ca).






November 2002
 


Potential for Discovery of Hydrocarbons in the
Bas-Saint-Laurent and Gaspésie Resource Regions

Background

Oil and gas exploration companies have been attempting to develop the hydrocarbon resources in the Bas-Saint-Laurent and Gaspésie resource regions for more than 140 years. The first drilling work was not based on in-depth geological information, but instead was done near places where surface seepage of petroleum had been observed.

At the turn of the last century, the Service des mines de Québec recommended that the geology of the Gaspé peninsula be studied. As soon as the first surface geology maps appeared, the petroleum companies of the day, including Imperial Oil, rushed in to drill and verify the potential of several major anticlinal axes, including the Mississippi and Haldimand. The results were negative. Next, the arrival of the geophysical method known as seismic reflection enabled other oil companies to continue the exploration research and set up drilling sites targeted by seismic operations. After a number of commendable but unfruitful attempts the petroleum companies, such as Gulf, Esso, Petrofina and their partners, returned to exploring less complex geological areas with already proven potential.

As a result, the Bas-Saint-Laurent and Gaspésie resource regions have not benefited for a number of years from the assistance and new geoscientific data needed to support exploration research in this high-risk activity sector and generate the new private investment essential to success. Exploration in Bas-Saint-Laurent and Gaspésie therefore needed direct encouragement and new basic information to gain a better understanding of the subsurface geology.

Finally, good shows and a discovery

In view of recent developments at Val-Brillant where a junior exploration company succeeded in identifying significant crude petroleum shows in large quantities and another junior exploration company announced startup of operations on an initial deposit of natural gas near Gaspé, regional authorities have asked the ministère des Ressources naturelles for assistance. To help them continue to evaluate oil and gas potential, these partners have requested support in the form of improved information about this extensive territory.

The Ministère becomes involved

During the autumn of 2000 the Ministère began carrying out a 98-kilometre geophysical seismic reflection survey program to better assess the structural nature and hydrodynamics of hydrocarbon formation in the Val-Brillant area.

More than 6,000 geophones like this one were monitoring constantly.

Since the official publication of the autumn 2000 survey results at the MINESPACE 2001 conference (Canadian Institute of Mining, Metallurgy and Petroleum), exploration companies have made twenty requests for geophysical survey data on the Val-Brillant area. And, the Direction du développement des hydrocarbures has delivered 90 new permits covering more than 1,700,000 hectares for exploration research in these areas.

Map showing location of current exploration research permits in Bas-Saint-Laurent, Gaspésie and on Île d'Anticosti. (PDF Format, 178 kb)

The power for transmitting seismic pulses though the subsurface was provided by four vibrator trucks producing a fully synchronized force of 120 tonnes.

In view of the results obtained and the interest generated in universities and research facilities as well as among exploration companies, the Ministère, in September 2001, announced that new work would be carried out to better assess oil and gas potential in Bas-Saint-Laurent and Gaspésie. A call for tenders was issued in this regard and the selected supplier, a consortium made up of GPR International Inc., Boyd PetroSearch Inc. and Kinetex Inc., was mandated to conduct 10 new seismic profiles aver a total of 345 kilometres between Mont-Joli and Cap-Chat in the north and between Nouvelle and Chandler in the south. One of the profiles cuts across the Gaspé peninsula from north to south between Cap-Chat and Miguacha. The work was carried out in two stages. Phase I of this new program was completed on October 25, 2001, covering 117 km. Preliminary findings confirm that the data is of excellent quality. Phase II (230 km) was completed July 18, 2002.

Presentation of results

Acquisition of new basic information at a cost of $2.3 million has enhanced the value of these regions and helped target the most favourable areas for pursuing development of hydrocarbon potential. The bank of already-existing geological data compiled by the Ministère together with the addition of new geophysical data will permit assessment of hydrocarbon resources in this vast area to continue.

Seismic profile of the Lake Humqui anticline, showing an amplitude anomaly on the structure's ridge at a depth of 2,500 meters.(PDF Format, 238 kb)

The ministère des Ressources naturelles was the project manager for all stages of these surveys. Processing is underway and the geological interpretation will be presented at the 23e Séminaire d'information sur la recherche géologique to be held November 27 and 28, 2002 at the Château Frontenac in Québec.

We invite you to attend the visual presentations as well as the conference entitled Une nouvelle image structurale : Résultats des Méga-transects de la sismique réflexion à travers la ceinture appalachienne de la péninsule gaspésienne presented by Claude Morin and Jean-Yves Laliberté from the Direction du développement des hydrocarbures.

Map showing location of seismic profiles obtained in 2000, 2001 and 2002 (PDF Format, 135 kb)