| | | | |
| | |||
| 
| |
Diamond exploration is a high-risk activity that requires a long-term commitment to reap the high associated rewards. These rewards however, can be substantial. Diamondex Resources Ltd. has a highly qualified management and technical team dedicated to the thorough diamond evaluation of its property portfolio held in the Canadian North. Typical exploration programs include: heavy mineral sampling, airborne and ground geophysical surveying, GIS/ GPS and bathymetric surveying and diamond drilling. Over time, the continuous innovation of science and technology have proven to be an instrumental and invaluable resource to the success of the modern prospector, and Diamondex is at the forefront of experimenting and incorporating new exploration techniques. Diamondex, in conjunction with De Beers Canada Mining and the University of British Columbia, have recently evaluated the use of seismic surveys in diamond exploration.
The following is a brief overview of what Diamondex Resources' exploration program entails.
The first stage in any exploration program is to identify a prospective area. When moving into a new area all available data is considered to narrow the prospective region. A variety of techniques used include the application of geological studies, remote sensing, structural interpretation and a review of historical data.
Once a prospective region has been identified, general reconnaissance begins and then specific target areas defined. This objective is commonly accomplished through heavy mineral sampling, an exploration technique widely used in diamond exploration.
In regions that have been glaciated, the movement of glacial ice has transported material and deposited it over a vast area. These deposits are collectively called glacial drift; a term that encompasses till, eskers, outwash and many other specific types of glacially transported material. As kimberlites are soft and tend to weather easily, any kimberlite that lay in the glacier's path would have been scoured out, with the kimberlite material incorporated into the drift and dispersed down-ice across the landscape away from the source location. There is a group of minerals that are commonly associated with kimberlites, and are collectively known as kimberlite indicators minerals. These minerals typically include: pyrope garnet, picroilmenite, chrome-diopside, chromite, and olivine. These minerals have high-densities (i.e. are heavy) and tend to be concentrated in glacial drift. Heavy mineral sampling is an effective method to identify possible kimberlite sources. The procedure involves collecting 25-kilogram parcels of glacial drift that are processed and mineralogically studied. Indicator mineral presence in a heavy mineral sample indicates a possible kimberlite source could be in the region up-ice from that sample location. Heavy mineral samples are collected along traverses established perpendicular to the glacial dispersion direction and the results are plotted on topographic maps. If positive samples are present, additional samples are collected up-ice until a likely source area is isolated. Potential source areas are often coincident with lakes and further studies are necessary to identify and refine targets for drilling. The exploration cost from collecting and examining one heavy mineral sample for indicator minerals ranges from C$800 to C$1200. The processing of a heavy mineral sample means the glacial material is treated by various techniques to produce a concentrate of heavy minerals. The initial 25 kg sample is reduced to 3-50 grams of discrete mineral grains that is then "picked." Picking requires a highly experienced mineralogist using a binocular microscope to look at all the grains in the sample, identifying and "picking" out any kimberlitic indicator minerals that may be present. Geophysics Geophysical surveys are based on the principle that various rock types have differing physical properties, such as magnetic susceptibility and density. These physical properties can be measured directly either from the air, or from the ground. In airborne surveys, specialized equipment mounted in small planes or helicopters is used to collect data regarding the varying magnetism or electromagnetic conductivity of rocks over large areas. Computer programs are then used to convert the data into a visual format that geophysicists can use to identify areas of anomalous values for follow-up work. Airborne surveys are typically flown with a helicopter towing a 'bird' attached to a cable. These surveys are mainly electromagnetic and magnetic, and are normally flown along lines 50 to 200 meters apart and from 25 to 100 meters above the ground. These airborne surveys are guided by a global positioning system (GPS), a radar-altimeter and a computer with a touch server mounted on the helicopter control panel. Approximately 400 line-kilometers of survey can be completed in a single day. Ground geophysical surveys include the use of hand-held equipment to obtain more accurate data than is possible through airborne techniques. Ground surveys are typically completed after detailed examination and computer processing of the airborne survey data. Ground surveys are done on a much smaller scale and are used to further assess the quality of airborne targets in order to assist in pinpointing the location of target anomalies for the placement of drill rigs. In a typical ground-based survey, geophysicists traverse an area in a grid pattern taking measurements with instrumentation strapped to the geophysicist in backpacks or in harnesses. Ground surveys are usually horizontal loop electromagnetic (HELM) and magnetic (MAG) and a single worker can cover up to seven-line-kilometers in an average day. Recently, geophysical techniques such as capacitive coupled resistivity (CCR) and gravity have been added to the ground geophysical survey repertoire. Ground resistivity (CCR) provides a more detailed display of airborne resistivity values calculated from airborne EM data. Gravity helps to delineate the fundamental density contrast between many host rocks and kimberlite intrusions. Data obtained from ground surveys, like that from airborne surveys, undergoes significant computer processing in order to produce maps for interpretation of rock properties and the location of drill holes. Geophysical surveys are commonly successful in locating kimberlites that may or may not be visible at the Earth's surface (commonly, kimberlites are found hidden under lakes). Detecting kimberlites with these surveys ultimately depends on the differences in physical properties of the kimberlite and the country-rocks that host the kimberlite. In regions dominated by flat-lying sedimentary rocks and granites, there is often a significant magnetic contrast between the kimberlite pipes and surrounding rock layers. This difference produces clearly visible anomalies in the geophysical data that allow kimberlite pipes to be identified - even if they are not visible at surface. Seismic Survey The application of seismic methods and techniques to kimberlite exploration in Canada's north has proven to be a success. In 2000, Diamondex Resources, in partnership with De Beers Canada Mining Inc. and the University of British Columbia undertook and completed the first-ever 2D seismic survey over a known kimberlite deposit to determine if seismic methods could be used to determine the presence of, and to delineate further the Snap Lake/King Lake kimberlite dyke system at depth. Results from the study confirm the drill data, defining a shallowly-dipping (<30?) kimberlite dyke body extending from near-surface to depths in excess of 1450 m. Like other geophysical surveys, the success of a seismic survey relies on differences in physical properties between the target body (kimberlite) and the surrounding country-rocks, in this case, the seismic properties of the rocks are important. In general, kimberlite is less dense and more porous than the surrounding country rock, so the seismic velocity is expected to be less than the surrounding country rock. Seismic high-resolution reflection methods should therefore be expected to be useful in the exploration and delineation of kimberlite dykes and sills. Seismic reflection surveys are useful in delineating bodies that have shallow orientations. Typically, kimberlite dykes occurring in the Canadian north have been found to have dips less than 30°, thus are considered likely to be detected by seismic methods. Theoretical studies are currently ongoing to determine the wider-spread applicability of seismic methods for kimberlite exploration in the region. Initial studies in the Snap Lake/King Lake area have proven successful, enhancing the prospectivity of these methods as an effective exploration tool. Geographic Information Systems (GIS) The geographic information system (GIS) is a dynamic computer-based approach to managing spatial (map) data acquired during the life of an exploration program. Any feature that has a geographic position (i.e. drill hole collars or sample locations) is recorded in a database along with characteristics about each feature. Having an organized spatially based storage system allows exploration geologists to "ask questions" of the database and view the results. Viewing the results in a familiar map format allows geologists to identify trends in the geology and concentrate exploration efforts more effectively and efficiently. Global Positioning Systems (GPS)/Bathymetric Surveys Another technology that works hand-in-hand with GIS is global positioning systems (GPS). The GPS networks of satellites surrounding the globe allow the user to locate their position within metres almost anywhere on the earth. As many kimberlites are known to occur beneath lakes, a valuable application of GPS involves linking a GPS unit to a water depth sounder in a boat, with the resultant position and depth data being fed into a GIS. The depth information is then converted into a colour-coded map allowing the geologist to view the shape of the lake bottom, and when combined with other data, identifies potential drill targets. Drilling The final, and most expensive component in kimberlite target evaluation, is drilling. Many kimberlite targets lie beneath lakes and consequently most drill programs in the North occur during the winter months of February to May, when lakes are frozen. The average drill rig weighs ~10 tons, and requires about 5 feet of ice to provide a stable platform in order to drill into a kimberlite target from the ice surface. A wide-tracked vehicle, such as a Nodwell, generally tows the drill between sites during the winter months. If the distance between sites is substantial, the drill is dismantled and moved by helicopter, a process that normally takes 3-8 hours, and can cost in excess of C$3-5000 depending on the distance between drill sites. The drill rig operates 24 hours per day and is operated by 2 two-person crews, each working 12-hour shifts. The rig is capable of drilling holes at angles from -45° to -90° (vertical). Exploration drilling usually entails drilling holes that are 1?-inches in diameter. Core from these holes is retrieved from the drilling operation, and placed in core boxes for the company geologist to log and interpret. Kimberlite intersections from the drill hole are sampled and are processed to determine diamond content. A standard exploration drill hole is about 200 meters in length and takes two to three days to complete. The total cost including camp costs, helicopter, fuel, wages, etc. is about C$350 per meter of drilling. Larger drills, drilling larger diameter holes (in some case up to 50 cm) are often used to sample a kimberlite body after initial exploration drilling has verified the presence of a kimberlite body. A wide range of drilling techniques is available. Small-diameter core drilling may be used during initial target testing to determine if a kimberlite pipe is responsible for an anomaly. Often, when kimberlite bodies have been discovered and verified by initial core drilling, reverse-circulation (RC) drilling is then used to obtain larger samples of that body to further assess the economic potential of that kimberlite. Unlike conventional core holes, RC drilling methods produce small rock chips that are brought to surface by high-pressure air or water. The RC drilling results in a larger sample faster of kimberlite than that typically obtained from a conventional drill hole. These larger samples are then processed similarly to the core samples, producing results that should be statistically more representative of the deposit than the narrow-diameter core samples.
| | ||||||||||||||||||||||||||||||
| | |
|  | |
)
)
)