Geology & Exploration
The West Mali Gold Belt, a part of the Birimian greenstone belt, is a prolific gold producing region, with current annual production of more than 1.5 million ounces gold per year.
Rock in the tropics generally weathers in place and the permit area is no exception. The deposit is generally overlain by laterite and hardpan, with up to 50 metres of saprolite, grading to hard rock below. (Saprolite is a chemically weathered rock. Rainwater percolates through the rock, gradually altering feldspars to clays and sulphides to oxides, leaving gold in a free state, rather than being encapsulated in base metal sulphides). There is evidence that grades increase with depth, roughly doubling below 100 metres depth.
Merrex has identified a major gold bearing shear zone, termed the Siribaya Structure, which has been the primary focus for exploration work on the project to date. Gold mineralization associated with the Siribaya structure is present in tectonic and hydrothermal breccias, and in stockwork quartz vein systems associated with felsic dykes. Trenching, pitting, RAB & diamond drilling have identified structurally controlled anomalous and ore-grade gold mineralization over a strike length in the order of 10 kilometres.
Based on positive results from initial soil sampling, pitting, and trenching, Merrex initiated an aggressive rotary air blast (RAB) drilling programme (622 holes, ~31,000m), which confirmed the continuity of gold mineralization throughout the interpreted structures on the Siribaya permit.
To date, Merrex has focused its efforts on a 10km zone of gold anomalies which have been correlated with a regional magnetic anomaly in the northern portion of the license block, dubbed the Siribaya Structure
. Drilling performed to date on the Siribaya Structure has yielded ore-grade intercepts along the entire length. Since 2005 over $13,000,000 has been spent on exploration at Siribaya.
After completing a compilation of both historic and recent geochemical data, Merrex identified four priority targets with significant gold bearing mineralization coincident with the Siribaya Structure; Zones 1A, 1B, Timeta, and Bambadinka. (See attached map
The majority of recent work has been concentrated on Zone 1B
. On the basis of this work, Merrex produced a geological model and outlined a mineralized zone roughly three kilometres long, 7-12m average true width, at least 270m deep, with grades ranging from 2-5 g/t gold. This zone remains open along strike and at depth.
is interpreted to contain mineralized stockwork veins and stringers similar to what has been defined at Zone 1B. In late 2007, drilling at Zone 1A was put on hold when significant gold assays were received from Zone 1B. Merrex returned to this area in the 2010 RC drill program, to further define the mineralization at this anomaly.
occupies the southern portion of the Siribaya structure. Timeta includes the site of historic artisanal gold workings (long inactive) some 30 metres deep, 100 metres long and up to 20 metres wide. The workings exploited an easterly striking quartz vein roughly 1.0-1.5 metres wide. Additional drilling is planned for this zone, in consideration of its position on the Siribaya Structure, as well as the size of the artisanal workings.
lies to the west of the main Siribaya Structure. The zone is roughly five kilometres long by two kilometres wide. Numerous gold-in-soil anomalies have been identified within this zone. Pitting and trenching suggests that the gold is confined to the surface laterite cover, which could indicate a significant and easily worked near-surface deposit. 2,200 metres of mechanized auger drilling was completed in the summer of 2010 and a significant new gold trend is indicated. (Click here for map and results
(the area between Zone Bamabadinka and the Siribaya Mega-Structure) appears to be a significant new gold trend. Recent soil and termite mound geochemical survey results indicate extensive new gold amonalies that will require follow-up drilling.
In addition to the anomalous target areas directly corresponding to the Siribaya Structure, the overall Siribaya Project area (comprising six contiguous permits) covers several other areas of interest. In particular, the Babara and Kofia
permits cover an extensive zone of gold-in-soil anomalies, of larger extent than those encountered over the Siribaya Structure. The extensive anomalous zones coincide with distinct linear corridors observed in aeromagnetic data. Merrex carried out surface geochemical sampling over this area during the 2006-2007 seasons and again in 2009. Soil samples collected at Babara and Kofia, and initial termite mound sampling at Babara during the 2009 exploration season have been assayed and analysed. (Click here to see map showing the previous soil geochemical anomalies and selected high assays of termite mound sampling
The 2009 termite mound geochemistry program of approximately 2,000 samples within the central Babara region returned assays of up to seven grams per tonne with many termite mound samples being higher than the corresponding surface soils. Termite mound sampling is used in conjunction with surface soil geochemistry to identify gold-anomalous target areas with termite sampling being significant because termites will carry soil and rock particles to surface from as deep as the water table so the resulting samples represent samples from depth rather than a surface sample only. The very positive results from the 2009 surface soils and termite mound sampling and the coincident presence of the extensive significant structures identified by the 2009 airborne magnetic survey prompted this renewed interest in the Babara-Kofia Permits Area.
Click here to view soil sampling geochemistry results.
Click here to view termite mound geochemistry results.
The Babara field camp, originally constructed by Merrex as temporary accommodation during the 2008 field season, has been expanded and upgraded by IAMGOLD to accommodate the increased exploration program requirements at this new exploration area.
Working in concert with IAMGOLD Corporation ("IAMGOLD"), Merrex has completed the initial phase of a 14,500 metres RC reconnaissance drill program (August 2010).
The gold mineralization in both Zones 1A and Zone 1B has continuity. The Zone 1A mineralization extends for at least two kilometres and Zone 1B for at least three kilometres. The gold mineralization in both Zones 1A and 1B remains open to both the north and south within the 10 kilometre long 1A and 1B substructures, and is also open to depth. Additionally, multiple new and significant gold mineralized zones with continuity are present within each of the 1A and 1B substructures. These new zones also are open north, south and at depth.
Although some of the RC drilling results could be used in a future resource estimate, this program was not intended to expand the NI43-101 resource estimate; rather it was designed to explore new areas of the Siribaya Mega-structure and begin defining the potential magnitude of the mineralised areas within the Siribaya Mega-structure. The RC results will also aid identification of future diamond drill target areas. Approximately 4.5 of the proposed six lines of RC drill holes were completed prior to the onset of the seasonal rains. The lines are 500 metres apart, consisting of drill holes oriented at 270° with a dip of -50° to approximately 100 metres target depth at 50 metre spacing, and have been placed east-west across the entire width of the 1A and 1B substructures. The first Line of drill holes, RC-L-1, is approximately 250 metres north of the Zone 1B NI 34-101 Resource area; the remaining five lines of drill holes are to the south of Zone 1B starting 40 metres south of the Zone 1B NI 43-101 Resource area and thereafter at approximately 500 metres step-outs. The southern-most line reached the old Berekegni artisanal underground gold workings on the 1B substructure and the major RAB anomaly at Zone 1A.