The Aïn Kerma Gold Prospect (ONHYM) Tan Tan Province, Guelmin - Es Semara Region, Southern Morocco. Field Visit Report

Transcription

1 The Aïn Kerma Gold Prospect (ONHYM) Tan Tan Province, Guelmin - Es Semara Region, Southern Morocco. Field Visit Report 1. Introduction The field visit took place on Wednesday, the 21 st July. It took place during the week (19 th - 24 th July) of Agricola s initial visit to the Mineral Exploration Branch of the Moroccan State Bureau for Mines and Hydrocarbons (ONHYM) which is based in Rabat. The visit was lead by Amine Adil, ONHYM s Project Geologist. James Negaard of Agricola Resources, and Paul Hugman were present during the visit as was Stephanie Porter of Stella E&D who had organised the visit and made available the photographs. On the following day a visit was made to the Azougar N Tilili polymetallic (Au-Ag-Cu-Pb- Zn) property which permitted comparison of the style of mineralisation at the two properties. 2. Location The prospect area is located in rugged terrain some 30km ENE of the town of Tan Tan and some 50km from the Atlantic seaboard at Tan Tan Plage (Figure 1). It is situated on the northern side of the Draa River valley. From Tan Tan, access to the property is initially (some 15km) by the main road to Guelmin and then by temporary tracks drivable only by off-road 4WD vehicles. 3. Regional Geology The area of interest (Figure 1) is situated in the south-western part of the Anti-Atlas which is a WSW-ENE trending chain of hills and mountains. This chain is composed of a Paleoproterozoic basement overlain by late Neoproterozoic to mid-paleozoic strata which have been faulted and folded during the Hercynian Orogeny. The Anti-Atlas is essentially a complex anticlinal structure and the Precambrian outcrops in a series of inliers, formerly called boutonnières, flanked by the thick successions of Paleozoic strata. 1

2 Figure One Ain Kerma Location Diagram The Prospect Area is located in hilly terrain within an apparent faulted block on the northwestern margin of the Bas Draa Precambrian Inlier (Figure 2). The block appears to contain a broad anticlinal structure which allows the exposure of the green-grey gravels of the late Neoproterozoic Ouarzazate Supergroup. These gravels are overlain by the carbonate sequence of the Lower Cambrian Tata Group. These carbonates are relatively resistant to erosion and tend to form the higher ground. 2

3 Figure 2 Ain Kerma Geological Setting The age of the mineralization is unknown but the structures and alterations appear late tectonic. This suggests the mineralisation must be late Hercynian or younger. The proximity of the Atlantic Margin (Figure 2) and the tensional regime associated with the opening of the Atlantic suggests that the structures could be Mesozoic in age. 4. The Aïn Kerma Gold Prospect At Aïn Kerma, there are some fifty parallel to sub-parallel NW-SE trending structures that are frequently filled with quartz. Surface sampling has shown the presence of interesting gold values in at least two of these structures, AK-1 and AK-4. ONHYM s introductory summary stated the following. The AK-1 structure extends for some 400m and gold values range from g/t Au, with an exceptional value of 147 g/t Au. The AK-4 structure extends for 800m and within a 300m section values range from 4.7 to 56g/t Au over widths of 0.3 to 1.2m. All the known mineralised veins are hosted by green-grey fine gravels of late Neoproterozoic age. As a general rule, these structures do not appear to extend into the overlying carbonates. 3

4 Photo One - Ain Kerma Oasis Photo 1 is of the small Ain Kerma Oasis (where the trees are on the left-hand side of the photo). The view is taken looking northwest from the proximity of the AK1 structure. One can also make out the brown-coloured, northwest-dipping carbonates especially in the hillside on the right. Photo 2 is of the carbonates forming the hill to the northeast of the AK-1 structure. The axial zone of the broad anticlinal structure can be made out on this photograph. Photo 2 - Hill to the northeast of the AK-1 structure 4

5 Figure 3 is a geological sketch of the Prospect Area. It must be stressed that it is only a sketch and accuracy is lacking in certain areas The AK-1 Structure Figure 3 The AK-1 structure starts some 300m to the southeast of the Ain Kerma Oasis and extends in a south-easterly direction for some 750m (Figures 3 & 4). 5

6 Figure 4 6

7 The structure is typified by the presence of a white quartz fill ranging in width from a few decimetres to some 60cm (Figure 5). Figure 5 The more massive quartz (Photo 3) outcrops due to its resistance to erosion, and it is this that has been sampled. The samples are narrow channels taken across the siliceous material. The whole structure is probably somewhat wider, being partially covered by soil (there is a need for digging trenches). There are only 12 sample sites over a strike length of about 700m, - probably insufficient. During the field visit it became evident that there is a close relationship between the iron oxides and the gold content. The iron oxides (Photos 4 & 5) tend to fill fractures within the quartz veins and are probably more recent than most of the quartz and probably have formed at a lower temperature. At several localities cavities occur in the veins and are normally associated with the iron oxides (Photo 6). The higher contents of both iron oxides and gold occur towards the extremities of the veins where they are in closest proximity with the overlying limestones. Could the limestones be ponding the later and more pregnant fluids? 7

8 Photo 3 The green-grey gravels are at times oxidised to a reddish colour. This occurs on the margins of the veins and in minor structures between veins. Evidently these areas will need to be sampled to see if they are running gold. Photo 4 Photo 5 8

9 Photo 6 Another question is whether there was any reaction between the carbonates and the goldbearing fluids. There was no evidence of this during the visit but no worthwhile examination was made. Four drill-holes were drilled beneath the outcrop of the AK-1 structure. The structure was found to dip steeply northeast (80º-90º). The drilled holes were angled at 56º-70º with the horizontal. The description of the structure was white quartz with occasional micro-fissures with traces of hematite and limonite. No anomalous gold values were recorded. ONHYM regarded the results of this drilling as being negative and discontinued activities. However, the lack of gold values is not surprising when the paucity of iron oxides is taken into consideration. Within the AK-1 structure there are high gold values on surface (95 & 147 ppm Au), and these high values are associated with the presence of iron oxides. The distribution of the gold values in the vein is obviously going to be highly irregular and hence drill-holes with negative results have to be expected The AK-4 Structure The AK-4 structure is situated some 1.5 km ENE of the Ain Kerma Oasis and extends in a NW-SE direction for approximately a kilometre (Figures 3 & 6). It is very similar to the AK- 1 Structure being typified by a white quartz fill that in this case can range up to several metres in width (Photos 7 & 8). The structure is hosted almost entirely by the green-grey gravels. At least the quartz content dies out in the overlying limestones. 9

10 Photo 7 Photo 8 Some 25 narrow surface channel samples were collected over the length of the structure (Figure 7). In one part of the structure, towards the north-western end, some six samples were collected from a 300m long section which returned values ranging from ppm Au. This part of the structure is typified by the presence of iron oxides (Photo 9). 10

11 Photo 9 Four drill-holes were angled beneath the structure. The structure was intersected at depth in each hole, and was found to be sub-vertical (85-90º). However no gold values were reported. The 4 holes were stretched out over 800m.The separation between holes varied from m. The comments made for AK-1 are also valid for AK Other Structures Several other similar structures returned gold values such as AK-46 and AK-49, both of which are in the vicinity of AK-4. In AK-49, 3 out of 5 samples returned values ranging from ppm Au and in AK-46, 8 samples returned over 1ppm Au with high values of 7.7 & 11.5 ppm Au. Low anomalous gold values are also reported from AK-50 and AK Comparison with Azougar N Tilili In general terms, the structures at Azougar N tilili are similar to those at Ain Kerma. However, there are two basic differences to note. The mineralised structures at Azougar N Tilili are emplaced in silicoclastic strata that overlie the Lower Cambrian carbonates, whilst at Ain Kerma the slicoclastic strata underlie the carbonates.. Also at Azougar there is Pb (Ag), Zn & Cu mineralisation much of which is said form early in the paragenesis. As at Ain Kerma the gold is associated with iron oxides that fill late fractures and the mineralising phase appears to be late in the paragenesis. 11

12 5. Conclusions & Recommendations High gold values are associated with iron oxides filling fractures in vein quartz that develops along late fractures. The gold occurs late in the paragenetic sequence and there is no reason why it should not be epithermal. To date surface sampling of the siliceous structures, particularly where there are iron oxides filling fractures, has been insufficient. Zones of ferruginous alteration between the principal structures, particularly if there is associated silicification, require sampling. This is a project that requires thorough sampling and an open mind to identify novel types of mineralisation. Paul Hugman 28 th August