DEBA
Deba is located at 13º 12’N, 01º 04’E (map 1) at the south-west end of the Sirba River Belt. Exploitation consists of 50,000 m2 of alluvial workings and shallow pits spread out along a ~60º trend (map 4, photo DB-1). The pits follow the edge of a cuirasse-capped plateau which probably attracted the first prospectors to the area. I was able to trace a well defined linear zone of breccia approximately 1 m thick in many of the pits oriented ~60°, 80º S. The hanging wall rocks are a massive brown sericitic or kaolinitic meta-tuff (?) with a patchy fine scale stockwork of white quartz-kaolinite veinlets (photo DB-2). The kaolinite has probably replaced either albite or K-feldspar during the weathering process. The footwall rocks have a well developed stockwork and darker coloration due to chloritization (photo DB-3). Discontinuous glassy, quartz veins up to 10 cm thick are also present in this zone, though many of these do not appear to have been worked. Bleaching from kaolinization is most intense around the ore zone and decreases away from it.
The host rock sequence in the immediate vicinity of the pits consists of fine-grained massive to laminated meta-tuffs and medium-grained massive lithic meta-tuffs (DB-5 and DB-6). Pyrite molds are common in all the outcropping rocks. The foliation is moderate to strong and subparallel to bedding. Several linear zones of silicified pyritic breccia crop out immediately south of the pits. The texture of brecciated and rebrecciated quartz veins and ferruginous silica with pyrite molds is similar in many respects to many of the jasperoid breccias around Carlin type deposits in the western United States (photos DB-7).
Shearing does not appear to be an important feature of the Deba ore zone. The ore zone is relatively unfoliated compared with the surrounding rocks. The material in the fault zone is breccia, not mylonite. The ore zone is also notably less pyritic than the surrounding rocks. The jasperoids and brecciation rather than foliation suggest that this is a shallow level deposit.
Nineteen samples were taken of dump and alluvial material and four pit samples along the main trend (table 1) whose average gold content is 0.65 g/t. Many of the dump and alluvial samples have anomalous gold values and four exceed 1 g/t. The pit samples do not differ significantly from the other sample types despite the sampling bias toward in situ quartz veins and veinlets. Nearly all the samples have highly anomalous arsenic values.
Deba was explored by a Canadian aid group which included several drill holes. Results of both the Canadian work and my reconnaissance are inconclusive and require further work to adequately explore the Deba anomaly and surrounding area, much of which is covered by thin residual soil and colluvium.
Deba Site Map
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Deba prospect showing sample locations, local soil and rock types, structural orientation, and artesianal pits and trenches. Surveyed by string box and compass. |
TABLE 1
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SAMPLE |
Au ppm |
As ppm |
Description |
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DB-1 |
3.62 |
1770 |
Very fine grained pale limonitic kaol inized schist with 2 mm limonite filled cubic molds. |
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DB-2 |
0.39 |
1240 |
Fine grained dark chloritic (?) schist with dense stockwork of kaolinized veinlets. |
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DB-3 |
1.62 |
1760 |
Fine grained dark very limonitic kaolinized schist with vuggy limonitic milky quartz veinlets. |
|
DB-4 |
0.51 |
680 |
Alluvium with black and white quartz fragments. |
|
DB-5 |
0.25 |
730 |
Medium grained dark chloritic lithic meta-tuff with kaolinized feldspar crystals. Stockwork of kaolinized veins and clear quartz veins with black wisps. |
|
DB-6 |
0.11 |
570 |
Fine grained dark.very limonitic kaolinized lithic meta-tuff. |
|
DB-7 |
0.09 |
1260 |
Hand sample lost in shipping. |
|
DB-8 |
2.34 |
1300 |
Hand sample lost in shipping. |
|
DB-9 |
2.51 |
950 |
Hand sample lost in shipping. |
|
DB-10 |
0.03 |
136 |
Hand sample lost in shipping. |
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DB-11 |
0.41 |
545 |
Hand sample lost in shipping. |
|
DB-12 |
0.21 |
245 |
Hand sample lost in shipping. |
|
DB-13 |
0.05 |
144 |
Alluvium -red-brown clay soil-milky quartz fragments-hard schist fragments. |
|
DB-14 |
0.06 |
166 |
Hand sample lost in shipping. |
|
DB-15 |
0.08 |
740 |
Hand sample lost in shipping. |
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DB-16 |
0.99 |
73 |
Hand sample lost in shipping. |
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DB-17 |
0.03 |
<10 |
Fine grained dark hematitic schistose lithic meta-tuff. |
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DB-18 |
0.03 |
114 |
Vuggy silicified limonite-hematite-quartz breccia. |
|
DB-19 |
0.05 |
23 |
Very fine grained vuggy hematitic limonitic silicified breccia. |
|
DB-20 |
0.02 |
53 |
Dark vuggy hematitic limonitic siliceous breccia with clasts of milky quartz and porous limonitic fragments. |
|
DB-21 |
0.02 |
285 |
Hand sample lost in shipping. |
|
DB-1P |
0.62 |
520 |
Vuggy brecciated milky quartz stockwork with 2% limonite filled cubic molds in pale kaolinized schist. |
|
DB-2P |
1.64 |
2700 |
Very fine grained dark limonitic hematitic kaolinized schist. |
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DB-3P |
0.46 |
775 |
Limonitic milky quartz vein in massive kaolinized saprolite. |
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DB-4P |
0.21 |
104 |
Vuggy milky quartz vein with 0.1 mm limonite filled cubic molds. |
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PHOTO DB-2. Kaolinized quartz stockwork in the kaolinized hangingwalI along the main fault structure at Deba. |
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PHOTO DB-3. Close-up of the kaolinized stockwork of veinlets in the chloritized footwall of the main fault structure at Deba. |
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PHOTO DB-4. Main fault structure exposed in a pit at Deba. Note the difference in alteration between the hangingwall (brown) and the footwall (grey). |
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PHOTO DB-5. Laminated meta-tuffs just outside of the ore zone, Deba. |
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PHOTO DB-6. Coarse grained massive lithic metatuff near the ore zone at Deba. |
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PHOTO DB-7. Pyritic jasperoid breccia near the ore zone at Deba. Note the brecciated milky quartz and laminated structure. Silica replacement of a carbonate rich zone? |