Kartuni ProjectIn early 2002 an investigation was made of the Kartuni River area, to the north of the Puruni River. Work done included regional multi-element geochemical sampling and geological mapping. Fieldwork showed that published drainage maps in this area contained several errors, particularly in the headwaters, which have been corrected in our digital database. Lower down in the Kartuni drainage, some areas had been investigated in detail in the 1970’s by the UN, but higher in this drainage only a handful of people have previously visited the area.
When the Kartuni River is high, logistics are relatively easy, with road access to Million Mountain from Bartica or Georgetown, easy boat access to Payuka Falls, a short portage, then boat access to within 20km of the headwaters, depending on the water level. In the dry season boat access is difficult. A new road to Toroparu and a tractor trail beyond that now provides an alternative route to within 7km of the headwaters.
Drainage geochemistry has resulted in the identification of a number of areas with high gold in stream sediment & BLEG samples. One area in the highest part of the Kartuni drainage contains 8 samples with 1.0-3.46ppm Au in –80# SS samples (INAA) and max 708ppb Au in BLEG samples. If thresholds are reduced slightly, 19 samples contain over 0.3ppm Au in one district 18km x 14km (E-W x N-S). Almost no pannable gold was seen at drainage sample sites, suggesting that gold is very fine grained. No significant gold assays were obtained from the few quartz vein samples in this area. The NW part of this area is anomalous for As (max 62ppm) & Sb (6ppm). Some drainages are also anomalous for Mo (max 8ppm).
A number of other anomalous areas with less impressive gold geochemistry are located further downstream. In the NE of the project area one site also has a spectacular SS Pb anomaly (2548ppm). Only three out of 1900 stream sediment samples collected by GGMC to date in Guyana contain over 900ppm Pb, the rest all contain less than 65ppm. The other two high Pb SS samples are in the centre of the project area, where one sample has 2095ppm Pb with 0.9ppm Au, and the adjacent drainage has 940ppm Pb. The significance of these numbers is unknown; there is no associated Cu or Zn anomaly.
A large area at the east of the project has a consistent area Mo & Sb anomalous area, with a partly overlaping low level tungsten anomaly at the north end. This area includes the historical mineral occurrence of Bennetts workings, where diamonds were also reported. The source of these is not clear.
The geology of the Kartuni area is complex, in that a broad zone of NW-SE trending Mazaruni-Group meta-volcanics and meta-sediments occurs in the upper and lower reaches of the Kartuni, but a locally N-S zone of strongly deformed gneissose syn-tectonic granites, amphibolites and narrow slivers of ultramafic rocks (Devil’s Hole Gneisses) occurs in the north-centre of the area. This zone is bounded in the west by intrusions of gabbro and dolerite that appear to have undergone hydrothermal alteration, but are not deformed. These, along with a thin sliver of serpentinised peridotite rocks are thought to be part of the Badidku Suite, which are described elsewhere in Guyana as being emplaced into the gneiss zones. All units have been intruded by Younger Granites, and Younger Basic rocks.
The area with very high drainage Au geochemistry occurs just east of the N-S, presumably fault controlled zone of gneissose rocks. The geology in this zone consists predominantly of NW-SE trending basic and intermediate volcanics and volcaniclastics, with lenses of quartzite and phyllite. Locally meta-diorite intrusions occur.
The following diagrams summarise available information.
Location map(667K)
Gold anomaly and auction block map (614K)
Geological map(395K)
JERS radar map (1010K)REFERENCES :
Dove, G.A. 1948. Julian Ross-Kartuni Area, Cuyuni River. Map GGMC Cartographic Dept.Heesterman, L.J.L, Kemp, A.W, Arjune, B.K. & Cole, E.. Kartuni Project. Geology Geochemistry and Structure.