Guyana Geology & Mines Commission

In late 2002 an investigation was made in the Pashanamu and Puruni River area, between previous areas investigated (Morabisi North, Kartuni and Upper Puruni). Work done included regional multi-element geochemical sampling, geological mapping and compilation of historical data. Fieldwork showed that published drainage maps in this area contained several errors, particularly in the headwaters, which have been corrected in our digital database. Despite the fact that diamond mining occurred in the SW of this area in the 1920’s, very little previous geological work had been done.

At the time when fieldwork was done, access was by road to Million Mountain, then by boat up the Puruni River. When water is high this is not difficult, with only a short portage at Payuka Falls. Since that time a road built for a proposed hydroelectric project in the upper Mazaruni, and abandoned in the 1980’s has been re-opened. This now gives access from Peter’s Mine to the southern part of the project area along the watershed with the Mazaruni. Improved access has lead to a “shout” in the area around the historical No Man’s Land diamond field, and a new settlement has been built (Oranapai New Road). In late 2004 an investigation of this diamond area was made by A. Crawford (report in preparation).

Drainage geochemistry has resulted in the identification of a number of areas with high gold in stream sediment samples. Some of these are already held under valid exploration permits, but a number of these areas were not previously known to be of interest, or considered too remote.

In the Pashanamu River stream sediment samples in anomaly Area 1 contain between 0.05 and 2.8ppm Au, and pannable gold was seen at several sites. The highest values occur at the western edge of this area, within existing claims, but the remaining area still contains between 0.05 and 0.5ppm Au in SS samples, and at one site good pannable gold (average 10 grains per pan). Structural data and geochemistry suggest the possibility that a number of N-S structures are mineralised in this area.. The geology of this area is complex, consisting of high grade schists (some with kyanite), greenschist facies andesitic volcanics, and both foliated gneissose granites and equigranular granites.

In geochemistry anomaly Area 2 stream sediments contain between 0.06 and 0.18ppm Au. Again some of the catchments with the best stream sediment gold values are already held in valid claims, but one catchment with 0.18ppm Au in stream sediments is unclaimed. The auction block in this area also contains known diamond occurrences, first identified by Conolly in 1926.

In Area 4 stream sediment samples contain 0.04-0.8ppm Au. Structural interpretation suggests the possibility that primary gold mineralisation may be related to a combination of N-S and NW-SE trending structures. Carter in 1960 described finding nuggets at approximately 185400E 704100N. Drainage samples also show this area as anomalous for gold, though as this is a larger drainage with more highly anomalous branches upstream, it is likely that this represents downstream accumulation from area 4. This area lies within a broad NW-SE trending zone with a consistent arsenic (max 18ppm) and low level antimony anomaly. A few stream sediment samples also contain a small amount of silver (max 4ppm), manganese (3100ppm) and Bi (Max 6.6ppm). In this zone chemistry also mirrors geology, with moderately high Cu (max 62 ppm), Co and Ni related to the presence of meta-volcanics, including meta-basic rocks.

Currently the area is closed to applications, but the blocks on the attached maps will be offered for auction. One block contains known alluvial diamond occurrences west of Arabagai Falls, the other areas have anomalous gold in drainage samples. The following diagrams summarise available information.

Conolly 1926. The Mazaruni Diamond Field.
Hawkes, D.D. 1960. Geology of an area south of the Puruni River.
Hawkes, D.D. 1961. Explanatary notes Puruni SW 1:200,000 scale geological map.
Heesterman, L.J.L, Kemp, A.W. & Nestor, G.A (2001). Upper Puruni Project. A summary of Geochemistry, Geology & Structure in the Headwaters of the Puruni River.
Heesterman, L.J.L, Kemp, A.W, Arjune, B.K. & Crawford, A.A.. (2002). Morabisi North - Kamawari project. A Summary of geochemistry, geology & Structure.
Heesterman, L.J.L, Kemp, A.W, Arjune, B.K. & Cole, E.. Kartuni Project. Geology Geochemistry and Structure.
Heesterman, L.J.L, Arjune, B. Cole, K. & Kemp, A.W. (2005). Pashanamu Project. Geology Geochemistry and Structure (In preparation).
Schielly, H. 1967. Geological and geophysical investigation east of Enachu, Mazaruni River.