Platinum Bedrock Targets

Target 1: Kaburi Anorthosite

The Kaburi anorthosite is likely a part of a layered mafic intrusion of the older greenstone age rocks of 2.2 Ga age. The anorthosite itself has a plagioclase composition and mafic mineral abundance consistent with being part of a layered mafic intrusion rather than an anorthositic massif. Additionally, lead isotope similarities between the anorthosite and adjacent gabbroic rocks across the Kaburi River to the west imply that they are co-magmatic and part of a layered sequence. Further, very high chromium concentrations in soils suggest the presence of ultramafic layers, further indicating the presence of a layered mafic intrusion in this area. Platinum, palladium, and related elements exhibit anomalously-high concentrations in soils and biogeochemical samples (Yari-Yari tree leaves) in discrete areas within the anorthosite layer, defining a linear trend of Pt-Pd anomalies, and suggesting the presence of a PGM reef of the Merensky and J-M type in underlying bedrock.

Target 2: Semang Dike

The large mafic dike at Semang trends in a N-S direction for approximately 25 miles and, estimating from its topographic expression, may be as much as a mile wide. The dike is mapped as Avanavero age (1.6 – 1.8 Ga), younger than the age of the Kaburi anorthosite, mafic rocks underlying Mazaruni River sediments at Aruwai, and the platiniferous layered mafic intrusion known as Mochila in Venezuela. Because of its younger age, the Semang dike was not initially a PGM exploration target for GlobalMin, but dredge concentrate sampling along the entire length of the Mazaruni River from Bartica to Peaima Falls indicated high concentrations of PGMs and chromium in the area of Tiboku Falls to Bow Falls near Semang. Follow-up rockchip sampling of the mafic dike at Tiboku Falls revealed fresh gabbroic rock containing 203 ppb Pt and 48-96 ppb Pd. Repeated sampling and assaying of these rocks confirmed these concentrations. Continued exploration using soil sampling has resulted in the definition of areas containing high concentrations of Pt-Pd-Cu-Ni-Co-Cr in soils in discrete zones on northern portions of the dike proximal to airmag anomalies. The close relationship between airmag anomalies coming from bedrock features and soil PGM anomalies indicates the presence of significant bedrock PGM mineralization in this area. Additional, strong airmag anomalies are present over the dike in discrete areas to the south that have not yet been explored by GlobalMin, but it is likely that additional PGM-mineralized zones will be discovered in these areas during the Prospecting Licence stage of GlobalMin’s continued exploration.

Target 3: Aruwai

A reach of the Mazaruni River from Aruwai to Chitigokeng Falls has been found to contain anomalous concentrations of PGMs in dredge concentrates, with the reach from the airstrip and camp above Aruwai Falls to Melville Creek containing a profound abundance of PGMs. It is possible to estimate that as many as 100K ounces of Pt and 50K ounces of Pd may be present in the alluvial sediments in this area. GlobalMin has determined that these PGMs are dominated by Pt-Pd-Sn minerals (eg. Rustenburgite and Atokite) as well as Pt-Fe alloys and PGM sulfides and arsenides. The Rh mineral Hollingworthite is also present. Notably lacking at Aruwai, and other areas in northern Guyana as well, are minerals and analytically-determined concentrations of Os-Ir-Ru. This lack of measurable Os-Ir-Ru and abundance of Pt-Pd-Sn minerals is also indicative of the source of Pt-Pd being found in Guyana’s alluvial sediments being layered mafic intrusions, not ultramafic bodies of the zoned, alpine, or Alaska type. Exposures of bedrock underlying the Roraima Formation just to the north of Chitigokeng Falls and in drill core samples taken by GlobalMin just to the south of Aruwai Falls, show that the Mazaruni River is eroding the older greenstone rocks in this area. These older rocks in Venezuela and at Kaburi are the rocks known or inferred to be mineralized with PGMs and may be the source of alluvial PGMs at Aruwai. Airmag and groundmag surveying at Aruwai reveal both circular and linear anomalous zones that may be related to bedrock sources of the profound PGM anomaly at Aruwai. It is the additional exploration of these zones that GlobalMin intends to pursue during the Prospecting Licence phase of its future efforts at Aruwai.