The SF Tin project is located in the west-central region of Bolivia, 60km southeast of the city of Oruro, in the Potosi department (Figure 1). The 2 sq-km property encompasses the historical open pit and underground workings from Spanish Colonial times, which exploited the deposit on a minor and limited scale.
Figure 1: Location of the polymetallic Sn-Zn-Ag project
The mineralisation is hosted within a window of Silurian age (423 – 419 Ma) clastic sediments comprising interbedded and layered units of greywacke/sandstone (Scc), as well as interbedded sandstone, siltstone, and shale units (Sll – Sun). The Silurian aged sedimentary rocks which host the mineralisation are unconformably overlain by volcano-sedimentary and pyroclastic ignimbrites (Tvm) of Cenozoic age (66 – 0 Ma), with dacitic to rhyodacitic compositions across much of the surrounding area (Figure 2).
Figure 2: Geological plan map
The mineralisation appears to be structurally controlled along a NW to NNW trending zone, which comprises a stockwork framework formed by a series of mineralised stringers, < 1cm, as well as mineralised quartz veins which range in thickness from 1 to 30 cm. Mineralised hydrothermal breccias, ranging in thickness from 1 cm – 30 m are also observed within the sequence, with disseminated mineralisation occurring within the matrix and clasts of the breccia, as well as cross cutting mineralised stringers.
Tin is hosted within cassiterite (SnO2), while sphalerite (ZnS) is the primary zinc ore mineral. Quartz, pyrite, marcasite, and various clay minerals such as kaolinite, illite, and smectite constitute the bulk of the gangue minerals, with minor amounts of oxides such as goethite, limonite and hematite also occurring within the host rocks.
Figure 3: Property boundary of the Tin project highlighting location of completed drill holes.
Figure 4: Cross section OF drill hole ESF001 (Rio Tinto) & DDH-SF-001 (WHG)
Figure 5: Cross section OF drill hole ESF002 (Rio Tinto) & DDH-SF-002a (WHG)
Table 1: Tin (Sn), Zinc (Zn), Lead (Pb), and Silver (Ag) assay results of selective boreholes and intercepts.