PROJECTS - Don Sixto (La Cabeza)
Geochemistry
AMD carried out regional rock chip and lag sampling and in the Don Sixto project area, stream sediment and lag sampling in conjunction with BLEG analysis were tried with limited success. While each of the various geochemistry survey methods had specific advantages rock chip sampling proved to be the most applicable method and was carried out in detail in the Don Sixto prospect area. It was the use of this method that delineated the El Cuello, El Ojo, La Luna, La Mandibula, El Labio East, El Labio West, El Labio South, La Barbilla, El Cachete, and La Oreja prospects. The drilling programme, both reverse circulation and diamond core provided additional rock geochemistry samples.
Rockchip Geochemistry
AMD utilized rock chip sampling as the preferred geochemistry survey method for delineation of mineralisation and drill targets. Rock geochemistry included selective rock and vein sampling, composite chip sampling and channel sampling. Composite sampling at Don Sixto was over 4m, 10m or 25m intervals. This method consists of collecting rock chips at measured 0.5m spacing over the total sampling width to make up the required 4-5kg sample. The chips collected at each 0.5m spacing represent the total sampling width. In order to minimize a bias on the overall sampling, vein material was sampled and analysed separately. A combined total of 2,396 samples comprising 782 rock chip composites and 281 channel sampling were collected in 1997 and 1998.
All rock chip samples were assayed for gold (50g Au F.A/A.A finish, 10ppb detection limit) and for a 37-element ICP analysis including Ag, Al, As, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, La, Li, Mg, Mn, Mo, Na, nb, Ni, P, Pb, Sb, Sc, Sn, Sr, Ta, Te, Th, Ti, U, V, W, Zn Zr. In addition Hg was assayed by the cold vapour method with a 10ppb detection limit. Sample preparation and gold assay were done by American Assay Laboratories (A.A.L) in Mendoza while the ICP analysis was done at their laboratory in Reno, Nevada. Chemical standards prepared by Geostandards Pty Ltd and Gannet Laboratories Ltd., both of Australia were routinely inserted at 20-sample intervals in the rock chip sample series.
Evaluation of the multi-element suite indicates a variation in element associations across the project area. A generalised geochemical association for each of the prospects is given below.
- El Cuello : Au-Ag-As-Hg-(Sb-Cu)
- La Luna : Au-Ag-As-Hg-(Sb)
- El Ojo : Au-As-Sb-(Ag-Mo)
- La Mandibula : Au-Ag-As-(Hg-Sb-Mo)
- El Labio East : Au-Ag-(Hg)
- El Labio West : Au-Ag-(As-Hg-Cu-Zn)
- El Cachete : Au-Ag-Cu-Pb-Zn-(As-Mo)
- La Barbilla : Au-Ag-(As)
- La Oreja : Au-Ag-As-Hg-(Sb-Pb-Zn)
