Property Description and Location
The Namiquipa Project (Figure 1) is located in the Municipality of Namiquipa, Chihuahua State, Northern Mexico, approximately 145 kilometres west-north-west of the city of Chihuahua. The Project is within the Namiquipa Mining District adjacent to the village of El Terrero.
The Project consists of three concessions (Tasmania, America and Rolys – Figure 2) currently totalling 4,400 hectares. An application to surrender 2,000 hectares from the Tasmania concession has been lodged and is pending.
Figure 1, Namiquipa Location
Figure 2, Project Concessions
The Namiquipa Project is within the lower volcanic sequence (LVS) of the larger Sierra Madre Occidental Volcanic (SMOV) geologic zone which hosts several economically important epithermal silver deposits in the top 10 silver producers globally.
The stratigraphy at Namiquipa comprises multiple andesitic volcanic units and a basal rhyolite dome. It is transected by north-south oriented Ag-Pb-Zn bearing quartz veins, and north-west oriented faults. The historically mined America and Princessa veins exhibit highest grades within the competent andesite.
Mineralisation occurs as argentite and tennantite-tetrahedrite-yellow to red sphalerite-galena-chalcopyrite bearing quartz veins with peripheral illite-pyrite grading out into chlorite alteration.
The volcanic sequence displays moderate silica-adularia alteration over broad zones in permeable host rocks. Gangue minerals include magnesium carbonate, chalcedonic silica and locally kaolin, the latter of which occurs with bonanza Ag grades and is indicative of acid sulphate waters collapsing down north-west cross structures. South plunging flexures host ore shoots.
Statistical analysis of geochemical data suggests that an early quartz-sulphide event (ie Au-Cu-As-Sb) has been overprinted by a carbonate-based metal Ag-Pb-Zn event.
History / Exploration
The project includes the La Venturosa silver mine which was the site of underground mining operations for silver, lead and zinc from 1929–1936, 1948–1955 and 1990-2002. Mining was on a very small scale in the 1929-1936 period. More extensive mining took place in the latter two periods when both oxide and sulphide resources were exploited. Historically the mine produced 14.37moz silver, 32,550t lead (produced from 1.16mt mined oxide/sulphide material) and 43,530t zinc (from just sulphide material).
Mining has taken place over a strike length of just 1,250m and to a depth of only 250m (in places) and generally down to 100m. Mining ceased in 2002 due to flooding and low metal prices.
Figure 3, La Venturosa silver mine’s Princessa Shaft head frame and ore bin
In 2010 the previous owner (Cerro Resources) recovered and digitised a large amount of data on the historic workings and undertook ground magnetic and induced polarization work programs. Drilling followed the mineralized trend to the north and south of the La Venturosa silver mine. These included areas where mining is reported to depths of 100m and along strike in both directions from the existing mine workings.
In 2011/2012 a total of 86 diamond holes for a total of 31,125 metres were drilled. The drilling confirmed the system consists of multiple veins and assays returned high values of silver, lead and zinc.
In 2013 a further IP program was completed and later interpreted.
In 2014 a further 6 diamond core holes (2,511m) were drilled to test vein extensions and IP anomalies. Whilst the drilling suggests the extension of buried andesite host rocks may be restricted it also identifies that the known eastern bounding fault was active during mineralisation, with the eastern bloc down dropped. There exists a western bounding fault which might represent a target for buried underground mineable quartz-argentite mineralisation with reported elevated silver grades. There is ample justification for futher interpretative work.