La Juanita Proyect
Fomicruz has focused the exploration efforts in the eastern sector of the project, where several quartz veins were detected. The largest veins, called Vein 1 and Vein 2, show anomalous concentrations of gold.
The La Juanita project is located in the East part of the Deseado Massif, 65 km to the north of the Tres Cerros locality, along national road 3, and 30 km north of the recently opened Don Nicolas Au-Ag mine. The mineral rights are secured by four mining properties that cover an area of 3350 ha.
The project is dominated by markedly different lithologies in different sectors (Fig. 1). In the western sector (west of road 3), Jurassic igneous rocks dominate; those include granitoids from the La Leona Formation and volcanic rocks from the Chon Aike Formation (ignimbrites and rhyolitic domes), as well as several andesitic volcanic dikes. In the eastern sector (east of road 3), sandstones of the La Golondrina and La Juanita Formations (Permic), and a few granitoids (Jurassic) are the dominant rocks. In addition, large part of the eastern sector, is covered by relatively thin and younger gravel plains.
Fomicruz has focused the exploration efforts in the eastern sector of the project, where several quartz veins were detected. The largest veins, called Vein 1 and Vein 2, show anomalous concentrations of gold. Vein 1 is oriented with an azimuth of 80º, it is about 300 m long, with a width of 3.5 m, and dipping to the NNW. Vein 2, shows a general orientation of 110º, it is almost 500 m long, but is discontinuous at ground surface, and its maximum width is 0.4 m. This vein is hosted by the La Juanita and La Golondrina Formations.
The work accomplished in the eastern part of the project included geological mapping, rock and lag geochemical surveys, a magnetometric survey, rock sampling for determination of alteration minerals, and the drilling of eight diamond boreholes. While carrying out the surface sampling and magnetometric surveys during the last field trips, a few previously unknown short veins, similar to Vein 1, were discovered in the NE part of the project.
At surface, the rock geochemical surveys were carried out mainly on the veins. Vein 1 showed gold concentrations of up to 0.32 g/t, while Vein 2 showed Au concentrations of up to 2.59 g/t. The concentrations of Ag are anomalous, slightly above 20 g/t. The lag geochemical survey, consisted of a pilot test over an area of 400 by 500 m, including outcrops of Vein 2. Results from this test helped to infer the optimal separation of samples, the best indicator elements, and other parameters that should be considered if carrying out a wider survey to discover other veins like Vein 2.
The magnetometric survey covered and area of approximately 8.5 km2, in the eastern part of the project. A preliminary evaluation of the collected magnetic data seems to indicate that the areas of veins with altered host rocks may be inferred from some products of processing the magnetic data; however, that still have to be better interpreted. Magnetometry is a potentially useful method of exploration for the project, because 35 to 40 % of the eastern sector is covered by young sediments, and thus, this geophysical method may reveal the locations of veins masked by the sediments.
In 2014, eight diamond boreholes (555 m) were drilled in the La Juanita project, to test the continuity of the veins at depth as well as their dip and dip direction, and to determine the contents of elements in comparison to those at surface.
Five boreholes were drilled in Vein 1 (371 m) and three in Vein 2 (184 m), showing that Vein 1 is continuous up to at least 50 m of vertical depth, and its estimated vein dip is 56º NNW, while Vein 2 is continuous up to at least 25 m of vertical depth and its dip varies from 50º to 70º NNE, depending on the investigated portion of the vein. At maximum investigated depths, the thicknesses of the veins, although with variations, are similar than at surface; and in both veins, the maximum concentrations of Au are higher at depth than at surface (0.57 vs 0.32 g/t Au in vein 1, and 3.93 vs 2.59 g/t Au in vein 2).
Fomicruz’s geologists think that the eastern sector of the project shows potential for discovery of more mineralized rocks at depth in the known veins, as well as for discovery of new veins, that may be covered and masked by the young gravel plains. In addition, the western sector, which is almost unexplored by the Company, conveys potential for discovery of mineralized rocks in rhyolitic volcanic domes and breccias.
Figure: Geological map of the La Juanita project showing lithologies, and locations of boreholes and areas covered by geochemical and magnetometric surveys