Emerita Gold Corp. announces the completion of geophysical exploration programs at its 100% owned Las Morras Property in the Extremadura Region of western Spain. The geophysical surveys consisted of Very Low Frequency (VLF), Induced Polarization (IP) and Electrical Resistivity Tomagraphy (ERT) surveys over the Central and Northwest target areas. The surveys identified several anomalies that are interpreted to represent shear zone structures coincident with the previously identified gold geochemical anomalies (see news releases dated August 29 and April 8, 2013). These interpreted structures will be evaluated as potential bedrock sources for the gold identified in the soils over the geophysical features by trenching and, if appropriate, drilling.
As previously reported, geochemical surveys have identified two areas with strong gold anomalies referred to as the Central and the Northwestern areas . In the Central area two gold geochemical anomalies have been identified, both approximately 300 meters wide and extending in an east-west direction 500 meters and 800 meters, respectively. These anomalies extend beyond the survey limits to the east and also to the west (see press release dated April 8, 2013).
The Northwestern area is characterized by a single gold anomaly (Figure 3) that extends approximately 700 meters long and over 100 meters wide in an east-west direction. This anomaly also extends beyond the limits of the survey area to the west and to the east (see press release dated August 29, 2013).
Geological mapping indicates that these gold anomalies are underlain by zones of strong shearing in bedrock. The shear zones are developed within the Precambrian Schist-Greywacke Complex (SGC) and are characterized by a zone of high strain and local quartz-gold veining, with predominantly a east-west direction. Outcrop is limited and the geophysical surveys are designed to improve the targeting of the follow up program.
Geophysical surveys (VLF, IP and ERT) were carried out during October and November 2013, with interpretation completed in mid December, to identify geophysical anomalies representative of bedrock structures potentially related to mineral occurrences. The surveying was performed in both, the Northwestern area and the Central area.
The VLF survey consisted of 27 linear kilometres in both the Northwestern and Central areas, where measurements were performed every 10 meters. As shown in Figure 4, in the Northwestern area 8.9 linear kilometres were surveyed on 14 lines oriented north-south, with lines ranging from 350 to 1,100 meters each. In the Central area 18.1 linear kilometres were surveyed on 20 lines with north-south orientation and lines ranging from 550 to 1,100 meters each (Figure 6). The spacing between lines was determined according to the results of the geochemical campaign (see press release dated August 29, 2013), ranging from 50 to 100 meters.
The IP and ERT surveys consisted of 10.4 linear kilometres in both the Northwestern and Central areas. Both the IP and ERT surveys were measured simultaneously with the same device. The spacing between electrodes was 10 meters, which allows detection of features up to 120 meters depth. Figure 5 shows the distribution of the 11 lines of the IP and ERT surveys for the Central area, where 6.93 linear kilometres were surveyed. All lines were 630 meters in length oriented in north-south direction excepting one line with an east-northeast orientation. In the Northwestern area 5 lines were measured by IP and ERT, for 3.47 linear kilometres. The lines varied in length, from 630 to 950 meters. The spacing between lines was determined based on the results of the geochemical campaign (see press release dated August 29, 2013), ranging from 100 to 450 meters.
VLF and ERT-IP images/profiles clearly indicate several subvertical anomalous geophysical zones, characterized by resistivity-chargeability highs (i.e. 300-5,000 Ωm, and >150 ms) (Figure 6).
Geophysical Survey Interpretation
The VLF survey showed conductive anomalies in both the Northwestern and Central areas which have a predominantly east-west orientation. However, some alignments of northwest- southeast direction have also been identified. These VLF anomalies correspond to fault orientations seen in mapping and with the geochemical data.
The IP and ERT surveys allowed the identification of bodies and zones with high chargeability values in the case of IP and high/low resistivity values in the case of ERT. The survey identified bodies with a broad east-west orientation in both the Northwestern and Central areas, which are coincident with the VLF results.
The geophysical data, together with geologic information and geochemical data from the two target areas, identified features having characteristics that would be expected from a shear zone system. This shear zone system is interpreted to represent a possible source of the gold found in the area and will be the focus for follow up trenching and, if merited, drilling. The geophysical anomalies are coincident with geochemical anomalies found in the central and northwest areas. Furthermore, both the geochemical and geophysical anomalies are open along their strike, particularly to the east. The extent of the anomalous body in the Central target area, based on the geochemical and geophysical results, is 1,200 meters long, 90 meters wide with an extension to a depth of at least 120 meters based on the IP/IRT, corresponding to the bottom of the geophysical profiles. In the Northwestern target area the anomalous body is 600 meters long, 80 meters wide and continues to a depth of 100 meters, corresponding to the bottom of the geophysical profiles.
The identification of geophysical anomalous areas (i.e., faults zones and bodies of high resistivity and high chargeability) represent the prospective targets for trenching and drilling.
Both electromagnetic (EM) and DC-geoelectrical methods were selected to perform the survey. These methods are well-known to be suitable for cost-effectively identifying geophysical characteristics for geological features such as shear zones with low sulphide mineral concentrations. The selected techniques were Very Low Frequency (VLF) (Klein and Lajoie, 1980), Electrical Resistivity Imaging (ERI) (Griffiths and Barker, 1993) and Induced Polarization (IP) (Keller and Frischknecht, 1966).
The VLF measuring was carried out with an ENVI system (Scintrex) equipped with a VLF sensor module. The VLF sensor consists of three orthogonal coils designed to make it an omni- directional system.
The acquiring system for the ERT-IP was a Terrameter LS resistivimeter (ABEM SE) with 12 channels and 250 W Tx ouput. The array was implemented by 4 multicore reels of 16 take-outs each, steel electrodes and connections, up to 64 electrode configuration system.
Details and Figures