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Geophysical technical report geophysical study of induced polariztion and electric resistivity in location of possible sulfated zones for gold mineralization

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Ⅰ、Program introduction

On May 28, 29 and 30, 2019, at the request of Mr. Eli Kervahal, Geoprospecto - Solutions in Geophysics, carried out a geophysical study campaign through the geoelectric characterization of the subsurface geological materials, through induced polarization and electro resitivity, which had as objective to locate possible gold mineralization, that occur associated with sulfate zones (primary gold), for the confirmation of the geophysical anomalies. In the electro resistivity we find possible regions with low resistivity values (less 300 Ohm.m) that may indicate the presence of fractures and faults. While induced polarization, identify high load ability values to pinpoint possible sulfide zones. In this context, due to the history of geophysical studies in Brazil, using induced polarization, the incidence of gold mineralized zones associated with quartz veins, the load anomalies indicate values above 50 mV / V or milliseconds.

Study area

The study area is located around 35 km from the district of Casa de Tábuas, in the city of Santa Maria das Barreiras, Garimpo Forquilha, State of Pará, with the following coordinates 571509 LESTE and 9039248 North / Datum WGS84. The access to the Fork Fork takes the BR-158 from the Casa de Tábuas District, covering about 20 km of paved road and then following 15 km by unpaved road.

Ⅱ 、Eletro resistivity method

The method of electro resistance is based on the introduction of electric current in the ground, from an arrangement called an electrode arry. In general, this device consists of four electrodes, according to Figure 1.

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Electrodes A and B are referred to as current electrodes, by means of which a subsurface electric current is applied. This circuit is connected to an ammeter, by means of electric cables. The electrodes M and N are conventionalized as potential electrodes, used to measure the potential difference created by the current circuit, whose measurement is carried out by a voltmeter connected between them.


Ⅲ、Survey Program

Six electrical resistivity survey lines were performed with the Dipole-Dipole array (F). Each survey line has electrode spread of 230 m length with electro spacing of 5 m and 10 m. 19 levels of investigation are performed. To conduct the geo-referencing of the CE stations, Garmin Etrex 10 GPS was used. The geographic coordinates were located at Universal Transversal of Mercator - UTM, WGS 84 / Zonal 22 South. The survey lines were setup in place with the help of field assistants. The geophysics survey aimed at profiling the subsurface and to facilitate the positioning of the potential locations with promising subsurface characteristics for future investigations.

For the geophysical survey of IP / Resistivity, model GD-10 from the GD SERIES D.C. GEO-ELECTRICAL SYSTEM was used in the electrical resistivity profiling. GD-10 is manufactured by the Geomative Inc. (Figure 4). Twenty-four stainless steel electrodes with 12.5 mm diameter and 50 cm length, and 24 non-polarizable lead sulphate electrodes were used (Figure 5). Multi-core electrode cabling was used to connect the electrodes to the measurement equipment, in order to perform automated measurements. IP acquisition is performed in time domain, with paste-paste windows and current injection intervals (5A) of 8s and 16s. This is achieved through the constant voltage injection of 1000 V from an external source (7 kVA generator).

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Figure 2 - Map of the location of the 6 IP Lines / Resistivity in Forklift (Source: Google Earth, 2019).

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Figure 3 - Equipment GD SERIES D.C. GEO-ELECTRICAL SYSTEM, model GD-10, manufactured by Geomative

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Figure 4 - Stainless steel electrode and non-polarizable lead sulphate electrode.



Ⅳ 、Interpretation of results

Line 01 

In Line 01 (230 m in length and 54 m in depth) , two IP anomalies detected were considered strong, due to the fact that they have a value around 270 milliseconds. For this reason, it is recommend to confirm these anomalies through borehole drill between pickets 9 and 14 (depths between 17 and 54 meters) and between pickets 17 and 18 (depths between 9 and 27 meters),. They are named Zone 1 and Zone 2 respectively, with a slope of 60º, to confirm the possible sulphide zone. Due to the high chargeability value, there is a great possibility of success in the detection of gold accumulation (Figure 5).

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Figure 5 - Line 01

Line 02 

In Line 02 (115 m in length and 37.7 m in depth), two IP anomalies detected were considered strong, due to the fact that they have a value around 88 milliseconds. For this reason, it is recommend to confirm these anomalies through borehole drill between pickets 10 and 12 (depths between 19 and 38 meters) and between pickets 14 and 15 (depths between 6 and 38 meters),. They are named Zone 1 and Zone 2 respectively, with a slope of 60º, to confirm thepossible sulphide zone. Due to the high chargeability value, there is a great possibility of success in the detection of gold accumulation (Figure 6).

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Figure 6 - Line 02

Line 03

In Line 03 (230m in length and 54 m in depth) , only one IP anomaly detected were considered strong, due to the fact that it has a value around 280 milliseconds. For this reason, it is recommend to confirm these anomalies through borehole drill between pickets 10 and 16(depths between 19 and 54 meters), named Zone 1 respectively, with a slope of 60º, to confirm the possible sulphide zone. Due to the high chargeability value, there is a great possibility of success in the detection of gold accumulation (Figure 7)

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Figure 7 - Line 03

Line 04

In Line 04 (230m in length and 54 m in depth) , only one IP anomaly detected were considered strong, due to the fact that it has a value around 358 milliseconds. For this reason, it isrecommend to confirm these anomalies through borehole drill between pickets 9 and 14 (depths between 16 and 54 meters), named Zone 1 respectively, with a slope of 60º, to confirm the possible sulphide zone. Due to the high chargeability value, there is a great possibility of success in the detection of gold accumulation (Figure 8).

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Figure 8 - Line 04

Line 05

In Line 05 (230 m in length and 46.2 m in depth) , two IP anomalies detected were consideredstrong, due to the fact that they have a value around 576 milliseconds. For this reason, it is recommend to confirm these anomalies through borehole drill between pickets 8 and 10 (depths between 27 and 46 meters) and between pickets 12 and 16 (depths between 26 and 46 meters),. They are named Zone 1 and Zone 2 respectively, with a slope of 60º, to confirm the possible sulphide zone. Due to the high chargeability value, there is a great possibility of success in the detection of gold accumulation (Figure 10).

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Figure 9 - Line 05

Line 06

In Line 06 (230m in length and 46 m in depth) , only one IP anomaly detected were considered strong, due to the fact that it has a value around 182 milliseconds. For this reason, it is recommend to confirm these anomalies through borehole drill between pickets 8 and 14 (depths between 13 and 54 meters), named Zone 1 respectively, with a slope of 60º, to confirm the possible sulphide zone. Due to the high chargeability value, there is a great possibility of success in the detection of gold accumulation (Figure 10).

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Figure 10 - Line 06


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