Manganese
Campo Formoso - BA
The area of mining process no. 870.997/2021 occupies 73.36ha and is located in the municipality of Campo Formoso, Bahia, Brazil.
HIGHLIGHTS
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LOCATION AND LOGISTICS
The area of mining process No. 870.997/2021 covers 76.36 hectares and is located in the municipality of Campo Formoso, Bahia, near the municipal headquarters.
The nearest city is Campo Formoso itself, located 7 km away, with 5.5 km on well-maintained asphalt and 1.5 km on a dirt road, also in good condition. Campo Formoso is approximately 410 km away from Salvador, Bahia.
Fig 1. Geographical Location of the Visited ANM Process
Fig 1. Local geology with rolling mesh and identified lithologies.
Fig 2. Map of main access routes to the visited site, highlighting the district of "Missão do Sahy," where the southern route begins (featuring gentler slopes in the mountainous terrain).
The Campo Formoso region offers excellent infrastructure to support a mining project. In addition to the city having various options for hotels/guesthouses, specialized workshops, heavy equipment rental, and other positive aspects (such as banks and medical services), the neighboring city of Senhor do Bonfim is only 26 km away and also provides options to meet all the needs of a small-scale mining operation.
Fig 3. The images illustrate the access routes to the visited area, consisting of dirt rural roads in good condition and mountainous terrain.
GEOLOGICAL CONTEXT AND REGIONAL MINERAL POTENTIAL
The visited mining site is located within the Contendas-Jacobina-Mirante Lineament, in the central part of the São Francisco Craton. The formation of this lineament, characterized by a mountainous relief extending 500 km in a NNE-SSW direction, is associated with the tectonic overlap of the Itabuna-Salvador-Curaçá Belt over the Jequié Block, both of which rest upon the Gavião Block.
This geotectonic origin resulted in numerous deformational events that altered rocks, created geological structures, and enabled diverse mineral occurrences/deposits. This is the regional context of the so-called "Serra de Jacobina." As a result, the entire geographical terrain surrounding this mountainous zone exhibits favorable conditions for mineral fertility.
Fig 4. Regional geology of the area under focus by the ANM process. Note that the predominant geological influence in the visited region is the Cruz das Almas Formation, which belongs to the Jacobina Group
The main rocks present in the visited region that influence its geology are from the Cruz das Almas Formation (composed of metavillites, sandstones, quartzites, and schists) and the Missão do Sahy Formation (Metachert, manganiferous formation, BIFs, and phyllites).
Mineral extraction is common in the region, with some cities having over 10 decades of activity in mining and prospecting, such as gold and quartz mining in Jacobina, gemstones in Pindobaçu, chromium and limestone in Campo Formoso, manganese in Senhor do Bonfim, and quartzite in Jaguarari. In this regard, the surroundings of the visited area are marked by a high mineral potential for various types of substances, as exemplified below, which are of great relevance for the technical observations that will be described in this report.
Fig 5. Map of mineral occurrences, with a yellow highlight detailing the region of the visited area.
REGIONAL OCCURRENCES OF MANGANESE.
In the context of the Jacobina mountain range, which includes the surroundings of Campo Formoso and Senhor do Bonfim, the metallogenesis of manganese is similar: this substance was concentrated through hydrothermal processes along shearing structures, an origin that indicates characteristic for the quality of the ore in general: a high frequency of other metals associated with manganese, such as iron and copper. However, within high strain zones of the mineralized layer, it is usually possible to observe boudins with high-purity massive manganese.
Fig 6. Example of a manganese mineralized zone in the region. In RED: Zone with Iron contamination. In BLUE: Zone rich in massive manganese.
REGIONAL OCCURRENCES OF GOLD AND OTHER METALS.
However, within high strain zones of the mineralized layer, it is usually possible to observe boudins with high-purity massive manganese. Some of the most famous metallic occurrences within the Serra de Jacobina are gold ore deposits, which are primarily more frequent from the city of Pindobaçu to the south of the mountain range (towards Miguel Calmon), where metaconglomerates and quartzites altered by hydrothermal activity host most of the gold mines and prospecting sites.
The northern sector of the Serra de Jacobina, where the visited ANM process is located, near Campo Formoso, does not have a history of gold prospecting or extraction. However, the geological context and structures observed in the field suggest the possibility of positive anomalies, as the same geological processes of fluid alteration and element reconcentration occurred in the rocks present there. The existence of chromium deposits and copper occurrences less than 7 km away from the area, within the same geological context, also support the hypothesis of a positive regional potential for other metallic elements in the area.
EXTRACTION OF QUARTZITES – QUARRIES IN OPERATION.
In the last two decades, the Serra de Jacobina has been extensively explored for the extraction of ornamental stones, specifically quartzite.
One of the most notable geological characteristics of the rocks in this mountain range is the concentration of Fuchsite in the quartzites and conglomerates of the Serra do Córrego, Rio do Ouro, and Cruz das Almas Formations, which gives the rocks a greenish color and adds greater value to the extracted material. The local topography allows for large volume deposits for quarry openings, and the center-north location in the state of Bahia favors the logistics of transporting these materials to other regions, such as Espírito Santo.
The visited ANM process includes rocks of this nature, which may present feasibility for a quartzite extraction project. The cities of Jaguarari, Campo Formoso, Senhor do Bonfim, and Pindobaçu are examples of producers of blocks and are located near the evaluated region.
LOCAL GEOLOGY
The field activities allowed for the definition of 3 main geological compartments within the visited process, which are not defined here as Formations or individual units, but rather as zoning of distinct mineral potentials, making it easier to interpret and plan for the utilization of possible substances/ores in the area.
ZONE OF MANGANESE-BEARING METASEDIMENTS.
This zone covers the southern sector of the polygon and concentrates the main manganese occurrences in the area, with old prospecting sites and several outcrops enriched in the metal.
As mentioned in the chapter above, the manganese concentrations in the Serra de Jacobina are associated with geological structures that altered the rocks and channeled fluids enriched with silica, manganese, iron, and other metals. The same typology was observed in the occurrences cataloged within the area: fine metasediments, such as phyllites and oxidized arkosic sandstones, sheared, with the presence of quartz veins/veinlets and many manganese and iron oxides precipitated in pockets and/or fracture planes within the rock, with pyrolusite and psilomelane being the main ore minerals present.
In addition to this primary typology, there are also supergenic manganese concentrations above the enriched layers due to surface processes. This material, although of good concentration, has a smaller volume.
The zone of manganese-bearing metasediments does not limit the occurrence of the metal to this region, but rather demonstrates the area within the polygon with the best characteristics of high strain shear zones containing manganese ore. It is in this zone that new exploratory studies regarding this ore should be focused.
"Old excavation at point P26."
"Boulders of ore associated with supergene enrichment in soil."
Example of a block of massive ore with few contaminants.
"Old excavation at point P26."
"Outcrop of in situ ore N000° (N-S) at point P3."
"Showing details of iron oxide contamination in the material, a common characteristic of manganese in the region."
"Showing details of iron oxide contamination in the material, a common characteristic of manganese in the region."
"Outcrop of in situ ore N000° (N-S) at point P3."
ZONE OF METARENITES AND QUARTZITES.
This zone is bounded to the south by manganesiferous metasediments and to the north by crystalline basement rocks, thus occupying the entire central region of the mining process.
The zone of metarenites and quartzites comprises a wide variety of siliciclastic rocks; however, ferruginous (oxidized) metarenites, white metarenites, and various quartzites (light-colored, greenish, and grayish) predominate.
In addition to these rocks, large quartz veins are noticeable, along with fault systems, breccias, fractures, and shear zones, which may contain various mineralizations, such as manganese, gold, and other metals.
Outcrop of dark gray quartzite at point P4
Large white quartz vein identified near the ANM point at point P29
Example of very fine-grained, heavily fractured oxidized metarenite at point P9
Outcrop of dark gray quartzite at point P4
The compartmentalization of this zone occurs along rock layers dipping steeply to the east, with layer orientation following the trend of the Serra de Jacobina, and foliation between N060° and N350°. Contact regions, where different lithotypes meet, are typically associated with structures that alter the chemical composition and physical characteristics of the rock. For this reason, in the northern contact zone with crystalline basement rocks, for example, alterations such as sericitization, kaolin formation, and other completely altered metasediments were observed.
The zone of metarenites and quartzites thus presents a positive potential for:
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Identification of various metallic occurrences;
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Identification of quartz veins with high purity;
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Identification of rock masses for the extraction of quartzite blocks;
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Identification of other non-metallic substances associated with ductile and brittle geological structures.
Fig 7. Outcrop of metasediments in a contact zone between geological units, with sheared, altered, and deformed rocks, including the presence of quartz veining and iron oxides—positive characteristics for identifying metals such as gold. Point P4.
PREVIOUS MINERAL POTENTIAL AND EXTRACTION OF IDENTIFIED SUBSTANCES
According to the preliminary data obtained, field data, and mining history information, it was possible to determine that the central and southern regions of the visited polygon are the ones of greatest interest in the short term for the advancement of various mineral exploration activities, as these areas host the main occurrences of manganese ore, quartzites, and other possible substances, as already described above.
Based on this information, the following interpretations are made for each mineral possibility:
MANGANESE ORE
It presents positive and very promising mineral potential; however, some characteristics of the existing ore must be taken into consideration before determining the feasibility of its extraction, such as:
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Chemical quality of the ore: Although the samples appear to have few impurities, such as iron oxide and silica, the hydrothermal association of this metal leads to the possibility of contamination, as described in item 2.1. A more representative chemical characterization of the deposit is needed beyond the CHIP samples already collected in previous stages.
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Volume and waste/ore ratio: The mining process visited, in the southern sector, where the manganese ore occurs, is narrow, about 120m, which prevents other promising outcrops from being included in the reserve calculation for the deposit. In addition to this information, there is also the waste/ore ratio, which varies significantly at the visited points and may influence the calculation of the recoverable ore volume. In this regard, further research stages are required, which will be described and suggested.
Fig 8. Example of a high-quality manganese ore sample obtained from the visited area, but still with the presence of impurities such as silica (yellowish colors).
From a strategic perspective, the manganese ore is located in an area with favorable characteristics for water and energy supply, access, and ore transportation (including via railway, with the FCA – Ferrovia Centro Atlântica being present in Campo Formoso). Additionally, according to Mr. Jose Raimundo (guide during the field visit), the main surface owner is in agreement with the progression of research and extraction activities.
QUARTZITE
It shows positive potential due to the high likelihood of significant volume in different locations, as well as the surface characteristics of some outcrops found, such as point P30, which represents a micro-region with the presence of green quartzite (currently in high demand in the ornamental stone market).
Despite these positive characteristics, when considering the idea of producing blocks from this material, it is necessary to take into account the constant presence of brittle structures (fractures and faults) that could compromise quarrying and the opening of pits, which were observed in many of the visited outcrops.
Fig 9. Illustration of varied quartzite samples from different outcrops in the visited area.
From a strategic perspective, access for production transportation, depending on the location within the area, would be via a secondary road to the south, through routes leading to the district of "Missão do Sahy," due to the steep slopes of the roads heading north toward Campo Formoso. Aside from this aspect, the area presents technical justifications for further development and investment in new research phases for this substance.
OTHER METALS AND MINERAL SUBSTANCES
As explained in the sections above, the local geological context allows for the possibility of mineralization of other metals in the rocks and geological structures. For example, samples were collected from a brecciated zone with manganese precipitation at point PXX, which, in addition to this material, includes evidence of hydrothermal activity—very promising characteristics for the identification of volatile elements, sulfides, and other base metals, for instance.
Fig 10. It is possible to see in detail the angular fragments of white metarenite, quartz veins, and associated oxides.
The Serra de Jacobina itself denotes significant metallogenetic potential, allowing for the identification of a wide variety of mineral substances in more detailed research stages. In the case of the area in focus, there is, for example, a possibility, albeit small, of quartz, gold, and chromium.
ROCK SAMPLING
During the field visit, 8 samples were collected, subdivided according to the objective of each, based on the principle of a more detailed description in the office, with cataloging for sending to the laboratory and specific chemical tests in the case of manganese ore and other specific rocks, as well as polishing tests to verify the aesthetic quality of the quartzites.
GENERAL CONSIDERATIONS
The previous chapters clearly indicate the existence of positive prior mineral potential for manganese ore and quartzite. Thus, the scenarios outlined below encompass research activities designed to advance work on both possibilities.
MANGANESE ORE
Due to the geological characteristics of the deposit type, as mentioned in item 6, it is recommended that complementary research stages be carried out for a more detailed assessment of volume, depth, surface occurrence, and mineral chemical quality. To achieve this, it is expected, in addition to a detailed mapping of the rocks and structures in the region, the development of sampling, and, at a minimum, geophysical acquisitions/modeling.
ORNAMENTAL ROCK - QUARTZITES
The sandstone and quartzite zone includes good occurrences and outcrops of quartzites with strong potential for advancing research, which should focus on the surface spatialization of the rocks and, mainly, on the structural characterization of the massifs. Detailed mapping should be used to identify the behaviors of the main fracture and fault families that could compromise the potential quarrying/extraction of blocks.
OTHER OCCURRENCES
Due to the positive potential of the region for the presence of various substances, a more detailed survey of the entire area is necessary, which will allow for the determination of the feasibility of advancing to more specific stages for other types of ore, such as those previously mentioned.
FINAL CONCLUSIONS
ABOUT THE GEOLOGY, it is concluded that:
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The study area is located in a region with occurrences of metasedimentary rocks and geological structures of high mineral potential from the Jacobina Group, predominantly consisting of quartzites, metarenites, and rocks altered by hydrothermalism.
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The geology of the area is favorable for the identification of different substances and ores.
ABOUT THE CURRENT MINERAL POTENTIAL, it is concluded that:
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With the reconnaissance data, it was possible to define 3 zones of distinct mineral potentials, with the southern sector being of the greatest interest due to the large occurrences of manganese ore. The other two zones are secondary in terms of mineral potential, but they may still indicate the existence of economically viable substances (such as quartzites).
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Despite being promising, especially for manganese, the real mineral potential of the visited ANM process will be defined after the advancement of the activities proposed in Tables 3, 4, and 5, and the results presented, where the best strategy for continuity, production, or interruption of the projects will be determined.
ABOUT THE STRATEGIC POINTS, it is important to highlight that:
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The logistics for the transportation of a possible block and/or gold extraction should be well planned, but initially, it presents good development conditions.
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The presence of FCA – Ferrovia Centro Atlântica Railway, 8 km away, facilitates the design of a large-scale transportation logistics for manganese ore. However, if this is not a viable option, transportation by highways to the nearest port (Aratu – 390 km) is also plausible.
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The area is close to a power source, while water should be sourced from the surrounding areas, without major difficulties.
