SUMMARY

INTRODUCTION 3

PARTICIPANTS 5

LOCATION OF THE VISITED MINES 6

GEOLOGICAL SETTING 7

DAILY REPORT 19

August, 4th: Arrival in Salvador 19

August, 5th: Braúna Mine - Lipari Mineração Ltda. 19

August, 6th: Ipueira Mine - Ferbasa (Jacuricí Complex) 23

August, 7th: Coitezeiro Mine - Ferbasa (Campo Formoso Complex) 25

August, 8th: Caraíba Mine - Mineração Caraíba S/A 27

August, 9th: Fazenda Brasileiro Desenvolvimento Mineral (FBDM) - LeaGold Mining Corp. 31

FINANCIAL REPORT 39

ACKNOWLEDGMENT 40

REFERENCES 41

INTRODUCTION

The Student Chapter of the Federal University of Rio Grande do Sul (SEG-UFRGS) organized a field trip

in 2019 to visit mining facilities in the Bahia state, northeastern Brazil. From August 4th to August 9th, the

group visited five mines in the north of the state which explore primary deposits of diamond, chrome, copper and gold. The group was able to understand the magmatic deposits and get closer to the industry.

Bahia is one of the Brazilian states most wanted by large mining companies due to its iron, nickel, gold and about 80 other types of mineral reserves. Being the main producer of chromium; the second in copper and the third in gold, the state also ranks as the fourth largest mineral producer in the country [1]. The state's highlight in the sector is also reflected in the workforce, being among one of the states that most opened jobs in the mining sector in 2018 [2].

The companies of the visited mines list among the six main producers companies in the state in 2017. They are in decreasing order: Mineração Caraíba S.A., Cia De Ferro Ligas Da Bahia, Fazenda Brasileiro

Desenvolvimento Mineral Ltda. and Lipari Mineração Ltda. Together they contributed to more than 25% in

the commercialization of the state's mineral production [3]. The group for this Field Trip was composed of 10 students of the UFRGS Student Chapter, a geologist

from Vale do Rio Doce and a geologist from Águia Fosfatos. During the field trip, the group stayed in the cities of Feira de Santana, Andorinha, Jaguarari and Teofilândia as they are close to the visited mining companies. The Table 1 indicates the itinerary of the field trip.

Table 1: Itinerary of the SEG UFRGS Field Trip 2019 - Bahia Magmatic Deposits.

DATE ACTIVITIES

Sunday, August 4th Arrival in Salvador, car rental and departure to Feira de Santana.

Monday, August 5th Visit to the Braúna Mine - Lipari Mineração Ltda.Review of mining safety proceduresPresentation of the mine and discussion of the metallogenetic modelVisit to the drill core warehouseVisit to the open pit mine and the beneficiation plantDeparture to the city of Andorinha

Tuesday, August 6th Visit to Ipueira Mine - FERBASA (Jacuricí Complex)Visit to the long-term geology sectorReview of mining safety proceduresPresentation of the mine and discussion of the metallogenetic modelVisit to the drill core warehouseVisit to the underground mineReturn to Andorinha

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Wednesday, August 7th Visit to Coitezeiro Mine - FERBASA (Campo Formoso Complex)Visit to the long-term geology planning groupReview of mining safety proceduresPresentation of the mine and discussion of the metallogenetic modelVisit to the drill core warehouseVisit to the open pit mineDeparture to the city of Jaguarari

Thursday, August 8th Visit to Caraíba Mine - Mineração Caraíba S/A

Review of mining safety proceduresVisit to the underground mineVisit to the long-term geology sectorVisit to the short-term geology sectorVisit to the open pit mineDeparture to the city of Teofilândia

Friday, August 9th Visit to Fazenda Brasileiro Desenvolvimento Mineral (FBDM) - LeaGold Mining Corp.

Review of mining safety procedures Presentation of the mine and discussion of the metallogenetic model Visit to the drill core warehouse Visit to the open pit mine Visit to the underground mine Return to Salvador

Saturday, August 10th Return to Porto Alegre - Rio Grande do Sul

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PARTICIPANTS

Ten members of the SEG UFRGS Student Chapter, who are all undergraduate students of Geology, joined the field trip. They were chosen to participate for having written a motivational letter which was evaluated by the professor advisor José Carlos Frantz. Furthermore, two geologists who work in the Brazilian mineral industry were invited to join the Field Trip with the aim of putting together students and professionals, so that both groups could benefit from scientific exchange. The Table 2 indicates the participants of the Field Trip and their home institution.

Table 2: List of participants of the field trip.

NAME OCCUPATION INSTITUTION SEG MEMBER ID

Luiz Henrique Cadaxa Undergraduate student SEG UFRGS S.C.President

910016

Natanael Cezário Undergraduate student SEG UFRGS S.C.Vice-president

910017

Alice Justi Coan Undergraduate student SEG UFRGS S.C.Secretary

913526

Nicole Padilha Undergraduate student SEG UFRGS S.C.Member

913371

Gabriel Endrizzi Undergraduate student SEG UFRGS S.C.Member

914851

Martin Ströher Undergraduate student SEG UFRGS S.C.Member

914848

Jhenifer Paim Undergraduate student SEG UFRGS S.C.Member

912081

Isadora Munari Undergraduate student SEG UFRGS S.C.Member

914849

Bénédicte Kifumbi Undergraduate student SEG UFRGS S.C.Member

913379

Maurício Guimarães Undergraduate student SEG UFRGS S.C.Member

914845

Bruno dos Santos Geologist Vale do Rio Doce -

Rafael Diniz Geologist Águia Fosfatos -

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LOCATION OF THE VISITED MINES

The figure 1 shows the location of the mines visited, which were Braúna Mine (Lipari Mineração Ltda.), Fazenda Brasileiro Mine (LeaGold), Caraíba Mine (Mineração Caraíba S/A), Ipueira Mine - Jacuricí Complex (FERBASA) and Coitezeiro Mine - Campo Formoso Complex (FERBASA). The total route traveled was more than 1000 km long.

Figure 1: Satellite image from Google Earth illustrating the route, main roads and mining location.

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GEOLOGICAL SETTING

São Francisco CratonThe South American continent consists in Precambrian nuclei delimited by two Phanerozoic accretionary

provinces: the Patagonian platform, in the west, and the Andean belt, in the south (Heilbron et al., 2017). The South American Platform (Fig. 2) is the oldest and relatively stable part of the continent constituted by the Precambrian nucleus not affected by the Andean orogenies (Schobbenhaus and Brito Neves, 2003).

The shield areas of South America, known as “Brazilian shields”, are made up of two lithospheric types: cratons and Brazilian orogenic systems. According to the traditional definition, cratons are continental portions, which have maintained tectonic stability. In other words, they are pieces of the continental crust not involved in orogenic processes.

Five Neoproterozoic cratons were recognized on the South American platform: the Amazon Craton, the São Luis Craton, the São Francisco Craton, the Paranapanema Craton and the Rio de la Plata Craton. These ancient cratons later formed the stable portion of the Andean Orogenesis together with the Brasiliano Orogen.

Figure 2: South American tectonic subdivision delimiting the South American platform, the shields and the accretionary provinces (From Schobbenhaus and Brito Neves, 2003).

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The San Francisco Craton (SFC) and its exposed margins in the southeastern Brazil represent the most studied portions of the Precambrian nucleus of the South American Plate. Its counterpart in the reconstructions of West Gondwana corresponds to the Central West African belt exposed in Gabon (Feybesse et al., 1998) (Fig. 3). The São Francisco Craton exhibits the shape of a horse's head, with a maximum length and width of 1100 and 900 km, respectively (Heilbron et al., 2017).

The basement of the SFC includes rock units with more than 1.8 Ga (Almeida, 1977). Archean TTG gneisses, granitoids, greenstone belts, Paleoproterozoic plutons and supracrustal successions are the main lithological assemblies of the basement, exposed at its south and northeast tip (Alkmim and Martins-Neto, 2012). The cratonic cover consists of units younger than 1.8 Ga (Almeida, 1977) and occurs in three distinct morphotectonic domains within the Craton: the São Francisco basin, the Paramirim aulacogen (Alkmim and Martins-Neto, 2012), and the Recôncavo-Tucano-Jatobá Rift (Milani and Thomas-Filho, 2000) (Fig. 3c). In addition to Proterozoic sedimentary successions, the São Francisco basin also contains Phanerozoic units (Permo-Carboniferous and Cretaceous rocks) absent in the Paramirin aulacogen and in the Rio Pardo basin. The Recôncavo-Tucano-Jatobá Rift is mainly filled with sediments from the Upper Jurassic and Lower Cretaceous (Heilbron et al., 2017).

Figure 3: a) Southern Brazil digital elevation model showing the topography associated with the SFC and its marginal strips. b) The San Francisco and Congo Cratons in the reconstruction of Gondwana. c) SFC

limits and structures of Proterozoic covers (From Alkmim et al., 2012; 2013).

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The limits of the Craton are drawn based on the variations in the deformation of the supracrustal rocks and the involvement of the chronic basement by the Orogenesis Brasiliana (Alkmim et al., 1993). At the southern end of the Craton, the Paleoproterozoic orogenic belt covers the region of the Quadrilátero Ferrífero mineral province and the Mineiro belt (Teixeira et al., 2015). The orogenic domain of eastern Bahia in the northeast portion of the Craton is composed of a mosaic of several archaean blocks sutured at about 2.0 Ga (Barbosa and Sabaté, 2004).

The essential features of the terrains that make up the São Francisco Craton are found in Bahia, occupying the eastern part of the state surrounded by the river that gives the Craton its name. The

geotectonic units that form the base of the São Francisco Craton in Bahia are:

- the Gavião Block, which is composed mainly of gneiss-amphibolite and tonalite-granodiorite

associations orthogneisses of the amphibolite facies aged 2.8–2.9 Ga as well as greenstone belts. There is also an old core of trondhjemite-tonalite-granodiorite (TTG) with ages varying from 3.4 to 3.2 Ga. (Barbosa et al., 2004);

- the Serrinha Block, which contains gneisses, amphibolites and orthogneisses of amphibolite facies, mainly of granodiorite composition, aged between 2.9 and 3.5 Ga;

- the Archean greenstone belts (3.2–2.9 Ga) from Contendas - Mirante, Umburanas,

Riacho de Santana and Mundo Novo and the Paleoproterozoic greenstone belts (2.0-2.1 Ga) from

Capim and Rio Itapicuru. They are at greenschist facies and are composed of komatiites with spinifex

textures that vary to mafic and felsic lavas with intercalations of pyroclastic rocks, siliciclastic and chemical sediments;

- the Jequié Block, which is formed mainly by enderbite and charnockite (ages varying between 2.7 and 2.6 Ga) as well as migmatite and granulite. The predominant metamorphic degree is at granulite facies (Barbosa and Sabaté, 2000);

- the Itabuna-Salvador-Curaçá belt of granulite facies. The Salvador-Curaçá segment is exposed in the northeast of Bahia, while the Itabuna-Salvador segment occurs in the southeast. These segments are mainly formed of tonalite, charnockite with basic and ultrabasic enclaves and supracrustal rocks less abundant.

The Greenstone Belt of Itapicuru River The Greenstone Belt of Itapicuru River(RIGB) is the largest and economically the most important

Paleoproterozoic greenstone belt located in the northeast portion of the São Francisco Craton (Fig. 4). The economic importance of RIGB lies in the occurrence of several gold mineral deposits hosted in small to medium-sized shear zones (ie, orogenic type; Groves et al., 1998) in its southern (Weber belt) and northern central (Mello et al., 2006).

The RIGB stratigraphy consists of volcanic sedimentary rocks represented from the bottom upwards by a succession of (i) tholeitic basalts with intercalated chemical sedimentary rocks; (ii) andesites, dacites and riododites interspersed with pyroclastics; and (iii) volcanic ash and pelites, with subordinate arches, conglomerates and chemical sediments (Fig. 4) (Kishida and Riccio 1980; Silva 1984). This volcano-sedimentary sequence is intruded mainly by gabbroic sills and granite-gneiss domes of granodiorite and

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tonalite composition, in general with calcium-alkaline affinity (Kishida and Riccio, 1980; Silva, 1987). The regional metamorphism is at greenschist facies, except near the edges of the granite-gneiss domes, where the metamorphic degree reaches the amphibolite facies (Silva, 1984). The structural feature commonly observed in supracrustal rocks is the succession of large synclines and anticlines bordered by fragile-ductile shear zones on a regional scale, with a general NS orientation, mostly greenstone, and EW for NW-SE in the southern sector (Mello et al., 2006).

Figure 4: Geological map of the Itapicuru River greenstone belt (From Mello et al., 2006).

Fazenda Brasileiro MineThe Greenstone Belt of the Itapicuru River is an area recognized for hosting large gold mineralization. In

this context, the Fazenda Brasileiro Mine, one of the largest gold mines in Brazil, has proven ore reserves of 2,760,000 t, with an average content of 1.0 g Au/t. The Fazenda Brasileiro Mine is located in the northeastern region of the State of Bahia, south of the Greenstone Belt of the Itapicuru River, more precisely in the Weber Belt.

The mineralized zone of the Fazenda Brasileiro deposit extends for 8 km around the Barrocas granodiorite dome, along a 200 m thick EW shear zone, plunging from 45 to 60 ° S (Fig. 4) (Reinhardt and Davison, 1990). The main mineralized bodies consist of systems of quartz-carbonate-albite veins, rich in

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sulfide, hosted by quartz-carbonate-chlorite shale, interpreted as a hydrothermally altered mafic intrusion (Teixeira et al., 1990) and, subordinately, by carbonaceous metapelites. The alterationparagenesis generally present in the vicinity of the vein systems that host gold includes quartz + albite + carbonate ± biotite ± sphene + ilmenite + rutile + sulfides (mainly arsenopyrite, pyrrhotite and pyrite to a lesser extent) (Mello et al., 2006 ).

The system of veins that host gold consist of simple tabular veins or it can form sets of intersecting veins, similar to a stock. As shown in Fig. 5, they are grouped into six distinct types:

- Type I: irregular, 0.5-4m thick gaps, consistent with foliation (E-W / 45–50 ° S);

- Type II: concordant with foliation, centimetric foliated and boudinated veins;

- Type III: centimetric “en echelon” veins, parallel to the E-W foliation, plunging to the north;

- Type IV: NW-SE, 0.3 to 0.5 m thicksub-vertical veins;

- Type V: E-W breccias with 25-45 ° N plunging;

- Type VI: discordant veins that reach the centimeter-thick N-S, generally sterile.

Figure 5: Typology of quartz veins at the Fazenda Brasileiro Mine (From Mello et al., 1996).

Cupriferous deposit of Caraíba The cupriferous province of the Curaçá River Valley is inserted in the northern sector of the Itabuna-

Salvador-Curaçá Orogen (OISC), a Paleoproterozoic tectonic entity that forms the basis of the São Francisco Craton (CSF). It consists of a belt of granulitic rocks 800 km long, from Archaean to Paleoproterozoic, which was deformed and metamorphised due to the collision of the Gavião, Jequié and Serrinha blocks at the end of the Riaciano (Teixeira et al., 2010) (Fig. 6). The OISC corresponds to the portion of rocks aged around 2.0 Ga, located east of the Gavião and Jequié blocks and west of the Serrinha block. To the south, it corresponds to the Atlantic Coastal Belt or Itabuna Belt, which constitutes a northern extension of the Mineiro Belt, and to the north to the Salvador-Curaçá Belt, which has a branch to the east, in the portion on which the Recôncavo-Tucano-Jatobá rift system is based (Kosin et al., 2003).

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Figure 6: São Francisco Craton limit; the rectangle represents the northern stretch of the Itabuna-Salvador-Curaçá Orogen (OISC) (Adapted from Teixeira et al., 2010).

Lithostratigraphically, the Itabuna-Salvador-Curaçá Orogen consists of three mappable units, named: (i) the Caraíba Complex, composed of igneous units from a bimodal suite metamorphosed at granulite facies with TTG's and sometimes granites as felsic representatives, and gabbro-dioritics lenses as mafic representatives, with mafic-ultramafic intrusives (including those in the Curaçá Valley); (ii) the Tanque-Novo Ipirá Complex, representative of a volcano-sedimentary sequence metamorphosed at high amphibolite to granulite facies, subdivided into six informal units, which include aluminous, kinzigitic gneisses with or without garnet, graphite, in addition to limestone and quartzite, among other lithotypes; (iii) the São José do Jacuípe Suite, a mafic-ultramafic unit, represented by magnesian gabbro-norites comparable to greenstone belts rocks, age analyses indicate for these lithotypes ages before 2.7 Ga (Kosin et al., 2003) (Fig. 7). There are also bodies of intrusive granitoids of various compositions, including granites, monzonites and syenites of Paleoproterozoic age, exhibiting varying degrees of metamorphism and deformation, and associated with different stages of orogenesis. They are sin- to post-tectonicbodies, including the Granitoid Riacho da Onça, represented by augen gneisses that have enclaves of ultramafic rocks and rocks of the Caraíba Complex, and the Itiúba syenite, the biggest intrusion of this type in the state of Bahia, placed on a pull-apart type of transition regime (Kosin et al., 2003).

Intruded in the Caraíba and Tanque Novo-Ipirá complexes there are several mafic-ultramafic bodies, of varying dimensions, which sometimes contain copper sulfide mineralization, mainly in the form of bornite and chalcopyrite. The set of these copper mineralized bodies constitutes the Vale do Rio Curaçá Cupriferous Province, which covers an area of about 1700 km², partially embracing the municipalities of Juazeiro,

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Jaguararí and Curaçá (Teixeira et al., 2010). The mafic-ultramafic bodies are composed of ultramafic cumulates (abundant pyroxenite and rare peridotite) and mafic cumulates (melanorite, norite, gabronorite), in addition to leuconorite and rare anorthosite. These rocks have been the subject of a series of studies carried out by different authors, who have attributed them to several petrogenetic hypotheses (Teixeira et al., 2010).

Figure 7: Geological map of the northern segment of the Itabuna-Salvador-Curaçá Orogen (OISC) (Adapted from Kosin et al., 2003).

Caraíba Mine In the Rio Curaçá Valley region, where the Caraíba Mine is located, the basement is tonalitic to

quartzmonzodioritic, with gabroic levels overlapping with a supracrustal pelitic sequence at the base and chemistry at the top. The supracrustal rocks, belonging to the Tanque Novo-Ipirá unit, are represented by graphite leptinite, feldspar quartz gneiss, silimanite garnet biotite gneiss, amphibolite, banded iron formation, calcium silicate rock, marble and quartzite (Teixeira et al., 2010). The whole set was subjected to at least three phases of progressive deformation that generated open and closed folds, with vertical axial planes, N-S oriented axes and smooth plunges to the south (Teixeira et al., 2010).

The mineralization consists of copper sulphides, with a predominance of calcoplrite + bornite paragenesis, in a ratio of 70% to 30%. In addition to chalcopyrite and bornite, there are other sulfides associated with the ore, such as covelite, cubanite, digenite, pyrite, pyrrhotite and pentlandite (Teixeira et al., 2010). Sulphides are generally accompanied by magnetite. There are two types of mineralization associated with hyperstenites and norites and rocks rich in mica (glimmerites): (i) disseminated ore, in a network,

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occupying the interstices of the silicate layer of the host rocks and (ii) epigenetic ore, filling the structural plans of the mafic-ultramafic rocks and, secondarily, in the regional embedding, especially in the calcium-silicate rocks. The disseminated ore occurs only in pyroxenites while fracture ore occurs both in pyroxenites and norites as well as in the calcium-silicatic rocks embedding the mafic-ultramafic body. The mineralization controlled by tectonic also forms gaps, with orthopyroxenite clasts surrounded by chalcopyrite (Teixeira et al., 2010).

The Kimberlites of Braúna The kimberlites are rare but widespread magmatic rocks of great scientific and economic value due

mainly to the mantle xenolites and diamonds they usually bring, which provide direct information about the Earth's internal structure and composition. Braúna's kimberlites represent the oldest known primary source of diamonds in the São Francisco Craton.

The Kimberlitic Province of Braúna (Fig. 8) is located in the Archaean Serrinha Block, which is located in the northwest region of the São Francisco Craton. The Serrinha Block forms an ellipsoidal mega-structure that remained relatively rigid during the collision of at least three blocks to form the Itabuna-Salvador-Curaçá orogen (Barbosa and Sabaté, 2004; Oliveira et al., 2010). The Serrinha Block is divided into 3 litostratigraphic sequences:

1. Archean basement of migmatitic gneisses and plutons of calcium-alkaline to granodioritic composition of the TTG type, with N-S foliation;

2. Supracrustal Paleoproterozoic sequences from the Rio Itapicuru Greenstone Belt and the Rio Capim Group (Costa et al., 2011; Oliveira et al., 2011);

3. Paleoproterozoic granitic intrusions (Silva et al., 2001; Mello et al., 2006; Oliveira et al., 2010). The Kimberlitic Province of Braúna is located in the southern portion of the Northeastern Batolith, which

is the most important Trondhjemitic Paleoproterozoic batholith on the Rio Itapicuru Greenstone Belt. It is controlled by a fracture system with NW-SE orientation, this system houses three kimberlitic pipes (Braúna 03, 04 and 07) and nineteen dikes, which can be connected as single segments, with N30 ° W orientation.

The pipe morphology varies from circular to elliptical and is strongly controlled by joints and faults. The dikes form segments 1 km long and 1 to 5 m wide on the surface. In depth, the dikes are often branched, varying from 20 cm to 1.3 m in width. Braúna kimberlites are typically massive or brecciated and normally carry kimberlitic autoliths, as well as mantle and crust xenolites.

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Figure 8: Geological context of the Kimberlitic Province of Braúna. A) Geological map of the São Francisco Craton, showing the location of the Kimberlitic Province of Braúna. B) Geological map of the Serrinha Block and the Greenstone Belt Rio Itapicuru, with the location of the Kimberlitic Province of

Braúna (black star) (From Donatti et al., 2013).

Braúna 3 and Braúna 7 are the pipes with the most significant volume, they are composed of three lobes, each with subvertical contacts to the northeastern granodiorite (75 ° - 85 °). Brecciated kimberlites are typically seen in the pipe contacts and in rare cases in the central portion of the pipes. Kimberlite dikes are

commonly observed between kimberlitic pipes and in some cases represent connections between pipes,

showing that they acted as feeders during the formation of pipes (Lorenz and Kurszlaukis, 2007). Braúna's kimberlitic pipes and dikes are relatively small, with areas not exceeding 10 ha.

    Aphanitic kimberlites are common, but the most abundant types are macrocratic kimberlites, which are composed of macrocrystal phlogopite and olivine. Most kimberlites contain macrocratic serpentinized olivine and microcrystals in a fine-grained matrix of serpentine and calcite, as well as secondary pyrite. In the aphanitic kimberlites of fine texture, calcite and serpentine of the matrix include olivine, spinel, ilmenite, perovskite, apatite and phlogopite. As the matrixserpentine do not show pseudomorphic textures, its origin is interpreted as olivines alteration.     Crustal xenolites are abundant in Braúna's kimberlites and their textures are usually obliterated by

pervasive alteration. The most common crustal xenolites are granodiorites from the Northeast Batolith, where the kimberlitic magma was placed, as well as amphibolites and gneisses. Mantle xenoliths are relatively rare and highly transformed. They are predominantly peridotites containing garnet.

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Braúna's kimberlites (Fig. 9) have a relatively heterogeneous mineralogy, geochemistry and isotopic composition. Following Mitchell’s (1995) definition that discriminates mineralogically between South African Kimberlites and orangeites, Braúna’s kimberlites were identified as being transitional between these two groups (Donatti et al., 2013). The compositions of Brauna's kimberlite are best explained by a magma derived from a metasomatised cratonic lithosphere with some minor magmatic input from the asthenospheric mantle, probably derived from the rapid decompression associated with the large-scale extension of the lithosphere during the rupture of Rodinia, with age Neoproterozoic (Li et al., 2008). However, the long-term inflow of convective mantle fluids, along with thermal disturbances, may have preconditioned the source region of Braúna's kimberlitic magma at the base of the Craton before Neoproterozoic magmatism.

Figure 9: Geological map and surface exposure of Brauna's kimberlites (From Donatti et al., 2013).

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The Jacurici Complex The Ipueira-Medrado “sill” chromite deposit is located in the northeastern region of the state of Bahia.

The “sill” is actually part of the Jacurici Complex, which is characterized by segments of a chromite mineralized mafic-ultramafic conduit-like intrusion tectonically disrupted in a north-south regional trend.

Chromite measured reserves have an average of 4.5 Mt with 30 to 40% Cr₂O₃ (Mineração Vale do Jacurici

S.A., 1999, internal report) and have been explored by Mineração Vale do Jacurici S.A. (Companhia Ferro-Ligas da Bahia (FERBASA) since 1974.

The chromite ore in the Ipueira-Medrado segment is mined in a single layer 5 to 8m thick, with a continuity of 7km in length along the mafic-ultramafic body. The thickness and continuity of this chromite layer is considerable, as it is hosted by a sequence of mafic-ultramafic cumulatic rocks less than 300m thick. This thickness of the chromite layer is shown to be unusual, compared to other stratiform deposits, due to its great thickness.

The Jacurici Complex is intrusive in granulite-gneissic terrains of the Caraíba Granulitic Complex (Barbosa et al., 1996) and is located in the northeast segment of the São Francisco Craton. The area where the Jacurici Complex intrudes is located along the Serrinha Block, a land of Archean age, composed of granite-greensonte rocks and medium-grade metamorphic gneiss. The metallogenesis of the Jacurici Complex have been studied sice long time and the ore formation is considered to be triggered by crustal contamination in a conduit-like intrusion (Marques and Ferreira Filho, 2003; Marques et al., 2003, 2017; Friedrich et al., 2019).

The Ipueira-Medrado segment is also tectonically broken into two segments that emerge on the flanks of a synform fold. It consists mainly of ultramafic rocks, dunites, harzburgites and pyroxenites that make up more than 80% of stratigraphic units. There are three main zones recognized in this sill, which are listed from the bottom to the top: Marginal Zone, Ultramafic Zone and the Mafic Zone (Marques and Ferreira Filho, 2003).

The Marginal Zone consists of a very sheared margin of the sill. This zone has a thickness of 5 to 20m and consists of highly deformed rocks in contact with the surrounding rocks. The Ultramafic Zone is 250m thick and makes up more than 80% of the stratigraphic section. It is subdivided into three subunits: Lower Ultramafic Unit, Main Chromite Layer and the Upper Ultramafic Unit. The Mafic Zone is 40m thick and forms the upper part of the sill. The rocks range from melanorites to leuconorites and are locally metamorphised.

The Main Chromite Layer (Fig. 10) is 5 to 8 m thick and consists of three sublayers. The lower sublayer has a thickness that varies from 0.5 to 1m, with solid chromite (lumpy ore). This sublayer does not have continuity through the Ipueira-Medrado segment and is better developed in the Medrado area. Chromitites with chain-texture form a distinct and easily recognized sublayer in the lower portion of the Main Chromite Layer. This sublayer has a thickness that varies from 0.3 to 0.6 m in thickness, is rich in chromite and is characterized by having fine chromite texture aggregates surrounding large orthopyroxene crystals.

The upper sublayer is homogeneous, with 4 to 6m of thick chromite (lumpy ore) and is continuous through the intrusion. The Main Chromite Layer has generally acute contacts with the embedding rocks, both of the Lower Ultramafic Unit and of the Upper Ultramafic Unit, and acute contacts are also common among the sublayers.

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Figure 10: Stratigraphy of Ipueira-Medrado segment, indicating the location and thickness of the Main Chromite Layer (From Marques et al., 2003).

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DAILY REPORT

August, 4th: Arrival in Salvador The first day of our field trip was dedicated to travel and accommodation. We traveled by plane from

Porto Alegre (Rio Grande do Sul) to Salvador (Bahia). Then we rented two cars at the airport and headed to Feira de Santana, which was the best city to stay the night, although we still had to travel more than 200 km to arrive at the first mine, the other cities closer to it were either too expensive or did not have an inn.

August, 5th: Braúna Mine - Lipari Mineração Ltda. The Braúna Mine is located at latitude 10 º 55 ’ S and longitude 39 º 25 ’ W, in the state of Bahia, Brazil

(Fig. 11). It is approximately 7 km south of the munipality of Nordestina and 330 km northwest of Salvador (Fig. 12). The Field Trip group arrived at the mine by road, through the BA-120.

Figure 11: Approximate location of the development.

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Lipari Mineração Ltda. was founded in 2008 and employs more than 400 people directly. It is a Brazilian private mining company that owns and operates the Braúna Diamond Mine. Braúna Mine is the first diamond mine in South America, developed from a deposit of kimberlite, the primary source of diamond rock. The Mine is an open pit mining operation that uses its own fleet and equipment to feed a processing plant of 2,000 tons of kimberlitic ore a day, 24 hours a day, 7 days a week.

The FieldTrip members were received by the mine's security team, for explanation of mining safety procedures and verification of the equipment allowed to enter the enterprise. Electronic equipment, such as cameras and cell phones, were left at the reception due to security and in compliance with the company's internal rules.

Then the FieldTrip members were received by geologist Vinícius Andrade, who made an initial explanation about the kimberlitic deposits of the area, with emphasis on the Braúna Mine deposit. Afterwards, the company's drill core warehousewas visited, where the students and the professionals who were traveling with the group were able to view the lithologies present in the deposit and better understand the control of mineralization.

The group visited the lookout point to overlook the open pit (Fig. 13A). Lipari’s geologist informed that it was not possible to see kimberlite exposures in outcrops due to the region's tropical climate. Furthermore the group was not allowed to visit the open pit due to the company’s internal rules. So the view of the kimberlites was limited to drill core samples (Fig. 13B), which add up to 550 m of solid and brecciated kimberlites, which carry autoliths and xenolites from the Northeast Batolith. Amphibolites and gneisses were also found, with texture obliterated by the generalized alteration, in addition to more rare and altered mantle rocks (peridotites with garnet). The kimberlitic body is hypoabissal and exposes several textures with different sizes of crystals ranging from 0.5 mm (microcrystals) to 10 mm (megacrystals), the main minerals

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Figure 12: Location of the municipality of Nordestina.

are plagioclase, olivine (fresh and serpentinized), abundant phlogopite, ilmenite, diopside (serpentinized), calcite, perovskite apatite, pyrite (secondary) and garnet defined as being of eight different types, with garnet being the mineral index of the diamond content, more specifically the “G10” garnet (spinio diopside garnet). Most Braúna kimberlites have uniform magmatic textures, but segregative textures have also been observed.

The group monitored and interacted with the technical team that works with the collection of garnets in sieved soils to define targets of interest (Fig. 13C). The geologist also explained about the geophysical techniques used in the area, where the company works mainly with the magnetometry technique. Then the students were sent to the beneficiation plant (Fig. 13D), which is made up of a crusher, where diamonds larger than 60 mm are released, and successively the granulometry of the rock is reduced. Subsequently, the samples pass through the atomic absorption XRT where the carbon composition is absorbed and detected by the machine and expels the diamond, where a space is opened on the mat and it falls into a concentrating support. The rest of the samples that do not fall pass through a secondary crusher where diamonds smaller than 20 mm are released. The samples then go through a fluorescence and density process to identify the diamonds. Afterwards the samples pass through a conveyor where the diamonds are collected. The final step is separation by dense liquids, with which the company recovers 99.9% of the diamonds. Diamonds smaller than 1 mm have no economic value and are stored.

Figure 13: A) The Field Trip group at the open pit lookout; B) The group at the drill core warehouse listening to the explanation about the kimberlite deposits; C) Technical team presentation; D) The group visit to the beneficiation plant. Notes: pictures provided by the company; detail photos of the core samples were

not authorized.

The exploration of diamonds in Brazil had a lot of strength in the 90s with the company De Beers, when it passed through many states of Brazil, one of them was Bahia. In the municipality of Nordestina 15

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kimberlitic bodies were mapped. In the 2000s, the company Valdiam intensified its exploration in the Nordestina region, arranging drill cores and analyzing the samples using the “book sample” method to define the percentages of the ore. The result was that they found 7 more kimberlitic bodies. Since 2010 the company is called Lipari and has continued exploring the region (near the mine and brownfield). In 2018 another kimberlitic body was found. The open pit operation is concentrated in the Braúna 3 kimberlite deposit, one of the 21 kimberlite occurrences currently explored and developed by Lipari.

The company has projects to expand the production of the ore through the implementation of underground operations, since the open pit mine is expected to operate until 2022. After this period, the mine operation will be 100% underground.

The company recently received an independent engineering study by SRK Consulting Inc. (Canada) that provided a conceptual mine plan for the Braúna 3 kimberlite mine below the pit, with the construction of an access ramp from inside the final pit (Fig. 14).

Figure 14: Image from the underground mine implementation project (Adapted from SRK Consulting Inc. study).

SRK indicated that an underground mine is technically feasible and the characteristics of the kimberlitic ore body are favorable to the use of the mining method called sub-level retreat or open benching. This underground mining method has been successfully implemented in several kimberlite diamond mines in Canada and South Africa.

After the end of the visit the group drove to the municipality of Andorinha, near the next mine visited.

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August, 6th: Ipueira Mine - Ferbasa (Jacuricí Complex) On August 6th, the group visited the Ipueira Mine, located in the municipality of Andorinha, which is 441

km from Salvador, Bahia. The mine is currently managed by Mineração Vale do Jacurici S.A. - FERBASA (Companhia de Ferro Ligas Bahia). FERBASA, which is a private national company based in Pojuca, Bahia, was founded in 1961 and today is one of the 10 largest companies in Bahia.

In the north of the São Francisco Craton there are several mineralized Mafic-ultramafic Complexes, including the Jacurici Complex, which is formed by important chromium reserves. This complex is deformed and tectonically broken, constituting several bodies oriented along an N-S strip with more than 70 km. 15 bodies with potential for mineralization were identified (Fig. 15A). The largest segment is called Ipueira-Medrado “Sill”. This segment is divided into two parts (Ipueira and Medrado), which occur for about 7 km x 500 m x 300 m thick and host most of the complex's chromite deposit in a massive chromite layer up to 8 m thick (Fig. 15B) (Marques and Ferreira Filho et al., 2003). Ipueira Mine is the main mine in operation in the district, with started with an open pit and later advanced to an underground operation, focusing on chromite exploration (Fig. 15C) (Marques et al., 2017).

At the entrance to Ipueira Mine, the group was instructed to leave telephone devices and cameras in the car for security and confidentiality reasons. Then the group was sent to the Mine Exploration and Geological Research Department, where they met the geologist Francisco Xavier Bezerra and other geologists responsible for this department (Fig. 16A). Geological models developed using Vulcan software and drilling schedules with core samples up to 1200 m in new targets of the company were presented. The group also

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Figure 15: Geological map with the location of the Jacurici Complex and the Ipueira Mine (Adapted from Marques et al., 2017).

attended the lecture on safety at the mine and was guided in the use of safety equipment to visit the underground mine. Later, the lecture by geologist Francisco explains that the ore occurs between the rocks dunite and harzburgite, and can be massive and disseminated (Fig. 16B). The mafic-ultramafic rocks follow the stratigraphic order: (i) gabbro; (ii) pyroxenite; (iii) harzburgite; (iv) chromite; and (v) dunite (Fig. 16C). The Main Chromite Layer is composed of solid chromite. The Ipueira body is formed from magmas contaminated by crustal material (Marques et al., 2003, 2017). At certain intervals, the ore contains high levels of phosphorus. In metal alloys this element occurs as a contaminant and weakens the steel when it exceeds certain amounts (Cezario et al., 2017). The processing of the ore consists of: (i) removal of the blocks; (ii) crushing; (iii) classification; and (iv) separation of the desirable waste. The main waste is phosphorus and silica. Chromium ore is sold to China as sand, but the largest production is for domestic consumption in the country. The group was able to visit the drill core warehouse and observe the stratigraphic sequence of hole MV1-94.85 ° (Fig. 16B and D). The company allowed the group to take some core samples with chromite.

Figure 16: A) Visitors at the Mine Exploration and Geological Research Department; B) Core sample MV1-94.85 °, disseminated chromite; C) Core samples with thick layers, approximately 6m of solid

chromite (red) located between the layers of dunite (yellow) and harzburgite (blue); D) Visitors at the drill core warehouse with geologist Francisco Xavier Bezerra, wearing a white helmet. Note: photos provided by

the company.

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In the afternoon, the group was given safety equipment to visit the underground mine, which is currently the mine with the largest production of chromium from the FERBASA Company. They visited the sector responsible for mine planning, managed by mining engineers, civil engineers, geologists and mining technicians, all working together to make the underground mine viable. The group and the mine geologist Eduardo Cardoso Vieira Filho went approximately 330m below the surface, in a minibus. The visitors watched the drilling work (fan drilling) in one of the mine's galleries. The drilling was planned to find the chromium ore layer on the deepest flank of the mineralization. Then they visited an inactive gallery and observed its interior projected on the marbles, which allows greater stability for the constructions inside the mine and greater security of the advance of the ramps until the arrival in the layers of interest. They also saw a newly opened gallery with views of the mining front of the chromite layers approximately 4 m thick.

After the visit, the group returned the safety equipment to the responsible sector and thanked the staff that guided the visit. Then the participants returned to their inn in the municipality of Andorinha, so they could continue their trip the next day.

August, 7th: Coitezeiro Mine - Ferbasa (Campo Formoso Complex) On August 7th the group visited another mine managed by FERBASA, Coitezero Mine, in the Campo

Formoso Chromitic District, which is located approximately 419 km from the capital Salvador. The operations there began in 1961, with the open pit mining method, a model that continues today, with explosives and mechanical dismantling. Although the Complex has 9 mines bordering the north of the Serra da Jacobina, the production is currently concentrated on the Coitezeiro mine, which is the main mine for the extraction of the ore.

The Campo Formoso Complex is located in the northern portion of the São Francisco Craton (Fig. 17), one of the main cratonic areas of the Brazilian Shield, which during the trans-Amazonian cycle was extensively tectonized and metamorphosed, generating trends of preferential N-S orientation. The rocks that form the base of the Complex are gneisses and migmatites, of Archean age, that host the basic-ultrabasic intrusions. Superimposed on the basement are volcanic and sedimentary rocks (composed of phyllites and shale chlorite). In the older portions, granitic intrusions and diabase dikes occur. The Campo Formoso Complex is characterized as a stratiform massif due to the cumulative texture of the ultramafic rocks, the rhythmic alternation of the rocks and the interleaved chromitites. The rocks that make up the complex are mainly serpentinized cumulatic peridotites. The complex underwent major hydrothermal alteration as a result of the intrusions of the granite pluton of Campo Formoso which affected the serpentinized rocks and also underwent profound supergenic alterations, reaching up to 30 m of alteration. The hydrothermal mineralogical assembly is composed of serpentine, talc, carbonates (calcite, dolomite), tremolite and magnetite. The ore is mainly in massive and disseminated form, through layers with thicknesses ranging from a few centimeters to several meters (reaching up to 12m), the mineralized levels are interspersed with serpentinized peridotites (Fig. 18D).

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Figure 17: Geological map with location of the Campo Formoso Complex (Adapted from Lord et al., 2004).

The group started the mine visit in the morning and were instructed to store cell phones and cameras in the car for safety reasons. Then the visitors were introduced to the geologist Harlem Enckel Souza Cunha who accompanied and guided them throughout the visit. The group was directed to a room for the first stage of the visit, which consisted of introducing the mine's safety procedures and providing guidance on the use of safety equipment. Afterwards the group attended a lecture on the regional and local geology of the mine.

The participants then had the opportunity to visit the company's drill core warehouse, where they could describe the core samples, analyze the rocks of the region, the spatial and interval continuity of the ore, as well as discuss the observed structures and minerals. The geologist Enckel showed and also allowed the students to test one of the techniques used by the company's geologists, which consists of the identification of the massive ore, disseminated or sterile, indicated by the color of the core sample when scratched by the metallic hammer, where the brown color is the characteristic concentration of the ore and a grayish color is related to the proximity of the disseminated ore to the sterile zones. After that, the group went to the company cafeteria, where they had lunch.

After lunch, accompanied by the geologist Enckel, we walked the entire length of the open pit mine, the focus of our visit, as there would be no time to visit the underground mine. There we made a cross section of the entire pit (Fig. 18A), which currently has more than 8 benches with approximately 20 m each. The group was able to directly observe structures in Z (Fig. 18C) and structures in M (generated by the folding of the region), faults, dikes and interdigitation of the layers, which consists of their duplication due to the open of the magmatic chamber. The company allowed the group to collect samples of the serpentinite, chromatite and kammemerite mica (purple mica that alters chromite and contains chromium in its structure).

The company plans to make a pushback to the south of the mine, in order to increase the pit size so that there is greater production and use of the resources disposed in the mine, which has an inferred resource of

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around 3 million tons and an inferred resource of 444 thousand tons, with chromite contents of 38% in the lump type chromite while for the other types it is 18%, and recovery of 92% of the ore [5].

As soon as the group finished the cross section, they stopped at the lookout point to take a picture, and returned to the administrative center. Finally, the visitors returned the safety equipment and proceeded to the destination of the next visit, the municipality of Jaguarari.

Figure 18: A) View of the west wing of the mine, with the path taken by the students around the pit; B) The group at one of the lookout points, after finishing the cross section; C) Z structure, characteristic of fold flank; D) Interleaving of layers of serpentinized peridotite with layers of chromite.Note: photos provided by

the company.

August, 8th: Caraíba Mine - Mineração Caraíba S/A On October 8th, the group visited Mineração Caraíba S/A, located in Jaguarari city, in the Pilar district,

about 480 km away from Salvador, north of Bahia. The Curaçá River Valley, located in the northern region of the state of Bahia, is characterized by mafic-

ultramafic bodies of the most varied sizes, containing mineralizations of copper sulfides. All these mineralized bodies form the Cupriferous Province of the Curaçá River Valley, which embraces an area of about 1700 km², including the municipalities of Juazeiro, Jaguarari and Curaçá (Fig. 19). Both these bodies and the basement suffered firstly high-grade metamorphism, reaching granulite facies; and then by retrometamorphism during the evolution of the Itabuna-Salvador-Curaçá Orogen - dated from Archean to

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Paleoproterozoic (Garcia, 2017). The bodies and the basement reached then the amphibolite facies and suffered partial migmatization and also granitic intrusions. With the progressive uplift of the terrain, reactions of the retrometarmophism continued to occur, located mainly in the focus of shear zones, causing a paragenesis of greenschist facies in restricted regions.

Figure 19: Simplified geological map of the Curaçá River Valley, with the locations of the Caraíba, Surubim and Vermelhos targets (Adapted from Teixeira et al., 2010).

The lithological sequence was subjected to at least three deformation phases, which resulted in the general N-S trend with a low plunge to the south of the mineralizations. The mafic-ultramafic bodies are composed of cumulates (mainly pyroxenites) and occasionally gabbros and gabronorites. Sulphides occur mainly associated with hyperstenites, norites and rocks enriched in mica (phlogopite). Magnetite invariably accompanies sulfides. The ore shows evidence of mantle origin, which was deformed by tectonic and metamorphic processes, affecting the mafic-ultramafic sequences and the body's host rocks. The sum of all

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these processes resulted in a mineralization controlled by tectonism and enrichment caused by hydrothermalism of magmatic origin (Teixeira et al., 2010).

As soon as the group arrived at the mine, the members watched a video about operating and safety procedures that should be followed during visitation in all sectors of the complex. After that, geologist Anderson Oliveira and other trainee geologists and mine engineers from the short-term sector were introduced and guided the group to the underground mine (Fig. 20B). The mine has already been in operation for about 40 years, being currently approximately 1400 m deep and adding up to 105 km of distance on underground paths. The visitors entered to a depth of about 900 m, where the temperature reached up to 40°C (Fig. 20C and D). The company allowed the group to collect samples from the underground mine.

The group was able to visualize the sulfide copper mineralizations in the mafic-ultramafic bodies of the Curaçá River Valley, the main ore minerals were chalcopyrite and bornite (Fig. 20A). The sulphide ore had a ratio of 30% bornite to 70% chalcopyrite, which was very evident during the visit to the galleries. Still in the underground, the group was also able to observe the mine transport system to the surface.

Figure 20: A) Sulfide ores (chalcopyrite and bornite) at the mining front; B) Junior mine engineer explaining the mine's operating principles to the group; C) Photo of the group of participants of the field trip

in one of the galleries; D) Visitors analyzing the gallery.

Back on the surface, we had lunch at the company's restaurant and headed for the long-term exploration sector. We were introduced to the junior geologist Tercio Nunes, who gave a presentation of the general context of the mine. The Mineração Caraíba deposit was discovered in 1871, and in 1944 the National

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Department of Mineral Production (DNPM) identified the productive potential. However, the economic viability of the business was only possible in 1974, through the National Bank for Economic and Social Development (BNDES). There are two ongoing projects in Caraíba: Pilar - south of the valley; and Vermelhos - north of the valley; both of which are underground mines. Tercio explained that the ore host rocks are mafic and ultramafic - mainly pyroxenites. These pyroxenites occur as two types: phaneritic crystals of up to 1 cm, which are associated with low copper levels (<2% wt); and aphanitic pyroxenites, associated with higher levels, reaching up to 20% copper. Gabbros and norites are also eventually associated with ore minerals. Other copper minerals are also more rarely found, such as calcocite, and surface malachite and azurite. The importance of the occurrence of K-feldspatization, associated with phlogopite - both with a direct relationship with the occurrence of ore - was also highlighted, a phenomenon that is still being deepened.

The visitors were then sent to the short-term sector for a presentation organized by geologist Anderson Oliveira, who explained the planning and operation of the mine and the sector's duties - which include content estimates, body details by Fandrill surveys, geomechanics of rocks with open galleries, modeling, among other tasks. It is common for short-term geologists to work at the underground mine to carry out a visual estimate of the mining front to improve the geological model of the mine.

Afterwards the group drove by car (Fig. 22A) with Anderson and other trainee geologists from the company to an already abandoned mine at Mineração Caraíba (Fig. 22B and C) - which became unviable due to the decrease in the ratio of sterile proportion and open pit operations compared to the current copper value in the market. There it was possible to visualize the various intrusions of ultramafic bodies mineralized with copper, in addition to structural features of the area - visible in shear structures that cut the ultramafic bodies, which are responsible for the entry of hydrothermal fluids. At the end of the visit, the group was able to analyze some core samples obtained in the pit (Fig. 21 and 22D), and Anderson gave us valuable remarks of his experience as an exploration geologist in the mining sector.

Figure 21: Core samples of pyroxenite with disseminated chalcopyrite and bornite, hydrothermal alteration and carbonate veins with bornite. The red rectangle indicates gneiss brecciated with chalcopyrite

veins. The box length is 1 m.

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Figure 22: A) Transport by carof the group inside the company complex. B) View from the top of the deactivated mine; C) Field Trip group with the geologists of the mine in the deactivated mine; D) Analysis of

the core samples.

Finally, the group said goodbye to the mine staff and thanked them for the visit, left the safety equipment at the reception and headed to the city of Teofilândia, about 300km away from Mineração Caraíba, to prepare for the visit to Fazenda Brasileiro Mine the next day.

August, 9th: Fazenda Brasileiro Desenvolvimento Mineral (FBDM) - LeaGold Mining Corp. (Brazilian Farm Mineral Development)

Fazenda Brasileiro Desenvolvimento Mineral (FBDM) is a development located in the state of Bahia, northeast Brazil, located 180 km from the state capital, Salvador.

The mining district of Maria Preta, in the municipality of Teofilândia, Bahia, started its exploration by the Vale do Rio Doce company in the 1960s by the Rio Doce Geologia e Mineração S/A (DOCEGEO) exploration department (Fig. 23). The mining began at Greenstone Belts Rio Itapicurú (RIGB) in 1972 and the discovery of gold took place in 1976. In 1984 the open pit operation began and continues until today. Currently, the main operation is underground, which occurs since 1988. Then the mine became known as

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Fazenda Brasileiro Desenvolvimento Mineral (FBDM). It covers an area of 63,400 hectares and started the production initially with pile leaching process.

Figure 23: Location and local geology of the FBDM (From the RPA Technical Report NI 43-101, 2018).

Vale do Rio Doce was the first owner of the area and carried out exploration activities until 2003, exploring high-grade ore. DOCEGEO recovered more than 1,288,000 m of drill cores until the open pit mine opened, producing about 61,500 ounces of gold. From 2003 to 2015, the company Yamana Gold Inc. acquired the FBDM property, intensifying its exploration, producing about 905 thousand m of drill cores, with estimates of 2,399,000 tons of ore with contents of 3.39 g / ton (approx. 261,500 ounces). In 2015, the area became property of Brio Gold, which drilled approximately 220 million m of core samples until 2018. After that year, Leagold Mining Corporation based in Vancouver, Canada acquired FBDM and curently performs the operation in the region.

On the morning of August 9th, we arrived at the mine. In the mine parking lot, the cars were parked in reverse, according to safety procedures. The group was searched at the reception of the mine, in order to check for any undue objects, mainly knives and cameras. Only one of the Field Trip participants was allowed to carry his phone and take pictures during the visit. The visitors went then to a presentation room to watch an institutional video of the company and the main safety procedures that any employee and visitor must follow. Afterwards the group was conducted a five-question test to verify the understanding of what was shown. Then the group was taken to the company's amphitheater, where the geology technician and FBDM mine operation supervisor Jorge Santos de Oliveira presented the general geological context and history of the area, production data and the mining company's system (Fig. 24).

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Figure 24: Reception and introduction to the mine. A) Geologist Jorge giving the presentation; B) Group ready for the visit.

The Greenstone Belt Rio Itapicuru (RIGB) is Paleozoic in age and has aN-S trend of about 60 km in length located in the São Francisco Craton in the state of Bahia. The FBDM is a gold deposit with lode hosted in veins with Precambrian epigenetic age, structurally controlled, with hydrothermal alteration with metamorphism at greenschist facies and even amphibolite facies in some places. This metamorphism is triggered by the intrusion of granitoids. The RIGB is divided into three main domains: (i) Mafic Volcanic Rocks - with pillow lavas and massive tholeitic basalt; (ii) Felsic Volcanic Rocks - Calci-alkaline andesites, riodacites and pyroclastic rocks; and (iii) Clastic Sedimentary Rocks - fine grains and conglomerates of volcanic origin.

The mining company is located in volcanic and sedimentary rocks of the greenstones belts, which is limited on one side with the Serrinha block, formed by granitoids and with a base composed of gneisses and archean migmatites. The gold host rock is a chlorite shale (CLX) rich in magnetite and carbonates of gabbroic origin, where there is also a higher concentration of sulfides and oxides that are lithologically and structurally controlled. The mineralized body is found in the Weber Belt, which is Archean in age and has an E-W direction with plunging areas between 40 ° to 70 ° and folds to the south, situated between metagabbros (sill) to the north and quartz-carbonate-chlorite shale to the south, which is thought to have a basaltic origin of ocean floor.

The main trend of mineralization can be closely related to the intrusion of the Dome of Barrocas (which deformed the Weber Belt). The lower mineralized layer is narrower when compared to the upper layer and has a general southward plunge. These characteristics suggest that FBDM is a type of deposit classified with epigenetic origin.

Locally the Weber Belt is a gold mineralized body that incorporates several deposits in the region, one of them the FBDM. It has Archaean age and is approximately 10 km long. Besides that it is folded to the south. Its simplified stratigraphy model consists of basal units composed of a sequence of turbidites with metapelites, metacherts and greywackes; differentiated mafic sills composed of iron-rich metagabbros and metaanorthosite lenses at the top; above, (marker horizon) composed of metariodacites, metachert and graphite metapelites; and the last units composed of metagrabros, mafic shales and metabasalts. From south to north, the Weber Belt was divided into four distinct sequences according to the Table 3.

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Table 3: Four distinct sequences of the Weber Belt.

The hydrothermal fluids migrated through areas of weakness and contact, changing parts of the gabbros. The sedimentary layer that surrounds the chlorite shale (metapelites) served as a trap for the fluids. The carbonaceous host rock originated by hydrothermalism in a structural shear control.

The presence of arsenopyrite is a good indicator of higher gold content. Pyrite indicates a reducing environment. Other minerals associated with the mineralized body are albite, quartz and biotite paragenesis with amphibole. The gold extraction in the mining economic area (stope) is now estimated at 1g / ton, due to the removal of more dispersed fractions and possible mineralized bodies. The main mineralization occurs in quartz veins containing sulfides. Veins families vary in centimeter to metric width. In the figure 25, it is possible to analyze some estimates of gold content and reserves. The mining company extracts between 1 and 1.2 million tons of ore per year (~ 100 to 120 tons / month) [4].

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Figure 25: Simplified reserve estimates (Adapted from RPA Report).

Sublevel Open Stoping is the mining method used in the operation, which consists of the backward upward mining of the galleries. The oxidized ore is processed using a pile leaching method, with 75% recovery, but it does not have good results with sulfides. Larger Au-free grains are removed by magnetic separation. Only sulfide is observed, free gold occurs only in the quartz veins. Coal in “Poupa” (CIP) is the technology used to remove gold from the sulphide part. Large amounts of carbon can cause problems for the beneficiation plant. The modeling of ore bodies and geostatistical analysis is performed by the Vulcan and Leapfrog softwares.

The development cycle involves: (1) loading explosives; (2) detonation and exhaustion of gases; (3) cleaning; (4) removal of loosen blocks (with scaler equipment); (5) scraping off 1 (with LHD equipment); (6) laying steel cables to secure the rocks; (7) scraping off 2 (with LHD equipment); (8) drilling marking; (9) drilling and (10) cleaning.

Still in the morning, the group was taken to the drill core warehouse (Fig. 26). The drilling is made by a fan-shaped net with a length of 200 m. To cubage the deposit samples are made perpendicular to the fan with a 25-25 m net. The core samples are 75 mm in diameter (larger diameters are usedin smaller areas). Some sulfides, such as arsenopyrite, were visualized, as well as families of fractures, alterations and lithological interactions were shown. The alteration is based on oxidation, sulfide, silicification, biotitization, sericitization, amphiboliticization and albitization. In core samples it was possible to clearly identify arsenopyrite crystals with 2 cm in diameter without deformation and the hydrothermal alteration reaching the CLX’s cut by quartz veins with some sulfides, very abundant pyrrhotite and some subordinate arsenopyrite.

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Figure 26: A and B) The group at the drill core warehouse; C and D) Detail of the core sample with sulphides (pyrite and chalcopyrite) mineralized in rock quartz veins.

At the end of the morning, the group was invited to have lunch at the company's restaurant, where we were able to enjoy the local food.

In the afternoon, we had the opportunity to visit the underground mine (Fig. 27), where the group reached up to 600 m in depth in relation to the topographic level of the mine. It was possible to observe a very foliated rock (chloriteshale) with the presence of many veins of quartz concordant with foliation. Some of these veins have important concentrations of sulfide that host the ore; others, usually folded, are not as expressive. In the gallery it was possible to observe populations of faults in the right direction, which displaced the main mineralized area, where geologists are planning new galleries to contemplate more mineralizations. Drilling (fandrill) is used to characterize the mineralized body in more detail. The group's transport inside the mine complexwas carried out by company vehicles, as well as trained drivers of the staff. The members of the group who had beard were invited to shave it to be allowed to visit the underground mine, as it is a safety rule at the FBDM for the use of the respiratory mask and eventual use of the portable compressed oxygen emergency equipment. At this stage of the visit, we were guided at all times by the chief responsible for the security team.

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Figure 27: A) The Field Trip group in the underground mine; B) Monitoring of the assembly of the frandrill to detail the underground pit; C) Analysis of the mine front walls; D) Sulphide in quartz veins and

fractures.

Still with the company's cars, we also visited the open pit mine Cava Sul 1 (also called Canto Sequence) - South Open Pit 1 (Fig. 28). There it was possible to verify the carbonaceous host rock closely related to carbon-rich volcanic clusters. The control of mineralizations is evidently structural in the area, where the ore plunge is to the east, due to its shear zones (associated with deformations) and the percolation of post-genetic hydrothermal fluids, with plunging to the south, in agreement with the main foliation. The veins in general have levels of sulfides and carbonates at their edges (in the contact with the host rock) and more siliceous centers. Groups of veins plunging to the north are generally richer in content, as are restricted boudins.

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Figure 28: Visit to the open pit mine.

It is believed that sulphide mineralization occurred after the deformation of the rocks in the region, with

the shear zones being the main paths so that hydrothermal fluids with the presence of Au, Ar, W, SiO₂ could lodge between the fissures and mineralize, namely the fluids are not syngenetic. The deformation of the area along an E-W shear zone is complex and incorporates several phases of ductile and brittle deformation. A first phase shows intense shear and formation of few folds, and a second phase generated asymmetric folds towards the north which also produced ductile-brittle shear zones. The main mineralization, in the form of sulfide containing quartz veins, is associated with the second deformation event. The carbonate-rich host rock has been linked to carbonate fluids.

At the end of our day at Fazenda Brasileiro Desenvolvimento Mineral, the group returned the individual protection equipment to the staff and was searched again, this time to certify that is has not occurred any kind of sample removal from the mine.

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FINANCIAL REPORT

This Field Trip was mostly sponsored by the Stewart Wallace Fund Grant. The geologists Bruno dos Santos from Vale do Rio Doce and Rafael Diniz from Águia Fosfatos, who have travelled with the student’s group, paid for their own expenditures. Besides that, Bruno dos Santos has voluntarily contributed with BRL 1,000.00 to the Field Trip. Furthermore the Student Chapter members contributed with BRL 480.00 each. The rest of the Field Trip expenditures were paid off by the SEG UFRGS Student Chapter funds, which was possible due to several fund-raising activities long the year. The financial statement of the Field Trip is detailed in table 4 below.Table 4: Financial statement of the Field Trip.

*-Exchange rate at June 24th, 2019: 1 USD = 3.73 BRL

EXPENDITURES $ (BRL) $ (USD)

10 airplene tickets (Porto Alegre-Salvador) 9,421.60 2,525.90

Car rental 1,064.00 285.25

Petrol 774.28 207.58

Road toll 40.00 10.72

Accomodation (for 10 persons):

- Feira de Santana 500.00 134.05

- Andorinha 500.00 134.05

- Senhor do Bonfim 610.00 163.54

- Distrito de Pilar (Jaguarari) 640.00 171.58

- Teofilândia 540.00 144.77

TOTAL 14,089.88 3,777.45

SEG/Stewart R. Wallace Fund Grant 7,460.32 2,000.00*

Contribution from 10 SEG UFRGS members 3,893.28 1,043.77

SEG UFRGS Student Chapter funds 1,736.28 465.49

Bruno dos Santos contribution 1,000.00 268.10

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ACKNOWLEDGMENT

The field trip was supported by the Society of Economic Geologists through the Stewart Wallace Funding Program. The field trip was great because we had the engagement and technical support of many people. The

SEG UFRGS Student Chapter would like to thank: Lipari Mineração Ltda., especially to geologist Vinícius Andrade; Companhia de Ferro Ligas da Bahia (FERBASA), especially to geologists Francisco Xavier

Bezerra, Eduardo Cardoso Vieira Filho and Harlem Enckel Souza Cunha; Mineração Caraíba S/A, especially to geologists Anderson Oliveira and Tércio Nunes; LeaGold Mining Corp., especially to geologist Jorge Santos de Oliveira; and to our academic advisor Prof José Carlos Frantz.

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[1] COMPANHIA BAIANA DE PESQUISA MINERAL. Panorama da Bahia na Minerção Brasileira. Disponível em: http://www.cbpm.ba.gov.br/2019/06/3773/Panorama-da-Bahia-na-Mineracao-Brasileira.html. Acesso em: November 2th, 2019.

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