field trip report - segweb.org · field trip report . quadrilátero ferrífero, brazil . july...

14
Field trip report Quadrilátero Ferrífero, Brazil July 18-22 nd 2017

Upload: phungxuyen

Post on 30-Nov-2018

214 views

Category:

Documents


0 download

TRANSCRIPT

Field trip report Quadrilátero Ferrífero, Brazil

July 18-22nd 2017

Acknowledgment

We would first like to thank SEG (Society of Economic Geologists) for the financial

resource used for the trip. To UFPR (Universidade Federal do Paraná), which, even with financial

problems provided us transportation.

We thank the professors who collaborated with us for the trip, especially Professor

Rosaline Silva and Professor Lydia Lobato (Universidade Federal de Minas Gerais) for the

introductory lectures on regional geology and Fe and Au deposits and the UFMG SEG Student

Chapter for the warm welcome and the organization of the lectures.

We are grateful to AngloGold Ashanti, Companhia Siderúrgica Nacional (CSN) and Vale

for allowing us to visit their mines and to their geologists who accompanied us: Rogério, André,

Rafael, Frederico and Suellen (AngloGold Ashanti); Vitor (CSN); and Natércia (Vale).

Finally, we thank our academic advisor Professor João Carlos Biondi for the knowledge

shared and his partnership during the whole trip.

Members of the UFPR SEG Student Chapter who participated in the fieldtrip, pictured at Vale’s Fe mine.

Biondi (advisor), Bruno, Laisa, Luiza, Andressa, Daiane, Alberto, Matheus e Ivan.

Introduction

The technical visit to Quadrilátero Ferrífero (QF) began on July 17th and ended on July

22nd. UFPR SEG visited open pit mines of three companies, as well as a lecture about the regional

geology of QF at UFMG with SEG Student Chapter partners.

The purpose of the trip was to visit one of the largest mineral provinces in the world and

to understand the geological settings, as well as the metallogenesis. In addition to the geological

and economic importance, QF is a historical region for the development of mining in Brazil.

UFPR SEG also visited three mining companies: AngloGold Ashanti (Sabará, Minas

Gerais), Companhia Siderúrgica Nacional (Congonhas, Minas Gerais) and Vale (Nova Lima, Minas

Gerais). These mines are among the largest producers of Au or Fe in Brazil.

Participants

João Carlos Biondi Professor Academic advisor

Alberto Caixeta Botelho Undergrad student Vice-president UFPR SEG SC

Andressa de Araújo Silva Undergrad student Secretary UFPR SEG SC

Bruno Henrique de Moura Merss Undergrad student Member UFPR SEG SC

Daiane Munch Undergrad student Member UFPR SEG SC

Ivan Rossi Undergrad student Member UFPR SEG SC

Laisa Stingelin Colaço Undergrad student Member UFPR SEG SC

Luiza Silva de Freitas Undergrad student President UFPR SEG SC

Matheus Tonioti da Purificação Undergrad student Member UFPR SEG SC

Logistics and Location

QF is 1000 km (620 miles) from Curitiba, from where we started our trip. Transportation

was provided by UFPR.

Brazil – route from Curitiba (A) to Belo Horizonte (B)

Quadrilátero Ferrífero – map showing the mines visited (yellow) and cities of the

region (blue)

Activities

July 17th, 2017 - Start of the trip – Curitiba (PR) to Jundiaí (SP)

- Overnight in Jundiaí

July 18th, 2017 - Morning: Jundiaí to Belo Horizonte (MG)

- Afternoon: meeting and talks about QF with UFMG SEG Student Chapter

- Overnight in Belo Horizonte

July 19th, 2017 - Morning: visit at Lamego Mine – AngloGold Ashanti

- Afternoon: visit the drill core deposit of the Cuiabá Mine – AngloGold Ashanti

- Overnight in Conselheiro Lafaiete

July 20th, 2017 - Visit at Casa de Pedra Mine – Companhia Siderúrgica Nacional (CSN)

- Visit and overnight in Ouro Preto

July 21st, 2017 - Visit at Capão Xavier Mine / Mutuca - Vale

- Afternoon: visit the Mines and Metal Museum - Gerdau

- Overnight in Belo Horizonte

July 22nd, 2017 - Return to Curitiba, overnight in Jundiaí (SP).

Lectures on the Geology of QF and associated deposits

Two lectures on the geology and mineral deposits of QF were organized by UFMG SEG,

and held on July 18th at UFMG Geosciences Institute in Belo Horizonte and included participation

from 25 people.

"Examples of Iron Deposits in Quadrilátero Ferrífero", was presented by Professor

Rosaline Cristina Figueiredo e Silva. General aspects of the formations that compose the São

Francisco Craton were reviewed, specifically the stratigraphy of the Minas Supergroup, where

the iron deposits in the region are concentrated. These deposits are part of the Cauê Formation

and they are Paleoproterozoic superior type BIF composed by itabirites and massive hematite.

Hypogenic and supergenic processes are associated with high concentrations of iron.

"Gold in Brazil: main deposits, production and prospects", presented by Professor Lydia

Lobato, covered the main metallogenetic systems that generated the largest gold deposits in

Brazil: orogenic, IOCG and hydrothermal magmatic. Emphasis was given to Au-orogenic type

deposits in Rio das Velhas Greenstone Belt of São Francisco Craton, among them the Archean

deposits of Lamego and Cuiabá, both hosted in BIFs.

UFPR and UFMG SEG participants and professors Rosaline e Lydia.

Lamego and Cuiabá Mine – AngloGold Ashanti

The visit at Cabeça de Pedra pit from the Lamego Mine occurred on July 19th and was

accompanied by three geologists from AngloGold Ashanti (Rogério, André and Rafael). The mine

is an open-pit type and the mineral deposit is classified as Au meso to epithermal orogenic type.

The mineralization is hosted in the sedimentary and volcanic sequences of the Rio das Velhas

greenstone belt, metamorphosed in greenschist facies and arranged in an antiform fold dipping

to SE. Gold mineralization is related to formation of smoky quartz, which were fluid feeders that

promote the sulphidation of the iron layers of BIFs, generating Christmas tree structures (Fig. 1).

Gold occurs both in free

form in quartz veins, as well as

associated with pyrite and other

sulfides. The evolution of the deposit

is associated with the percolation of

gold rich thiosulfate fluids from

shear zones and destabilization of

the latter in the iron layers of BIFs

and in the contact with

carbonaceous phyllite above.

The visit at Cuiabá Mine, also owned by AngloGold Ashanti, was not possible due to

operational issues with the underground mine. In the meantime, it was possible to see the drill

core deposit, where the mine geology was presented to us by the geologists Frederico and

Suellen. The deposit is a stratabound type, hosted in BIFs and volcanoclastic sulfates. The

arrangement of the mineralized layers occurs in the folded flank of a sheath fold plunging to the

southeast. The high sulfur activity of the fluid promoted precipitation of pyrite and gold

(proximal), and pyrrhotite (distal).

1

Casa de Pedra Mine – Companhia Siderúrgica Nacional (CSN)

The visit at Casa de Pedra Mine took place on July 20th. It is the second largest ore

exporter in Brazil, with resources of 6 billion tons of high-grade ore (> 64% Fe) with production

of 30 million tons per year.

The mineral deposit explored in Casa de Pedra Mine is located between the Sinclinal

Moeda and Sinclinal Dom Bosco, composing the Cauê, Paleoproterozoic Formation of the Minas

Supergroup. The ore, composed of massive hematite and dolomites, is oriented according to NW-

SE lineaments, plunging 110/45. The hypothesis of formation of this deposit is through

hypogenic processes of carbonation of the silicate BIFs, conducted through NW faults, and

superimposed supergenesis with the leaching of part of the carbonate and concentrating high

grade ore.

In the main body, the primary feeder of the plant, the ore is friable hematite, with high

Fe content (68-69%). This ore forms due to the weathering of carbonated BIFs, concentrating

hematite in the residual form, as observed in the slopes of the mine (Fig. 2). BIFs also occur with

hydrothermal specularite, but these do not constitute large accumulations of Fe.

2

Capão Xavier Mine - Vale

Located in Nova Lima, near Belo Horizonte, Capão Xavier Mine produces about 15

million tons of Fe ore annually, with 62% content and 52% cutoff. The ore is composed of

compact goethite, hematite, friable hematite, specularite, compact dolomitic itabirite and

siliceous itabirite (Fig. 3). The mineralized body occurs between the dolomites of the Gandarela

Formation and the phyllites of the Batatal Formation, Paleoproterozoic of the Minas Supergroup,

São Francisco Craton.

The itabirites host formations of Fe mineralization, with intermediate

to low levels of MnO and MgO. The metamorphism was at a very low degree,

with weak deformation, evidenced by the presence of greenalite (diagenetic)

in the BIFs silicate facies. The iron formations are interpreted as a superior

type.

The higher content of itabirite ore occurs in hinge and axial planes of

folds. Supergenic processes were fundamental for the generation of the ore,

with the formation of weathering profile as shown in the figure. The gangue,

bauxite and geothite are the product of chemical leaching, friable hematite as

residual concentrate and massive hematite as supergenic concentrate.

3

Mines and Metal Museum - Gerdau

UFPR SEG Student Chapter

Committee 2017

João Carlos Biondi – Academic Advisor

Francisco de Azevedo, Jr. – Industry Advisor

Evandro Klein – Industry Advisor

Luiza Silva de Freitas – President

Alberto Caixeta Botelho – Vice President

Andressa de Araujo Silva – Secretary

Guilherme Fedalto - Treasurer