Project

Back to overview

Mineralogical and geochemical characterization of selected supergene profiles and reactive transport modeling of supergene enrichment and exotic mineralization at Chuquicamata, Chile

Applicant Fontboté Lluis
Number 129988
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geochemistry
Start/End 01.05.2010 - 30.04.2013
Approved amount 200'820.00
Show all

All Disciplines (2)

Discipline
Geochemistry
Mineralogy

Keywords (21)

ore; deposits; geochemistry; metallogeny; supergene; enrichment; acid; mining; drainage; ore deposits; supergene enrichment; exotic mineralization; acid rock drainage; tailings; Chañaral; porphyry copper; heavy metal; bacteria; stable isotope; neutralization potential; acid-base accounting

Lay Summary (English)

Lead
Lay summary
The project intends to apply the results and methodic developments recently reached in the field of acid mine drainage (AMD) to the study of exotic copper deposits. The study takes the example of supergene profiles at the giant porphyry copper Chuquicamata deposit and the nearby Exotica deposit. It focuses on the following main goals: 1) Mineralogical and geochemical characterization of selected supergene vertical profiles in Chuquicamata and Exotica using the methods developed for AMD studies. Main tools will be optical mineralogy XRD and differential XRD (DXRD), and sequential extractions. The mass-transfer from the sulfide fraction to the different secondary mineral groups will be quantified. Also porosity, density, permeability, structures, fractures, and faults observed in the core samples will be mapped in order to reconstruct the flow system for the reactive transport modeling. 2) The correlation degree between sulfide enrichment and neutralization potential (NP) of the host rock in Chuquicamata should give indication how the geometry and secondary mineralogy of supergene processes is influenced by the hydrothermal alteration pattern. Similarly, the correlation degree between alteration intensity, mineral assemblage and NP of the gangue mineralogy in the Exotica deposit will be examined. 3) A stable isotopic study will help to trace the principal oxidants implied in the formation of the oxidation profiles and in each studied sites (atmospheric oxygen or ferric iron). 4) Chlorine isotope composition of Atacamite and other Cl-bearing minerals should give indication of origin of chlorine in the supergene profile and for atacamite formation along the paleo-channel in the Exotica deposit. Together with sulfur and oxygen isotope data, this will help to answer the question if the waters that migrate laterally and form the Exotica deposit are purely meteoric or do they include basinal brines. If the second hypothesis is correct, it would open the possibility that the exotic Cu deposits are at least in part younger (even near present time) than the main supergene enrichment in Chuquicamata phase (thought to have essentially ceased around 9 Ma). In addition, the second possibilityopens the possibility of copper transport at higher pH as Cl-complexes. 5) Reactive transport modeling of different formation scenarios and calibration of the model: Based on the mineralogical, geochemical, and textural findings, different formation scenarios will be tested by reactive transport modeling and the model will be calibrated with the geochemical and mineralogical data set.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
The supergene enrichment at Chuquicamata revisited.
Pinget M.C. Fontboté L Dold B Ramirez F Vergara M. (2011), The supergene enrichment at Chuquicamata revisited., in SGA Biennal Meeting No 11., Antofagasta.
Exotic mineralization at Chuquicamata, Chile: focus on the copper wad enigma.
Pinget M.C. Dold B. Fontboté L, Exotic mineralization at Chuquicamata, Chile: focus on the copper wad enigma..
Present copper-rich “gel” formation in the giant porphyry copper deposit of Chuquicamata (northern Chile)
Lambiel F. Dold. B. Fontboté L., Present copper-rich “gel” formation in the giant porphyry copper deposit of Chuquicamata (northern Chile).

Collaboration

Group / person Country
Types of collaboration
Prof. Dr. Bernahrd Dold/Universidad Concepción, Chile Chile (South America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
SGA Biennal Meeting No 11 26.08.2012 Antofagasta, Chile
Chilean geological Congress 05.08.2012 Antofagasta, Chile


Associated projects

Number Title Start Funding scheme
144974 Acquisition of QEMSCAN Automated High-Resolution Mineral and Petrographic Analysis. 01.12.2012 R'EQUIP
146484 Mineralogical and geochemical characterization of selected supergene profiles and reactive transport modeling of supergene enrichment and exotic mineralization at Chuquicamata, Chile 01.05.2013 Project funding

Abstract

The project intends to apply the results and methodic developments recently reached in the field of acid mine drainage (AMD) to the study of exotic copper deposits. The study takes the example of supergene profiles at the giant porphyry copper of Chuquicamata and the nearby Exotica deposit. It will mainly focus on the following goals: 1) A first goal is to perform a mineralogical and geochemical characterization of selected supergene profiles in Chuquicamata and Exotica using the methods developed for AMD studies in order to track the mineralogical changes due to sulfide oxidation along selected vertical profiles in both mines. Main tools will be optical mineralogy and XRD and differential XRD (DXRD), and sequential extraction. The mass-transfer from the sulfide fraction to the different secondary mineral groups will be quantified. Also porosity, density, permeability, structures, fractures, and faults observed in the core samples will be mapped in order to reconstruct the flow system for the reactive transport modeling. 2) The correlation degree between sulfide enrichment and neutralization potential of the host rock in Chuquicamata should give indication how the geometry and secondary mineralogy of supergene processes is influenced by the hydrothermal alteration pattern (which largely controls the neutralization potential of the host rock). Similarly, the correlation degree between alteration intensity, mineral assemblage and NP of the gangue mineralogy in the Exotica deposit will be examined. This will be done by a detailed description of the mineralogy and geochemistry in the open pit of Exotica and with drill cores from the mined part to obtain information about the complete geometry of the system. 3) A stable isotopic study will help to trace the principal oxidants implied in the formation of the oxidation profiles and in each studied sites (atmospheric oxygen or ferric iron). 4) Chlorine isotope composition of Atacamite and other Cl-bearing minerals should give indication of origin of chlorine in the supergene profile and for atacamite formation along the paleo-channel in the Exotica deposit. Together with sulfur and oxygen isotopes, this will help to answer a central question: Are the waters that migrate laterally and form the Exotica deposit purely meteoric or do they include basinal brines, similar to those of the Salar de Talabre. If the second hypothesis is correct, it would open the possibility that the exotic deposits are at least in part younger (even near present time) than the main supergene enrichment in Chuquicamata phase (assumed to have essentially ceased around 9 Ma). In addition, the second possibility involves saline waters and opens the possibility of copper transport as Cl-complexes at higher pH.5) Reactive transport modeling of different formation scenarios and calibration of the model: Based on the mineralogical, geochemical, and textural findings, different formation scenarios will be tested by reactive transport modeling and the model will be calibrated with the geochemical and mineralogical data set.The project should be carried out in the frame of a Ph. D. thesis project (an excellent candidate is available) supervised jointly by the PI and Prof. B. Dold. The proposal seeks funding for three components: i) salary of the Ph.D. student, ii) analytical costs, iii) travel expenses.
-