thais carrino
DESCRIPTION
GEOLOGIC AND HYDROTHERMAL CHARACTERIZATION OF THE CHAPI CHIARA EPITHERMAL GOLD PROSPECT AND NEARBY TARGETS, SOUTHERN PERU, USING ASTER DATATRANSCRIPT
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GEOLOGIC AND HYDROTHERMAL
CHARACTERIZATION OF THE CHAPI
CHIARA EPITHERMAL GOLD PROSPECT
AND NEARBY TARGETS, SOUTHERN
PERU, USING ASTER DATA
Thais A. Carrino IG/University of Campinas
Alvaro P. Crsta IG/University of Campinas
Catarina L. B. Toledo IG/University of Braslia
Adalene M. Silva IG/University of Braslia
Johann L. Silva - IG/University of Campinas
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Introduction
Peru: main gold-producer country in Latin America
Main gold deposits are epithermal type of
the Miocene and Pliocene: located in the
northern sector (e.g.,Yanacocha, Lagunas
Norte)
Southern Peru: Au-Ag (base metals)
epithermal deposits of medium and low-
sized; there are important and recent
discoveries (e.g., Canahuire, Tucari, Santa
Rosa gold deposits)
Southern Peru focused in this
investigation
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Epithermal targets:
- Canahuire (Au-Cu-Ag) deposit
- Prospects: Chapi Chiara, Cerro
Millo, San Antonio de Esquilache
(each one inserted in paleo-
stratovolcanos of Miocene-
Pliocene ages)
Introduction
Study area
investigated by the use
of ASTER imagery
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Introduction
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Perspective view ASTER image and the targets analized
Introduction
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Materials
671 reflectance spectroscopy data
(TerraSpec spectroradiometer) 39 petrographic thin sections and
SEM-EDS
3
4
2
1 ASTER (Advanced Spaceborne Thermal
Emission and Reflection Radiometer)
image
(VNIR, SWIR, TIR bands)
04/19/2005
Mineralogic data for Chapi Chiara prospect (fieldwork: September 2011)
Visual and automatic analysis
of spectrum
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Methods ASTER VNIR-SWIR bands processing:
Crsta Technique
1
Principal Component Analysis Crsta Technique
Alunite 1, 3, 5, 7
Iron-bearing minerals 1, 2, 3, 4 Illite and/or smectite 1, 3, 5, 6
Kaolinite group minerals 1, 4, 6, 7
All PC4 (principal component #4) related to the investigated minerals (high
eigenvector values!!!)
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Methods ASTER VNIR-SWIR bands processing:
Crsta Technique
1
Regional hydrothermal alteration map
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Methods 2 ASTER TIR bands processing
Quartz Index (QI) (Rockwell & Hofstra, 2008)
Silica content Index (SI) (Ninomiya et al., 2005)
Carbonate Selective Principal Component Analysis
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Methods 2 ASTER TIR bands processing
Hydrothermal
quartz (Chapi
Chiara)
Yura Group:
quartzite,
carbonate
NW-SE structure
(Three main
deformational
phases: Peruvian,
Incaic and
Quechua)
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Results:
Chapi Chiara
prospect
Proximal zones
(ALTERATION):
Alunite + kaolinite +
quartz (vuggy) high
topographic areas
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Results: Chapi Chiara prospect
(mineralogy) SEM-EDS
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Results:
Chapi Chiara prospect
(mineralogy)
Alteration zoning:
Advanced argillic
Argillic
Propylitic
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Reference map from
Santos et al. (2011)
Results: Canahuire (main results derived from ASTER TIR bands processing)
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Results: Canahuire (main results derived from ASTER TIR bands processing)
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Results: Canahuire - predictive map (fuzzy logic)
Predictive map for Canahuire-type deposit using ASTER TIR
products and regional interpretations (lineaments and alteration)
INTEGRATION USING FUZZY LOGIC TECHNIQUE ...
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Results: Canahuire - predictive map (fuzzy logic)
... result in Canahuire
deposit correlated with
the descriptions of Santos
et al. (2011)
Priority for
targets nearby
Cerro
Chucapaca
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Results: San Antonio de Esquilache and Cerro Millo
San Antonio
de
Esquilache:
alteration
(kaolinite,
illite) related
to dioritic
intrusion
Cerro Millo:
new targets
for alunite +
kaolinite
identified
from ASTER
VNIR-SWIR
bands
processing
Reference
map from
Hennig et al.
2008)
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Conclusions
(1) ASTER imagery processing is an important and
strategic tool for characterizing geologic units
and hydrothermal targets in areas of well
exposed bedrock
(2) ASTER thermal infrared bands were crucial for
mapping structures, host rocks of Canahuire
epithermal gold deposit, and possible
hydrothermal quartz-rich targets in Chapi
Chiara prospect
(3) ASTER VNIR and SWIR bands were more
successful to map advanced argillic and/or
argillic alteration in the Cerro Millo, San
Antonio de Esquilache and Chapi Chiara
prospects
ASTER TIR products:
lithologies,host rocks
and predictive model
for Canahuire deposit-
type
ASTER VNIR-SWIR
products: alteration
Predictive map
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Conclusions
(4) Chapi Chiara:
we found an epithermal high-sulfidation type system, in a condition
of deep erosional level
decreasing chances of finding epithermal gold mineralization for
exploration (e.g., White & Hedenquist, 1995) mainly in the SW sector
of this prospect
Hypogene
minerals
formed
exclusively at
high
temperatures
Epithermal
system:
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(5) as proposed for Cerro Millo epithermal high-sulfidation gold
prospect (Hennig et al., 2008), a potential for porphyry-type
mineralization in deep levels is suggested for Chapi Chiara,
possibly related to dioritic intrusion, such as in San Antonio de
Esquilache
Conclusions
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Acknowledgements
Gold Fields Inc., for the use of the
TerraSpec spectroradiometer;
fieldwork
FAPESP: grant 2011/00106-8
Geologists: Teresa Guevara, Shirley
Custdio, Auri Muoz, Mariela Reyes
Universidade Estadual de Campinas
(University of Campinas - UNICAMP)
Universidade de Braslia
(University of Braslia - UnB)