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

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

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

Introduction

Perspective view ASTER image and the targets analized

Introduction

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

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!!!)

Methods ASTER VNIR-SWIR bands processing:

Crsta Technique

1

Regional hydrothermal alteration map

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

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)

Results:

Chapi Chiara

prospect

Proximal zones

(ALTERATION):

Alunite + kaolinite +

quartz (vuggy) high

topographic areas

Results: Chapi Chiara prospect

(mineralogy) SEM-EDS

Results:

Chapi Chiara prospect

(mineralogy)

Alteration zoning:

Advanced argillic

Argillic

Propylitic

Reference map from

Santos et al. (2011)

Results: Canahuire (main results derived from ASTER TIR bands processing)

Results: Canahuire (main results derived from ASTER TIR bands processing)

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 ...

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

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)

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

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:

(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

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)