Apx1 List of Sample

NO.

REPORT ON THE MINERAL EXPLORATION IN THE ORURO-UYUNI AREA OF THE REPUBLIC OF BOLIVIA

(PHASE III)

March 2002

JAPAN INTERNATIONAL COOPERATION AGENCY METAL MINING AGENCY OF JAPAN

MPN JR 02-035

PREFACE

In response to the request of the Government of the Republic of Bolivia, the Japanese Government decided to conduct the Mineral Exploration in the Oruro-Uyuni Area Project and entrusted the survey to the Japan International Cooperation Agency (JICA) and Metal Mining Agency of Japan (MMAJ). The JICA and MMAJ sent a survey team headed by Mr. HASHIMOTO Morio to the Republic of Bolivia from July 31, 2001 to October 20, 2001. The team exchanged views with the concerned officials of the Republic of Bolivia Government and conducted a field survey in the Oruro-Uyuni area. After the team returned to Japan, further studies were made and the present report has been prepared. We hope that this report will serve for the development of the Project and contribute to the promotion of friendly relations between our two countries. We wish to express our deep appreciation to the concerned officials of the Republic of Bolivia Government for their close cooperation extended to the team.

March, 2002

Takao Kawakami President Japan International Cooperation Agency

Naohiro Tashiro President Metal Mining Agency of Japan

ECUADOR

BRAZIL

Blanca Nieves PERU Oruro

18ﾟ Turaquiri Cuzco BOLIVIA La Paz Tambo Cosapa Quemado Oruro

P A Uyuni R Asu Asuni A G U A

Chullcani Antofagasta Y

C

H

I

L E ARGENTINA Julo Bella Vista

Sonia Susana Carangas Carangas Sabaya Lago Poopo 19ﾟ Culebra

Colchane Salar de Coipasa CHILE

Salinas de Mendoza Garci Mendoza

Cancosa Llica

Panizo 20ﾟ Sijsihua Salar de Uyuni Calorno Uyuni

Abra Napa Sailica

Loma Llena San Pedro City de Quemez San Juan Town, Village Colorado Luxsar Chiguana Study area Cachi Unu San Cristobal 21ﾟ San Augustin Study district Phase I Survey Ollague Sedilla Phase II Survey

Phase III Survey

69ﾟ 68ﾟ 67ﾟ

0 10 20 30 40 50 100km

Fig. I-1 Location Map of the Survey Area

SUMMARY

This report sums up the survey in Phase III (FY 2001, the final FY of the survey) implemented in the Oruro-Uyuni region of the Republic of Bolivia, under the technical cooperation. The survey findings, overall evaluation and exploration guidelines for Phase Ⅲ are summarized in the following paragraphs:

Survey Findings (1) Detailed Geological Survey (Scale 1/5,000): Four Districts In the Turaquiri District, many ore veins consisting mainly of manganese were confirmed northwest of the Main Turaquiri Vein. New gold mineralization was confirmed around intrusive rock. In the Chullcani District, monzodiorite intruded in the center part of the Chullcani Volcano and zonation of alteration minerals was confirmed centering on this intrusive rock. The intrusive rock could be interpreted as the center of hydrothermal activities. Geochemical anomalies of gold were found both in and around the intrusive rock. In the southern part of Jankho Kkollu Prospect (Sonia - Susana District), many lead and zinc bearing veins were confirmed around altered intrusive rock. Porphyry type mineralization was expected in the Santa Catalina Prospect (Sonia - Susana District), however, its positive showings were not confirmed in this survey. Many lead and zinc bearing veins were confirmed in Iranuta of the Mendoza District. It is presumed that these ore veins were formed by mineralization related to the rhyolitic intrusive rock in the north. The geochemical anomaly of gold confirmed in Mt. Chorka is interpreted to be caused by hypabyssal rock inferred to lay under it.

(2) Drilling Survey: Chullcani District (Two Drill Holes, 600 m) A dominant hydrothermal alteration zone was intersected. However, significant mineralization could not be confirmed.

Overall Evaluation Silver, lead, zinc and copper ore deposits can be expected in the deeper parts of the manganese veins confirmed in the Turaquiri District. A gold addition can also be expected around the intrusive rock. However, such mineralization is interpreted as rather small in size. Exposure of intrusive rock on the surface is confirmed in the Chullcani District.

( 1 )

Quartz-sericite alteration zone is distributed in the intrusive rock and areas around it, satisfying conditions for the precipitation of gold. A drilling result shows, however, that the geochemical anomaly of gold on the surface is not dominant underground. Possibilities that gold is deposited in the southeast area still remain, nevertheless, the gold mineralization may be weak in Chullcani District. Silver, lead, zinc and copper bearing veins were confirmed in the Jankho Kkollu Prospect (Sonia - Susana District). However, possibilities of a large deposit are low. Positive showings of an expected porphyry copper type mineralization in the Santa Catalina Prospect could not be confirmed in this survey. Such mineralization would be located quite deep if it exists. In the Mendoza District, both intrusive rock and epithermal gold-silver mineralization are expected in the deep parts of Mt. Chorka. High sulfidation gold and copper mineralization is expected in the northern slope and top of the mountain. However, the size of the mineralization may be small, because Mt. Chorka is interpreted as a single stratovolcano.

Recommendations for the Future There are no strong reasons for further exploration can be suggested as the result of the project, although the survey revealed detailed information for the geology and mineralization of the area. However, the recommendations for further explorations are summarized as follows, for re-evaluating the potentiality of the Oruo - Uyuni Area and adjacent Western Andes Region.

(1) Recommendations for exploration of epithermal type mineralization The analysis of remote sensing data is a useful tool for selecting a hydrothermal alteration zone from a wide area. The potential mineralized zone should be selected by geochemical investigations. Further detailed geological investigations should be mentioned from the following viewpoints. i) Existence of ore bringers (domes and intrusive rocks). ii) Existence of hydrothermal fluid (mineralized solution) paths (fractures, hydrothermal breccias and breccia pipes). iii) Repetitive supply of hydrothermal fluids (overlap of igneous activities).

The analytical study should be mentioned for the following viewpoints. a) Dissection degree of volcano: distribution of igneous rock age, homogenization temperature of fluid inclusions, geochemical anomalies and altered minerals, etc.)

( 2 )

b) Evaluation of the vertical position in mineralization: distribution of altered minerals, geochemical anomalies and gangue minerals.

Those districts with high potential that are narrowed down in this detailed geological survey should preferably conduct geophysical exploration and drilling exploration to reveal the geological structures and mineralization deep underground.

(2) Recommendations for exploration of porphyry type mineralization The mineralized age of Chilean porphyry copper deposits have a tendency to become younger from west to east. It shows the potentiality of this type mineralization in the volcanic region of the Western Bolivian Andes. But at the younger volcanoes, the porphyry type mineralization would be located quite deep underground if it exists. Therefore it is desirable for a detailed investigation of volcanic stratigraphy (especially in dating the age of volcanic rocks) of the Western Andes Region as basic information for the explorations. It also should be important information for the exploration of the epithermal type mineralization mentioned above.

( 3 ) Contents

Preface Location Map of the Survey Area Summary

Part I GENERAL REMARKS

Chapter 1 Introduction････････････････････････････････････････････････ 1 1-1 Background of Survey････････････････････････････････････････････ 1 1-2 Conclusions and Recommendations of Phase II Survey･･････････････････ 1 1-2-1 Conclusions of Phase II Survey･････････････････････････････････ 1 1-2-2 Recommendations of Phase II Survey････････････････････････････ 1 1-3 Outline of Phase III Survey････････････････････････････････････････ 2 1-3-1 Survey Area････････････････････････････････････････････････ 2 1-3-2 Survey Purpose･･････････････････････････････････････････････ 2 1-3-3 Survey Method･･････････････････････････････････････････････ 2 1-3-4 Survey Team････････････････････････････････････････････････ 3 1-3-5 Survey Period･･･････････････････････････････････････････････ 4

Chapter 2 Geographic Setting of Survey Area ･･････････････････････････････ 5 2-1 Topography and Drainage System ･･････････････････････････････････ 5 2-2 Climate and Vegetation ･･･････････････････････････････････････････ 5

Chapter 3 General Geology･････････････････････････････････････････････ 7 3-1 General Geology in the Surrounding Areas ･･･････････････････････････ 7 3-2 Characteristics of Mineralization in the Survey Area････････････････････12

Chapter 4 Comprehensive Analysis ･･････････････････････････････････････17 4-1 Relationship of Geology and Geological Structure with Mineralization ･････17 4-1-1 Geology････････････････････････････････････････････････････17

- i - 4-1-2 Geological Structure･････････････････････････････････････････ 17 4-1-3 Expected Types of Ore Deposits ･･･････････････････････････････ 17

4-2 Survey Findings by District･･･････････････････････････････････････ 22 4-2-1 Turaquiri District ･･････････････････････････････････････････ 22 4-2-2 Chullcani District ･････････････････････････････････････････ 22 4-2-3 Sonia – Susana District ･････････････････････････････････････ 27 4-2-4 Mendoza District ･･････････････････････････････････････････ 27 4-3 Potentialities of Ore Deposits ･････････････････････････････････････ 33

Chapter 5 Conclusions and Recommendations･････････････････････････････ 35 5-1 Conclusions ･･･････････････････････････････････････････････････ 35 5-2 Recommendations for the Future ･･････････････････････････････････ 37

Part II PARTICULARS

Chapter 1 Survey Method ･････････････････････････････････････････････ 39 Chapter 2 Geological Surveys ･････････････････････････････････････････ 41 2-1 Turaquiri District ･･･････････････････････････････････････････････ 41 2-2 Chullcani District･･･････････････････････････････････････････････ 51 2-3 Sonia – Susana District ･･････････････････････････････････････････ 67 2-4 Mendoza District ･･･････････････････････････････････････････････ 83 Chapter 3 Drilling Survey ･････････････････････････････････････････････ 97 3-1 Purpose of the Survey ･･･････････････････････････････････････････ 97 3-2 Drilling work ･･････････････････････････････････････････････････ 97 3-2-1 Overview of Drilling Work････････････････････････････････････ 97 3-2-2 Drilling Work by Each Drill Hole ･･････････････････････････････101 3-3 Results of the Survey ･･･････････････････････････････････････････102 3-4 Considerations ･････････････････････････････････････････････････118

- ii - Part III CONCLUSIONS AND RECOMMENDATIONS

Chapter 1 Conclusions ･･･････････････････････････････････････････････123 Chapter 2 Recommendations for the Future ･･･････････････････････････････127

REFERENCE AND COLLECTED DATA ････････････････････････････････････････ 129

APPENDICES ･････････････････････････････････････････････････････････････A－1

- iii - LIST OF FIGURES

Fig.Ⅰ-1 Location Map of the Survey Area Fig.Ⅰ-3-1 Geological Map of Bolivia Fig.Ⅰ-3-2 Schematic Geologic Map of the Area Fig.Ⅰ-3-3 Schematic Geologic Column of the Survey Area Fig.Ⅰ-3-4 Ore Deposits and Showings in the Area Fig.Ⅰ-4-1 (1) Idealized Model of Bolivian Type Deposit Fig.Ⅰ-4-1 (2) Idealized Lithocap and Underlying Porphyry Cu/Au Deposit Fig.Ⅰ-4-2 (1) Integrated Interpretation Map of the Turaquiri District Fig.Ⅰ-4-2 (2) Integrated Interpretation Map of the Chullcani District Fig.Ⅰ-4-2 (3) Integrated Interpretation Map of the Sonia-Susana District Fig.Ⅰ-4-2 (4) Integrated Interpretation Map of the Mendoza District Fig.Ⅱ-2-1 (1) Geological Map of the Turaquiri District Fig.Ⅱ-2-1 (2) Alteration Map of the Turaquiri District Fig.Ⅱ-2-1 (3) Geochemical Anomaly Map of the Turaquiri District Fig.Ⅱ-2-2 (1-1) Geological Map of the Chullcani District Fig.Ⅱ-2-2 (1-2) Geologic Section of the Chullcani District Fig.Ⅱ-2-2 (2-1) Alteration Map of the Chullcani District Fig.Ⅱ-2-2 (2-2) Distribution Map of Alteration Minerals in the Chullcani District Fig.Ⅱ-2-2 (3) Geochemical Anomaly Map of the Chullcani District Fig.Ⅱ-2-2 (4) Idealized Formation Process of the Chullcani Volcano Fig.Ⅱ-2-3 (1) Geological Map of the Sonia-Susana District Fig.Ⅱ-2-3 (2) Alteration Map of the Sonia-Susana District Fig.Ⅱ-2-3 (3) Geochemical Anomaly Map of the Sonia-Susana District Fig.Ⅱ-2-4 (1-1) Geological Map of the Mendoza District Fig.Ⅱ-2-4 (1-2) Geologic Section of the Mendoza District Fig.Ⅱ-2-4 (2) Alteration Map of the Mendoza District Fig.Ⅱ-2-4 (3) Geochemical Anomaly Map of the Mendoza District Fig.Ⅱ-3-1 Location Map of Drill Holes Fig.Ⅱ-3-3(1) Geological Map of the Drill Hole MJBO-1 Site Area

- iv - Fig.Ⅱ-3-3(2) Geologic Section of the Drill Hole MJBO-1 Fig.Ⅱ-3-3(3) Relative Mineral Abundance (Drill Hole MJBO-1) Fig.Ⅱ-3-3(4) Variations of 8-Elements Grades in Core (Drill Hole MJBO-1) Fig.Ⅱ-3-3(5) Geological Map of the Drill Hole MJBO-2 Site Area Fig.Ⅱ-3-3(6) Geologic Section of the Drill Hole MJBO-2 Fig.Ⅱ-3-3(7) Relative Mineral Abundance (Drill Hole MJBO-2) Fig.Ⅱ-3-3(8) Variations of 8-Elements Grades in Core (Drill Hole MJBO-2)

- v - LIST OF TABLES

TableⅠ-1-1 Contents of the Survey TableⅠ-1-2 List of Laboratory Test TableⅠ-1-3 Period of the Survey TableⅠ-2 Temperature & Humidity in Oruro City TableⅡ-2-1 Result of Chemical Analysis(Turaquiri) TableⅡ-2-2 Result of Chemical Analysis(Chullcani) TableⅡ-2-3(1) Result of Chemical Analysis(Jankho Kkollu) TableⅡ-2-3(2) Result of Chemical Analysis(Santa Catalina) TableⅡ-2-4 Result of Chemical Analysis(Mendoza) TableⅡ-3-1 Drill Hole Length and Core Recovery

TableⅡ-3-2 Result of Chemical Analysis (Drill Hole MJBO-1) TableⅡ-3-3 Result of Chemical Analysis (Drill Hole MJBO-2)

- vi - LIST OF APPENDICES

Appendix 1 Sample List of Laboratory Works Appendix 2 Microscopic Observations of Thin Sections Appendix 3 Microscopic Observations of Polished Sections Appendix 4 X-ray Diffraction Analysis Appendix 5 Sample Locality Appendix 6 Assay Results of Rock Samples Appendix 7 Assay Results of Ore Samples Appendix 8 Miscellaneous Data for the Drilling Survey Appendix 9 Geologic Core Logs of the Drill Holes

- vii - LIST OF PLATE

PL- 1 Geological Map of the Turaquiri District(1:5,000) PL- 2 Geological Map of the Chullcani District(1:5,000) PL- 3 Geological Map of the Sonia Susana District(1:5,000) PL- 4 Geological Map of the Mendoza District(1:5,000) PL- 5 Sample Location Map of the Turaquiri District(1:5,000) PL- 6 Sample Location Map of the Chullcani District(1:5,000) PL- 7 Sample Location Map of the Sonia Susana District(1:5,000) PL- 8 Sample Location Map of the Mendoza District(1:5,000) PL- 9 Geochemical Anomaly Map of the Turaguiri District(1:5,000) PL- 10 Geochemical Anomaly Map of the Chullcani District(1:5,000) PL- 11 Geochemical Anomaly Map of the Sonia Susana District(1:5,000) PL- 12 Geochemical Anomaly Map of the Mendoza District(1:5,000) PL- 13 Geological Sketch in the the Sonia Susana District (Jankho Kkollu)

- viii -

PART I GENERAL REMARKS Chapter 1 Introduction

1.1 Background of Survey To comply with the request of the Government of Bolivia, the subject mineral resources survey in the Oruro-Uyuni region of the Republic of Bolivia is undertaken by the Government of Japan, in conformity to the Scope of Work agreed by the two governments on December 10, 1999.

1.2 Conclusions and Recommendations of Phase II Survey 1-2-1 Conclusions of Phase II Survey In Phase II, geological surveys and geochemical explorations of varying precision were conducted in a total of 16 districts covering the districts surveyed in Phase I and ten new districts. The chemical analysis for stream sediments samples collected by SERGEOMIN was conducted. The survey in Phases I and II revealed that the hydrothermal alteration zones widespread in the Oruro-Uyuni region are likely to host epithermal ore deposits at depth. It is assumed an epithermal deposit rich in gold, silver, lead and zinc related with shallow volcanic rocks; an epithermal deposit of precious metals related with hypabyssal intrusive rocks; a high sulfidation type of gold, silver, copper ore deposit (quartz-alunite vein type); and a low sulfidation type (quartz- adularia vein type) are expected. Impregnation of gold and cooper ore deposits of the porphyry type is also possible in deep parts of the districts with extensive erosion. Hydrothermal activity could be interpreted as intensive in districts where domes, intrusive rocks, hydrothermal breccia and breccia pipes are distributed. Possibilities of deposition of epithermal ore deposits in these districts were assessed to be high. As for promising areas, the following districts could be identified from north to south: the Turaquiri, Chullcani, Sonia - Susana, Calorno, Mendoza (Co. Mokho and Co. Chorka Prospect), Panizo District (Panizo Prospect), Sailica District (Plasmar Mine) and Sedilla District (Eskapa Prospect).

1-2-2 Recommendations of Phase II Survey It was proposed in the Phase II survey that detailed geological surveys and geophysical exploration would be conducted in districts, which had high possibilities of ore deposition in Phase Ⅲ to obtain more detailed information. It was also proposed that borehole drilling would be conducted in some of these districts to confirm a three-dimensional model (geological structure, distribution of alteration, resistivity structure, geochemical variations and other factors) to assist the identification of promising districts.

- 1 -

1-3 Outline of Phase Ⅲ Survey 1-3-1 Survey Area The Oruro-Uyuni area is situated approximately between 150 km and 560 km south of La Paz, the capital city (Fig. I-1). The western half of the region is constituted by mountainous zones, altitude 4,000 m to 5,000 m, whereas the eastern half consists mainly of moderately inclined plateaus and saline lakes of altitudes up to 4,000 m above sea level. The four districts of the phase III survey are located in the northern part of the Oruro-Uyuni area.

1-3-2 Survey Purpose For effectively selecting a potential area for a mineral deposit in the short term, a geological survey to reveal the geological setting and occurrence of mineral deposits will be carried out in the Oruro-Uyuni region, Republic of Bolivia.

1-3-3 Survey Method During the Phase Ⅲ survey, geological surveys were conducted in four promising districts, which identified by the PhasesⅠand Ⅱ surveys (Turaquiri, Chullcani, Sonia - Susana and Mendoza Districts). A drilling survey was also conducted in the Chullcani District (See Table I-1-1). Sampling and laboratory tests were conducted ( Table I-1-2).

Table I-1-1 Content of the Survey Content Items and Quantity Districts: Turaquiri, Chullcani, Sonia - Susana, Mendoza Scale of Survey: 1:5,000 Coverage Area: Total 12 km2 Turaquiri District: 1.5 km2 Geological Survey Chullcani District 6.0 km2 Sonia - Susana District: 1.5 km2 Mendoza District: 3.0 km2 Length of geological survey route: Total 120 km

Location: Chullcani District Drilling Survey Length of drilling: 600 m (300 m×2) Inclination: 90ﾟ Road construction: 12 km

- 2 -

Tabele I-1-2 List of Laboratory Test Content Items and amount of Laboratory tests 1) Chemical Analysis (rock samples）(11 elements) 500 Geological 2) Chemical Analysis（ore samples）(11 elements) 10 surveys 3) Microscopic Observations of Thin Sections 20 4) Microscopic Observations of Polished Sections 10 5) X-ray Diffraction Analysis 70

Drilling Survey 1) Chemical Analysis（rock）(11 elements) 2) Microscopic Observations of Thin Sections 3) X-ray Diffraction Analysis

11 Elements of chemical analysis:Au,Ag,Cu,Pb,Zn,As,Sb,Hg,Mo,Ba,Sn

1-3-4 Survey Team The members of the Japanese survey team and their counterparts in Bolivia are as follows:

1) Survey Team Japan Bolivia Republic

Name Entity Name Entity HASHIMOTO Morio Fernando Murillo Salazar （Head/General） MINDECO (Coordinator) SERGEOMIN （Chief Geologist） （Chief Geologist）

TAKEBE Akimitsu Yerco Santa Cruz Salvatierra MINDECO SERGEOMIN （Geologist） (Geologist)

HIBI Fukuji Gribert Borja Navarro MINDECO SERGEOMIN （Geologist） (Geologist)

Manuel Menacho Leon SERGEOMIN (Geologist)

Guido Quezada Cortez SERGEOMIN (Geologist)

Mitsui Mineral Development Engineering Co., Ltd.

- 3 - 2) Inspection ITO Tadashi: MMAJ SHIOKAWA Satoshi : MMAJ PERU

3) Seminar SAKATA Tsuyoshi : MMAJ KURIHARA Masaomi : MMAJ HASHIMOTO Morio : MINDECO

1-3-5 Survey Period Survey Period is shown in Table I-1-3

Table I-1-3 Period of the Survey 2001 2002

July Aug. Sept. Oct. Nov. Dec. Jan.. Feb. Mar. 30 Preparation

Field survey 31 20

15 Laboratory 15 work 1 31 Reporting 5 Seminar ■

- 4 - Chapter 2 Geographic Setting of Survey Area

2-1 Topography and Drainage System The study area is located on two physiographic provinces, in the westernmost part of Bolivia, which are: first, the Altiplano or a flat plain at an elevation of about 3,700 m above the sea level with longitudinal and transversal elevations covering an area of about 100,000 km2. The most prominent geographic feature of the extensive Puna - Altiplano plateau, which is after the Tibetan plateau that is the world highest and large plateau (700 x 200 km), is that it is covered by an extensive array of Neogene volcanic centers. The second is a volcano chain that defines the natural border with Perú and Chile with altitudes of higher than 6,000 m.a.s.l. (Sajama, 6,542 m; Parinacota, 6,132 m; Payachatas, 5,982 m; Tunupa, 5,000 m.), It developed 620 km from north (Perú) to south (Argentina) running in the NW - SE direction.

The drainage of the area belongs to the central basins or lacustrine, which covers almost all the Altiplano and is formed by Lago Titicaca, Lago Poopó, Salar de Coipasa, Salar de Uyuni and Río Desaguadero. Lago Poopó is located in the Oruro department (Prov. Poopó, Sancari and Abaroa) at 3,868 m. Its main rivers are Pazña, Challapata, Conde, Sevaruyo, and Kimpara. The Lakajahuira River is the only drainage between Poopó and Salar de Coipasa, Ríos Lauca and Sabaya, and runs into Salar de Coipasa. The main rivers to drain into Salar de Uyuni are Río Grande or Quetena in the south and Río Chica Chica in the east. Among them, almost all the rivers are very small and intermittent, having water only during the rainy season (December - March) making it difficult for transportation because of a lack of bridges.

2-2 Climate and Vegetation Bolivia is in the south latitude (10° - 23°) so the climate should be tropical to subtropical however due to the altitude over 3,600 m in the study area, it is dry and cold. During nighttime, the temperature is almost always below zero. The rainy season corresponds to summer (December to March) and the annual precipitation is about 400 mm (Table 1). In some parts of the area due to the intensive cold, rain is converted to snow or ice. The maximum temperature of this season is about 22°C, and the minimum temperature is -5°C. The dry season is in wintertime, and the maximum temperature rises to 18°C and the minimum is -22°C, even the temperature makes it the best time for fieldwork. In winter, winds

- 5 - are very strong from the west and temperature difference between day and night are 30°C making it very cold during night. The humidity varies between 0 and 22% (Table I-2)

Table Ⅰ-2 Temperature and Humidity in Oruro City

Ene. Feb. Mar. Abr. May. Jun. Jul. Ago. Sep. Oct. Nov. Dic. Anual

Temp.Ambiente °C 11.5 11.0 10.5 9.2 5.8 3.4 2.7 4.9 7.2 9.4 10.9 11.7 8.2 Temp. Maxima Media 18.3 18.5 17.8 17.9 16.3 14.3 14.1 16.5 17.6 18.7 19.6 19.5 17.40 Temp. Minima Media 4.7 3.5 3.2 0.5 -4.7 -7.4 -8.7 -6.6 -3.2 0.2 2.3 3.9 -1.0 Precipitation mm. 87.1 48.8 64.3 25.4 8.2 3.7 5.8 5.6 22.7 26.5 27 39.5 364.6 Humedad Relativa 61 53 59 54 52 44 43 41 42 41 43 45 48 Direction y vel. Nudos E-7 E-6 E-6 S-5 S-3 S-2 NW-4 S-4 S-5 S-6 S-7 E-5 S-5 Station：Oruro，Province：Llocodo，Departament：Oruro

Period：1995 – 1999 Latitud Sur：17°58' ，Longitud Oeste：67°04' ，Altitud：3,702 m

To describe the vegetation of the area, it is necessary to divide the Altiplano in two sections: -Altiplano Central. - (18° - 20° 30' Lat. S) is distinguished by its cold and dry climate. As a result, large sand covers the pampas, which grows intermittently thola (lepidophyllum quadrangulare), yareta (azorella sp) and paja brava (stipa ichu). Some places cultivate quinua, potato, barley and other typical tubers. Around the slopes of the volcanic cones, there are small trees and bushes: Keñua, Kiswara and Thola. -Altiplano Sur.- (20°30"- 22°51"Lat. S) is a dessert and sandy zone, where parihuanas or flamencos (phoenicopterus chilensis) live. Around the western edge of Salar de Uyuni (Llica - Salinas de Garci Mendoza) are developed big areas of quinua crops.

- 6 - Chapter 3 General Geology

3-1 General Geology in the Surrounding Areas Bolivia is roughly divided into five geotectonic provinces, which from west to east, are called the Cordillera Occidental, Altiplano, Cordillera Oriental, Sub-Andes - Beni-Chaco Plain and Brazilian Shield. The survey area pertains to the Cordillera Occidental and the Altiplano. (Figs. I-3-1 and I-3-2)

Cordillera Occidental The Cordillera Occidental is extensively covered by Tertiary to Recent volcanic rocks that effused along the N-S uplifting axis of the Mesozoic to Paleozoic basement rocks, where continental to netric sediments lie between the volcanic bodies. The volcanic rocks that constitute the mountains are chiefly late Miocene to Pliocene andesite and rhyolite lava, while Quaternary dacite is also present in the vicinity of the mountaintops. The large-scale and widespread volcanic activity, characteristic of the Cordillera Occidental, was brought about by the subduction of the Nazca Plate under the South American Continental Plate. Accompanying the volcanic activity, numerous stratovolcanoes were formed.

Altiplano The Altiplano has the Proterozoic to Paleozoic basement extensively covered by formations of vast volcanic product and continental sediments of the Cretaceous to Recent age. The continental sediments are composed of late Cretaceous continental molasse sediments (red bed) and Eocene to Oligocene foreland basin sediments (sandstone, and alternated beds of sandstone and mudstone). Igneous activity took place in the Miocene to Pliocene time. Andesitic effusive activity continued during the Miocene time in the southern part whilst, in the northern part, effusive activity of rhyolitic pyroclastic rocks continued from the Miocene to Pliocene time, which caused a huge amount of continental volcanic product to be deposited. A schematic geologic column of the survey area is exhibited in Fig. I-3-3.

Cordillera Oriental The Cordillera Oriental is underlain by abyssal to terrigenous sediments of the Paleozoic age and marine to continental shelf carbonate rocks of the Mesozoic age. These are composed of thick sedimentary rocks of the Paleozoic to Mesozoic age (miogeosyncline sediments) deposited on the Precambrian basement, where thrust faults with N-S axes and complicated fold structures were formed by the Caledonian (Ordovician), Hercynian

- 7 - Quaternary

Intrusive Tertiary Mesozoic

Paleozoic BR AZ IL Precambrian

U

R

E

P BOLIVIA

La Paz

Oruro

Santa Cruz

E

L I

H Potosi C PARAGUAY

0 500km ARGENTINA

Fig.I-3-1 Geological Map of Bolivia

- 8 - Fig.Ⅰ-3-3Schematic Geologic Column of the Survey Area

70 69 68 67 66 65 64 63 62 61 60 59 58

10 10

11 PANDO 11 Cobija

12 12

13 13 BOLIVIA IN SOUTHAMERICA

P 14 E 14 R BENI U Trinidad 15 15 LA PAZ

Lago Titicaca 16 16 La Paz

17 COCHABAMBA SANTA CRUZ 17 Cochabamba 18 Oruro Santa Cruz de la Sierra 18 ORURO Arica Lago Poopo 19 Sucre 19 Salar de Coipasa

20 Potosí 20 Salar de Uyuni POTOSI CHUQUISACA 21 C 21 H IL TARIJA E Tarija PARAGUAY 22 22

23 23 ARGENTINA Antofagasta

70 69 68 67 66 65 64 63 62 61 60 59 58 69 68 67 66

ORURO 18 18

19 LAGO POOPO 19 C

H SALAR DE COIPASA I POTOSI L E

20 20 SALAR DE UYUNI

21 21

QUATERNARY NEOGENE PALEOGENE

CRETACEOUS 22 SILURIAN 22 ORDOVICIAN STUDY AREA ARGENTINA 23 23

69 68 67 66 Fig. I-3-2 Schematic Geologic Map of the Area - 9 - AGE BOUNDARIES IN MILLION YEARS CRUSTAL SHORTENING PERIODS (Ma) NORTHERN ALTIPLAND CENTRAL ALTIPLAND SOUTHERN ALTIPLAND 0 La Paz QUATERNARY Charaña (ss,sgl) (sh,cgl,tuff) Ulloma Stralovolcanoes ･･･Perez (ss,tuff,gravel) Stralovolcanoes PLIOCENE Topohoco (cgl,ss,tuff) 5 ･･･Toba 76 Umala Cerke (ss,si,tuff) ･･･Soledad Ignimbrites (lavas) ･･･Los Frailes Pomala (cgl) Crucero (ss.cgl,clay) 10 Carangas Bonete (tuff,lava) (lava) Caquiaviri Totora

(ss,cgl) (sh,ss) p Upper Quehua u o

r (ash-flow,tuff,ss)

Azurita G MIOCENE o

Abaroa/Mauri (cgl,ss) r

15 o (ss.cgl,lava,tuff) c o r

Kollo-kollu Huayllamarca o Rondal/Julaca (ss,sh) (cgl,ss) C (lava) Lower Quehua Coniri Chuquichambi (marl,gyp) (ss,cgl,tuff) 20 (cgl,ss)

Jalluma (marl,gyp) San Vicente (cgl,ss)

25

Berenguela 30 (ss) OLIGOCENE

35

Tiahuanacu Potoco Potoco (ss,sh) (ss,sh,cgl) (ss,sh,cgl) 40

45 EOCENE

50

55 PALEOCENE

Fig.I-3-3 Schematic Geologic Column of the Survey Area

- 11 - (Devonian to Triassic) and Andean (Cretaceous to Cenozoic) orogenic movements. Simultaneously with the close of the Hercynian movement (Permian to Triassic), the subject region became a tension field where peralkaline volcanic activity and intrusion of granitic plutonic rocks occurred. Afterwards, the plate subduction began, causing calc-alkaline volcanic activity, which lasted from the Jurassic to the Cenozoic time. At the time of the Andean orogenic movement (Tertiary), the Cordillera Oriental was uplifted by the E-W compressive stress, causing to form the fold and thrust fault zones. At the western side of the Cordillera, the andesitic volcanic activity, ensuing intrusion of hypabyssal rocks and overthrust towards the Altiplano side took place.

Sub-Andes - Beni-Chaco Plain The region consists of the folded mountains adjoining the eastern side of the Cordillera Oriental and the vast plain zones -- the Beni-Chaco Plain -- to the east. The folded mountains are composed of Paleozoic and Neogene rocks. In the eastern plain zones, these formations are extensively underlain by Quaternary lake sediments and talus sediments.

Brazilian Shield An extension of the Brazilian Shield stretches toward eastern Bolivia to form a tropical rain forest zone covering an area of 22,000 km2. The region is underlain by Proterozoic to Cretaceous rocks, mostly Proterozoic altered rocks such as gneiss, biotite schist and quartz schist. These altered rocks underwent laterization in the Tertiary or later time, and are covered by Quaternary alluvium.

3-2 Characteristics of Mineralization in the Survey Area Ore deposits of metallic minerals concentrate in the area that embraces the Cordillera Occidental, Altiplano and Cordillera Oriental, where copper mineralization accompanying alkali basalt, sedimentary copper mineralization accompanying late Tertiary red sandstone beds, so-called 'Bolivian type' polymetallic mineralization mainly of tin and silver, and epithermal mineralization mainly of gold and silver are known to be present.

In the Cordillera Occidental, small-scale epithermal gold-silver veins embedded in Miocene dacitic volcanic rocks are known to exist, a part of which is accompanied by sulfide minerals such as copper, lead, zinc and bismuth.

- 12 - Also present in the area are hydrothermal alteration zones, mainly argillized and widespread in dacitic volcanic rocks. Silicification and pyrite dissemination are observed partly in the alteration zones. Under these hydrothermal alteration zones, the occurrence of porphyry-type gold-copper deposits is expected.

From the Cordillera Oriental to Altiplano, the Bolivian type polymetallic vein deposits are found, while copper deposits accompanied by alkali basalt and red sandstone are present from the north to south of the central Altiplano. The Bolivian type polymetallic vein deposits, underlain by the upper Tertiary to Quaternary, have not yet been fully elucidated, but many of them are lead-zinc deposits with relatively low tin- tungsten contents and high copper contents. A variety of Bolivian type polymetallic vein deposits are known; they are roughly divided into those rich in silver and tin and those rich in silver, gold and copper.

Ore deposits rich in silver and tin are often seen in the Cordillera Oriental. These have mineralogically complex combinations of silver, tin, lead, zinc, tungsten, bismuth, gold, etc. These typical ore deposits are found at such mines as Cerro Rico de Potosi, Pulacayo and Huanuni, which are classified into two types: one rich in silver sulfate minerals and the other in which the lower tin zones became exposed as a result of denudation of the upper silver zones. Ore deposits rich in silver, gold and copper are seen in the Altiplano. The most typical deposit is the Kori Kollo mine currently under operation. The deposit has silver, gold and some copper, apparently resembling auri-argentiferous iron sulfide deposits, but it is classified into the polymetallic deposit as it contains lead, zinc, antimony, tin, etc.

The mines and ore showings existent in the survey area are shown in Fig. I-3-4 .

- 13 - - 15 - Chapter 4 Comprehensive Analysis

4-1 Relationship of Geology and Geologic Structure with Mineralization 4-1-1 Geology The survey area is extensively covered by volcanic rocks centering around the Cordillera Occidental, except crystalline schist and gneiss exposed in the inliers southeast of the Chulcani district and continental sediments of Tertiary or a later age observed in some parts of the Altiplano. The volcanic rocks generally form stratovolcanoes; alteration -- mainly argillization -- zones are widespread in the volcanic rocks. The known ore deposits are embedded in these alteration zones, presumably formed by the hydrothermal process.

4-1-2 Geological structure Except the San Cristbal deposit (trending NE-SW) and Eskapa district (trending N-S), mineralization is observed in fractures with the E-W trend; the trends are E-W at Turaquiri, E-W (N70°W) at Carangas and E-W (N80°E ~ N75°W) at Salinas de Garci Mendoza. The fractures with the E-W trend might have fulfilled an essential function for mineralization.

4-1-3 Expected types of ore deposits The following types of ore deposit are expected to be present in the survey area: [1] Copper deposits accompanying alkali basalt [2] Bedded copper deposits embedded in Paleogene red sedimentary rocks (The Corocoro-type) [3] Epithermal deposits [4] Bolivian type polymetallic vein deposits [5] Porphyry-type copper-gold deposits

Of these types, veinlet-type and disseminated copper deposits accompanying late Oligocene alkali basalt and the Corocoro-type deposits are not large enough to be exploration targets.

Bolivian type polymetallic vein deposits have a general tendency that sulfide mineral veins in the lower part change into barite-quartz or barite-chalcedony veins in the upper part, which is considered attributable to porphyry-type mineralization shifting to epithermal mineralization. Therefore, the presence of these veins may suggest emplacement of Bolivian type polymetallic vein deposits in the lower part and porphyry-type deposits in the deeper part.

The deposits are classified into following types although it is difficult. I Bolivian type polymetallic deposits

- 17 - (A) Ore deposits rich in silver-tin (mainly at Cordillera Oriental) Mineral assemblage : silver-tin-lead-zinc-tungsten-bismuth-gold Vein : sulfide vein Example : Potosí deposit, Pulacayo deposit, Huanuni deposit

(B) Ore deposits rich in silver-gold-copper (mainly at Cordillera Oriental) Mineral assemblage : silver-gold –small amount of copper (lead-zinc-antimony-tin) Vein : sulfide vein Example : Kori Kollo deposit

II Epithermal gold-silver-lead-zinc deposits related to shallow volcanic activity Mineral assemblage : (gold)-silver- small amount of lead-zinc-tin Vein : barite-quartz vein Example : San Cristóbal deposit

III Epithermal precious metal deposits related to shallow hypabyssal intrusive activity Mineral assemblage : gold-silver- lead- zinc- (copper) Vein : alunite-kaolin-quartz vein, barite-quartz vein with neutral alteration zone Example : Choquelimpie deposit, La Española deposit

IV High sulfidation type deposits (quartz-alunite vein type deposit) Epithermal gold-silver-copper deposit Mineral assemblage : (gold)-silver- copper (enargite) Vein : alunite- barite- quartz vein Example : Laurani deposit, Choquelimpie deposit, La Española deposit

V Low sulfidation type deposits (quartz-adularia vein type deposit) Sericitized zone with adularia, carbonate minerals Neutral argillic alteration zone Vein : quartz-adularia vein Example : peripheral part in the La Española mine

Figs. I-4-1 (1) and I-4-1 (2) indicate schematic models of hydrothermal ore deposits including the Bolivian type polymetallic vein deposits and porphyry copper-gold deposits accompanied by epithermal alteration, respectively.

- 18 - San Cristobal

Bonete Paleodepth(m) Mestizo ℃ 300-200 0 Ubina Pulacayo ℃ 235-180℃ 302-167 Porco EPITHERMAL EPITHERMAL XENOTHERMAL (BOLIVIAN TYPE) XENOTHERMAL Korikollo (BOLIVIAN TYPE) Avg.320℃ Cerro Rico de Potosi 371-231℃ Colquechaca-Oruro 407-255℃ 353-253℃ Chocaya Colavi 500 379-164℃ San Vicente Santa Isabel 359-172℃ Tasna 499-213℃ Huanuni 411-213℃ Chorolque 528-261℃

1000 Japo 306-230℃

Bolivar 327-198℃

Llallagua 1500 441-245℃

2000

(Heuschmidt 1997)

GEOLOGICAL SETTING HYDROTHERMAL OVERPRINT

Quartz-latite,dacite,rhyodacite or rhyolite porphyry(volcanic dome) Hydrothermal(ized igneous)breccia

Quartz-latite,dacite or rhyodacite porphyry (subvolcanic stock,dike or pipe) Propylitization/Chloritization(weak)

MIOCENE Felsic air-fall tuff(dome apron) Acid leaching

Felsic explosion breccia(dome talus) Advanced argillic alteration

Argillic alteration + silicification

Conglomerates Phyllic alteration and tourmalinization + (silicification/chloritization/pytitization) Argillaceous(and arenaceous) sediments with volcanic intercalations EARLY TO MID TO EARLY TERTIALY Ore dissemination

Veinlets,stockwork Carbonate beds

Vein Psammo-pelitic sequence CRETACEOUS W Sn Bi Cu

Shales and siltstones Zn-Pb Ag Au Sandstones,quartzites,diamictites and siltstones ORDOVICIAN- SILURIAN

Fault

Fig. I-4-1(1) Idealized Model of Bolivia Type Deposit

- 19 - Advanced argillic HS breccia/ (+argillic) lithocap stockwork Chloritic Acid-leached zone alteration A C A A A A C A A C A A C A A C A C C S A A C VOLCANIC A LS vein P S S EDIFICE P S S S P S S S P Sericitic S P S alteration P HS massive sulphide lode

P Propylitic P alteration SUB-VOLCANO BASEMENT 1 P P Porphyry stock P P K-silicate alteration with porphyry-type Km P Cu/Au mineralization 0 1 P

HS:High-sulphidation Ls:Low-sulphidation (After R.Sillitoe, 1995)

Fig.I-4-1(2) Idealized Lithocap and Underlying Porphyry Cu/Au Deposit

- 21 -

4-2 Survey Findings by District 4-2-1 Turaquiri district (Fig. I-4-2(1)) The Phase III survey revealed distributions of Middle to Upper Miocene sedimentary rocks, Miocene to Pliocene volcanic rocks and the presence of andesite intrusive rock. The Turaquiri deposits are interpreted as epithermal barite-quartz type deposit. It is associated with base metals and precious metals, which occur along the east-west fractures formed by the development of the caldera system. Many ore veins are confirmed northwest of this ore deposit. Most of them, however, are less than 10 cm in vein width and mineralizations of network and dissemination types are not confirmed. Variations in ore minerals are confirmed. Centering on the Turaquiri Vein, the veins change from lead and zinc veins to manganese dioxide veins in northwest and clayey veins farther outside. Showings of local gold anomalies are confirmed in this Phase.

4-2-2 Chullcani district (Fig. I-4-2(2)) Hydrothermal alterations distribute in andestic volcanic rocks (Middle Miocene to Pliocene) and Diorite in the Chullcani District. The igneous activity of Chullcani Volcano started around 6.5 Ma. Wide hydrothermal alteration zones were formed through the intrusion of diorite and andesite and by hydrothermal activity caused by intrusions. It is interpreted that subsequent erosion denuded the center part of the volcanic body and that dome and mesa of basalt were formed from Late Pliocene to Pleistocene (See Fig. II-2-2 (4)). Alteration minerals show a distribution of quartz-sericite in diorite and areas around it. Quartz zone surrounds quartz-sericite zone and cristobalite zone appears outside of the quartz zone. This suggests that intrusive rock of diorite is the center of hydrothermal activity. The geochemical exploration in Phase III also shows a geochemical anomaly of gold in a diorite intrusive rock body and areas around it. Anomalous parts of lead, zinc and molybdenum are also distributed in the same area. The MJB0-1 drill hole shows that hydrothermal alteration is dominant all over the cores, confirming the intense hydrothermal activity. Dissemination of pyrite and native sulfur are also detected. The assembly of alteration minerals suggests a temperature rise toward the deep part. A chemical analysis shows an anomaly of lead, arsenic and zinc in some parts. However, prominent mineralization is not confirmed. The MJB0-2 drill hole shows a continuation of diorite in some parts sandwiching andesite. Silicified and argillized zones with fault zone intersect the diorite body. The assembly of alteration minerals suggests that the condition is sufficient for gold precipitation. However, the

- 22 - Tma LEGEND 7995500 GN ( Qa) Alluvial deposit

78 ( Tch) Chingurari lava (Andestic lava tuff) MN Tch (Ttr) Turaquiri tuff (Dacitic welded tuff)

Tar ( Tma) Moun tuff (Dacitic tuff - lapili tuff) 75 PPsv ( Tar) Sandstone - Conglomerate

( PPsv) Bt - Hb Andesite Mn Tma Mn zone Argillized zone 70 Qa

Silicified zone 75 Tar Mn Mn Ttr 85 70° 75 Silicified vein 7995000 80 70° Mn Silicified vein with Fe, Mn oxide 75 Mn 70° Argillized vein Mn 75 PPsv 70° Mn Pb, Zn, vein 80 80 Mn 30° Mn Strike and Dip 75 - 23 75 Cu, Pb, 80 Zn, Mn 80 Mn Mineral Showing 80 Mn PPsv 78 Mn Ancient working 85 80 Tch Mn 80 Ttr 70 80 Cu,Pb,Zn Geochemical Anomaly

75 78 85 Au > 70ppb Mn80 Qa 85 Tma Pb Zn zone Au:3.5g/t Ag > 30ppm Cu > 90ppm

7994500 Pb > 400ppm

Zn > 230ppm PPsv 75 PPsv Mn As > 140ppm 80 Sb > 90ppm Ag,Cu,Pb,Zn Hg > 2ppm

Mo >80 ppm

Ba > 1500ppm

Sn > 10ppm

Cu,Pb,Zn

85

0 500m

7994000 560500 561000 561500

Fig. I-4-2(1) Integrated Interpretation Map of the Turaquiri District LEGEND

(Hsq) Alluvial deposits

(Ppv) Basalt (Mpvsv) Hornblende-biotite andesite MPvs GN (Mpsv) Pyroxene quartz diorite 7978000 MN (Mpv) (Pyroxene)-hornblende-biotite andesite (Mpvs) Tuff breccia ~ Lapilli tuff

4°00' Hsa PPv Hydrothermal breccia zone MPv MPv Argillized zone

Silicified zone 80 Silica vien PPv Fault 40 Lava flow band MPv Hsa Old working 7977500 Pyrite impregnation Hsa Manganese oxide

MPv Hsa Geochemical Anomaly

Au > 70ppb MPv MPv MPv Ag > 30ppm

MPsv MPvs Cu > 90ppm

Pb > 400ppm Hsa 7977000 MJBO-1 Zn > 230ppm MJBO-2 As > 140ppm MPvsv Sb > 90ppm

Hg > 2ppm

MPv MPv Mo >80 ppm MPv Ba > 1500ppm Hsa Sn > 10ppm MPv

MPv Alteration Mineral Zoning 7976500 Quartz Zone / Cristobalite zone MPv Sericite Zone MPv

MPvs Alunite Zone

MPv MPv

MPv

7976000

0 500m

518000 518500 519000 519500 520000 520500 521000

Fig. I-4-2(2) Integrated Interpretation Map of the Chullcani District - 25～26 - chemical analysis show that gold mineralization is only slightly higher than that for the MJB0-1 drill hole and prominent gold mineralization are not confirmed. The steep structure of alteration is confirmed in both drill holes.

In the Chullcani District, epithermal mineralization related to shallow activity of intrusive rock and high sulfidation type epithermal mineralization in some parts are estimated.

4-2-3 Sonia - Susana district (Fig. I-4-2(3)) Volcanic rocks in the Jankho Kkollu Prospect are correlated to the Negrillos Formation (Upper Oligocene to Lower Miocene). The Phase III survey revealed that dacite intruded into a stratovolcano and the center part of the volcano is exposed due to erosion. It is possible that the volcano was formed later than the time when the Carangas Formation was formed in the Middle Miocene age, instead of the Upper Oligocene to Lower Miocene ages. Many lead-zinc bearing barite-quartz veins are confirmed in areas south of the intrusive rock body. Limonite veins are confirmed north of the intrusive rock body. It is not clear whether their mineralization periods are the same or not, although there are mineral differences in the vein type. Judging from the existence of neutral hydrothermal alteration and intrusive rock, the mineralization of this area is estimated to be an epithermal silver, lead, zinc and copper mineralization related to a hypabyssal intrusive activity in a shallow place. However, ore veins in the south part are discontinuous and small in size. The veins in the north part are also very small. Geochemical anomaly of molybdenum shows that the porphyry type mineralization is expected for the Santa Catalina prospect. However, positive showings suggesting its existence are not confirmed in this survey.

4-2-4 Mendoza district (Figs. I-4-2(4)) Volcanic rocks consisting mainly of dark gray andesite lava and pyroclastic rocks dominate this area. All rocks have undergone hydrothermal alteration (argillization and silicification). A large number of lead-zinc bearing veins are confirmed in propylitic rocks in the Iranuta section. The mineralization in the Iranuta section does not contain tin and shows neutral alteration. This suggests that the mineralization corresponds to a epithermal type mineralization related to the activity of hypabyssal intrusive rocks in shallow depth. The average homogenization temperature of fluid inclusions is 258°C, suggesting that the mineralization in the Iranuta section is slightly below the epithermal ore deposits. Based on the results of the geochemical analysis, the distribution of geochemical anomalies

- 27 - Jankho Kkollu Santa Catalina

7917500 7916000

GN

MN 65 80 63 py GN 80 43°0405' py 70 80 MN py py 45 OMvn1 py 70 80 43°0405' py OMvn1 OMvn1 OMvn2

py

70 85

7917000 7915500 OMsv2

30 80 85 85 85 70 70 Pb, Zn 65 70 OMvn1 75 OMvn1 py 85 75 - 29

50 OMsv1 85 517500 518000 75 0 500m

70 80 80 LEGEND Pb 80 OMsv1 50 Lower to Middle Miocene volcanic Rocks Geochemical Anomaly

7916500 Au > 70ppb (OMvn1) Tuff to tuffbreccia 70 Ag > 30ppm OMsv1 v v

Pb,Zn OMvn1 v (OMvn2) Andesite Lava

v

80 80 Pb v Cu > 90ppm v

70 70 (OMsv1) Intrusive rock (dacite) OMsPv1b Pb > 400ppm x x 65 75 OMsv1 x (OMsv2) Intrusive rock (dolerite) Pb OMsv1 Zn > 230ppm OMsv1 65 OMsv1 As > 140ppm Pb 75 Sb > 90ppm OMvn1 Pb Argilized zone Hg > 2ppm Silicified zone Mo >80 ppm

Silicified or Quartz vein Ba > 1500ppm

Silicified or Quartz vein with Fe oxide Sn > 10ppm 0 100 200 300 400 500 Pb (Zn) vein

7916000 Strike and dip 514000 514500 515000 Pb, Zn Pb, Zn showing

fig. I-4-2(3) Integrated Interpretation Map of the Sonia-Susana District 7822500

GN

Pb 75 MN Iranuta

75 Pb 80 80 80 70 80 85

4°00' Pb Pb 80 80 85

75

7822000

L E G E N D 60 70

65 80 (OMv) Andesitic tuffbreccia - lava 65

75 80 (OMv) Dacitic tuff 80 80 80

Hydrothermal breccia zone 80 80 80 80 Argillized zone 85 80 80 75 80 75 Silicified zone 80

Quartz vein or silicified vein

Quartz vein or silicified vein with Fe oxide 74 7821500 Strike and dip

78 80 80 Fault

Pb Pb showing

Py Pyrite impregnation

V Vuggy silica 33

70

50 7821000 80

60 75

70 50 60 70

70

70 75 75 86

75 60 80 80 70 55

78

60 85

80 70 70 78 50

70 75 80 75 80 65 75

80 70 70 75 85 88 70 Geochemical Anomaly 7820500 80 Au > 70ppb

80 80 Ag > 30ppm

Cu > 90ppm 80 80

80 Pb > 400ppm

80 65 80 Zn > 230ppm

75 60 85 85 As > 140ppm 75 70 45 70 Sb > 90ppm

85 Hg > 2ppm Mo >80 ppm

80 Ba > 1500ppm

Sn > 10ppm V 7820000

V V 85 VV V V V V

V 80 65 85

V V V V V 80

V Py

75 80

80 V V V

V V Co. Chorka 7819500

85

V V 85

V

V

- 3 1 ～ 623000 623500 624000 624500 625000 3 2 - 0 500m

Fig. I-4-2(4) Integrated Interpretation Map of the Mendoza District and hydrothermal alteration minerals, the mineralization in the Iranuta section is believed to have been caused by rhyolite intrusive rocks in the north and that the mineralization is different from Co.Chorka. The acidic alteration, confirmed on the upper north slope of Co. Chorka and is inferred to be caused by magma, overlaps with geochemical anomalies of gold, copper, arsenic, antimony and mercury. A high sulfidation type mineralization is expected there. An existence of intrusive rock is estimated below places near the top of Co. Chorka because of dominant hydrothermal activity in the area. Possibilities for epithermal gold and silver ore deposits related to hypabyssal intrusive activity in shallow places are high. However the size of the mineralization may be small because Co. Chorka is interpreted as a single stratovolcano.

4-3 Potentialities of Ore Deposits Summarizing the results of three years survey, the possibility of existing base metal bearing epithermal precious metal ore deposits beneath the widely spread hydrothermal alteration zones in the Cordillera Occidental is presumably high. The existence of such ore deposits is expected where, 1) rock of ore bringer is located 2) passage of hydrothermal solution (mineralized fluid) is located 3) hydrothermal solution was repeatedly supplied, and the potentiality and location of ore deposits can be estimated from 4) the amount of erosion and 5) geochemical anomalies. 1) As regards to the ore bringer, a dome structure or intrusive rock has played a role of supplying the hydrothermal solution and heat. A number of intrusive rocks are observed in the district of Mendoza, Co. Kancha and Guadalupe mine.

2) As regards to the passage of hydrothermal solutions, the areas where fractures are well developed and the presence of hydrothermal breccia or breccia pipe is recognized are thought to be suitable. Since a number of known ore deposits occur in the east-west fractures (e.g. ore deposits of Salinas de Garci Mendoza, Todos Santos, Carangas and Turaquiri), the area where the east-west fractures are well developed is presumed.

3) As regards to the area where hydrothermal solution was repeatedly supplied, the area of volcanic complex seems to be more promising than the area of a single stratovolcano. In the area where old volcanic rocks (alteration) and young volcanic rocks (alteration) are co- existing, overprinting of mineralization can be expected. The size of the hydrothermal alteration zone is generally larger in the area where the hydrothermal solution was repeatedly supplied. Co. Kancha in the Mendoza district (dacite intrusions were 16.2 Ma and 8.0 Ma), and Sonia –Susana district (hydrothermal alteration was 17 Ma and 1.75 Ma)

- 33 - are examples.

4) The amount of erosion is estimated from the data of age determination, homogenization temperatures of fluid inclusion, geochemical anomalies and alteration minerals. In case the erosion is well advanced and mineralization is weak on the surface, an intense mineralization is not expected deep underground, so that the potential of the area is thought to be low.

5) As regards to the geochemical anomaly, useful information is obtained at the La Deseada mine, where anomalies of lead, arsenic and antimony (locally gold and copper) are located in the upper part of the mineralization, and anomalies of gold, silver, copper, lead, zinc and antimony are located in the lower part of mineralization. Taking the above factors and vein character into consideration, the location of a mineralized zone can be presumed.

The potential area can be selected by comprehensive study of the above factors.

- 34 - Chapter 5 Conclusions and Recommendations

5-1 Conclusions The surveys in Phases I and Ⅱ revealed that the hydrothermal alteration zones widespread in the Oruro-Uyuni region are likely to host epithermal ore deposits at depth. It is assumed an epithermal deposit, rich in gold, silver, lead and zinc, related to shallow volcanic rocks; epithermal deposit of precious metals related to hypabyssal intrusive rocks (upper part of porphyry type deposit?); high sulfidation type of gold, silver copper ore deposit (quartz-alunite vein type); and low sulfidation type (quartz-adularia vein type) are expected. Promising districts were identified. In PhaseⅢ, four districts were selected from these promising districts and surveys were conducted. The results of the surveys in these districts are summarized below.

Turaquiri district The Phase Ⅲ survey revealed distributions of Middle to Upper Miocene sedimentary rocks and Miocene to Pliocene volcanic rocks and the presence of andesite intrusive rock. Although signs of local gold anomalies are just confirmed in areas around this intrusive rock., it seem to be small in size. Many ore veins are confirmed northwest of the Turaquiri deposit. Most veins, however, are less than 10 cm in vein width and mineralizations of network and dissemination types are not confirmed. Variations of ore minerals are confirmed. Centering on the Turaquiri Vein, the veins change from lead and zinc veins to manganese dioxide veins in the northwest and clay veins farther outside. The foregoing observation suggests that veins beneath the manganese dioxide veins in the northwestern part of the area surveyed in Phase Ⅲ might change to silver-lead-zinc-copper bearing vein , but they are insufficient size for a bulk mining operation.

Chullcani district The igneous activity of Chullcani Volcano started around 6.5 Ma. Wide hydrothermal alteration zones were formed through the intrusions of diorite and andesite and hydrothermal activity caused by intrusions. It is interpreted that subsequent erosion denuded the center part of the volcanic body and that a dome and mesa of basalt were formed from Late Pliocene to Pleistocene (See Fig. II-2-2 (4)). Distribution of a quartz-sericite alteration zone shows that diorite intrusive rock is the center of hydrothermal activity. Dominant hydrothermal alteration is confirmed throughout the MJBO-1 drill hole, it is inferred to be a local center of hydrothermal fluid activity. The assemblage of alteration minerals

- 35 - suggests that a temperature rising toward the deep part. A chemical analysis shows anomalies of lead, arsenic and zinc in some parts. However, prominent mineralization is not confirmed. Silicified - argillized zone associated fault zone intersects diorite in the MJBO-2 drill hole. Geochemical analysis shows that gold mineralization is only slightly higher than that for the MJB0-1 drill hole and prominent gold mineralization are not confirmed. The steep structure of alteration is confirmed in both drill holes.

The facts that intrusive rock is exposed on the surface and the gold geochemical anomaly on the surface is not dominant in the drill holes suggest possibilities that gold mineralization was weak in general. However, because existing ore deposits are not necessarily embedded all over the intrusive rock and in domes as in the Todos Santos ore deposit surveyed in PhaseⅡ, and a quartz- sericite alteration zone stretches to the southeastern part and diorite may probably exist in the deep part, and hydrothermal breccia and breccia pipes are distributed in the adjacent southeastern part suggest intensive hydrothermal activity. Possibilities remain for epithermal gold ore deposition in the northeast part of the MJBO-2 drill hole related to an intrusive activity in shallow parts.

Sonia - Susana district In Jankho Kkollu prospect in the Sonia-Susana district, the survey revealed that the dacite intruded into a single stratovolcano and the center part of the volcano was exposed due to erosion. It is possible that the volcano was formed later than the time when the Carangas Formation was formed in Middle Miocene, instead of Upper Oligocene to Lower Miocene. Many lead-zinc bearing barite-quartz veins are confirmed in areas south of the intrusive rock body. The limonite veins are confirmed north of the intrusive rock body. Judging from the existence of neutral hydrothermal alteration and intrusive rock, the mineralization of this area is estimated to be a epithermal type silver, lead, zinc and copper mineralization related to a hypabyssal intrusive activity in a shallow place. However, ore veins in the south part are discontinuous and small in size. The veins in the northern part are also very small. Therefore, ore deposits are not expected to be large.

The geochemical anomaly of molybdenum shows that the porphyry type mineralization is still expected for the Santa Catalina Prospect. However, positive showings suggesting its existence, are not confirmed in this survey.

Mendoza district Volcanic rocks consisting mainly of dark gray andesite lava and pyroclastic rocks dominate this area. All rocks have undergone hydrothermal alteration (argillization and silicification). A

- 36 - large number of lead-zinc bearing veins are confirmed in propylitic rock in the Iranuta section. Based on the results of the geochemical analysis, the distribution of geochemical anomalies and hydrothermal alteration minerals, the mineralization in the Iranuta section is believed to have been caused by rhyolite intrusive rocks in the north and that the mineralization is different from Co. Chorka. These ore veins are believed to expose relatively deep parts of the vein systems as epithermal ore deposits and large-scale ore deposits are not expected.

The acidic alteration, confirmed on the upper north slope of Co. Chorka and is inferred to be caused by magma, overlaps with geochemical anomalies of gold, copper, arsenic, antimony and mercury. A high sulfidation type mineralization is expected there. An existence of intrusive rock is estimated below places near the top of Co. Chorka because of dominant hydrothermal activity in the area. Possibilities for epithermal gold and silver ore deposits related to hypabyssal intrusive activity in shallow places are high. However the size of the mineralization may be small because Co. Chorka is interpreted as a single stratovolcano.

5-2 Recommendations for the future There are no strong reasons for further exploration can be suggested as the result of the project, although the survey revealed detailed information for the geology and mineralization of the area. However, the recommendations for further explorations are summarized as follows, for in case of re-evaluating the potentiality of the Oruo - Uyuni Area and the adjacent Western Andes Region.

(1) Recommendations for exploration of epithermal type mineralization The analysis of remote sensing data is a useful tool for selecting a hydrothermal alteration zone from a wide area. The potential mineralized zone should be selected by geochemical investigations. Further detailed geological investigations should be mentioned with the following viewpoints. i) Existence of ore bringers (domes and intrusive rocks). ii) Existence of hydrothermal fluid (mineralized solution) paths (fractures, hydrothermal breccias and breccia pipes). iii) Repetitive supply of hydrothermal fluids (overlap of igneous activities).

The analytical study should be mentioned for the following viewpoints. a) Dissection degree of volcano: distribution of igneous rock age, homogenization temperature

- 37 - of fluid inclusions, geochemical anomalies and alteration minerals, etc. b) Evaluation of the vertical and lateral position in the mineralization system: distribution of alteration minerals, geochemical anomalies and mineral assemblage of veins.

Those districts with high potential that are narrowed down in this detailed geological survey should preferably conduct geophysical exploration and drilling exploration to reveal the geological structures and mineralization at deeper parts.

(2) Recommendations for exploration of porphyry type mineralization Th mineralized age of Chilean porphyry copper deposits have a tendency to become younger from west to east. It shows the potentiality of this type mineralization in the volcanic region of the Western Bolivian Andes. But at the younger volcanoes, the porphyry type mineralization would be located quite deep underground if it exists. Therefore it is desirable for a detailed investigation of volcanic stratigraphy (especially age dating of volcanic rocks) of the Western Andes Region as basic information for the explorations. It also should be important information for the exploration of the epithermal type mineralization mentioned above.

- 38 -