72 特 別 GENERAL OVERVIEW AND PROSPECTS OF THE MINING 講 演 AND METALLURGICAL INDUSTRY IN PERU Oscar J. PERALES P. Peru it is not surprising to find a great variety of natural 1. INTRODUCTION. resources and among them, the most important in the Peru- With a territorial surface area of approximately vian Industrial Structure: The Minerals. Geologically 1'300,000 km2 and around 23 million people, Peru is speaking, Peru is one of the richest and most varied coun- located in the middle part of South America, between 0-18•‹ tries on earth. It is included among the world's top seven latitude south and 69-81•‹longitude west. Peru borders on mineral producers, second in silver output, fourth in zinc the north with Ecuador, on the south with Chile and and eigth in copper. It is also an important world producer Bolivia, on the east with Brazil and Colombia and on the of lead, iron, gold, phosphates and a host of other minor west with the Pacific Ocean. The capital city, Lima, is minerals. Peru's metallic production includes 18 different situated around 12•‹ latitude south. metals and around 20 nonmetallic and related industrial The Peruvian territory is geographically divided into minerals. However, the Peruvian territory remains almost three natural regions. The partially desertic coastal virgin in terms of mining exploitation; technical evaluations region, or Coast, the highlands and the region of the estimate that only a small percentage, between 5 and 7%, tropical forest or Jungle. of Peru's total mining wealth is currently being developed. The Coastal region is a narrow band traversing from The resume shown in Table 1 illustrates the previous com- the Pacific Ocean on the west and raising gradually up to an ments. altitude of approximately 500 meters to the east. On the Table 1. PERU: MINING PRODUCTION AND coast there are valleys, prairies, small plateaus, and RESERVES. foothills. MAIN MINING PRODUCTS The highlands, also called La Sierra, have the Coast as (Thousands of FMT, period averages) its western limit and raise from an altitude of 500 m. from the western flank up to 1500-2000 m. on the eastern flank. The principal physiographic feature is the Andean Range or "Cordillera de Los Andes", which runs along the west coast of South America and crosses the country from north to south. This impressive chain of mountains is known to be one of the most intensively mineralized zones of the world. The tropical forest extends from the western flank of the Andes Range up to the eastern border. This region MAIN MINERAL RESERVES comprises approximately 60% of the Peruvian territory and (Thousands of MT) is further subdivided into two subregions according to altitude and climate. One is the "high forest", or rupa, and the other is "low forest", also called omagua. Owing to these different geographic peculiarities in *平 成6年6月16日 本 会 第92回 例 会 に おい て発 表 ** Assistant Professor . School of Metallurgy. National Engineering University. Lima-PERU. 平 成6年4月30日 受 理 (16) 資源処理技術 GENERAL OVERVIEW AND PROSPECTS OF THE MINING AND METALLURGICAL INDUSTRY IN PERU 73 The new concept of the Peruvian mining management country. One of the most important groups of porphyritic is to establish the best conditions to attract foreign invest- copper is located in the southern part of the country, mainly ment and consequently, give mining the boost and the injec- at Cuajone, Toquepala and Cerro Verde where production tion of fresh capital it needs. With the new mining law in is still in progress. Quellaveco deposit, also in the south, is place, attractive tax stability contracts on offer, coupled in the preliminary step of evaluation. Other porphyritic with the variety and richness of our mining deposits copper deposits occur in the norht, such as the Michi- together with an important experience in this business, quillay, La Granja and Cañariaco deposits which are Peru offers now the best conditions for mining and located near Cajamarca city. As an example, La Granja metallurgical development. deposit has probable reserves of 318.9 MMT with 0.78% Cu, 5 g/t Ag and 0.015% Mo. 2. MINERAL OCCURRENCE AND Besides the south eastern Peru, most of lead and zinc METALLURGICAL STRUCTURE deposits are related to the Peruvian geosyncline, (previous- Historically, mining activities in Peru started a long ly mentioned), generally as polymetallic deposits. For in- time ago. Our ancestors developed various and different stance in the zinc deposit of Antamina, located in Ancash, mining and metallurgical methods changing easily from proven and probable reserves amount to 166 MMT with lithic instruments into metallic ones. 1.3% Cu, 1.1% Zn, 0.04% Mo and 16 g/t Ag. It is en- Archeological evidence establishes that the use of visaged that the development of these areas would play an metals in Peru began around 900 years before Christian important role fo rthe future of La Oroya metallurgical com- Era. The ancient metallurgists of Peru worked on Copper, plex. Tin, Gold, Silver, Lead and were able to obtain alloys of The main sources of Peruvian vein gold production come Cu-Sn, Ag-Cu, Au-Cu, Ag-Au, Ag-Au-Cu, and sometimes from the region between Ica and Arequipa in the south and including Pt; for this purpose mastered techniques like foun- The Pataz area in the north eastern part of the country. dry, welding, laminate and so on. Those ancient Peru- Pataz area comprises a 130 Km strip along the eastern side vians established a culture with a well-defined personality of Marañon River. Depending of the mineralogical associa- reflected in their impressive metallurgical labors, most of tions and the ore grade, the principal metallurgical schemes them perfectly preserved until the present time. consist of cyanidation of gold-quartz-limonite ores by per- *Geologyand mineral occurrence. colation, (heap-leaching) or agitation systems. In the case The geology of Peru can be represented by the follow- where gold is associated with sulphide's, the ore is treated ing features: by direct cyanidation or after a flotation stage. The i) The Peruvian Geosyncline; this a basin where mostly recovery from solutions is by means of conventional marine sediments were deposited since the beginning methods of precipitation with zinc dust- fusion of pre- of the Mesozoic until the Andean uplift in early Ter- cipitates and refining or adsorption onto activated coal-elu- tiary times. tion-electrowinning. Ultimately, "Minera Yanacocha", a ii) The Volcanic (North+ South); these are mostly early joint venture society formed by Newmont Mining Corpora- to middle Tertiary in age and consist of innumerable tion from USA, BRGM from France and the Peruvian com- volcanic plugs, domes, cones, etc. pany Cia. de Minas Buenaventura, started the iii) The Coastal batholith; it extends along the Western metallurgical processing by dump leaching of the slope of the Cordilera. It is basically a granodiorite. Yanacocha disseminated gold-quartz-limonite deposit of iv) The Eastern Cordillera; its rocks are older than those the north of Cajamarca City. The estimated reserves are of the Andes. It has not yet been studied in detail. 12 MMT of mineral with 1.5 g Au/t.. This plant is the first The occurrence of mineral deposits is showed in the gold plant one in Peru operating in a big scale and its pro- Map of figure 1. It is rather impressive but obviously con- duction will represent an overall increase of around 50% in fusing due to the sizable number of these mineral occur- the total output of the yellow metal. rences. In order to simplify the situation let me show the Another important source of gold is Placer Deposit agrouped occurrences of our principal mineral resources. concentrated principally in Cuzco and Puno in southern Base and PreciousMetals. Peru; although the metal is also recovered from streams The copper deposits are distributed widely all over the throughout the Jungle. The San Antonio de Poto deposit, Vol.41,No.2('94― 夏) (17) 74 Oscar J. PERALES P. Fig. 1 PERU: Principals Metallic, Nonmetallics and Petroleum occurrences. (From Minerals Yearbook, 1990). near Lake Titicaca in Puno, reports geological reserves of timately associated with lead and zinc sulphide's. 122 MNm3 at 0.242 g Au/m3. Gold is also obtained as a Raw materials constitute more than 40% of all Peru- byproduct from the pyrometallurgical processing of vian exports to Japan, with nonferrous metals, principally polymetallic concentrates. Cu and Zn, earnings respectively US $ 29 MN and US $ The contribution of different sources of fine gold pro- 60.2 Mn in 1992. Particularly, Zinc exports have increas- duced during 1988 in presented in Table 2. ed in importance and now Peru is one of Japan's largest sup- In the case of metallic silver, most of the time it is pliers after Australia and USA. associated with the gold as free silver or alloyed as elect- Nonmetallicand related Industrial Minerals. rum. On the other hand, silver minerals are also found in- Coal (18) 資源処理技術 GENERAL OVERVIEW AND PROSPECTS OF THE MINING AND METALLURGICAL INDUSTRY IN PERU 75 Table 2. STRUCTURE OF THE GOLD PRODUC- yen reserves. Geologically speaking, the Bayovar deposit TION. was formed in a basin largely composed of quaternary YEAR 1988 sediments, occasionally fluctuating from the Eocene to the Miocene of the tertiary, with a highest potency of 2450 meters. The ore consists of fluorapatite, diatomite, fragments of marine fossils, sponge residues, limonite and ferromagnesian minerals. Sulfur and others. Eighty percent, (80%), of the Peruvian deposits of elemental sulfur are located in the south, principally in Tac- na region where it has been possible to identify up to 33 (Source: Commercial Mining Yearbook, 1988).