Tapajós The Amazonian Eldorado: São Jorge Gold Deposit

Brazil,Brasil, Amazon, amazônia, amazonia, minerals,geologia, geology, geological mapping, regional reconnaissance, geophysical, geophysics, geochem, geochemistry, geoquímica, geoquímico,  geofísico, exploração mineral, ouro,gold nuggets, pepitas, Amazônia, Tapajós, tapajos, consultant, consultants, consultores, geólogo, geóloga, geologo, geologa, geologist, áreas, negociações, metais base, cobre, estanho, ouro, export, caulim, descobertas, mineral discoveries, prospects, consultants, properties to sell, mineral areas, mineral exploration, base metals, copper, tin, porphyry, porphyries, titanium, cobalt, tantalite, rutile, ilmenite, columbite kaolin, garimpo, garimpeiro, garimpeiros, pista de pouso, trincheiras, poços, trenchs, pits, drilling, diamond drill holes, Carajas,Carajás, Pará, Pedro Jacobi, Progeo, evaluation, negotiations, negotiator, negociação, negociações,alunita, alunite, pyrophyllitem pirofilita, diásporo, sericita, sericite, chlorite, clorita, pirita, pyrite, chalcopyrite, calcopirita, galena, esfalerita, sphalerite, hydrothermal alteration, pipes, kimberlites, lamproites, diatremes, volcanoes, vulcão, diatremas, kimberlitos, diamantíferos, quartz, chalcedony, amethyst, ametista, quartzo,  calcedônia,fósseis,mineral specimens, collectors, topaz, topásio, cascalho, river flat, placers, golden, bearing, jazida, jazimentos, jazidas, orebody, ore, orebodies, deposits, mines, minas, céu aberto, open pit, underground, subterrânea, explotação, exploiting, economia mineral, economics, cash flows, volcanics, vulcânicas, granite, diorite, granodiorite, dacite, rhyolite, flows, lava, intrusions, return investment, programme, program, programas, pentlandita, nickel, sulfetos, sulfides, sulphide, oxides, iron laterites, gossan, ironstone, platinum, colecionadores, collectors, advance argillic alteration, phyllic, argílica, fílica, propilitização, propilitos, propylitization, propyllitization, sericitization, faults,  mineralization, terraces, production, evaluation, control, reports, data bank, locations, occurrences

by Pedro Jacobi

Historical background:Brazil,Brasil, Amazon, amazônia, amazonia, minerals,geologia, geology, geological mapping, regional reconnaissance, geophysical, geophysics, geochem, geochemistry, geoquímica, geoquímico,  geofísico, exploração mineral, ouro,gold nuggets, pepitas, Amazônia, Tapajós, tapajos, consultant, consultants, consultores, geólogo, geóloga, geologo, geologa, geologist, áreas, negociações, metais base, cobre, estanho, ouro, export, caulim, descobertas, mineral discoveries, prospects, consultants, properties to sell, mineral areas, mineral exploration, base metals, copper, tin, porphyry, porphyries, titanium, cobalt, tantalite, rutile, ilmenite, columbite kaolin, garimpo, garimpeiro, garimpeiros, pista de pouso, trincheiras, poços, trenchs, pits, drilling, diamond drill holes, Carajas,Carajás, Pará, Pedro Jacobi, Progeo, evaluation, negotiations, negotiator, negociação, negociações,alunita, alunite, pyrophyllitem pirofilita, diásporo, sericita, sericite, chlorite, clorita, pirita, pyrite, chalcopyrite, calcopirita, galena, esfalerita, sphalerite, hydrothermal alteration, pipes, kimberlites, lamproites, diatremes, volcanoes, vulcão, diatremas, kimberlitos, diamantíferos, quartz, chalcedony, amethyst, ametista, quartzo,  calcedônia,fósseis,mineral specimens, collectors, topaz, topásio, cascalho, river flat, placers, golden, bearing, jazida, jazimentos, jazidas, orebody, ore, orebodies, deposits, mines, minas, céu aberto, open pit, underground, subterrânea, explotação, exploiting, economia mineral, economics, cash flows, volcanics, vulcânicas, granite, diorite, granodiorite, dacite, rhyolite, flows, lava, intrusions, return investment, programme, program, programas, pentlandita, nickel, sulfetos, sulfides, sulphide, oxides, iron laterites, gossan, ironstone, platinum, colecionadores, collectors, advance argillic alteration, phyllic, argílica, fílica, propilitização, propilitos, propylitization, propyllitization, sericitization, faults,  mineralization, terraces, production, evaluation, control, reports, data bank, locations, occurrences

In 1992 Pedro Jacobi working as a consultant showed to Rio Tinto Zinc one of the best available opportunities in Brazil: the Tapajos Gold Province. goldgold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro

Tapajos was already a major gold producing region at that time. In spite of its undeniable economic potential not a single major mining company was engaged in exploration in that area. goldgold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro

The idea was to start a comprehensive exploration program, claiming the best geological environment and evaluating the best occurrences. As such a number of targets were selected to be visited by RTZ's personnel. gold gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro

Amongst these was a garimpo called São Jorge. gold gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro

S. Jorge was a small open cast operation controlled by a garimpeiro called Wilton Amorim. Wilton was working on top of an altered granite saprolite, in the vicinities of the Cuiabá-Santarém federal road.

This target received higher priority. And the RTZ's geologists started to work.

During the first trip, Jones Belther sampled quartz veins and host rocks. Results were considered interesting. Later Marcelo Pinto, Lincoln Sciepierski and Ivanir Luchesi, in different visits, collected channel-samples in the pit's floor. Best channel sample result averaged more than 2g/t Au over a 60m interval. gold gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro

Negotiations between Pedro Jacobi, on behalf of RTZ, and Wilton were extended for a long period.

Three years later a preliminary soil grid program outlined a large (1700 x 300m) gold anomaly (>100ppb Au) which encompassed the Wilton pit. At this time it was recommended to RTZ a drilling program to evaluate the target.

Marcelo Pinto was appointed the project manager. From 1995 to 1997, Rio Tinto carried out a comprehensive program. Exploration work comprised of soil, auger and channel sampling, ground and airborne geophysical surveys, as well as over 4000 meters of diamond drilling. More than 25 diamond drill holes have been drilled at this property.

In 1998 Altoro has acquired a three-year option from Rio Tinto to earn a 100% interest in the project. Today Altoro is still seeking for investors.

Geology and Mineralization:

São Jorge area is underlain by the following Proterozoic units: the Parauari granodiorite (1.9-2.2Ga), acid volcanics with subordinated pyroclasts and sediments (Iriri's Formation 1.7-2.0Ga) and the Maloquinha intrusive granitic suite (1.5-1.9 Ga). The São Jorge coarse to medium grained hornblende-biotite sieno-monzogranite of Parauari's age is intruded in older sub-aerial volcanics. Mineralization is related to a depressed area inside the 10 x 6km intrusion. This depression is due to the erosion of a softer, intensely altered, zone which is controlled by the intersection of two major (NW-SE and NE-SW) structures.

A large volume of material was eroded from this altered granite to the alluvial flats of São Jorge's main stream creating rich gold alluvial deposits.

Inside this area a large mineralized endogranitic stockwork zone (1200 x 300m) was developed. A close inspection of these fractures shows that they have been developed in a ductile-brittle environment. Large volumes of hydrothermal solutions were pumped trough this low-pressure zone resulting in the São Jorge deposit. Hydrothermal fluids have, destroyed part of the magnetite which is a common accessory in the main monzogranite. As such the mineralized zone may be detected by the combination of mag and gamma.

Alteration at São Jorge is, also, structurally controlled.

Dominant alteration style is phyllic, represented by sericite-quartz-pyrite-chalcopyrite assemblage which envelopes a propylitic, chlorite-carbonate-sulfide assemblage.

Localized potassic alteration was observed in depth. These minerals occur filling the thin fractures of the stockwork zone. Alteration is mostly restricted to the vein/veinlet selvages. In a few zones it may reach thickness of 3 to 4m.

No pervasiveness was observed. As such the São Jorge ore is constituted by hard and fresh granodiorite and by a much smaller volume of soft quartz-sericite-carbonate-chlorite-sulfide veins. This setting may allow the use of autogenous milling processes helping unaltered granites, with higher work index, to be separated from the ore. As a result a very rich material will be concentrated with low costs.

The density of the stockwork zone controls gold grade distribution.

There is a very good correlation between gold and sulfides. If a regression is made, pure sulfides will assay more than 30g/t Au. The Cu/Au correlation is striking too. The best intersections are restricted to thin gold rich quartz-Py-Cpy-chlorite veins.

The São Jorge stockwork zone is covered by a 2-6m thick transported soil, a stone line and by a 20-35m thick mineralized saprolite. Supergene processes have remobilized and reconcentrated gold in this, partially eroded, lateritic profile.

Reserve Calculations:

A preliminary gold resource of more than 2Moz was calculated by Rio Tinto over the elliptical stockwork zone (900 x 100m).

Altoro, after the agreement, established resources of 3.2 million tons grading 1.3 g/t gold (130,000 oz contained gold) in the oxidized zone, and 9.5 million tons grading 2.4 g/t gold (730,000 oz contained gold) calculated to a 200m depth in the primary mineralization.

Future: ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, gold

São Jorge is a large, low grade, open pittable gold deposit, few kilometers away from a federal road. ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, gold

This deposit will be mined economically if the operator is able to upgrade it.

Two possible routes are: ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, gold

a) Reducing the internal waist through selective mining process. ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, gold

b) Use of autogenous milling processes to produce a rich quartz-sulfide concentrate discarding the high work index fresh granite. Brazil,Brasil, Amazon, amazônia, amazonia, minerals,geologia, geology, geological mapping, regional reconnaissance, geophysical, geophysics, geochem, geochemistry, geoquímica, geoquímico,  geofísico, exploração mineral, ouro,gold nuggets, pepitas, Amazônia, Tapajós, tapajos, consultant, consultants, consultores, geólogo, geóloga, geologo, geologa, geologist, áreas, negociações, metais base, cobre, estanho, ouro, export, caulim, descobertas, mineral discoveries, prospects, consultants, properties to sell, mineral areas, mineral exploration, base metals, copper, tin, porphyry, porphyries, titanium, cobalt, tantalite, rutile, ilmenite, columbite kaolin, garimpo, garimpeiro, garimpeiros, pista de pouso, trincheiras, poços, trenchs, pits, drilling, diamond drill holes, Carajas,Carajás, Pará, Pedro Jacobi, Progeo, evaluation, negotiations, negotiator, negociação, negociações,alunita, alunite, pyrophyllitem pirofilita, diásporo, sericita, sericite, chlorite, clorita, pirita, pyrite, chalcopyrite, calcopirita, galena, esfalerita, sphalerite, hydrothermal alteration, pipes, kimberlites, lamproites, diatremes, volcanoes, vulcão, diatremas, kimberlitos, diamantíferos, quartz, chalcedony, amethyst, ametista, quartzo,  calcedônia,fósseis,mineral specimens, collectors, topaz, topásio, cascalho, river flat, placers, golden, bearing, jazida, jazimentos, jazidas, orebody, ore, orebodies, deposits, mines, minas, céu aberto, open pit, underground, subterrânea, explotação, exploiting, economia mineral, economics, cash flows, volcanics, vulcânicas, granite, diorite, granodiorite, dacite, rhyolite, flows, lava, intrusions, return investment, programme, program, programas, pentlandita, nickel, sulfetos, sulfides, sulphide, oxides, iron laterites, gossan, ironstone, platinum, colecionadores, collectors, advance argillic alteration, phyllic, argílica, fílica, propilitização, propilitos, propylitization, propyllitization, sericitization, faults,  mineralization, terraces, production, evaluation, control, reports, data bank, locations, occurrences

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Brazil,Brasil, Amazon, amazônia, amazonia, minerals,geologia, geology, geological mapping, regional reconnaissance, geophysical, geophysics, geochem, geochemistry, geoquímica, geoquímico,  geofísico, exploração mineral, ouro,gold nuggets, pepitas, Amazônia, Tapajós, tapajos, consultant, consultants, consultores, geólogo, geóloga, geologo, geologa, geologist, áreas, negociações, metais base, cobre, estanho, ouro, export, caulim, descobertas, mineral discoveries, prospects, consultants, properties to sell, mineral areas, mineral exploration, base metals, copper, tin, porphyry, porphyries, titanium, cobalt, tantalite, rutile, ilmenite, columbite kaolin, garimpo, garimpeiro, garimpeiros, pista de pouso, trincheiras, poços, trenchs, pits, drilling, diamond drill holes, Carajas,Carajás, Pará, Pedro Jacobi, Progeo, evaluation, negotiations, negotiator, negociação, negociações,alunita, alunite, pyrophyllitem pirofilita, diásporo, sericita, sericite, chlorite, clorita, pirita, pyrite, chalcopyrite, calcopirita, galena, esfalerita, sphalerite, hydrothermal alteration, pipes, kimberlites, lamproites, diatremes, volcanoes, vulcão, diatremas, kimberlitos, diamantíferos, quartz, chalcedony, amethyst, ametista, quartzo,  calcedônia,fósseis,mineral specimens, collectors, topaz, topásio, cascalho, river flat, placers, golden, bearing, jazida, jazimentos, jazidas, orebody, ore, orebodies, deposits, mines, minas, céu aberto, open pit, underground, subterrânea, explotação, exploiting, economia mineral, economics, cash flows, volcanics, vulcânicas, granite, diorite, granodiorite, dacite, rhyolite, flows, lava, intrusions, return investment, programme, program, programas, pentlandita, nickel, sulfetos, sulfides, sulphide, oxides, iron laterites, gossan, ironstone, platinum, colecionadores, collectors, advance argillic alteration, phyllic, argílica, fílica, propilitização, propilitos, propylitization, propyllitization, sericitization, faults,  mineralization, terraces, production, evaluation, control, reports, data bank, locations, occurrences