Tapajós The Amazonian Eldorado: Mineralization

Tapajós The Amazonian Eldorado: Mineralization
by Pedro Jacobi
	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 old, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro Placer deposits: More than 90% of the gold in Tapajós was extracted from thousands of alluvial deposits spread over large areas. A number of alluvial gold districts have produced more than 3Moz of gold during their mining history. Garimpos like Cuiu-Cuiu, Canta-Galo, Abacaxis and Patrocínio are classical examples of these large sedimentary systems.gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro Alluvial gold deposits are everywhere in Tapajós.gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro A quick view of satellite imagery will show 200km stretches virtually covered by mineralized placer deposits. This situation allowed the establishment of hundreds of thousands of garimpeiros. In spite of the rudimentary mining and exploration methods several rich bonanzas were found attracting prospectors from all parts of Brazil. Due to the early successes most miners thought that there was no need for improvements and the "sluice-box and pump" was used in almost all deposits. gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro During the early days the approach used to mine placer deposits was simple. The garimpo owner sold little 10 x 10m blocks to the miners. He controlled all distribution of supplies and fuel. The only accepted currency was gold itself. As such most garimpos became a shopping business rather than a mining one. It did not matter if one is getting rich or poor in the mine front provided that he pays for fuel and suppliesdots gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro As a consequence the districts were flooded with people. Soon placers were exhausted and garimpeiros started to migrate from one district to another . It was the beginning of the end of garimpeiro's alluvial mining in Tapajos. gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro During the 90's, mineral explorationists were attracted by a simple formula: the larger the mineralized placer the larger the primary source will be. Nevertheless the Tapajos geology wasn't that simple and several companies lost their money guided by that "rule". gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro In general these alluvial deposits are recent. Nevertheless during geological mapping of areas like Nova Brasília and Samauma, we observed that older sedimentary units also existed. In Nova Brasília garimpeiros were mining the so-called "segundo cascalho" which means the second pebble layer. In this case they were extracting gold from an older sedimentary horizon buried under the recent Quaternary flat. This extremely rich conglomerate horizon lies 10-20m under today's surface. Age is, very likely, Tertiary. It sits unconformably on top of weathered cataclastic gneiss. A marker horizon of peat rests 1-1.5m on top of this unit. gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro In spite of this, garimpeiros were eager to dismantle up to 20m of barren clay and intercalated sand to mine this thin (0.1-2m) ore horizon.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 the Samauma region another tectonic setting was observed. Gold was transported from 20-40m high terraces to the recent alluvial deposits. Erosion has rounded the topography making difficult to the observer to visualize these terraces. Nevertheless a large area in the vicinity of the Crepori River is covered by partially eroded gold bearing paleo-terraces. Paleo-placers in Tapajós are unknown to most explorationists. gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro Quite a few have huge volumes and high grades and may generate interesting economic deposits. gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro From the exploration point of view these vertical movements and the subsequent erosion that affected the up-faulted blocks will explain most of the exploration failures (see discussions).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 Primary deposits: Most primary gold deposits in Tapajós are associated to Proterozoic rocks. The relationship between Proterozoic granitoids and volcanics with gold imposed a barrier for many explorationists. Most of them believed that gold deposits associated to granites are small and the chance of a world class discovery in Tapajos was non existent. gold, copper, molly, mineral exploration, brazil, amazon, geology, consultant, properties, minerals, tantalite, porphyries, consultants, quartz, amethyst, diamonds, tapajos, garimpo, garimpeiro This mistake is usual amongst geologists that can't see anything but established geological models. 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 Mineral exploration is a subjective and creative business and as such there is no room for narrow-minded people. ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, The most important primary mineralization in Tapajos are: 1- Quartz veins: ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, In almost all districts quartz-sulfide veins are abundant. In general quartz veins are narrow and discontinuous. Quartz veins are known in all kinds of terrain and ages in Tapajos. Gold is often visible and quite frequently occur associated to rich clusters. Grades may be very high. Sulfides are mostly pyrite and secondarily chalcopyrite and galena. Pirrotite, molibdenite and sphalerite are described in a few areas. Carbonates are common. Single quartz veins may have the grade but seldom the volume. 2- Chlorite (sericite)-quartz-sulfide veins: ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, Important high-grade mineralization is associated to large chlorite-quartz-sulfide veins. These veins are filling open spaces in competent rocks affected by brittle deformation. Hydrothermal alteration is restricted to the selvages and is never pervasive. Host rocks vary from granites and volcanics to gneisses. Main sulfides are pyrite, chalcopyrite, pirrotite and galena. Whenever Cpy is present gold grades are bound to be exceptionally high, frequently above 30g/t. Massive sulfides, in mineralized areas, are extremely rich (up to 300g/t Au). Good correlation between copper and gold is common in several districts in Tapajos. These "juice" veins have been found in quite a few areas and will generate several economic deposits in Tapajos. An example of this type of mineralization is the Ouro Roxo gold deposit. 3-Stockworks : ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós, During our preliminary reconnaissance, in 1993, a number of gold bearing stockworks frequently associated to large alteration systems were discovered. Latter, such discoveries help to attract some of the "non believers" back to the Tapajos. In general stockworks are associated to the upper portion of granitic intrusions ( São Jorge) to volcanics intruded by granitic bodies (Pison) to porphyry type intrusions ( Batalha and V6) and to epithermal-porphyry deposits (V3). ouro, cobre, molibdenita, pórfiros, exploração mineral, amazônia, brasil, geologia, consultor, áreas, garimpos, minerais, quartzo, tantalita, ametista, citrino, diamantes, tapajós,