Opala em vulcânicas

Opala em vulcânicas

PRECIOUS OPAL IN VOLCANIC SEQUENCES by S. Paradis1, G.J. Simandl2 and A. Sabina3

Ref: opala, vulcânica, jásper, ágata

Paradis, S., Simandl, G.J. and Sabina, A. (1999): Opal Deposits in Volcanic Sequences; in Selected British Columbia Mineral Deposit Profiles, Volume 3, Industrial Minerals, G.J. Simandl, Z.D. Hora and D.V. Lefebure, Editors, British Columbia Ministry of Energy and Mines. IDENTIFICATION SYNONYMS: Hydrothermal or "volcanic opal". COMMODITIES (BYPRODUCTS): Precious opal (common opal, chalcedony, jasper, agate). EXAMPLES (British Columbia - Canada/International):   Klinker (082LSW125), Northern Lights (093E 120), Whitesail Range (maps 93E10W and 93E11E) and a precious opal occurrence near Falkland, Eagle Creek (093K 095); pale green and apple green common opal occurs at Savona Mountain (092INE158); Queretaro Mines (Mexico), Virgin Valley (Nevada, USA), Tepe Blue Fire Opal Mine (Idaho, USA). GEOLOGICAL CHARACTERISTICS CAPSULE DESCRIPTION: Opal occurs commonly in seams of volcanic ash or lahars sandwiched between successive lava flows. It occurs mainly as open space fillings and impregnations. Common opal, opalized wood and to some extent "fire opal" are widespread within Triassic or younger volcanic sequences, but precious opal is rare. Where opal occurs in massive volcanic rocks, it occurs also as open space fillings, however the opal-bearing areas are much smaller. Regardless of volcanic hostrock, the precious opal occurrences are discrete, whereas common opal occurs over large areas. TECTONIC SETTINGS:  Volcanic arcs, rifts, collapsed calderas, hot spot related volcanism and others. DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING:  Volcanic sequences formed in subaerial or shallow marine environments where porous, pyroclastic or lacustrine rocks are interbedded with lava flows. AGE OF MINERALIZATION: Tertiary or younger, commonly Miocene. HOST/ASSOCIATED ROCKS: Common host rocks are rhyolite, basalt, andesite and trachyte lavas, lahars and other volcaniclastic rocks. Associated rocks are perlite, bentonite, scoria, volcanic ash and diatomite; volcanic rocks may be intercalated with lacustrine sedimentary rocks. DEPOSIT FORM: Favourable opal-bearing horizons are commonly stratabound. Occurrences of precious opal within these horizons are commonly considered as erratic, controlled by permeability at the time of opal deposition. Individual precious opal-bearing fractures or lenses may grade into common opal and agate over distances of centimetres. TEXTURE/STRUCTURE:  Opal occurs as open space fillings in irregular cavities, narrow discontinuous seams, partially-filled pillow tubes, fractures, vesicles, matrix in volcaniclastic rocks and replacing wood fragments and logs. Common opal may form miniature stalagmites and stalactites within cavities, nodules in clay or diatomite beds and "thunder eggs". ORE MINERALOGY [Principal and subordinate]: Precious opal; "fire opal", chalcedony, agate, common opal. GANGUE MINERALOGY [Principal and subordinate]: Common opal, agate, fragments of host rock, clays, zeolites, quartz, jasper, celadonite, manganese and iron oxides. ALTERATION MINERALOGY:  Opal-bearing cavities may have zeolite and celadonite coatings, but so do the barren cavities. There is no known alteration which is specific to precious opal. WEATHERING: In arid environments, opal in surface outcrops may desiccate, become brittle and crack. Such material is not suitable as a gemstone. However, these opal bodies may be gem-quality at depth. ORE CONTROLS: Open spaces and other permeable zones open to the silica-bearing solutions. GENETIC MODELS: In many large opal districts, it is believed that during the longer periods of volcanic inactivity, shallow lakes developed. Forests grew along the lake-shores and driftwood accumulated in the lakes. Volcanic eruptions covered everything with pyroclastic materials capped by lava flows resulting in aquifers, perched water tables, and anomalies in the thermal gradient. This in conjunction with subsequent brittle tectonic deformation resulted in ideal conditions for the formation of hydrothermal systems. A variety of silica forms, including silica sinter, opaline silica, chalcedony and common opal are believed to have formed by deposition of silica-bearing fluids. The dissolved SiO2 content in water is well known to be temperature dependent with the maximum dissolution at around 325°C, however, the conditions needed for the precipitation of precious opal in volcanic environment are not well understood. At least a portion of the opal-CT in volcanic rocks is believed to precipitate directly from supersaturated solutions. The temperatures of formation for precious opal are expected to be relatively low by analogy to sedimentary-hosted precious opal deposits, but temperatures as high as 160°C are reported from fluid inclusion studies. No precious opal is reported from active hydrothermal fields, such as Geyser Valley, Yellowstone or Whakarewarewa (New Zealand). This suggests that the precious opal forms only under very specific physico-chemical conditions. Eh and definitely pH may be important. Chemical composition of hydrothermal fluids in terms of silica concentrations, as well as Na, K, Cl, Ca, SO4, HCO3, B, Li and other elements may be important. The composition of the silica-bearing fluid is probably modified during migration through the permeable host rock, specially if the latter contains zeolites and/or clays. Zeolites act as molecular sieves and are well known for their cation exchange properties. ASSOCIATED DEPOSIT TYPES:  Associated deposits can be beds of diatomaceous earth (F06), volcanic ash (E06), zeolite deposits (D01, D02), perlite and a variety of semi-precious or ornamental silica gemstones, such as jasper (Q05), moss agate (Q03), and chalcedony. Other deposit types occurring in the same setting are hot-spring Au-Ag (H03), hot-spring Hg (H02), agate (Q03) and hydrothermal Au-Ag-Cu: high sulphidation (H04). It is possible that these deposit types are the source of primary amorphous silica. COMMENTS: Precious opal is characterized by a play of color. The term common opal, as used here, covers any opal that does not show this play of colors. Some common opal specimens may be used as gemstones, but in general they have substantially lower value than precious opal. The term "Fire Opal" describes a common opal having a transparent orange to red-orange base color. Such opal is commonly faceted. Precious and common opal coexist within the same deposits. Common opal and opaline silica are also commonly associated with the spectacular hydrothermal systems characterized by hot springs pools and geysers, mud pots, geyser terraces and fumaroles where it may be deposited as common opal, opaline silica or silica sinter. The well known examples of such systems are: Yellowstone hot springs; Geyser Valley in Kamchatka and now inactive Waimangu Geyser (Taupo volcanic zone, New Zealand). It is possible that some of the precious opal is formed by the dissolution of the previously formed common opal, silica sinter in the same conditions as sedimentary rock-hosted precious opal deposits. EXPLORATION GUIDES GEOCHEMICAL SIGNATURE: Mn oxide fracture coating was observed in the proximity of the Klinker deposit. In some cases the indicator elements used in exploration for epithermal metalliferous deposits such as Hg, Sb and As may be indirectly applied to precious opal exploration. GEOPHYSICAL SIGNATURE: N/A, except for detecting perched water tables and faults (mainly VLF and resistivity). Thermometry may have use where precious opal is associated with recent hydrothermal activity. OTHER EXPLORATION GUIDES:  Boulder tracing is commonly used in opal exploration. Unmetamorphosed or weakly metamorphosed (zeolite facies) terrains (gem opal deteriorates and becomes brittle if subject to moderate temperatures); Tertiary or younger volcanic rocks. Areas containing known occurrences of precious or common opal, opalized wood and possibly chalcedony. Opal occurrences hosted by volcaniclastic rocks are commonly confined to the same lithologic unit over a large area. The presence of warm springs in an appropriate setting may also be considered as an indirect exploration indicator. At the Klinker deposit, mineralogical zoning within vesicule fillings may be used to delimit the most favourable areas. For example the common opal occurs only within broad areas of agate mineralization and precious opal only in small areas within the common opal mineralization. ECONOMIC FACTORS TYPICAL GRADE AND TONNAGE:  Grade and tonnage for volcanic-hosted opal deposits are not well documented, largely because the opal extraction is done by individuals or family type businesses. The precious opal distribution within most deposits is erratic, "Bonanza-type". The deposits at Querétaro were discovered in 1835 and are still in production. Furthermore, the term "grade" as commonly used for metalliferous deposits is much harder to apply to gemstone deposits and especially to opal deposits. For example "fire opal" ranges in value from $CDN 5 to 300 per gram. Average commercial precious opal will sell probably around $CDN40 per gram, the top quality stones may sell for $CDN 1400.00 per gram. ECONOMIC LIMITATIONS: Some of the common opal specimens may be used as semi-precious or ornamental stones, but in general they have substantially lower value than precious opal. Gem opal contains up to 10% water, which contributes to the translucency of the specimens. Precious opal from some localities, such as Virgin Valley in Nevada, are generally not suitable for gems because they crack too easily; however the opal from many other volcanic-hosted occurrences is as stable as that from the Australian sedimentary-hosted deposits. Deposits located in intensely weathered terrains are easier to mine than deposits in unaltered rocks. Prices of the best quality opal have risen steadily since 1991. There is a relatively good market for precious opal, nevertheless strong marketing and value-added processing are considered essential parts of successful opal mining operations. END USES:  Precious opal is highly priced gemstone; "fire opal" may be faceted, opalized wood is a speciality ornamental stone commonly used for book ends. IMPORTANCE: Volcanic rock-hosted opal deposits are numerous, but most of today's high quality opal production comes from Australian sedimentary-hosted deposits.

Diamantes em kimberlitos

Diamantes em kimberlitos

KIMBERLITE-HOSTED DIAMONDS by Jennifer Pell Consulting Geologist

Ref: kimberlito, diamante, brecha, tufos, xenocristais, indicadores, olivina, ilmenita, piropo, espinélio, eclogito, granada, manto

Pell, J. (1998): Kimberlite-hosted Diamonds, in Geological Fieldwork 1997, British Columbia Ministry of Employment and Investment, Paper 1998-1, pages 24L-1 to 24L-4. IDENTIFICATION SYNONYMS: Diamond-bearing kimberlite pipes, diamond pipes, group 1 kimberlites. COMMODITIES (BYPRODUCTS): Diamonds (some gemstones produced in Russia from pyrope garnets and olivine). EXAMPLES (British Columbia - Canada/International): No B.C. deposits, see comments below for prospects; Koala, Panda, Sable, Fox and Misery (Northwest Territories, Canada), Mir, International, Udachnaya, Aikhal and Yubilenaya (Sakha, Russia), Kimberly, Premier and Venetia (South Africa), Orapa and Jwaneng (Botswana), River Ranch (Zimbabwe). GEOLOGICAL CHARACTERISTICS CAPSULE DESCRIPTION: Diamonds in kimberlites occur as sparse xenocrysts and within diamondiferous xenoliths hosted by intrusives emplaced as subvertical pipes or resedimented volcaniclastic and pyroclastic rocks deposited in craters. Kimberlites are volatile-rich, potassic ultrabasic rocks with macrocrysts (and sometimes megacrysts and xenoliths) set in a fine grained matrix. Economic concentrations of diamonds occur in approximately 1% of the kimberlites throughout the world. TECTONIC SETTING: Predominantly regions underlain by stable Archean cratons. DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: The kimberlites rise quickly from the mantle and are emplaced as multi-stage, high-level diatremes, tuff-cones and rings, hypabyssal dikes and sills. AGE OF MINERALIZATION: Any age except Archean for host intrusions. Economic deposits occur in kimberlites from Proterozoic to Tertiary in age. The diamonds vary from early Archean to as young as 990 Ma. HOST/ASSOCIATED ROCK TYPES: The kimberlite host rocks are small hypabyssal intrusions which grade upwards into diatreme breccias near surface and pyroclastic rocks in the crater facies at surface. Kimberlites are volatile-rich, potassic ultrabasic rocks that commonly exhibit a distinctive inequigranular texture resulting from the presence of macrocrysts (and sometimes megacrysts and xenoliths) set in a fine grained matrix. The megacryst and macrocryst assemblage in kimberlites includes anhedral crystals of olivine, magnesian ilmenite, pyrope garnet, phlogopite, Ti-poor chromite, diopside and enstatite. Some of these phases may be xenocrystic in origin. Matrix minerals include microphenocrysts of olivine and one or more of: monticellite, perovskite, spinel, phlogopite, apatite, and primary carbonate and serpentine. Kimberlites crosscut all types of rocks. DEPOSIT FORM: Kimberlites commonly occur in steep-sided, downward tapering, cone-shaped diatremes which may have complex root zones with multiple dikes and "blows". Diatreme contacts are sharp. Surface exposures of diamond-bearing pipes range from less than 2 up to 146 hectares (Mwadui). In some diatremes the associated crater and tuff ring may be preserved. Kimberlite craters and tuff cones may also form without associated diatremes (e.g. Saskatchewan); the bedded units can be shallowly-dipping. Hypabyssal kimberlites commonly form dikes and sills. TEXTURE/STRUCTURE: Diamonds occur as discrete grains of xenocrystic origin and tend to be randomly distributed within kimberlite diatremes. In complex root zones and multiphase intrusions, each phase is characterized by unique diamond content (e.g. Wesselton, South Africa). Some crater-facies kimberlites are enriched in diamonds relative to their associated diatreme (e.g. Mwadui, Tanzania) due to winnowing of fines. Kimberlite dikes may display a dominant linear trend which is parallel to joints, dikes or other structures. ORE MINERALOGY: Diamond. GANGUE MINERALOGY (Principal and subordinate): Olivine, phlogopite, pyrope and eclogitic garnet, chrome diopside, magnesian ilmenite, enstatite, chromite, carbonate, serpentine; monticellite, perovskite, spinel, apatite. Magma contaminated by crustal xenoliths can crystallize minerals that are atypical of kimberlites. ALTERATION MINERALOGY: Serpentinization in many deposits; silicification or bleaching along contacts. Secondary calcite, quartz and zeolites can occur on fractures. Diamonds can undergo graphitization or resorption. WEATHERING: In tropical climates, kimberlite weathers quite readily and deeply to "yellowground" which is predominantly comprised of clays. In temperate climates, weathering is less pronounced, but clays are still the predominant weathering product. Diatreme and crater facies tend to form topographic depressions while hypabyssal dikes may be more resistant. ORE CONTROLS: Kimberlites typically occur in fields comprising up to 100 individual intrusions which often group in clusters. Each field can exhibit considerable diversity with respect to the petrology, mineralogy, mantle xenolith and diamond content of individual kimberlites. Economically diamondiferous and barren kimberlites can occur in close proximity. Controls on the differences in diamond content between kimberlites are not completely understood. They may be due to: depths of origin of the kimberlite magmas (above or below the diamond stability field); differences in the diamond content of the mantle sampled by the kimberlitic magma; degree of resorption of diamonds during transport; flow differentiation, batch mixing or, some combination of these factors. GENETIC MODEL: Kimberlites form from a small amount of partial melting in the asthenospheric mantle at depths generally in excess of 150 km. The magma ascends rapidly to the surface, entraining fragments of the mantle and crust, en route. Macroscopic diamonds do not crystallize from the kimberlitic magma. They are derived from harzburgitic peridotites and eclogites within regions of the sub-cratonic lithospheric mantle where the pressure, temperature and oxygen fugacity allow them to form. If a kimberlite magma passes through diamondiferous portions of the mantle, it may sample and bring diamonds to the surface provided they are not resorbed during ascent. The rapid degassing of carbon dioxide from the magma near surface produce fluidized intrusive breccias (diatremes) and explosive volcanic eruptions. ASSOCIATED DEPOSIT TYPES: Diamonds can be concentrated by weathering to produce residual concentrations or within placer deposits (C01, C02, C03). Lamproite-hosted diamond deposits (N03) form in a similar manner, but the magmas may be of different origin. COMMENTS: In British Columbia the Cross kimberlite diatreme and adjacent Ram diatremes (MINFILE # - 082JSE019) are found near Elkford, east of the Rocky Mountain Trench. Several daimond fragments and one diamond are reported from the Ram pipes. EXPLORATION GUIDES GEOCHEMICAL SIGNATURE: Kimberlites commonly have high Ti, Cr, Ni, Mg, Ba and Nb values in overlying residual soils. However, caution must be exercised as other alkaline rocks can give similar geochemical signatures. Mineral chemistry is used extensively to help determine whether the kimberlite source is diamondiferous or barren (see other exploration guides). Diamond-bearing kimberlites can contain high-Cr, low-Ca pyrope garnets (G10 garnets), sodium-enriched eclogitic garnets, high chrome chromites with moderate to high Mg contents and magnesian ilmenites. GEOPHYSICAL SIGNATURE: Geophysical techniques are used to locate kimberlites, but give no indication as to their diamond content. Ground and airborne magnetometer surveys are commonly used; kimberlites can show as either magnetic highs or lows. In equatorial regions the anomalies are characterized by a magnetic dipolar signature in contrast to the "bulls-eye" pattern in higher latitudes. Some kimberlites, however, have no magnetic contrast with surrounding rocks. Some pipes can be detected using electrical methods (EM, VLF, resistivity) in airborne or ground surveys. These techniques are particularly useful where the weathered, clay-rich, upper portions of pipes are developed and preserved since they are conductive and may contrast sufficiently with the host rocks to be detected. Ground based gravity surveys can be useful in detecting kimberlites that have no other geophysical signature and in delineating pipes. Deeply weathered kimberlites or those with a thick sequence of crater sediments generally give negative responses and where fresh kimberlite is found at surface, a positive gravity anomaly may be obtained. OTHER EXPLORATION GUIDES: Indicator minerals are used extensively in the search for kimberlites and are one of the most important tools, other than bulk sampling, to assess the diamond content of a particular pipe. Pyrope and eclogitic garnet, chrome diopside, picroilmenite, chromite and, to a lesser extent, olivine in surficial materials (tills, stream sediments, loam, etc.) indicate a kimberlitic source. Diamonds are also usually indicative of a kimberlitic or lamproitic source; however, due to their extremely low concentration in the source, they are rarely encountered in surficial sediments. Weathered kimberlite produces a local variation in soil type that can be reflected in vegetation. ECONOMIC FACTORS TYPICAL GRADE AND TONNAGE: When assessing diamond deposits, grade, tonnage and the average value ($/carat) of the diamonds must be considered.. Diamonds, unlike commodities such as gold, do not have a set value. They can be worth from a few $/carat to thousands of $/carat depending on their quality (evaluated on the size, colour and clarity of the stone). Also, the diamond business is very secretive and it is often difficult to acquire accurate data on producing mines. Some deposits have higher grades at surface due to residual concentration. Some estimates for African producers is as follows: Pipe Tonnage (Mt) Grade (carats*/100 tonne) Orapa 117.8 68 Jwaneng 44.3 140 Venetia 66 120 Premier 339 40 * one carat of diamonds weighs 0.2 grams ECONOMIC LIMITATIONS: Most kimberlites are mined initially as open pit operations; therefore, stripping ratios are an important aspect of economic assessments. Serpentinized and altered kimberlites are more friable and easier to process. END USES: Gemstones; industrial uses such as abrasives. IMPORTANCE: In terms of number of producers and value of production, kimberlites are the most important primary source of diamonds. Synthetic diamonds have become increasingly important as alternate source for abrasives. SELECTED BIBLIOGRAPHY Atkinson, W.J. (1988): Diamond Exploration Philosophy, Practice, and Promises: a Review; in Proceedings of the Fourth International Kimberlite Conference, Kimberlites and related rocks, V.2, Their Mantle/crust Setting, Diamonds and Diamond Exploration, J. Ross, editor, Geological Society of Australia, Special Publication 14, pages 1075-1107. Cox, D.P. (1986): Descriptive Model of Diamond Pipes; in Mineral Deposit Models, Cox, D.P. and Singer, D.A., Editors (1986), U.S. Geological Survey, Bulletin 1693, 379 pages. Fipke, C.E., Gurney, J.J. and Moore, R.O. (1995): Diamond Exploration Techniques Emphasizing Indicator Mineral Geochemistry and Canadian Examples; Geological Survey of Canada, Bulletin 423, 86 pages. Griffin, W.L. and Ryan, C.G. (1995): Trace Elements in Indicator Minerals: Area Selection and Target Evaluation in Diamond Exploration; Journal of Geochemical Exploration, Volume 53, pages 311-337. Gurney, J.J. (1989): Diamonds; in J. Ross, A.L. Jacques, J. Ferguson, D.H. Green, S.Y. O'Reilly, R.V. Danchin, and A.J.A. Janse, Editors, Kimberlites and Related Rocks, Proceedings of the Fourth International Kimberlite Conference, Geological Society of Australia, Special Publication Number 14, Volume 2, pages 935-965. Haggerty, S.E. (1986): Diamond Genesis in a Multiply-constrained Model; Nature, Volume 320, pages 34-37. Helmstaedt, H.H. (1995): "Primary" Diamond Deposits What Controls Their Size, Grade and Location?; in Giant Ore Deposits, B.H. Whiting, C.J. Hodgson and R. Mason, Editors, Society of Economic Geologists, Special Publication Number 2, pages 13-80. Janse, A.J.A. and Sheahan, P.A. (1995): Catalogue of World Wide Diamond and Kimberlite Occurrences: a Selective Annotative Approach; Journal of Geochemical Exploration, Volume 53, pages 73-111. Jennings, C.M.H. (1995): The Exploration Context for Diamonds; Journal of Geochemical Exploration, Volume 53, pages 113-124. Kirkley, M.B, Gurney, J.G. and Levinson, A.A. (1991) Age, Origin and Emplacement of Diamonds: Scientific Advances of the Last Decade; Gems and Gemnology, volume 72, Number 1, pages 2-25. Kjarsgaard, B.A. (1996): Kimberlite-hosted Diamond; in Geology of Canadian Mineral Deposit Types, O.R. Eckstrand, W.D. Sinclair and R.I. Thorpe, editors, Geological Survey of Canada, Geology of Canada, Number 8, pages 561-568. Levinson, A.A., Gurney, J.G. and Kirkley, M.B. (1992): Diamond Sources and Production: Past, Present, and Future; Gems and Gemmology, Volume 28, Number 4, pages 234-254. Macnae, J. (1995): Applications of Geophysics for the Detection and Exploration of Kimberlites and Lamproites; Journal of Geochemical Exploration, Volume 53, pages 213-243. Michalski, T.C. and Modreski, P.J. (1991) Descriptive Model of Diamond-bearing Kimberlite Pipes; in Some Industrial Mineral Deposit Models: Descriptive Deposit Models, editors, Orris, G.J and Bliss, J.D., U.S. Geological Survey, Open-File Report 91-11a, pages 1-4. Mitchell, R.H. (1991): Kimberlites and Lamproites: Primary Sources of Diamond; Geoscience Canada, Volume 18, Number 1, pages 1-16. Nixon, P.H. (1995): The Morphology and Nature of Primary Diamondiferous Occurrences; Journal of Geochemical Exploration, Volume 53, pages 41-71. Pell, J.A. (1997): Kimberlites in the Slave Craton, Northwest Territories, Canada; Geoscience Canada, Volume 24, Number 2, pages 77-96. Scott Smith, B.H. (1996): Kimberlites; in Undersaturated Alkaline Rocks: Mineralogy, Petrogenesis and Economic Potential, R.H. Mitchell, editor, Mineralogical Association of Canada, Short Course 24, pages 217-243. Scott Smith, B.H. (1992): Contrasting Kimberlites and Lamproites; Exploration and Mining Geology, Volume 1, Number 4, pages 371-381.

Mirabela Nickel: a próxima bola da vez

Mirabela Nickel: a próxima bola da vez

O ano mal começou e a lista das empresas que podem ser compradas não para de  engordar.
Entre as empresas cotadas estão:

• Ouro: Regis Resource, Medusa e Perseus
• Energia: Santos pode ser comprada pela Shell
• Cobre: PanAust
• Niquel: MIrabela Nickel

A Mirabella é uma empresa Australiana que controla 100% do depósito de níquel   sulfetado de Santa Rita na Bahia a 260km de Salvador.
Este depósito de níquel sulfetado de baixo teor foi descoberto por geólogos  da Estatal Baiana e vendido para a Mirabela. Santa Rita tem 160Mt de minério a  0,52%Ni e 0,13%Cu . O cobalto também é recuperado na operação a céu aberto de  baixo custo.
Cogita-se que Mirabela seja a maior empresa de níquel que pode ser comprada  no momento.

O Geólogo e a Geologia

O Geólogo e a Geologia

Entrevista dada pelo Geólogo  Pedro Jacobi à  O Globo, publicada no Guia de Profissões pela Ediouro

 

O Globo: Como é seu dia a dia no trabalho?

O meu trabalho consiste na direção dos vários projetos  e aquisições  da minha empresa no Brasil, nas áreas de diamantes, ouro, metais básicos e ferro. Coordeno a empresa e os profissionais no Brasil e mantenho contato constante com os nossos escritórios, sócios e acionistas em Seattle, nos Estados Unidos, e em Perth, na Australia.

Com o fuso horário, a carga de trabalho diária e sempre superior a 11 horas,incluindo fins de semana. 

O Globo: Como conseguiu seu primeiro emprego?

Foi  por  intermédio do Geólogo americano Gene Tolbert, fundador   da Terraservice, a precursora da DOCEGEO,  e descobridor de Carajás. Em 1971, ele foi, pessoalmente, buscar 11 geologos, ainda estudantes, nas principais escolas do pais para trabalhar com ele. Eu era um deles.

Estudava na Universidade Federal do Rio Grande do Sul.

O Globo: O que há de melhor e de pior na sua rotina de trabalho?

A busca constante de minérios escondidos, torna a prospecção mineral uma das mais abrangentes, desafiadoras e compensadoras áreas da geologia. O sucesso e sempre o fruto do trabalho criativo e inteligente.

No entanto, não há prospecção  mineral sem insucessos. Na maioria das vezes, são esses insucessos que fazem empresas inteiras desaparecerem do mercado.

O Globo: Quais são os maiores desafios que enfrenta um geólogo?

Na exploração mineral, o profissional deve ser capaz de aliar profundos conhecimentos de geologia com estratégias e pensamentos  criativos, conhecendo os modismos teóricos e passageiros das várias áreas da ciência. O geólogo deve ter a mente inquisitiva e procurar entender as leis naturais e relações de causa e efeito que regem o universo,aplicando esse conhecimento em sua área de atuação.

DESCOBRIR MINÉRIOS,  POCOS  DE PETRÓLEO OU MINAS DE DIAMANTE,PRESERVAR O MEIO AMBIENTE, SER EXECUTIVO DE EMPRESA DE MINERACAO E ESTUDAR  OUTROS PLANETAS....

Dificil acreditar que atividade tão diferentes  como essas caibam todas na mesma profissão. A explicação esta na definição da própria geologia

É a ciência que estuda as características do planeta TERRA, tanto do seu interior quanto de sua superfície. A orígem , a composição e as estruturas do planeta são os principais objetos  do estudo do geólogo.

Depois que termina a graduação, o Geólogo pode se especializar em diversas áreas, entre as quais:

• PROSPECÇÃO MINERAL: descoberta de bens minerais – metais básicos, gemas, petróleo, gás e demais combustíveis, fosseis, minerais industriais. Existem várias áreas de conhecimento abrangidas pela prospecção, como geoquímica, geofísica, interpretação de imagens de satélites e GIS.
• GIS: sistema de informações Geográficas- ferramentas fundamentais ao Geólogo explorador.
• GEOLOGIA DE MINAS: mineração e controle do dia- a- dia, das minas, que abrange diferentes atividades.
• GEOLOGIA AMBIENTAL: prevenção e proteção do meio ambiente. O Geólogo trabalha  na preservação e avaliação de riscos e de impactos ambientais causados pelo Homem.
• GEOLOGIA DE ENGENHARIA E GEOTÉCNICA :  planejamento de cidades, obras de engenharia, como estradas, pontes, edifícios, barragens etc...
• GEOLOGIA ECONÔMICA: avaliação das chances de sucesso de projetos  minerais, minas e demais atividades  correlatas
• GEOLOGIA MARINHA: um dos ramos em expansão da  carreira, estuda e atua na preservação dos mares e seus recursos.
• ASTRONOMIA E CONQUISTAS ESPACIAIS: por meio da geologia são compreendidos os processos de formação e desenvolvimento dos planetas e demais objetos cósmicos.
• EDUCAÇÃO: ensino, tanto no nível básico quanto no superior.

A geologia permite que o profissional atue em qualquer lugar do mundo. Por isso, o domínio de uma língua estrangeira, em especial o inglês, é fundamental. A rotina de trabalho pode variar bastante em uma função para outra e, em alguns casos, geólogos podem trabalhar ate dez horas por dia. Também é comum, quando fazem trabalho de campo, passarem dias em locais de difícil acesso e sem conforto.

VOCE É CURIOSO E CRIATIVO? GOSTA DE PESQUISAR E ESTUDAR?  TEM RESISTÊNCIA FÍSICA PARA TRABALHAR POR VÁRIAS HORAS EM LOCAIS SEM CONFORTO? GOSTA DA NATUREZA?

COMO É O CURSO?    Dura, em média, cinco anos. Inicialmente, a ênfase é em disciplinas básicas, como quÍmica, matemática e física, mas são estudadas matérias mais especificas como mineralogia, geologia estrutural, paleontologia e topografia. Posteriormente o curso concentra-se nas matérias específicas da geologia.

COMO É O MERCADO?  Em alta entre 2004 a 2008. O ciclo de baixa de 2008 a 2009 está acabando e estima-se que a procura deva durar vários anos se não décadas. Há muitas oportunidades na área de prospecção  mineral e em  atividades ligadas ao meio ambiente. Geólogos também podem ocupar altos cargos em empresas do setor mineral e de Ciências da Terra. E é cada vez maior o número de Geólogos-Empresários, donos de empresas de mineração e de meio ambiente.

QUANTO GANHA?     O salário médio inicial varia bastante. Estima-se que o salário mínimo de um geólogo júnior deve estar em torno de 06 (seis) vezes o Salário Mínimo comum, vigente no País. Naturalmente o salário evolui conforme a experiência do profissional. Consultores experientes cobram a partir de mil dólares por dia. Geólogos analistas, que avalizam transações de  empresas de mineração em bolsas de valores, são, também, muito bem remunerados. O Geólogo tem um salário entre o topo dos profissionais correlatos.

Brazilian Gold em vias de ser comprada

Brazilian Gold em vias de ser comprada 
Depois de quedas sucessivas as junior companies de mineração estão com os seus valores de mercado muito baixos. Em alguns casos o valor da empresa é várias vezes inferior ao seu patrimônio certificado por auditores externos. Mercado em baixa é hora de ir às compras...
Essa é a oportunidade que muitos investidores procuram: comprar participações em empresas com um sólido portfólio.   Como já havíamos indicado em matérias passadas algumas mineradoras apresentam verdadeiras oportunidades de lucro.

(veja  )
É o caso da Brazilian Gold, uma empresa que investe em projetos de ouro no Brasil e conseguiu identificar reservas entre indicadas e inferidas em torno de 2,6 milhões de onças de ouro. Só em um projeto, o S. Jorge, no Tapajós o valor líquido presente, descontados os custos do dinheiro, equivale a mais de 600 milhões de dólares.
A Brazilian Gold, apesar deste patrimônio todo em ouro vale hoje somente 17 milhões de dólares: um verdadeiro chamariz aos vorazes investidores.
Como era de se esperar os primeiros interessados já começam a aparecer. Os chineses estão demonstrando um grande interesse por mineradoras de ouro com bons projetos. Em geral eles querem minas com grandes recursos e é aí que a Brazilian Gold aparece como uma empresa a ser comprada. Na semana passada a mineradora de ouro chinesa Kingwell Group Ltd, listada em Hong Kong já tornou público o seu interesse em comprar, no mínimo, 51%  da Brazilian Gold Corporation. A Kingwell é a proprietária de uma mina de ouro em Shandong e acredita que o ouro deverá subir acima de $2.000/oz em dois anos. Se a Kingwell comprar ela vai ter, em consequência,  inúmeros desdobramentos e novas oportunidades de retorno no Brasil, especialmente no Tapajós onde ficam os projetos da Brazilian Gold.