It is now possible to bracket the age of the Minas Supergroup with reasonable precision between about2580 Ma. (base of the Moeda Formation) and 2050 Ma. (top of the Sabará Formation) on the basis of precisezircon U-Pb age determinations from both granitic rocks of the basement and detrital zircons from quartzitesand graywackes of the Proterozoic metasedimentary sequences of the Quadrilátero Ferrífero.Three major unconformities subdivide the stratigraphic column into three sequences. The first sequencecomprises the Moeda, Batatal, Cauê and Gandarela Formations from 2580 to 2400 Ma.. The second sequencecomprises the Cercadinho, Fecho do Funil, Taboões and Barreiro Formations (the Piracicaba Group) datedat 2400 to 2150 Ma.. The third sequence contains only the synorogenic sediments of the Sabará Formation,deposited during the Transamazonian Event between 2150 and 2050 Ma.. This event folded andmetamorphosed the Minas Supergroup for the first time.The Sabará Formation of the Piracicaba Group has very different sedimentological characteristics fromthe other formations of this group and is exceptionally thick (about 3500 m), we therefore propose to upgradeit to the rank of a Group.Zircon age histograms of the Moeda quartzite (sample QF-1) and Sabará graywacke are similar, indicatinga common Archean source, i.e. the Belo Horizonte Complex north of the Quadrilátero Ferrífero. This impliesthat sedimentation of the Minas Supergroup in the western Quadrilátero Ferrífero is autochthonous.Periods of carbonate and Iron Formation platform sedimentation (Cauê, Gandarela and partly Fecho doFunil Formations) coincide with minor frequency of age plots of detrital zircons, indicating also a stabletectonic environment.Comparison of the Minas Supergroup with the Transvaal Sequence of South Africa revealscorrespondence not only in age but also in thickness, position of the major unconformities, lithologicalcompositions and in the position of gold and pyrite bearing quartz-pebble conglomerates.

Gold-bearing placer conglomerates, dated between 2.2 and 2.8 Ga, have been identified at the base of the Moeda Formation in the Gandarela syncline. Intensive investigation of outcrop and underground exposures, both old and new, and borehole intersections around the western and southern margin of the syncline, has defined a palcoenvironment consisting of an upland fluvial drainage system in the north, leading southward to an alluvial fan and braided plain depository. Heavy mineral concentrates, composed predominantly of coarse rounded pyrite, are concentrated in the matrix of cobble conglomerates that occur in the form of discrete bars and sheets. The mineralogy and geochemistry of the ore closely resembles that of Witwatersrand placers as does the composition of the gold. Gold concentrations are equal to those of the average Witwatersrand gold deposit and therefore these deposits may make a significant contribution to Brazil's future gold production.

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In this paper a brief review is given of master and doctoral thesis as well of articles published duringthe last 16 years, concerning the geology of the Serra do Espinhaço in Minas Gerais, Brazil. The differentproposals of a subdivision of the Archean basement and sedimentary sequences of Pre-Espinhaço age arereviewed. The existing geochronological data are insufficient for a complete understanding of these units.The Espinhaço rift started its evolution about 1800 Ma ago with continental sediments with intercalationof acidic and basic volcanics evolving in the upper part of the sequence to shallow marine sedimentation.Aspects of stratigraphy and sedimentology of the Espinhaço Supergroup as well as those of structuraland economic geology are briefly discussed. Diamonds washed in the Sopa-Brumadinho conglomeratesand in alluvials remains the principal mineral resource as about 160 years ago predicted by L.W. vonEschwege. In recent years exploration work was successful to identify the gold deposit at Riacho dosMachados in the northern extension of the Serra do Espinhaço.A chapter resumes the geodymamic models presented during the considered period. Finally, suggestionsfor future investigations are listed.

O trabalho apresenta uma resenha da obra “Geognostisches Gemälde von Brasilien und wahrscheinlichesMuttergestein der Diamanten “ de Wilhelm Ludwig von Eschwege por ocasião do sesquicentenário da suamorte em 1o de fevereiro de 2005. A obra foi publicada, em pequena tiragem, em 1822. Trata inicialmentedos grandes divisores de água: um de direção aproximada leste – oeste, separando a bacia do rio Amazonasdas dos rios Paraná e Paraguai, que Eschwege batiza de “Serra das Vertentes”, o outro divisor separa a baciado Rio São Francisco dos rios que correm diretamente ao Oceano Atlântico o qual chama de “Serra doEspinhaço”, incluindo nela a Serra da Mantiqueira. Em segundo lugar apresenta um esquema estratigráficobaseado nos modelos usados na Europa, como, por exemplo, aquele proposto em 1787 por AbrahamGottlieb Werner, professor da Academia de Minas de Freiberg na Alemanha. A Primeira FormaçãoPrimitiva é formada pelo embasamento cristalino, a Segunda Formação Primitiva corresponde às seqüênciassupracrustais dobradas (representadas pelos Supergrupos Rio das Velhas, Minas e Espinhaço), a Terceira oude Transição abrange essencialmente o atual Grupo Bambui e uma quarta subdivisão reúne depósitossuperficiais como aluviões e coberturas terciárias e quarternárias. Percebe-se que suas idéias a respeito dageologia do Brasil são fortemente influenciadas pela escola netunista de Werner. Descreve aindamacroscopicamente os principais tipos de rocha encontrados no Brasil, define os novos termos “itacolumito”e “itabirito” e introduz o termo “tapanhoacanga” na nomenclatura geológica, todos com suas localidadestipo.Tapanhoacanga, hoje reduzida para canga, é de origem indígena de tapanhu = escravo negro e acanga= cabeça (ou a = cabeça e canga = osso). A última parte do “Quadro geognóstico... “ trata da ocorrência dosdiamantes no Brasil e de sua possível rocha matriz, na sua opinião formados em concreções limoníticasoriginadas das rochas ferruginosas da Segunda Formação Primitiva.Palavras-chave: História da Geologia, Quadrilátero Ferrífero, Serra do Espinhaço, estratigrafia precambriana,itabirito, itacolumito, canga, diamantes ABSTRACT: ESCHWEGE’S “GEOGNOSTICAL SKETCH OF BRAZIL AND THE PROBABLE SOURCE ROCK OFDIAMONDS”: BRIEF COMMENTS ON HIS VISION OF BRAZILIAN GEOLOGY. This small brochure waspublished in 1822 by the German geologist Wilhem Ludwig von Eschwege (1777 – 1855) and is nowtranslated to Portuguese for the first time completely as a memorial of his passing away 150 years ago.Initially, Eschwege reports on the physical geography of Brazil and suggests the names “Serra das Vertentes”(Watershed Mountains) and “Serra do Espinhaço” (Backbone Ridge), running East – West the first and North– South the second, separating the great hydrographic basins in Brazil. A main chapter is dedicated to a veryfirst proposal of a stratigraphic scheme based on European models of the time and heavily influenced by A.G. Werner, the principal protagonist of the neptunism, which interpreted all rocks as being precipitated fromaqueous solutions. He distinguishes four stratigraphic divisions: the First Primitive Formation containinggranite, gneiss, and mica schist, corresponding in more modern terms to the crystalline basement; the SecondPrimitive Formation is formed by itacolumite (quartzite), itabirite (iron formation) and schist, representedby the Rio das Velhas, Minas, and Espinhaço supergroups. The third or Transitional Formation composed byslates, quartz schist, greywacke, and massive limestone corresponds to the Macaúbas and Bambui groups. Thefourth and uppermost formation encloses all superficial deposits, such as alluvial, river gravels and a peculiarferruginous conglomerate called by the native tapanhoacanga, which means Negro head. His argumentationis heavily influenced by neptunistic thinking. Eschwege still describes in great detail the principal rock types,as known at this time in Brazil and introduces the terms itacolumite, itabirite and (tapanhoa)canga into thegeological nomenclature. The second part is dedicated to the occurrence, distribution and origin of Braziliandiamonds. He considers that they are formed within any rock of his Second Primitive Formation, due to theoccasional founding of limonitic concretions with inclusions of diamonds.Keywords: History of geology, Quadril