TERRENOS KHONDALÍTICOS: PRINCIPAIS DOMÍNIOS PARA MANGANÊS, GRAFITA, OURO E ZINCO NO ESTADO DO RIO DE JANEIRO E REGIÕES LIMÍTROFES
Bibliographic record
Abstract
ResumoTerrenos khondalíticos representam um significativo componente de áreas de fácies granulito/UHT e os gnaisses que ocorrem associados a esses complexos são, principalmente, tipos aluminosos. Estes terrenos representam uma história de acresção crustal, ocorrendo nas zonas de junções/suturas das massas continentais como, por exemplo, nas que propiciaram a formação do supercontinente Gondwana. Nos Terrenos Khondalíticos presentes no Estado do Rio de Janeiro e em suas regiões limítrofes, registram-se diversas ocorrências de Mn/grafita, Au e Zn/Ag, cujas expressões podem ter caráter tanto regional quanto local. No geral, as mineralizações citadas estão situadas em regiões formadas por intercalações de gnaisses aluminosos, com ou sem sillimanita, e de rochas ortogranulíticas. Nesses terrenos, afloram camadas de gnaisses grafitosos (teor de C~2%). Essas camadas podem estar acompanhadas de corpos de gonditos, alterados para óxidos-hidróxidos de manganês, como nas faixas khondalíticas Marangatu e Palma-Guaçuí, ou somente mineralizados em grafita, como na Faixa Khondalítica São Fidélis. Na Faixa Khondalítica Palma-Guaçuí, particularmente no segmento entre Palma (MG) e Laje do Muriaé (RJ), ocorre um pacote de gnaisse grafitoso sulfetado, interpretado como um antigo folhelho negro, com cerca de 20 km de extensão, contendo mineralizações auríferas. O ouro ocorre na forma livre e como inclusões (ouro invisível) em piritas dos tipos framboidal (singenética), flor de girassol (diagenética) e maciça (metamórfica). A sequência metassedimentar à qual se relaciona a mineralização de zinco de Rio Claro (possivelmente uma extensão da Faixa Khondalítica Marangatu) é bastante semelhante àquelas encontradas em depósitos canadenses sedimentares-exalativos de Zn-Pb-Ag, do tipo Shuswap e Monash. As rochas sílico-carbonáticas da Unidade Lídice, que encerram as zonas sulfetadas, foram geradas em ambiente plataformal raso, possivelmente com um componente evaporítico.Palavras Chave: Terrenos khondalíticos, manganês, grafita, ouro, zinco.AbstractKHONDALITIC TERRAINS: MAIN DOMAINS FOR MANGANESE, GRAPHITE, GOLD AND ZINC IN THE STATE OF RIO DE JANEIRO AND SURROUNDING REGIONS. Khondalite terrains represent a significant element in areas with granulite/UHT facies and the gneiss rocks that occur associated to these complexes are, especially, aluminous type. These terrains represent a history of crustal accretion, occurring in suture zones of continental masses as, for example, in those which contributed to the formation of the supercontinent Gondwana. In khondalite terrains in the State of Rio de Janeiro and in its neighboring regions, there are several occurrences of Mn/graphite, Au and Zn/Ag, whose expressions may have both regional and local character. In general, those mineralizations are located in regions consisting of intercalation of aluminous gneiss, with or without sillimanite, and of ortogranulite rocks. In those terrains, layers of graphitic gneiss (C content ~ 2%) arise. Such layers may be accompanied by gondite bodies, changed to oxide-hidroxide of manganese, as in Marangatu and Palm-Guaçuí Khondalitic Belts, or only mineralized in graphite, as in São Fidelis Khondalitic Belt. In Palma-Guaçuí Khondalite Belt, particularly in the segment between Palma (MG) and Laje do Muriaé (RJ), there is a set of sulphide graphite gneiss, considered as an ancient black shale, about 20 km long, containing auriferous mineralizations. Gold occurs in free form and as inclusions (invisible gold) in pyrites of framboidal type (syngenetic), sunflower type (diagenetic) and massive type (metamorphic). The metasedimentary sequence to which Rio Claro zinc mineralization relates (possibly an extension of Marangatu Khondalitic Belt) is quite similar to those found in sedimentary-exhalative Canadian deposits of Zn-Pb-Ag, Shuswap and Monash types. Silic-carbonate rocks of Lidice Unit, which delimit the sulfide zones, were generated in shallow platformal environment, possibly with a evaporitic component.Keywords: Khondalitic terrains, manganese, graphite, gold, zinc.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.004 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; both teacher heads agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".