Kimberlito Canastra-1 (São Roque de Minas, MG): geologia, mineralogia e reservas diamantíferas

Chaves, Mario Luiz de Sá Carneiro; Brandão, Paulo Roberto Gomes; Girodo, Antonio Carlos; Benitez, Leila

doi:10.1590/s0370-44672008000300014

Cited by 5 publications

(1 citation statement)

References 7 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Isto já havia sido demonstrado no caso do kimberlito Canastra -1, pesquisado preliminarmente em 1974, mas somente com uma nova campanha explorató-ria, em 1991, foram identificados teores economicamente viáveis (Chaves et al, 2008). Tal fato "abre" a perspectiva de exploração de dezenas de outras intrusões de natureza semelhante na região.…”

Section: Conclusãounclassified

Kimberlito vargem-1 (Coromandel, MG): bulk sample confirma mineralização diamantífera

Chaves¹

2012

Rem: Rev. Esc. Minas

Self Cite

View full text Add to dashboard Cite

ResumoO kimberlito Vargem-1, a sudeste de Coromandel (MG), ocorre sob o leito e margens do Rio Santo Inácio, o qual possui depósitos aluvionares lavrados desde longa data. Entretanto, a presença de diamantes na intrusão foi sempre questionada, pois teria uma química mineral desfavorável à mineralização. Agora, amostragem de grande volume, em execução por firma mineradora, revelou a presença de diamantes, com pesos inferiores a 1 ct, em um dos poços pesquisados. Esse fato "abre" nova perspectiva exploratória em dezenas de intrusões já identificadas em tal região. Palavras-chave:Kimberlito Vargem-1, Coromandel, diamante. AbstractThe kimberlite southeast of Coromandel (MG)

show abstract

Section: Conclusãounclassified

Kimberlito vargem-1 (Coromandel, MG): bulk sample confirma mineralização diamantífera

Chaves¹

2012

Rem: Rev. Esc. Minas

Self Cite

View full text Add to dashboard Cite

show abstract

U–Pb SHRIMP geochronology of zircon from the Catoca kimberlite, Angola: Implications for diamond exploration

et al. 2012

View full text Add to dashboard Cite

We present the first age determinations of zircon from the diamondiferous Catoca kimberlite in northeastern Angola, the fourth largest kimberlite body in the world. The U-Pb ages were obtained using a Sensitive High Resolution Ion Microprobe II (SHRIMP II) on zircon crystals A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 2 derived from tuffisitic kimberlite rocks and heavy-mineral concentrates from the Catoca kimberlite. The SHRIMP results define a single weighted mean age of 117.9 ± 0.7 Ma (Mean square weighted deviation MSWD = 1.3). More than 90% of the results indicate a single age population. There is no evidence for variable ages within single crystals, and no diffusional profiles are preserved. These data are interpreted as the maximum age of the kimberlite eruption at Catoca. The U/Th values suggest at least two different sources of zircon crystals. These different populations may reflect different sources of kimberlitic magma, with some of the grains produced in U-and Th-enriched metasomatized mantle units. This idea is consistent with the two populations of zircon identified in this study. One population originated from a depleted mantle source with low total REE (less than 25 ppm), and the other was derived from an enriched source, likely from the mantle or a carbonatite-like melt with high total REE (up to 123 ppm).The tectonic setting of northeastern Angola is influenced by the opening of the south Atlantic, which reactivated deep NE-SW-trending faults during the early Cretaceous. The eruption of the Catoca kimberlite can be correlated with these regional tectonic events. The Calonda Formation (Albian-Cenomanian age) is the earliest sedimentary unit that incorporates eroded material derived from the diamondiferous kimberlites. Thus, the age of the Catoca kimberlite eruption is restricted to the time between the middle of the Aptian and the Albian. The new interpretation will be an important guide in future exploration for diamonds because it provides precise data on the age of a diamond-bearing kimberlite pulse in Angola.

show abstract

Cretaceous mantle of the Congo craton: Evidence from mineral and fluid inclusions in Kasai alluvial diamonds

Kosman

Kopylova

Stern

et al. 2016

Lithos

View full text Add to dashboard Cite

Alluvial diamonds from the Kasai River, Katanga Province, Democratic Republic of the Congo (DRC), were studied in order to constrain the composition, thermal state, and diamond forming fluids of the ancient lithospheric mantle of the Congo craton. The diamonds originate from Cretaceous kimberlites of the Lucapa graben in northeastern Angola. We report carbon isotope compositions (δ 13 C VPDB ), nitrogen concentrations ([N]), and nitrogen aggregation states of 138 diamonds, as well as compositions of mineral and fluid inclusions in the diamonds. Diamonds emplaced by kimberlites of the northeastern Lucapa graben and eroded into alluvials along the Kasai river contain 25-2900 ppm [N], show 0-88% N aggregation and δ 13 C isotopic compositions spanning -27‰ to -2‰ with a mode near mantle-like values.In situ cathodoluminescence (CL), secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (FTIR) reveal large heterogeneities in [N], N aggregation and δ 13 C, indicating diamonds grew episodically from fluids of distinct sources. Fluid inclusion compositions of fibrous diamonds analyzed by electron probe microanalysis are moderately to highly silicic, matching compositions of diamond-forming fluids from other DRC diamonds. Regional homogeneity of Congo fibrous diamond fluid inclusion compositions suggests spatially extensive homogenization of Cretacious diamond forming fluids within the Congo lithospheric mantle. Electron probe microanalysis (EPMA) of trapped silicate inclusions revealed both peridotitic (Fo 91-95 and En 92-94 , 78% of the suite) and eclogitic parageneses (Crpoor pyrope and omphacite with 11-27% jadeite, 17% of the suite) within diamonds (11% remainder unknown). Clinopyroxene-garnet thermobarometry suggest diamond formation at 1350-1375 °C, whereas[N] aggregation thermometry yields diamond residence temperatures between 1000 and 1275 °C, if the assumed residence time is 0.9-3.3 Ga. Integrated geothermobaromtery indicates heat fluxes of 41-45 mW/m 2 during diamond formation and a shallow lithosphere-asthenosphere boundary (LAB) 175-189 km. The shallow LAB may result from a higher than average cratonic geotherms and the position of the Kasai block near the Congo cratonic margin. The hotter mantle may be attributable to contemporaneous rifting of the southern Atlantic, multiple post-Archean reactivations of the craton, and/or proximal Cretaceous plumes.iii Preface Samples used in this research were acquired from the Denver Museum of Nature and Science with the help of Curator James W. Hagadorn and James F. Hurlbut. I completed all polishing, EPMA, and FTIR of the samples. In situ carbon isotope and nitrogen concentration analyses were undertaken at the Canadian

show abstract

Kimberlito Canastra-1 (São Roque de Minas, MG): geologia, mineralogia e reservas diamantíferas

Cited by 5 publications

References 7 publications

Kimberlito vargem-1 (Coromandel, MG): bulk sample confirma mineralização diamantífera

Kimberlito vargem-1 (Coromandel, MG): bulk sample confirma mineralização diamantífera

U–Pb SHRIMP geochronology of zircon from the Catoca kimberlite, Angola: Implications for diamond exploration

Cretaceous mantle of the Congo craton: Evidence from mineral and fluid inclusions in Kasai alluvial diamonds

Contact Info

Product

Resources

About