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Romaria mine, Romaria, Bagagem River valley, Coromandel district, Minas Gerais, Brazil

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Latitude & Longitude (WGS84): 18° 52' 40'' South , 47° 35' 3'' West
Latitude & Longitude (decimal): -18.87778,-47.58444
Köppen climate type:Aw : Tropical savanna, wet
Other/historical region names associated with this locality:Romaria (former Água Suja)


This diamond mine was opened around 1867 following discovery of diamonds in the nearby Água Suja stream, a tributary of the Bagagem river. The mine closed in 1984. While most diamonds in the Coromandel district were obtained from alluvial deposits, at Romaria diamonds were mined from a lithified conglomerate in the river bottomland. This conglomerate has been interpreted as a debris flow deposit consisting of materials reworked from surrounding metasedimentary bedrock including the Neoproterozoic Araxá Group and Cretaceous sedimentary rocks (Suguio et al., 1979; Andrade and Chaves, 2009). As the debris flow apparently followed modern topographic contours, it is most likely of Quaternary age. Fleischer (1998), however, presented evidence that normal block faulting led to erosion of the original diamondiferous conglomerate on the upthrown (west) side of the faults, with deposition occurring in alluvial fans on the down-dropped side. He correlated localized outcrops of this material for a little over 40 km in a NW-SE direction, and suggested existence of a faulted lineament along nearly the entire length of the Bagagem River valley. The diamonds were probably reworked from the Mata da Corda Group of Late Cretaceous age, a resistant unit that caps the mesas on either side of the Bagagem River valley.

Lithic clasts in the conglomerate are up to 0.8 meters in size, and include schist, phyllite, quartzite, basalt, reworked conglomerate, vein quartz, and siliceous concretions rich in opal. The matrix is arenaceous, and contains considerable kaolinite and illite. Framework grains include mm-scale grains of heavy minerals including pyrope, staurolite, "hornblende," epidote, kyanite, monazite, tourmaline, zircon, and anatase. The opaques include magnetite, hematite, goethite, and ilmenite. The pyrope is chromium-rich, with chromium/calcium oxide ratios plotting mostly in the G4, G5, and G9 fields, indicating poor likelihood of associated diamonds (Grütter et al., 2004). Nevertheless, diamonds from the area are large and clear, although commonly abraded and fractured, and suggest a proximal source, but that has yet to be identified.

Modified by NK, January 2017


Mineral List


18 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Mesoproterozoic
1000 - 1600 Ma



ID: 1376944
Mesoproterozoic Tectonic assemblages, metamorphic schist belts, melanges

Age: Mesoproterozoic (1000 - 1600 Ma)

Comments: Rocks distinguished in compilation sources primarily as part of a tectonic assemblage, belts of schist and mylonite of mixed parentage, and tectonic melanges.

Lithology: Tectonic assemblages, metamorphic schist belts, melanges

Reference: Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d. [18]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License



This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Draper, D. (1911): The diamond bearing deposits of Bagagem and Agua Suja,in the state of Minas Geraes (sic), Brazil. Transactions of the Geological Society of South Africa, 14: 8-19.
Suguio, K., Svisero, D. P., and Filitti, F. W. (1979): Conglomerados polimiticos diamantiferos de idade cretácica de Romaria (MG): um exemplo de sedimentação de leques aluviais. 2nd Simpósio Regional de Geologia Rio Claro, 1: 217-229.
Fleischer, R. (1998): A rift model for the sedimentary diamond deposits of Brazil. Mineralium Deposita, 33: 238-254.
Grütter, H. S., John J. Gurney, J. J., Menziesc, A. H., and Winter, F. (2004): An updated classification scheme for mantle-derived garnet, for use by diamond explorers. Lithos, 77: 841-857.
Andrade, K. W., and Chaves, M. L. S. C. (2009): Geologia e a redistribuição sedimentar pós-Cretácica dos depósitos diamantíferos da região ao sul de Coromandel (MG). Geonomos, 17(1): 27-36.
Coelho, F. M. (2010): Aspectos geológicos e mineralógicos da mina de diamantes de Romaria, Minas Geras. tese, Universidade de São Paulo, Instituto de Geociêncas.
Andrade, K. W., and Chaves, M. L. S. C. (2011) Geologia e mineralogia do kimberlito Grota do Cedro (Coromandel, MG). Geonomos, 19(1): 39-45.

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