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Vargem I, Santo Inácio River valley, Coromandel, Coromandel district, Minas Gerais, Brazil

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Latitude & Longitude (WGS84): 18° 33' 17'' South , 47° 1' 50'' West
Latitude & Longitude (decimal): -18.55500,-47.03056
GeoHash:G#: 6uww3y1mk
Köppen climate type:Aw : Tropical savanna, wet


The list of large diamonds found in alluvial deposits this area is impressive. Characters of the diamonds suggest they were not transported far from a primary kimberlite or lamproite source. The Vargem I kimberlite was analyzed as early as 1977, but the preliminary results indicated a poor chance that it contained diamonds. By virtue of several tons of alluvial matrix supplied by GAR Mining, another study of the chemistry of heavy minerals–primarily pyrope garnets–was undertaken,using the well-known evaluation system for kimberlites developed by Gütter et al. (2004), whereby certain ratios of calcium and chromium (as oxides) have been found to be associated with diamondiferous kimberlites more so than other ratios. Chaves (2012) reanalyzed garnets from Vargem-1, and not only found several samples showing favorable CaO/Cr2O3 ratios (plotting in the G10 field), but also found loose diamonds. Although less than 1 carat in size and of subeconomic potential, this discovery shows that other kimberlites in the area previously thought to be infertile for diamonds also should be examined more carefully and exhaustively. The Vargem I find helps solve the old puzzle of failing to find potential primary kimberlite sources near sites where alluvial diamonds have been recovered.

NK, January 2017


Mineral List


2 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: 3187036
Mesoproterozoic crystalline metamorphic rocks

Age: Mesoproterozoic (1000 - 1600 Ma)

Lithology: Low grade unclassified metamorphic rock

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

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)
Chaves, M. L. S. C. (2012): Kimberlito Vargem-1 (Coromandel, MG): bulk sample confirma mineralização diamantifera. Revista Escola Minas, Ouro Preto, 65(4): 509-511.
Grütter, H. S., Gurney, J. J., Menzies, A. H., and Winter, F. (2004): An update classification scheme for mantle-derived garnet for use by diamond explorers. Lithos, 77: 841-857.

Mineral and/or Locality  
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