IMPORTANT DIFFERENCES BETWEEN GLACIAL AND FLUVIAL SYSTEMS IN RELATION TO DIAMOND GEOLOGY Guilherme M. Gonzaga Goyaz Minérios gmg@terra.com.br Ruth G. Gonzaga Gonzaga Geology & Research ruth.gonzaga@gonzagageo.com
Large off-craton diamonds Fluvial vs. Unkown local primary sources Indicator minerals Large ratio of high quality gems Dodecahedral or more complex morphology Brown spots (500-550 ) Gonzaga & Gonzaga (2014) 2
Permo-Carboniferous glaciogenic sediments in Brazil Diamonds in the Permo- Carboniferous sequence No diamonds in the same sequence Carvalho, B.M.V. de (2014) Confined Turbidite Sand-Sheets in the Paraná and Paganzo Basins. Gonzaga & Gonzaga (2014) 3
Transportation in glacial systems Fluvial vs. Glacial Transport of material must occur downhill Decrease in size and increase in roundness Morphology: single population Gonzaga & Gonzaga (2014) 4
Alberuni s India (1030) One of these plains is India, limited in the south by the abovementioned Indian Ocean, and on all three other sides by the lofty mountains, the waters of which flow down to it. But if you have seen the soil of India with your own eyes and meditate on its nature if you consider the rounded stones found in the earth however deeply you dig, stones that are huge near the mountains and where the rivers have a violent current; stones that are of smaller size at greater distance from the mountains, and where the streams flow more slowly; stones that appear pulverised in the shape of sand where the streams begin to stagnate near their mouths and near the sea if you consider all this, you could scarcely help thinking that India has once been a sea which by degrees has been filled up by the alluvium of the streams. Alberuni s India. An account of the religion, philosophy, literature, geography, cheonology, astronomy, custos, laws and astrology of India about A.D. 1030 Teresi, D. (2008). Descobertas Perdidas - As raízes antigas da ciência moderna, dos Babilônios aos Maias. Gonzaga & Gonzaga (2014) 5
Transportation in glacial systems Fluvial vs. Glacial Transport of material must occur downhill Movement of water uphill due to hydrostatic pressure Transport of clasts to higher altitudes Decrease in size and increase in roundness Push-broom action: transport of larger clasts leaving smaller ones behind Morphology: single population Subglacial vs. supraglacial Time of residence Gonzaga & Gonzaga (2014) 6
The formation of a glacial till Sá Rego, F.M. de & Gonzaga, G.M. (2012). Diamictito Quebradinha (Grupo Santa-Fé) na região de Pintópolis-MG e sua provável relação com os diamantes do rio Acari. Gonzaga & Gonzaga (2014) 7
Supraglacial Sá Rego, F.M. de & Gonzaga, G.M. (2012). Diamictito Quebradinha (Grupo Santa-Fé) na região de Pintópolis-MG e sua provável relação com os diamantes do rio Acari. Gonzaga & Gonzaga (2014) 8
Subglacial Sá Rego, F.M. de & Gonzaga, G.M. (2012). Diamictito Quebradinha (Grupo Santa-Fé) na região de Pintópolis-MG e sua provável relação com os diamantes do rio Acari. Gonzaga & Gonzaga (2014) 9
The Darwin boulders Evenson, B.E. et al. (2009) Enigmatic boulder trains, supraglacial rock avalanches, and the origin of Darwin s boulders, Tierra del Fuego. Gonzaga & Gonzaga (2014) 10
Permo-Carboniferous glaciogenic sediments in Brazil Diamonds in the Permo- Carboniferous sequence No diamonds in the same sequence Carvalho, B.M.V. de (2014) Confined Turbidite Sand-Sheets in the Paraná and Paganzo Basins. Gonzaga & Gonzaga (2014) 11
Permo-Carboniferous glaciogenic sediments in Brazil Stollhofen, H; Werner, M.; Stanistreet, I.G. & Armstrong, R.A. (2008) Single-zircon U-Pb dating of Carboniferous-Permian tuffs, Namibia, and the intercontinental deglaciation cycle framework. Gonzaga & Gonzaga (2014) 12
Prospection projects The transport of diamonds by glacial systems will generate a population with characteristics that are distinct to those of populations of diamonds transported by fluvial systems or originated from a nearby primary source. Therefore, understanding and applying these concepts to paleogeographic, plate tectonics and provenience studies are of uttermost importance to prospection projects not only for diamonds, but also for other heavy minerals of economic interest like ruby and sapphire. Gonzaga & Gonzaga (2014) 13