Figure 6: Plot of weight percentages of SiO2/20, Na2O+K2O and TiO2+MgO+FeO(total) from the sand-rich sediments in this study area. A: Tertiary quartz sands (Amazonian provenance). B: Pleistocene Meuse + Rhine sands, North Limburg, the Netherlands. C: Pleistocene Meuse sands, South Limburg, the Netherlands. D: Plio- Pleistocene quartzofeldspathic Allier sands, France. E: Pleistocene-Holocene basement-rich, basalt-poor Allier sands, France. F: Pleistocene alkali basalt-rich, basement-poor sands, Allier River, France. G: Holocene andesitic sands, Atlantic Zone Rivers, Costa Rica. H: Placers, Costa Rica Atlantic beach and Caqueta River, Colombian Amazones (almost purely ferromagnesian sands).