One of the most remarkable placer gold fields in the world is found in the Andean piedmont in the department of Madre de Dios in southern Peru. Gold was discovered in the 1970s in the District of Huepetuhe, where a small stream that drains into the Río Inambari, approximately 20 kilometers downstream from the narrow gorge where the Inambari exits the Andean foothills. The current channel did not exist until a few tens of thousands of years ago, because it was blocked by a low ridge that deflected the main channel 90º west into the precursor of the Huepetuhe. This diversion created a near-perfect sediment trap for the gold being carried out of the Andes. Eventually, the river eroded a channel through the outlying ridge and created a depositional plain south of Madre de Dios, creating a mega gold field that stretches from the Río Colorado (West) to the city of Puerto Maldonado. Enormous amounts of alluvial gold have been funnelled into the Inambari due to the tectonic peculiarities of the Altiplano and the climatic history of the Quaternary Period. The headwaters span a 260-kilometer swath of the Andean highlands that constitute the northern border of the Altiplano, which was formed by a process known as ‘crustal shortening’ where a section of the South American plate was chipped off (rather than subducted) and relocated on top of the South American plate. The gold mining landscapes of Southern Peru and the Bolivian Yungas. Left: Industrial and wildcat mines in the context…This article was originally published on Mongabay
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