Complex sentence: Pascua-Lama is an open pit mine of gold, silver, copper and other minerals located in the Andes mountains, south of Atacama, straddling the border between Chile and Argentina at an altitude of over 4,500 metres.
Split into simpler sentences: Pascua-Lama is an open pit mining proyect of gold, silver, copper and other minerals. Pascua Lama is located in the Andes mountains, south of Atacama, straddling the border between Chile and Argentina at an altitude of over 4,500 metres.