Complex sentence: Pascua-Lama is the name of a mine that is planned to be built in an area approximately 150 kilometers southeast of Vallenar, Chile and 300 kilometers northwest of San Juan, Argentina.
Split into simpler sentences: Pascua-Lama is the name of a mine that will be built in an area that borders Argentine and Chile. It's location is approximately 150 kilometers southeast of the city of Vallenar, Chile and 300 kilometers northwest of the city of San Juan, Argentina.