The formation originated in marine and continental (terrestrial) conditions, and bears evidence of submarine volcanism as well as large explosive eruptions.

[5][6][7] Albeit early, this is not the first recorded instance of Andean volcanism in northern Chile as the Triassic and Jurassic formations of Cifuncho, Agua Chica, Pan de Azúcar and Posada de los Hidalgos that underlie La Negra Formation do also bear evidence of volcanism.

The magmas originated in a parcel of Earth's mantle that was metasomatized by fluid derived from the tectonic plate that was subducting beneath what is now Chile.

Metamorphism is more pronounced in the brecciated parts of lava flows and near Antofagasta if compared with La Negra Formation near Tocopilla.

[2] Inside the intrusions that are hosted within La Negra Formation there are several vertical or near-vertical veins bearing chalcopyrite, magnetite and actinolite.

[4] The manto-type copper and silver deposits found in La Negra Formation make up the northern portion of the Chilean Iron Belt.