Evolución tectónica de la porción centro-occidental de México y su relación con los yacimientos minerales asociados

Abstract

The present paper shows the existence of metallic provinces or belts in the central-occidental part of Mexico whose distribution and origin are related to the following tectonic processes: l. The formation of a submarine volcanic are with high content of pellitic sediments in the back-arc region. The mineralization is synsedimentary of copper-pyrrhotite in the are and polimetallic in the back-arc. These rocks have an epizonal metamorphism in green schists facies. We propose here the term "Metamorphic Volcanosedimentary Sequence" for these rocks ofPermo-triassic age. 2. Calcoalkaline magmatic intrusions of continental margin origin of Late Jurassic age, which are forming the Puerto V allarta batholith and sorne othcr intrusive rocks in Baja California. There are no mineralizations reported associated to these rocks. 3~ Uplifting, erotion and the deposition of progradatius deltas with the formation of chemical ore deposits associated 'to terrigenous sediments with Pb,Zn and Ag mineralizations. 4. The formation of an Early Cretaceous island are with a marginal basin. This basin is the result of extensional tectonics in the baak-arc region. This geologic setting contalns the most important polimetallic massive sulphur deposits in Mexico. We propose here the term "Unmetamorphosed Volcanosedimentary Sequence" for this lithologic assemblage. 5. Lateral migrations of the continental magmatism occurred from Late Cretaceous to Middle Tertiary and defmed the metallic provinces of the central-occidental part of Mexico. The most important associations are: Fe(Ti,Cu,Sn); Cu,Au; Pb,Zn,Ag(Au,Cu); Au,Ag(Pb,Zn,Cu); Sn; CaF2 ; Mn and Hg,Sb(Mn). This proyinces show a distribution of belts semiparallel to the recent coastal line; in sorne of them, there are overlaps due to heterochronous processes. 6. Placer deposits have been developed in recent times on the littoral and continental shelf with mineralization of magnetite, hematite, rutile and zircon.