Metallogeny in ecuadorian andes

Document Type

Article

Publication Date

1-7-1972

Abstract

A general description and a genetic classification is given of the most significant mineral deposits and metalliferous indications of the Republic of Ecuador. The principal classes of metallic mineral deposits are: (1) disseminated mineralization, (2) polymetallic veins, (3) fracture-fillings and stockworks, (4) stratabound deposits, (5) residual and alluvial deposits. Class 1 deposits apparently result from the normal high metal values present in eugeosynclinal basic effusives with later concentrations by intrusives. The metallogeny of classes 2, 3, and 4, appears to be due to numerous successive igneous activities redistributing the earlier primary mineralization in class 1 deposits. The principal epochs of mineralization are Paleozoic, Jurassic to Middle Cretaceous, Late Cretaceous to Early Tertiary, Middle and Upper Tertiary and Pleistocene. Typical metal assemblages appear to correspond to each epoch of mineralization. These are distributed vertically in the Andean ranges: between 500 and 2,000 meters above sea level: Cu-Mo and Au-rich quartz veins; between 1,500 and 3,000 m: Au-Cu-Ag-Pb-Zn; between 2,500 and 4,000 m: Ag-Hg; between 3,500 and 5,000: Ag-Zn7Pb-Au-As. From 3,000 to more than 6,000 m hot mineral springs and native sulfur of volcanic origin prevail. This vertical distribution defines two large metalliferous districts: 1) the Azuay-Cafiar silver district (between 2,500 and 4,000 m) and 2) the Loja copper district (between 1,000 and 2,000 m). Mineralized (and barren) intrusives and mineralization are both clearly controlled by geologic structures. The mineralized (or barren) intrusives are controlled by north-south (NNE-SSW to NNW-SSE) major Andean faults. Certain types of mineralization (veins, fracture-filling, etc.) appear to be controlled both by the major north-south faults and by east-west transverse fault zones. © 1972 Society of Economic Geologists, Inc.

Publication Title

Economic Geology

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