Porphyry-type metallization and alteration at La Florida de Nacozari, Sonora, Mexico

Journal of Research of the U.S. Geological Survey
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Abstract

Pervasive secondary biotite-rich mineral assemblages, characteristic of potassic alteration found in the cores of most commercial porphyry copper systems, are associated spatially with a conspicuous color and a geochemical anomaly at La Florida de Nacozari, Sonora. These composite biotite-magnetite assemblages, with or without actinolite, quartz, rutile, sphene, chalcopyrite, and pyrite assemblages, are primarily the result of early dispersed biotitic (EDB) alteration of andesite. The bulk of the near-surface copper in the area, however, was introduced later by the veins that cut the EDB-altered andesite. These late veins are distinguished by a quartz-calcite-chlorite±laumontite±chalcopyrite assemblage, and the chalcopyrite in these veins may reflect upward remobilization of deep EDB copper by fluids associated with the emplacement of nearby coarse-grained granite. Fluid-inclusion relations in the late veins suggest that their fluids were nonboiling and relatively dilute.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Porphyry-type metallization and alteration at La Florida de Nacozari, Sonora, Mexico
Series title Journal of Research of the U.S. Geological Survey
Volume 6
Issue 1
Year Published 1978
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Mineral Resources Program
Description 14 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Research of the U.S. Geological Survey
First page 59
Last page 72
Country Mexico
State Sonora
Other Geospatial La Florida De Nacozari
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