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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.

Geospatial Extents

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
First page:
59
Last page:
72
Country:
Mexico
State:
Sonora
Other Geospatial:
La Florida De Nacozari