Halogen contents of igneous minerals as indicators of magmatic evolution of rocks associated with the Ray porphyry copper deposit, Arizona
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Abstract
The contents of Cl, F, and H2O+ (calculated) in some hydrous igneous minerals in intrusive rocks of Laramide age (70-60 m.y.) near Ray, Ariz., appear to be related to the age and the chemistry of the whole-rock samples. Apatite and biotite in younger, more silicic rocks contain more F but less Cl and H2O+ than apatite and biotite in older, more mafic rock; the same relations hold for F and H2O+ in sphene. Correlations of the abundance of Cl, F, and H2O+ in hornblende with rock chemistry and age are not as strong as for apatite, biotite, and sphene; igneous (?) epidote does not contain Cl and F in amounts detectable by electron microprobe analysis. The contents of Cl, F, and H2O+ in whole-rock samples decrease with increasing differentiation index and decreasing age. Data for a single pluton of variable composition mirror the results for a suite of different plutons and dikes. The data are satisfactorily although not exclusively explained by postulating that the melts each contained progressively less Cl, F, and H2O and that the hydrons minerals consumed most of the Cl, F, and H2O in the magmas. The data may also be explained by postulating that (1) the stocks evolved Cl-bearing water during their ascent and crystallization, or that (2) Cl and H2O were concentrated during differentiation of the stocks but the minerals failed to record their buildup. Both alternative explanations find problems with and require special conditions to satisfy field, chemical, and experimental data. If many of the special conditions are not met, a nearby batholithic parent to the stocks is not a favorable source of the mineralized fluids at Ray. Propylitic alteration of biotite results in Cl-poor chlorites and may have provided some Cl to hydrothermal fluids; biotite may have also supplied some F to propylitizing fluids through alteration.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Halogen contents of igneous minerals as indicators of magmatic evolution of rocks associated with the Ray porphyry copper deposit, Arizona |
| Series title | Journal of Research of the U.S. Geological Survey |
| Volume | 4 |
| Issue | 1 |
| Year Published | 1976 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Description | 27 p. |
| First page | 91 |
| Last page | 117 |
| Country | United States |
| State | Arizona |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |
| Google Analytic Metrics | Metrics page |