| Abstract: | Three epidote-bearing tonalitic plutons from the North American Cordillera were studied in detail. These three plutons have close petrographic and chemical similarities. Epidote is always euhedral against biotite but shows highly embayed, vermiform contacts with plagioclase and quartz. Rounded to highly embayed hornblendes are enclosed in epidote as well as in magmatic plagioclase. The pistacite content of epidote, atomic Fe3+/(Fe3+ + Al), is approx 23-27%. These and other textural relations, the lack of alteration of minerals, and the involvement of epidote in flow banding show that the epidote is magmatic, crystallized later through reaction with hornblende in the presence of a melt phase. The observed relations agree with experimental data on crystallization of epidote from synthetic granodiorite at 8 kbar total P. Plutonic rocks bearing magmatic epidote must have formed under moderately high P, corresponding with lower crustal depth, under fairly oxidizing conditions.-L.di H. |
| Genre: | Article |
| ProdID: | 70013165 |
| Citation Author: | Zen, E. A.; Hammarstrom, J. M. |
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| Citation End Page: | 518 |
| Citation Issue: | 9 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geology |
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| Citation Number Of Pages: | 4 |
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| Citation Search Results Text: | Magmatic epidote and its petrologic significance.; 1984; Article; Journal; Geology; Zen, E. A.; Hammarstrom, J. M. |
| Citation Start Page: | 515 |
| Citation Volume: | 12 |
| Citation Year: | 1984 |
| Type: | citation/reference |
| Text: | Magmatic epidote and its petrologic significance.; 1984; Article; Journal; Geology; Zen, E. A.; Hammarstrom, J. M. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1984 00:00 -0600 |
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