| Abstract: | Consistent core-to-rim decreases of 87Sr/86Sr ratios and coincident increases in Sr concentrations in plagioclase phenocrysts of varying size (~ 1 cm to 2 mm) are reported from samples of the 1982 and pre-1982 (~ 200 ka) eruptions of El Chichon Volcano. Maximum 87Sr/86Sr ratios of ~ 0.7054, significantly higher than the whole-rock isotopic ratios (~ 0.7040-0.7045), are found in the cores of plagioclase phenocrysts, and minimum 87Sr/86Sr ratios of ~ 0.7039 are found near some of the rims. Plagioclase phenocrysts commonly display abrupt fluctuations in An content (up to 25 mol %) that correspond to well-developed dissolution surfaces The isotopic, textural and compositional characteristics suggest that these plagioclase phenocrysts grew in a system that was periodically recharged by higher-temperature magma with a lower 87Sr/86Sr ratio and a higher Sr concentration. Rim 87Sr/86Sr ratios in plagioclase phenocrysts of rocks from the 200 ka eruption indicate that, at that time, the magma had already attained the lowest recorded 87Sr/86Sr value of the system (~ 0.7039). In contrast, cores from plagioclase phenocrysts of the 1982 eruption, inferred to have grown in the past few thousand years, have the highest recorded 87Sr/86Sr ratios of the system. Collectively, the Sr isotopic data (for plagioclase and whole rock), disequilibrium textural features of the phenocrysts, known eruption frequencies, and inferred crystal-residence times of the plagioclases are best interpreted in terms of an intermittent magma chamber model. Similar processes, including crustal contamination, magma mixing, periodic recharge by addition of more mafic magma to induce plagioclase disequilibrium (possibly triggering eruption) and subsequent re-equilibration, apparently were operative throughout the 200 ky history of the El Chichon magma system. |
| Genre: | Article |
| ProdID: | 70022362 |
| Citation Author: | Tepley, III, F. J.; Davidson, J. P.; Tilling, R. I.; Arth, J. G. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 1411 |
| Citation Issue: | 9 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Journal of Petrology |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 15 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Magma mixing, recharge and eruption histories recorded in plagioclase phenocrysts from El Chichon Volcano, Mexico; 2000; Article; Journal; Journal of Petrology; Tepley, III, F. J.; Davidson, J. P.; Tilling, R. I.; Arth, J. G. |
| Citation Start Page: | 1397 |
| Citation Volume: | 41 |
| Citation Year: | 2000 |
| Type: | citation/reference |
| Text: | Magma mixing, recharge and eruption histories recorded in plagioclase phenocrysts from El Chichon Volcano, Mexico; 2000; Article; Journal; Journal of Petrology; Tepley, III, F. J.; Davidson, J. P.; Tilling, R. I.; Arth, J. G. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sat, 1 Jan 2000 00:00 -0600 |
| Publisher: | |
