| Abstract: | Mount Veniaminof volcano, Alaska Peninsula, provides an opportunity to relate Quaternary volcanic rocks to a coeval intrusive complex. Veniaminof erupted tholeiitic basalt through dacite in the past ???260 k.y. Gabbro, diorite, and miarolitic granodiorite blocks, ejected 3700 14C yr B.P. in the most recent caldera-forming eruption, are fragments of a shallow intrusive complex of cumulate mush and segregated vapor-saturated residual melts. Sensitive high-resolution ion microprobe (SHRIMP) analyses define 238U-230Th isochron ages of 17.6 ?? 2.7 ka, 5+11/-10 ka, and 10.2 ?? 4.0 ka (2??) for zircon in two granodiorites and a diorite, respectively. Sparse zircons from two gabbros give 238-230Th model ages of 36 ?? 8 ka and 26 ?? 7 ka. Zircons from granodiorite and diorite crystallized in the presence of late magmatic aqueous fluid. Although historic eruptions have been weakly explosive Strombolian fountaining and small lava effusions, the young ages of plutonic blocks, as well as late Holocene dacite pumice, are evidence that the intrusive complex remains active and that evolved magmas can segregate at shallow levels to fuel explosive eruptions. ?? 2007 The Geological Society of America. |
| Genre: | Article |
| ProdID: | 70030203 |
| Citation Author: | Bacon, C. R.; Sison, T. W.; Mazdab, F. K. |
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| Citation End Page: | 494 |
| Citation Issue: | 6 |
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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: | Young cumulate complex beneath Veniaminof caldera, Aleutian arc, dated by zircon in erupted plutonic blocks; 2007; Article; Journal; Geology; Bacon, C. R.; Sison, T. W.; Mazdab, F. K. |
| Citation Start Page: | 491 |
| Citation Volume: | 35 |
| Citation Year: | 2007 |
| Type: | citation/reference |
| Text: | Young cumulate complex beneath Veniaminof caldera, Aleutian arc, dated by zircon in erupted plutonic blocks; 2007; Article; Journal; Geology; Bacon, C. R.; Sison, T. W.; Mazdab, F. K. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1130/G23446A.1 |
| Date Other: | Mon, 1 Jan 2007 00:00 -0600 |
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