| Abstract: | We report geochronological and geochemical data for the calc-alkalic Lowland Creek volcanic field (LCVF) in westcentral Montana. 40Ar/ 39Ar age determinations show that the LCVF was active from 52.9 to 48.6 Ma, with tuff-forming eruptions at 52.9 ?? 0.14 and 51.8 ?? 0.14 Ma. These dates span the age range of vigorous Eocene igneous activity in the Kamloops-Absaroka-Challis belt. The LCVF evolved upward from basal rhyolites (SiO 2>71 wt%) to dacites and andesites (SiO 2 > 62 wt%). Compositional change parallels a transition from early explosive volcanism to late effusive activity. Four geochemical components can be detected in the rocks. A component with 206Pb/204Pb < 16.5 and epsilon;Nd near-15 is predominant in anhydrous, two-pyroxene dacites; hydrous rhyolites, rhyodacites, and dacites with epsilon;Nd below-10 are dominated by a second component; hydrous rocks with 206Pb/ 204Pb > 18.3 and epsilon;Nd>-9 contain a third component; and an andesite with low Nd content and epsilon;Nd near-9 probably contains a fourth component. The first three components probably derive from the lower and middle crust, whereas the fourth is probably from the lithospheric mantle. ?? 2010 by The University of Chicago. |
| Genre: | Article |
| ProdID: | 70037118 |
| Citation Author: | Dudas, F. O.; Ispolatov, V. O.; Harlan, S. S.; Snee, L. W. |
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| Citation End Page: | 304 |
| Citation Issue: | 3 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Geology |
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| Citation Number Of Pages: | 10 |
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| Citation Search Results Text: | 40Ar/39Ar geochronology and geochemical reconnaissance of the Eocene Lowland Creek volcanic field, west-central Montana; 2010; Article; Journal; Journal of Geology; Dudas, F. O.; Ispolatov, V. O.; Harlan, S. S.; Snee, L. W. |
| Citation Start Page: | 295 |
| Citation Volume: | 118 |
| Citation Year: | 2010 |
| Type: | citation/reference |
| Text: | 40Ar/39Ar geochronology and geochemical reconnaissance of the Eocene Lowland Creek volcanic field, west-central Montana; 2010; Article; Journal; Journal of Geology; Dudas, F. O.; Ispolatov, V. O.; Harlan, S. S.; Snee, L. W. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1086/651523 |
| Date Other: | Fri, 1 Jan 2010 00:00 -0600 |
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