| Abstract: | The isotopic ratios of H, O and C in water within the Long Valley caldera, California reflect input from sources external to the hydrothermal reservoir. A decrease in ??D in precipitation of 0.5??? km-1, from west to east across Long Valley, is caused by the introduction of less fractionated marine moisture through a low elevation embayment in the Sierra Nevada Mountain Range. Relative to seasonal fluctuations in precipitation (-158 to -35??.), ??D ranges in hot and cold surface and groundwaters are much less variable (-135 to -105??.). Only winter and spring moisture, reflecting higher precipitation rates with lighter isotopic signatures, recharge the hydrological system. The hydrothermal fluids are mixtures of isotopically heavy recharge (??D = - 115???, ??18O = - 15???) derived from the Mammoth embayment, and isotopically lighter cold water (??D = -135???, ??18O = -18???). This cold water is not representative of current local recharge. The ??13C values for dissolved carbon in hot water are significantly heavier (- 7 to - 3???) than in cold water (-18 to -10???) denoting a separate hydrothermal origin. These ??13C values overlie the range generally attributed to magmatic degassing of CO2. However, ??13C values of metamorphosed Paleozoic basement carbonates surrounding Long Valley fall in a similar range, indicating that hydrothermal decarbonization reactions are a probable source of CO2. The ??13C and ??18O values of secondary travertime and vein calcite indicate respective fractionation with CO2 and H2O at temperatures approximating current hydrothermal conditions. ?? 1990. |
| Genre: | Article |
| ProdID: | 70016035 |
| Citation Author: | White, A. F.; Peterson, M. L.; Wollenberg, H.; Flexser, S. |
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| Citation End Page: | 585 |
| Citation Issue: | 5-6 |
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| Citation Language: | English |
| Citation Larger Work Title: | Applied Geochemistry |
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| Citation Number Of Pages: | 15 |
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| Citation Search Results Text: | Sources and fractionation processes influencing the isotopic distribution of H, O and C in the Long Valley hydrothermal system, California, U.S.A.; 1990; Article; Journal; Applied Geochemistry; White, A. F.; Peterson, M. L.; Wollenberg, H.; Flexser, S. |
| Citation Start Page: | 571 |
| Citation Volume: | 5 |
| Citation Year: | 1990 |
| Type: | citation/reference |
| Text: | Sources and fractionation processes influencing the isotopic distribution of H, O and C in the Long Valley hydrothermal system, California, U.S.A.; 1990; Article; Journal; Applied Geochemistry; White, A. F.; Peterson, M. L.; Wollenberg, H.; Flexser, S. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Mon, 1 Jan 1990 00:00 -0600 |
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