| Title | Limits of hydrosphere-lithosphere interaction; origin of the lowest-known delta 18O silicate rock on Earth in the Paleoproterozoic Karelian Rift |
| Author | Bindeman, I.N.; Schmitt, A.K.; Evans, D.A.D. |
| Author Affil | Bindeman, I.N., University of Oregon, Department of Geological Sciences, Eugene, OR. Other: University of California, Los Angeles; Yale University |
| Source | Geology (Boulder), 38(7), p.631-634, . Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091- 7613 |
| Publication Date | July 2010 |
| Notes | In English. With GSA Data Repository Item 2010170. 30 refs. GeoRef Acc. No: 300246 |
| Index Terms | radioactive age determination; age determination; radioactive age determination; geochemistry; glacial geology; glaciation; hydrogen; hydrothermal alteration; isotopes; oxygen; Russia--Karelia; absolute age; ancient ice ages; Belomorian Belt; Commonwealth of Independent States; D/H; dates; Europe; glacial environment; gneisses; heterogeneity; hydrosphere; isotope ratios; Karelia Russian Federation; lithosphere; metamorphic rocks; metamorphism; metasomatism; meteoric water; monazite; nesosilicates; O-18/O-16; orthosilicates; paleogeography; paleohydrology; paleolatitude; Paleoproterozoic; phosphates; polymetamorphism; Precambrian; Proterozoic; protoliths; rift zones; Russian Federation; silicate rocks; silicates; slushball Earth; stable isotopes; supercontinents; U/Th/Pb; upper Precambrian; zircon; zircon group |
| Abstract | Geologic records of Earth's hydrosphere and meteoric precipitation older than 2 Ga are rare, although they provide insight into the past climate, rates of water- rock interaction, and intensity of plate tectonics. Here we report and describe in detail the lowest known delta 18O (-16 per mil to -25 per mil) terrestrial silicate rocks on Earth, found in Paleoproterozoic plagiogneisses from the Belomorian complex, Karelia, Russia. Geochronologic and oxygen isotopic data on zircons (+7 per mil to -26 per mil) and monazite (-17.5 per mil) imply that the protoliths of these rocks were ca. 2.5 Ga metasediments and metavolcanics that were hydrothermally altered prior to 1.85 Ga within an intracontinental rift zone, and involved ultralow delta 18O, ‹-25 per mil meteoric water. Paleogeographic reconstructions indicate that Karelia was at low to middle latitudes throughout the Paleoproterozoic Era. Ultradepleted delta 18O waters outside of polar regions or the interiors of large landmasses provide independent evidence for a moderately glaciated, so called "slushball" Earth climate between 2.45 and 2.4 Ga, in which low- or mid-latitude, mid-size continents were covered with glaciers while the ocean remained at least partially unfrozen to allow for intracontinental isotopic distillation in a large temperature gradient. In addition to these climatic inferences, the data are more readily explained by a depleted -10 per mil seawater reservoir during Paleoproterozoic time. |
| URL | http://hdl.handle.net/10.1130/G30968.1 |
| Publication Type | journal article |
| Record ID | 64004955 |