Yuanlin Chen, Huan Li, Shangyi Gu, Gary G. Lash, Chaoyang Zheng, Liuan Duan, Fan Yang
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引用次数: 0
Abstract
The Lomagundi Carbon Event (LE), the large, long-lived Paleoproterozoic positive carbon isotope excursion, is traditionally associated with a significant increase in atmospheric oxygen. However, the magnitude and extent of atmosphere–ocean oxygenation during this critical period of Earth’s history remain poorly constrained. Here, we present molybdenum isotope data and Ce anomaly values of Paleoproterozoic Jingshan Group marble samples deposited coincident with the peak of LE. Analyzed samples are characterized by near-modern seawater δ98Mocarb values (maximum = 2.13 ‰ ± 0.05), crustal Ce anomalies (average = 1.03), and δ98Mocarb values (average = 0.41 ‰). The great variation of Mo isotope values displayed by samples recovered from a thin stratigraphic interval likely reflect the existence of a small Mo reservoir during LE. We suggest that Mo removal from poorly oxygenated oceans under ferruginous conditions was responsible for the contraction of the Mo oceanic reservoir. Mo concentrations and isotope values of deposits coincident with this time interval appear to have been controlled by iron and manganese oxides shuttle. Placed in the context of Earth’s oxygenation history, our findings suggest that O2levels of the atmosphere–ocean system remained much less (1 % PAL) than the present level with occasional episodes of increased or pulsed atmospheric oxygen during the peak of LE.
期刊介绍:
Gondwana Research (GR) is an International Journal aimed to promote high quality research publications on all topics related to solid Earth, particularly with reference to the origin and evolution of continents, continental assemblies and their resources. GR is an "all earth science" journal with no restrictions on geological time, terrane or theme and covers a wide spectrum of topics in geosciences such as geology, geomorphology, palaeontology, structure, petrology, geochemistry, stable isotopes, geochronology, economic geology, exploration geology, engineering geology, geophysics, and environmental geology among other themes, and provides an appropriate forum to integrate studies from different disciplines and different terrains. In addition to regular articles and thematic issues, the journal invites high profile state-of-the-art reviews on thrust area topics for its column, ''GR FOCUS''. Focus articles include short biographies and photographs of the authors. Short articles (within ten printed pages) for rapid publication reporting important discoveries or innovative models of global interest will be considered under the category ''GR LETTERS''.