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Interpretation of Oxygen Isotopes in Phanerozoic Ophiolites and Sedimentary Rocks
Geochemistry, Geophysics, Geosystems ( IF 2.9 ) Pub Date : 2020-05-06 , DOI: 10.1029/2020gc009000
Yoshiki Kanzaki 1
Affiliation  

Two reactive transport models were developed to integrally simulate fluxes of oxygen isotopes from hydrothermal alteration of oceanic crust and weathering of continental rocks for a better understanding of the regulation of oxygen isotopes in the ocean. The hydrothermal alteration model consists of three boxes to represent pillow basalt, sheeted dike, and gabbro sections and simulates the steady‐state δ18O of solid rocks and porewaters in three individual sections along the spreading direction. The continental weathering model similarly calculates steady‐state δ18O profiles along the uplift direction. The two models were run in concert to simulate the evolution of seawater δ18O during the Phanerozoic, reflecting the relevant forcing factors to the corresponding parameter values of the models as functions of time. The seawater δ18O was calculated to have evolved from less than −5‰ in the early Paleozoic to between −2 and 0‰ for the Mesozoic and Cenozoic, as a result of declines in atmospheric CO2 and land area of igneous and high‐grade metamorphic rocks. The transition of seawater δ18O is similar to the δ18O trend that is commonly recorded in authigenic sedimentary rocks such as carbonates and cherts. The simultaneously simulated δ18O values for altered continental and oceanic rocks are decoupled from seawater δ18O because of kinetic inhibition and solid‐rock buffering at respective low and high temperatures and are similar to the shale and ophiolite δ18O records. Overall consistency between the simulation and observations supports the dynamic behavior of oceanic δ18O over the Phanerozoic eon.

中文翻译:

多生代蛇绿岩和沉积岩中氧同位素的解释

开发了两个反应性输运模型来整体模拟海洋地壳热液变化和大陆岩石风化引起的氧同位素通量,以更好地了解海洋中氧同位素的调控。热液蚀变模型包括三个盒子来表示枕玄武岩,片状堤,辉长岩和段和模拟稳态δ 18在沿扩展方向上的三个单独的部分ö固体岩石和孔隙水的。大陆风化模型同样地计算δ稳态18个沿隆起O方向轮廓。这两种型号均一致运行,以模拟海水的演变δ 18O在生代时代,将相关的强迫因子反映为模型的相应参数值作为时间的函数。δ海水18中计算的氧气已经从低于-5在早古生代演进‰至-2与0之间‰的新生代,如在大气CO下降的结果2的火成岩和和土地面积高变质岩。海水的过渡δ 18 O为类似于δ 18是通常记录在自生沉积岩如碳酸盐和硅质岩Ò趋势。该模拟同时δ 18个为改变大陆和海洋岩石O值是从海水中分离δ 18因为动力学抑制和固体岩石缓冲在相应低温和高温下的和O类似于页岩和蛇绿δ 18个ö记录。仿真和观测值之间整体一致性支持海洋δ的动态行为18 ö在显生宙。
更新日期:2020-05-06
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