کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5783369 1637958 2017 40 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Dehydroxylation and diagenetic variations in diatom oxygen isotope values
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Dehydroxylation and diagenetic variations in diatom oxygen isotope values
چکیده انگلیسی
Numerous studies have documented changes in the dissolution and reactivity of biogenic silica as it is transferred from the water column to sediment archives; here we present the first experimental data that demonstrate a physical mechanism by which the oxygen isotope (δ18Osil) values of biogenic silica (diatoms) are altered during early diagenesis. The δ18Osil value of diatom silica cultured at 19.3 °C was +31.9‰ ± 0.2‰ (n = 6); the same silica experimentally aged in an artificial seawater media at near silica saturation at 85 °C had an average δ18Osil value of +27.1‰ ± 0.6‰ (n = 20). The most significant change in the δ18Osil value was coincident with an initial reduction in the total silanol abundance, indicating that the timing of dehydroxylation reactions in natural sedimentary environments is associated with diagenetic changes in the recorded δ18Osil values. The rate of change in the experimental aging environment at 85 °C was rapid, with significant changes in both silanol abundance and δ18Osil values. Additionally, the silica-water fractionation relationship recorded by the experimentally-aged samples approaches the equilibrium quartz-water fractionation factor. The linear rate law was used to estimate the timing of these changes in low temperature environments; the initial and most significant change in silica reactivity and δ18Osil values is likely to occur on the order of 10's of years at 4 °C. Published silica-water fractionation factors for sedimentary diatoms most likely represent a combination of growth and diagenetic environments, and the δ18O value of diagenetic water needs to be addressed when using δ18Osil values to reconstruct paleoceanographic and paleoenvironmental conditions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geochimica et Cosmochimica Acta - Volume 199, 15 February 2017, Pages 185-195
نویسندگان
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