摘要
In this study, 13 groups of silicon and oxygen isotopes and major elements of the basalts near the East Pacific Rise 13°N are used to study the fractionation of silicon and oxygen isotopes. Among these data, δ30Si values of basalts vary from -0.4%o to 0.2%o with a mean value of δ30Si of （-0.18±0.22）%o. The δ180 values range from 4.1%o to 6.4%o with a mean δ180 value of （＋5.35±0.73） %0. Since the δ30Si values increase in the series of basalt-basaltic andesite- andesite, and δ180 values display a positive correlation with the SiO2 content, we propose that the fractionation of silicon and oxygen isotopes is influenced by the SiO2 content in igneous rocks. Compared with the igneous rocks from Manus Basin with clinopyroxene as their dominant mineral phase, MORBs in this study containing olivine and plagioclase as primary minerals have lower δ180 and δ30Si values, indicating that the fractionation of silicon and oxygen isotopes is also affected by different Si-O bridges in silicate minerals. Furthermore, our samples from the EPR are defined as E-MORB based on K/Ti ratios. Probably, the difference in δ30Si and δ30O between our samples and a normal MORB are cause by the enriched components in E-MORBs.
In this study, 13 groups of silicon and oxygen isotopes and major elements of the basalts near the East Pacific Rise 13°N are used to study the fractionation of silicon and oxygen isotopes. Among these data, δ30Si values of basalts vary from -0.4%o to 0.2%o with a mean value of δ30Si of （-0.18±0.22）%o. The δ180 values range from 4.1%o to 6.4%o with a mean δ180 value of （＋5.35±0.73） %0. Since the δ30Si values increase in the series of basalt-basaltic andesite- andesite, and δ180 values display a positive correlation with the SiO2 content, we propose that the fractionation of silicon and oxygen isotopes is influenced by the SiO2 content in igneous rocks. Compared with the igneous rocks from Manus Basin with clinopyroxene as their dominant mineral phase, MORBs in this study containing olivine and plagioclase as primary minerals have lower δ180 and δ30Si values, indicating that the fractionation of silicon and oxygen isotopes is also affected by different Si-O bridges in silicate minerals. Furthermore, our samples from the EPR are defined as E-MORB based on K/Ti ratios. Probably, the difference in δ30Si and δ30O between our samples and a normal MORB are cause by the enriched components in E-MORBs.
基金
The National Key Basic Research Program of China under contract No.2013CB429700
National Special Fund for the 12th Five Year Plan of COMRA under contract Nos DY125-12-R-02 and DY125-11-R-05
Shandong Province Natural Science Foundation of China for Distinguished Young Scholars under contract No.JQ200913
the National Natural Science Foundation of China under contract Nos 40830849,40976027 and 40906029
