The significance of PGE variations with Sr-Nd isotopes and lithophile elements in the Emeishan flood basalt province from SW China to northern Vietnam
The significance of PGE variations with Sr-Nd isotopes and lithophile elements in the Emeishan flood basalt province from SW China to northern Vietnam
复制标题
中国西南至越南北部峨眉山溢流玄武岩省PGE随Sr-Nd同位素和亲石元素变化的意义
DOI：
10.1016/j.lithos.2015.12.027
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发表时间：
2016
期刊：
影响因子：
3.5
通讯作者：
Hu Ruizhong
中科院分区：
文献类型：
--
作者：
Li Chusi;Ripley Edward M.;Tao Yan;Hu Ruizhong
新的亲铁-亲石元素和Sr-Nd同位素的二叠纪玄武岩和苦橄岩从北方越南，峨眉山溢流玄武岩省的最南端的发生，连同以前发表的数据，用于解决的问题，是否有任何有意义的相关性，这些元素和同位素之间存在一个省的规模。结果表明，玄武岩中εNd、（87 Sr/86 Sr）i与地幔标准化（Nb/Th）n呈负相关，而苦橄岩中εNd、（87 Sr/86 Sr）i与地幔标准化（Nb/Th）n不呈负相关。这表明苦橄岩中的地壳污染可以忽略不计，但在某些玄武岩中却很严重。全省苦橄岩和玄武岩的（Rh/Ru）n、（Pt/Ru）n、（Pd/Ru）n与Mg值呈负相关。这表明在岩浆分异过程中，Ru表现为相容性，而Rh、Pt、Pd表现为不相容性。Rh在天然玄武岩体系中的不相容行为也得到了（Pt/Rh）n随岩浆中Mg数减少而保持恒定的事实的支持。某些玄武岩样品的特征是ε Nd和（Nb/Th）n相对较低，Pd和Pt的亏损以及Cu的亏损（程度较轻）支持了岩浆中硫化物饱和是由硅质地壳混染和外部硫的加入共同触发的观点。在整个溢流玄武岩省内，只有越南北方宋达的苦橄岩显示出Ir相对于Ru的明显亏损。这些苦橄岩也具有较高的Al 2 O3/TiO 2和较低的地幔标准化的La/Yb（0.2-2.4）比从其他地方在该省，可能是由于参与了一个在这个位置的岩浆生成的Ir亏损，肥沃的地幔成分。
New analyses of siderophile–lithophile elements and Sr–Nd isotopes in the Permian basalts and picrites from northern Vietnam, the southernmost occurrence of the Emeishan flood basalt province, together with previously published data, are used to address the question of whether any meaningful correlation between these elements and isotopes exists at a province scale. The available data show that negative correlations between εNd,(87Sr/86Sr)iand mantle-normalized (Nb/Th)nare present in the basalts but not in the associated picrites. This indicates that crustal contamination is negligible in the picrites but significant in some of the basalts. The picrites and basalts from the entire province show negative correlations between (Rh/Ru)n, (Pt/Ru)n, (Pd/Ru)nand Mg-number. This indicates that Ru behaves compatibly whereas Rh, Pt and Pd behave incompatibly during magma differentiation. The incompatible behavior of Rh in natural basaltic systems is also supported by the fact that (Pt/Rh)nremains constant with decreasing Mg-number in the lavas. Depletions of Pd and Pt, and to a lesser degree Cu, in some basaltic samples characterized by relatively low εNdand (Nb/Th)nsupport the notion that sulfide saturation in the magmas was triggered by a combination of siliceous crustal contamination and addition of external sulfur. Within the entire flood basalt province only the picrites from Song Da, northern Vietnam show clear depletion in Ir relative to Ru. These picrites are also characterized higher Al2O3/TiO2and lower mantle-normalized La/Yb (0.2–2.4) than those from elsewhere in the province, possibly due to the involvement of an Ir-depleted, fertile mantle component in magma generation at this location.