Radiogenic Pb reservoir contributes to the rare earth element (REE) enrichment in South Qinling carbonatites
Radiogenic Pb reservoir contributes to the rare earth element (REE) enrichment in South Qinling carbonatites
复制标题
放射性Pb储层有助于南秦岭碳酸岩稀土元素（REE）富集
DOI：
10.1016/j.chemgeo.2018.07.019
复制
发表时间：
2018-09
期刊：
影响因子：
3.9
通讯作者：
Liu Yong-Sheng
中科院分区：
文献类型：
--
作者：
Chen Wei;Lu Jue;Jiang Shao-Yong;Ying Yuan-Can;Liu Yong-Sheng
碳酸盐岩和相关的碱性硅酸盐岩含有世界上最重要的稀土元素（REE）储量之一。这些矿床的稀土元素特征是轻稀土富集，在稀土元素标准化图解中，稀土元素从La到Lu的分馏作用明显。然而，稀土元素富集的来源仍然存在争议。南秦岭造山带沙熊洞碳酸盐岩是我国中部重要的稀土矿床之一。在这项研究中，在现场化学和同位素数据已获得的碳酸盐矿物从复杂的。我们的研究结果表明，方解石具有可变的微量元素丰度，特别是稀土元素。方解石的原位Pb同位素数据显示206Pb/204Pb（18.05 - 31.71）和207Pb/204Pb（15.49 - 16.36）比值变化极大。有趣的是，Pb同位素变化与REE富集呈正相关[即，(La/Yb）N和（La/Nd）N]。具有极端放射成因铅同位素组成的方解石显示上地幔C和O同位素组成（δ 13 Cavg =-5.74 ‰，δ 18 Oavg = 7.13 ‰）和亏损的87 Sr/86 Sr同位素比（~0.7030）。所观察到的各种稀土元素的富集伴随着可变的铅同位素组成内SXD方解石可能是一个封闭系统交代事件的结果。含铀矿物（即，自志留纪形成以来富集了丰富的铀成因铅，为交代作用提供了放射成因铅和轻稀土源。另外，观察到的化学和同位素组成可能表明参与两个地幔源（PREMA和不同的放射成因铅地幔水库）。
Carbonatite and related alkaline silicate rocks contain one of the most significant rare earth element (REE) reserves in the world. It is well-known that these REE deposits are characterized by a strong light REE enrichment with a steep fractionation from La to Lu in the chondrite-normalized diagram. However, the origin of their REE enrichment remains debatable. The Shaxiongdong (SXD) carbonatite in the South Qinling orogenic belt hosts one of the most important REE deposits in central China. In this study, in situ chemical and isotopic data have been obtained for carbonate minerals from the complex. Our results show that calcite has variable trace element abundances, especially REEs. In situ Pb isotope data for calcite reveal extreme variations of206Pb/204Pb (18.05–31.71) and207Pb/204Pb (15.49–16.36) ratios. Interestingly, Pb isotope variations display positive correlations with REE enrichments [i.e., (La/Yb)Nand (La/Nd)N]. Calcite with extreme radiogenic Pb isotopic compositions displays upper mantle C and O isotopic compositions (δ13Cavg= −5.74‰, δ18Oavg= 7.13‰) and depleted87Sr/86Sr isotopic ratios (~0.7030). The observed various REE enrichments accompanying the variable Pb isotopic composition within SXD calcite possibly result from a closed-system metasomatic event. The U-bearing mineral (i.e., pyrochlore) accumulating abundant uranogenic lead since their Silurian formation serves as the radiogenic Pb and LREE source for the metasomatism. Alternatively, the chemical and isotopic composition observed might suggest involvement of two mantle sources (PREMA and the distinct radiogenic Pb mantle reservoir).
登录
查看更多内容
影响因子：
4.5
作者：
Chakhmouradian, Anton R.;Zaitsev, Anatoly N.
通讯作者：
Zaitsev, Anatoly N.
影响因子：
0.9
作者：
R. H. Mitchell
通讯作者：
R. H. Mitchell
影响因子：
3.5
作者：
A. Cooper;Alice K. Collins;J. Palin;J. Spratt
通讯作者：
A. Cooper;Alice K. Collins;J. Palin;J. Spratt
南秦岭造山带碳酸岩成因：地壳循环及华北地块碰撞时间的意义
影响因子：
5
作者：
许成;许成
通讯作者：
许成
影响因子：
2.9
作者：
R. Zartman;B. Doe
通讯作者：
R. Zartman;B. Doe