SHRIMP zircon U–Pb geochronology, elemental, and Nd isotopic geochemistry of the Neoproterozoic mafic dykes in the Yanbian area, SW China
- 作者：Wei-Guang Zhu ; Hong Zhong ; Xian-Hua Li ; Hai-Lin Deng ; De-Feng He ; Kong-Wen Wu ; Zhong-Jie Bai
- 关键词：Neoproterozoic ; Mafic dykes ; Geochemistry ; Southwest China ; Rodinia
- 刊名：Precambrian Research
- 出版年：2008
- 期刊代码：75_03019268
- 类别：ear
- 出版时间：20 June 2008
- 卷：164
- 期：1-2
- 页码：66-85
- 文件大小：3363 K
摘要
Sensitive High-Resolution Ion Microprobe (SHRIMP) U–Pb zircon ages, geochemical and Nd isotopic data are reported for two groups of Neoproterozoic mafic dykes in the Yanbian area of Sichuan Province, SW China. The Group 1 and Group 2 dykes were dated at 792 ± 13 Ma and 761 ± 14 Ma, respectively. While Group 1 and Group 2 rocks are commonly high in Fe2O3 and TiO2 contents with similar MgO contents and Mg numbers, they exhibit distinct trace element features. Group 1 rocks with high 
Nd(T) values (+5.8 to +7.2) and total rare earth element (REE) contents (109–171 ppm), are characterized by LREE-enriched and “humped” trace-element patterns with slightly negative Nb–Ta anomaly, similar to typical alkaline basalts associated with continental rifts. Group 2 rocks have relatively low total REE contents (50.4–103 ppm) with relatively flat REE patterns and can be further divided into two sub-types. Group 2a rocks show MORB-like trace element patterns depleted in highly incompatible elements such as Th, Nb, Ta, La and Ce, whereas the Group 2b rocks exhibit flatter REE patterns than those of the Group 2a. The Nd(T) values of the Group 2a and Group 2b rocks are +5.4 to +7.2 and +4.5 to +5.3, respectively.
Nd(T) values (+5.8 to +7.2) and total rare earth element (REE) contents (109–171 ppm), are characterized by LREE-enriched and “humped” trace-element patterns with slightly negative Nb–Ta anomaly, similar to typical alkaline basalts associated with continental rifts. Group 2 rocks have relatively low total REE contents (50.4–103 ppm) with relatively flat REE patterns and can be further divided into two sub-types. Group 2a rocks show MORB-like trace element patterns depleted in highly incompatible elements such as Th, Nb, Ta, La and Ce, whereas the Group 2b rocks exhibit flatter REE patterns than those of the Group 2a. The Nd(T) values of the Group 2a and Group 2b rocks are +5.4 to +7.2 and +4.5 to +5.3, respectively.