Geochemical Characteristics of Cenozoic Basalts in Tengchong Block, the Southeastern Margin of Qinghai-Tibet Plateau, China: Constraints on the Nature of Mantle Source(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2018年第04期
- Page:
- 398-413
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Geochemical Characteristics of Cenozoic Basalts in Tengchong Block, the Southeastern Margin of Qinghai-Tibet Plateau, China: Constraints on the Nature of Mantle Source
- Author(s):
- YAO Jin; LI Shuang-qing; HE Jian-feng; CHEN Fu-kun
- School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China
- Keywords:
- basalt; olivine; mantle; pyroxenite; peridotite; subduction; fractional crystallization; Tengchong block
- PACS:
- P588.14+5；P595
- DOI:
- -
- Abstract:
- Tengchong block, located in the southeast margin of Qinghai-Tibet Plateau, is one of the most important parts of the eastern Tethys tectonic belt. Tectonic activities and strong magmatism have widely taken place in Tengchong block since Cenozoic, and the Cenozoic basalts widely developed in Tengchong block are great objects for studying the current mantle. Major, trace elements and Sr-Nd isotopic compositions of Cenozoic basalts in Tengchong block, and the geochemical compositions of olivines in these basalts were studied to explore the source characteristics of the current mantle in Tengchong block. The results show that the Cenozoic basalts in Tengchong block are enriched in LREE, LILE, Th, U, Pb, Zr and Hf, depleted in Sr, Eu, and they have relatively high N(87Sr)/N(86Sr) (0.705 964-0.706 277) and low N(143Nd)/N(144Nd) (0.512 416-0.512 467) without being significantly assimilated and contaminated during the ascending progress; the magma indicates an enriched mantle, which possibly results from oceanic crust subduction; the olivines have fine crystalline forms and low Fo values, Ni contents and various FeO/MnO ratios, respectively results from the separation and fractional crystallization of olivine in the early stage and the effect of partial melt; the CaO, MgO, FeO contents and FeO/MnO ratios of these basalts all fall into the region of pyroxenite partial melts, and its FC3MS is 0.84-1.17, suggesting that their mantle source is mainly composed of pyroxenite, which may be related to the subduction of oceanic crust and silicate metasomatism.
Last Update: 2018-07-27