Petrogenesis of Yanzhiba Granite in South Qinling: Constraints from Zircon U-Pb Ages, Geochemistry and Sr-Nd-Pb Isotope(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2016年第04期
- Page:
- 527-546
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Petrogenesis of Yanzhiba Granite in South Qinling: Constraints from Zircon U-Pb Ages, Geochemistry and Sr-Nd-Pb Isotope
- Author(s):
- WEI Long-meng; YANG Yi-zeng; ZHANG He; HE Jian-feng; CHEN Fu-kun
- School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China
- Keywords:
- geochemistry; petrogenesis; granite; zircon; U-Pb age; Sr-Nd-Pb isotope; Early Mesozoic; South Qinling
- PACS:
- P588.11
- DOI:
- -
- Abstract:
- Qinling orogenic belt is produced by long-time complicated orogenic processes with widely distributed Neoproterozoic to Mesozoic magmatic activities. Yanzhiba granitic pluton, which is located in the easternmost part of Wulong granitic plutons, is one of the major components of Early Mesozoic magmatism in Ningshan area of South Qinling. Zircon U-Pb dating results and geochemical characteristics of Yanzhiba pluton were reported. Zircon U-Pb dating results of five samples give (202.9±3.5), (201.0±3.0), (202.1±2.6), (200.4±5.4), (205.5±3.3)Ma, respectively. A mean U-Pb age of (201.9±1.5)Ma suggests that Yanzhiba pluton is formed in the middle and late stage of Early Mesozoic Wulong granitic plutons. Yanzhiba granitic pluton is characterized by high silica, alkali-rich, enrichment of large-ion lithophile elements, depletion in high field-strength elements, belonging to weakly peraluminous and high-potassic calc-alkaline series. Initial Sr isotopic composition ranges from 0.704 31 to 0.706 78,εNd(t) values are -5.2--2.0, and initial Pb isotopic composition is relatively high, including that (N(206Pb)/N(204Pb))(t)=17.737-18.191,(N(207Pb)/N(204Pb))(t)=15.511-15.574, and(N(208Pb)/N(204Pb))(t)=37.439-38.071. The high radioactive Pb isotopic composition implies that Yanzhiba granite has the affinity of Yangtze Block. Linear variations of initial Sr isotopic composition and εNd(t) values with the contents of SiO2 suggest that there is assimilation of the surrounding rocks during the rising and emplacement of Yanzhiba granitic magma. The initial Sr-Nd isotopic compositions are similar to those of Neoproterozoic volcanic sedimentary sequences in South Qinling (such as Yaolinghe, Wudang and Bikou Groups). Sr-Nd-Pb isotopic compositions indicate that the magma source of Yanzhiba granite originates from Neoproterozoic crustal materials with an affinity of Yangtze Block.
Last Update: 2016-07-19