Geochemical Characteristics and Its Continental Dynamic Implication of Neoproterozoic Volcanic Rocks in Luding Area of Sichuan, China(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2017年第04期
- Page:
- 459-475
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Geochemical Characteristics and Its Continental Dynamic Implication of Neoproterozoic Volcanic Rocks in Luding Area of Sichuan, China
- Author(s):
- LAI Shao-cong; ZHU Ren-zhi
- 1. State Key Laboratory of Continental Dynamics, Northwest University, Xi’an 710069, Shaanxi, China;2. Department of Geology, Northwest University, Xi’an 710069, Shaanxi, China
- Keywords:
- volcanic rock; geochemistry; continental dynamics; Neoproterozoic; Rodinia supercontinent; Yangtze Block; Sichuan
- PACS:
- P588.1
- DOI:
- -
- Abstract:
- Neoproterozoic volcanic rocks in Luding area of Sichuan, China, belong to the western margin of Yangtze Block, and are the important part of the northern “Xikang-Yunnan axis”. They are exposed in the convergent region between Longmenshan and Xianshuihe fault zones. The results show that the formation age of the volcanic rocks is (772.4±5.5)Ma, belonging to Neoproterozoic; mass fraction of SiO2 is 59.18%-72.44%, and the rock is a set of andesite-dacite-rhyolite of typical high-K calc-alkaline series with magmatic arc generation; the trace and rare earth elements have geochemical characteristics of typical islandarc volcanic rock; Nb and Ta are obviously depleted, and w(Nb)/w(Th), w(La)/w(Nb), w(Ta)/w(Yb) and w(Th)/w(Yb) are 0.72-1.77, 3.12-7.36, 0.13-0.29 and 1.06-5.21, respectively, so that the volcanic rocks are obviously different from the volcanic associations of continental rift-related and mantle plume; N(87Sr)/N(86Sr), N(143Nd)/N(144Nd), N(206Pb)/N(204Pb), N(207Pb)/N(204Pb) and N(208Pb)/N(204Pb) are 0.737 169-0.743 441, 0.512 091-0.512 549, 18.670 1-18.882 3, 15.663 3-15.677 4 and 38.717 2-39.177 4, respectively, and εNd(t) is -2.76-6.00; the tectonic setting in Neoproterozoic is island arc system. The Sr-Nd-Pb isotopic compositions suggest that the original magma should be derived from juvenile reservoir of a subduction zone. The upwelling of mantle material derived by subduction causes the crustal melting of continental marginal arc, and forms the continental marginal arc intermediate-acid volcanic rock association.
Last Update: 2017-07-28