Neogenic Zircons in Ertix Ductile Shear Zone of Xinjiang and Their Geochronological Significance(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2015年第04期
- Page:
- 15-23
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Neogenic Zircons in Ertix Ductile Shear Zone of Xinjiang and Their Geochronological Significance
- Author(s):
- GAO Jing-gang; LIANG Ting; LI Wen-yuan; ZHOU Yi; WANG Xiao-hu; ZHOU Ru-hong
- 1. Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education, Chang’an University, Xi’an 710054, Shaanxi, China; 2. School of Earth Science and Resources, Chang’an University,Xi’an 710054, Shaanxi, China; 3. Xi’an Center of Geological Survey, China Geological Survey, Xi’an710054, Shaanxi, China; 4. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
- Keywords:
- geochronology; ductile shear zone; zircon; isotopic age; granite; hydrotherm; magma; Xinjiang
- PACS:
- P597
- DOI:
- -
- Abstract:
- Two kinds of zircons from schistosed granitoid rock in Ertix ductile shear zone of Xinjiang are neogenic hydrothermal and residual magmatic. According to the zircon U-Pb concordia diagram with microanalysis data, there are primary magma crystallization age and ductile shear deformed event age, and the latter is distributed on lower intersection in concordia diagram. The primary magma crystallization ages are 329-447 Ma, and the primary magmatic zircons are from Silurian and Devonian rocks of northern Altay belt and also from Carboniferous granites of southern Altay belt; the ductile shear deformed event ages are apparent with 295-305 Ma and 267-286 Ma. Due to the zircon from undeformed regional dike swarm cutting ductile shear zone in Ertix ductile shear zone, SHRIMP zircon U-Pb age is 277-286 Ma, so that the concordia age (295-305 Ma) from deformed zircon concordia diagram is the main age of deformed event of ductile shear zone, and the apparent age of lower intersection model is lower. The neogenic zircon of ductile shear zone is characterized by clear edge of crystal, simple combination (110)+(101), slim columnar, 120° cone apex angle, wide oscillatory zoning and weak cathodoluminescence (CL) intensity, which are significantly different from the primary magmatic zircon. These features are popular in various ductile shear zones of Xinjiang. Two huge ductile shear zones in Late Carboniferous-Early Permian and Late Silurian widely develop in various tectonic belts, so that identifying the hydrothermal zircon of ductile shear zone is important for improving the accuracy of intrusive rock ages.
Last Update: 2015-07-20