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Zircon U-Pb Ages and Hf-isotope Compositions of Granitic Gneisses from the Susong Metamorphic Zone in the Dabie Orogen, China(PDF)

《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]

Issue:
2018年第01期
Page:
61-75
Research Field:
基础地质与矿产地质
Publishing date:

Info

Title:
Zircon U-Pb Ages and Hf-isotope Compositions of Granitic Gneisses from the Susong Metamorphic Zone in the Dabie Orogen, China
Author(s):
LI Yuan LIU Yi-can YANG Yang DENG Liang-peng
1. Key Laboratory of Crustmantle Materials and Environments, Chinese Academy of Sciences, Hefei 230026, Anhui, China; 2. School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China
Keywords:
granitic gneiss SHRIMP dating zircon UPb age continental rifting Susong metamorphic zone Dabie orogen
PACS:
P597
DOI:
-
Abstract:
The Susong metamorphic zone is a relatively lowgrade metamorphic unit, located in the southern part of the Dabie collisional orogen, China. This zone is mainly composed of mica-quartz schist, granitic gneiss, meta-basalt/amphibolite, meta-gabbro, rodingite, marble, graphite schist and phosphate rock series, etc. However, the forming ages and petrogenesis of these rocks are still largely controversial. For this reason, the zircon SHRIMP U-Pb dating and Hf isotope analysis on granitic gneisses from the Susong metamorphic zone in the Dabie orogen were performed. The zircon dating results reveal that the precursor ages of these granitic gneisses can be divided into two types, i.e. Late Archean (2.5-2.7 Ga) and Neoproterozoic (770-830 Ma), and that they experience epidote amphibolitefacies metamorphism in Late Triassic. The protoliths of Neoproterozoic granitic gneisses are derived from remelting of the Late Archean rocks with ~2.0 Ga metamorphic overprinting during Neoproterozoic continental breakup. In view of the agreement of Neoproterozoic igneous zircon age records of granitic gneisses with the protolith ages of Dabie ultrahighpressure metaigneous rocks, combined with their metamorphic characteristics, published data and regional geological setting, the granitic gneisses from the Susong metamorphic zone are further documented to be involved in Triassic subduction of the Yangtze Block and underwent epidote amphibolite-facies with possibly local highpressure eclogite-facies metamorphism, and then detached and offscraped from the subducting crust of the Yangtgze Block at shallow depths. Because of thrusting up, nappe, tectonic stack and erosion after continental collision and orogenesis, the relatively deeply subducted rocks may have been mixed into the Susong metamorphic zone.

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Last Update: 2018-03-08