Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8911502 | Lithos | 2018 | 52 Pages |
Abstract
The ongoing controversy on the timing of amalgamation of the Yangtze and Cathaysia Blocks (either prior to 890â¯Ma or later than 830â¯Ma) impedes a proper understanding of geological evolution of the South China Block and its role in the breakup of Rodinia supercontinent. In this study, we report ~850â¯Ma LA-ICP-MS zircon UPb ages and whole rock geochemistry of the Dongling granites from the southeastern Yangtze Block that did not receive much geoscientific attention as compared to the better-studied 830-760â¯Ma sedimentary and igneous rocks in the South China Block. The studied Dongling granites have high K2Oâ¯+â¯Na2O (7.44-9.09â¯wt%) and low MgO (0.07-0.54â¯wt%) and CaO (0.16-1.21â¯wt%) contents. Their high FeOT/(FeOTâ¯+â¯MgO) (0.82-0.94) and Ga/Al (> 2.6) values and HFSE abundance (Zrâ¯+â¯Nbâ¯+â¯Ceâ¯+â¯Yâ¯=â¯443-965â¯ppm) allow their grouping as A-type granite. In the chondrite normalized diagrams, these granites display right-inclined REE patterns and strong to moderate negative Eu anomalies (Eu/Eu*â¯=â¯0.32-0.70). The Dongling granites have variable and negative whole-rock εNd(t) (â14.6 to â8.6) and zircon εHf(t) (â12.8 to â4.4) with Paleoproterozoic two-stage Nd (2.20-2.69â¯Ga) and Hf model ages (2.01-2.41â¯Ga). Zircon saturation parameters (TZr) suggest > 850â¯Â°C temperature and other geochemical characteristics reveal low melting pressure (> 350 to <â¯700â¯MPa) and 1.9-2.6â¯wt% H2O content. Geochemical and isotopic characteristics indicate derivation of the Dongling A-type granites by partial melting of an ancient granulitic metasedimentary source, after a previous melt extraction episode. Emplacement of the Dongling A-type granites is inferred in an extensional setting following the arc-continent collision along the southeastern Yangtze Block margin. The oceanic slab continued to subduct underneath the southeastern margin of the Yangtze Block, leading to the extensive 840-820â¯Ma arc-related magmatism and coeval sedimentation. These arc-related igneous and sedimentary rocks indicate that the continental arc systems started from 850â¯Ma, and hint at the collision between the Yangtze and Cathaysia blocks after 850â¯Ma.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Si-Fang Huang, Wei Wang, Jun-Hong Zhao, Jian-Ping Zheng,