Geochronological and Geochemical Constraints on the Petrogenesis of Early Paleoproterozoic (2.40-2.32 Ga) Nb-Enriched Mafic Rocks in Southwestern Yangtze Block and Its Tectonic Implications

• Published in: Journal of earth science (Wuhan, China) Vol. 31; no. 1; pp. 35 - 52
• Main Authors: Liu, Guichun, Qian, Xin, Li, Jing, Zi, Jian-Wei, Zhao, Tianyu, Feng, Qinglai, Chen, Guangyan, Hu, Shaobin
• Format: Journal Article
• Language: English
• Published: Wuhan China University of Geosciences 01-02-2020; Springer Nature B.V; Guangdong Provincial Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-Sen University,Guangzhou 510275,China; Southern Marine Science and Engineering Guangdong Laboratory,Zhuhai 519082,China%Yunnan Institute of Geological Survey,Kunming 650216,China%State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China; Yunnan Institute of Geological Survey,Kunming 650216,China; School of Resource Environment and Earth Sciences,Yunnan University,Kunming 650091,China%Guangdong Provincial Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-Sen University,Guangzhou 510275,China
• Subjects: Asthenosphere; Biogeosciences; Earth and Environmental Science; Earth Sciences; Enrichment; Geochemistry; Geochronology; Geological surveys; Geology; Geotechnical Engineering & Applied Earth Sciences; Isotopes; Lava; Niobium; Orogeny; Petrogenesis; Petrology and Geochronology; Rock; Rocks; Surveying; Tectonics; Titanium dioxide; Zircon; geochemistry; Nb-enriched rocks; Early Paleoproterozoic; zircon dating; Yangtze Block
• ISSN: 1674-487X; 1867-111X
• DOI: 10.1007/s12583-020-1260-7

Recent geological survey has identified the Early Paleoproterozoic meta-mafic intrusions in the southwestern Yangtze Block. We present geochronological, whole-rock geochemical and Nd isotopic data for these meta-mafic rocks to better address the tectonic evolution of the Yangtze Block during the Early Paleoproterozoic Period. Geochronological data show that the meta-mafic rocks have zircon ages of 2 395-2 316 Ma. They have high TiO
2
contents of 1.40 wt.%3.66 wt.% and Nb concentrations of 13.7 ppm45.5 ppm, thus aregrouped as Nb-enriched mafic rocks. These mafic rocks are characterized by tholeiitic compositions with enrichment of LREEs and LILEs, and can be divided into two groups. Group 1 samples display E-MORB-like geochemical characteristics. Group 2 samples have positive ε
Nd
(
t
) values of 4.0–5.0. Geochemical data indicate that all meta-mafic rocks were likely derived from a depleted asthenospheric mantle. REE modeling indicates lower degree of partial melting for Group 2 samples (3%–10%) relative to Group 1 samples (15%–20%). Taking into account contemporaneous post-collisional granitoids in southwestern Yangtze Block, we propose that these meta-mafic rocks were formed in a post-collisional extension setting. These meta-mafic rocks can be compared with those in Africa, South America and Europe, and might be linked with the Arrowsmith orogenic belt. KEY WORDS: zircon dating, geochemistry, Early Paleoproterozoic, Nb-enriched rocks, Yangtze Block.