New identification and significance of Early Cretaceous mafic rocks in the interior South China Block

• Published in: Scientific reports Vol. 11; no. 1; p. 11396
• Main Authors: Su, Hui-Min, Jiang, Shao-Yong, Shao, Jia-Bin, Zhang, Dong-Yang, Wu, Xiang-Ke, Huang, Xi-Qiang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 31.05.2021; Nature Publishing Group UK; Nature Portfolio
• Subjects: Cretaceous; Dating; Geochemistry; Isotopes; Lava; Lead; Mesozoic; Rocks; Trace elements; China
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-91045-1

Abstract Early Cretaceous mafic rocks are first reported in the northern Guangxi region from the western Qin-Hang belt in the interior South China Block. A systematic investigation of zircon U–Pb dating, whole-rock geochemistry, Sm–Nd isotopes and zircon Hf–O isotopes for these mafic rocks reveals their petrogenesis and the mantle composition as well as a new window to reconstruct lithospheric evolution in interior South China Block during Late Mesozoic. Zircon U–Pb dating yielded ages of 131 ± 2 Ma to 136 ± 2 Ma for diabase and gabbro from Baotan area, indicating the first data for Early Cretaceous mafic magmatism in the western Qing-Hang belt. These mafic rocks show calc-alkaline compositions, arc-like trace element distribution patterns, low zircon ε Hf ( t ) of − 9.45 to − 6.17 and high δ 18 O values of + 5.72 to + 8.09‰, as well as low whole-rock ε Nd ( t ) values of − 14.27 to − 9.53. These data suggest that the studied mafic rocks are derived from an ancient lithospheric mantle source that was metasomatized during Neoproterozoic subduction. Thus, the occurrence of these mafic rocks indicates a reactivation of Neoproterozoic subducted materials during an extension setting at Late Mesozoic in the western Qin-Hang belt, an old suture zone that amalgamates the Yangtze and Cathaysia blocks.