Petrogenesis and Tectonic Implications of～2.33 Ga Luobuqigou Diabase-Gabbro in Northern End of Trans-North China Orogen of North China Craton
Zheng Haiping
Jiang Yuqi
Yu Wenming
Jing Guoqing
Xu Hongbo
Lyu Xiaohui
Abstract：The magmatic activities in the Early Paleoproterozoic are of great significance for understanding the tectonic evolution history and geodynamic processes of the Trans-North China Orogen(TNCO)in the North China Craton(NCC).In this study,the Early Paleoproterozoic diabase-gabbro was discovered for the first time in the Luobuqigou area of southern Chifeng at the northern end of the TNCO,and detailed petrography,whole rock geochemistry and zircon U-Pb-Hf isotope geochemistry studies were carried out.Zircon U-Pb isotopic dating reveals that the intrusion age of diabase-gabbro is 2 332 Ma.The geochemical characteristics indicate that the diabase-gabbro belongs to the tholeiitic basalt series.It shows positive anomalies of Rb,Ba,U and Pb,and negative anomalies of Sr,Nb,Th and Y.It has a relatively gentle right-dipping REE distribution pattern,with a weak enrichment of LREE relative to HREE,and the Eu anomaly is not obvious.Zircon εHf(t)value ranging from-4.4 to-0.8,and the single-stage Hf model age tDM1 range from 2 722 Ma to 2 873 Ma.Petrogenetic studies have shown that the diabase-gabbro magma originated from the enriched subcontinent lithosphere mantle with the participation of the asthenospheric mantle.The enriched mantle source is a 10%to 20%partially melted spinel-and garnet-bearing lherzolite mantle.Its magma evolution is dominated by the fractional crystallization of clinopyroxene,followed by olivine and plagioclase,and the influence of crustal contamination was limited.The comprehensive study shows that the～2.33 Ga diabase-gabbro in the Luobuqigou area of southern Chifeng at the northern end of the TNCO during the Early Proterozoic tectono-magmatic lull(TML)period,might beformed in a back-arc extensional rift environment.The study area might have experienced the geodynamic process of asthenosphere upwelling and lithosphere thinning caused by plate rollback.Our research results provide constraints and references for the tectonic evolution of the northern end of the TNCO in the NCC during the Early Paleoproterozoic.
Keywords：Luobuqigou diabase-gabbroEarly Paleoproterozoiczircon U-Pb-Hf isotopesback-arc extensional rift environmentnorthern end of Trans-North China Orogengeochemistry
Publication Date：2025-07-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：24( 2735-2758 )