Geochronology and Geochemistry of Late Triassic Intrusive Rocks in the Xiuyan Area, Liaodong Peninsula, Eastern North China Craton: Petrogenesis and Implications for Lithospheric Thinning

Abstract

The timing and mechanisms of lithospheric thinning and destruction of the North China Craton (NCC) remain controversial, and the overall geodynamics of the process are poorly understood. This paper documents Late Triassic igneous rocks including monzogranite, gabbro, and diorite from the Xiuyan District on the Liaodong Peninsula in the eastern NCC, which have LA-ICP-MS zircon U-Pb ages of 229.0 ± 0.4 Ma, 216.2 ± 0.9 Ma, and 210.6 ± 2.0 Ma, respectively. Monzogranite shows high-SiO 2 adakite affinity, negative ε Hf (t) values (−20.6 to −17.9), and old T DM2 ages (3.53-3.29 Ga), suggesting that their parental magma was derived from thickened Paleoarchean mafic lower crust and minor mantle materials that were also involved their generation. Gabbro is ultrapotassic, strongly enriched in LREEs and LILEs, depleted in HFSEs, and has evolved zircon Hf isotopes with negative ε Hf of −10.04 to −5.85 and old T DM2 ages (2.59 -2.22 Ga). These are diagnostic signatures of a crustal component, but their high contents of MgO, Cr, Co, Ni indicate that the primary magma originated from enriched mantle. Diorite is enriched in LILEs and LREEs, depleted in HFSEs (with negative Nb, Ta, and Ti anomalies), and contains negative ε Hf (t) values (−13.64 to −11.01). Compared with the gabbro, the diorite is relatively enriched in Nb, Ta and HREEs, and also contains younger T DM2 ages (2.11-1.94 Ga), suggesting that the diorite was formed by mixing between ancient lower crust-derived felsic magmas and asthenospheric mantle-derived magmas. Field observations, geochronology, geochemistry, and zircon Lu-Hf isotopes indicate that Late Triassic magmatism and tectonic activity resulted from deep subduction of the Yangtze Craton beneath the NCC in the Xiuyan area. This phase of tectonic activity was completed in the eastern NCC by the Late Triassic (216 Ma), and was subsequently followed by lithospheric thinning that began in the Late Triassic.

Two periods of magmatism in the Weishancheng ore concentration area, Henan Province: Evidences from zircon U‐Pb chronology, Hf isotopes and petrogeochemistry

“…It records multiple tectonic‐magmatic events from the early Palaeozoic to the Mesozoic. Previous studies indicate primarily two stages of magmatic activity in the Tongbai area (Figure 1): an Early Cretaceous (139–120 Ma; Jiang, Nie, Fang, & Liu, 2009; Chai, 2021; Zhang, 2021; Yang et al, 2021; Niu & Jiang, 2019; Yang et al, 2014) and an Early Silurian to Late Ordovician (444–425 Ma; Jiang, Nie, Fang, & Liu, 2009; Wang, 2014). The Liangwan and Taoyuan plutons are notable features within the Weishancheng ore concentration area.…”

“…Previous studies indicate that both the granite and mafic enclaves of the Liangwan pluton were formed during the same period, between 127 Ma and 137 Ma. For example, Jiang, Nie, Fang, and Liu (2009) reported zircon U‐Pb ages of 132.5 Ma to 137.0 Ma for the monzogranite. Zhang (2021) documented zircon U‐Pb ages of 129–132 Ma for the monzogranite and the mafic enclaves, while Chai (2021) obtained a zircon U‐Pb age of 127 Ma for both the quartz monzonite and mafic enclaves.…”

“…Previous studies have addressed its emplacement period. For example, Jiang, Nie, Fang, and Liu (2009) obtained zircon U‐Pb ages ranging from 426.7 to 470.3 Ma, Wang (2014) documented a zircon U‐Pb age of 443 Ma and Wang et al (2016, 2017) recorded zircon U‐Pb ages ranging from 440 to 444 Ma. Additionally, Gu (2017) constrained the formation age of the Taoyuan Complex ranging from 423.2 to 445.3 Ma.…”

“…The relationship between magma and gold and silver mineralization in the Weishancheng ore concentration area has been a subject of considerable controversy in previous studies. The U‐Pb geochronological results reveal that the intrusion ages of the two plutons are relatively close to the gold and silver metallogenic age (Chai, 2021; Chai et al, 2024; Gu, 2017; Jiang, Nie, Fang, & Liu, 2009; Li et al, 2023; Wang, 2014; Wang et al, 2016, 2017; Zhang, 2021). S‐Pb‐H‐O isotopes indicate that the magmatic intrusion exhibits a certain genesis relationship with gold and silver mineralization in this area, providing lead sources and mineralization materials for the mineralized zone (Chai, 2021; Chai et al, 2024; Li et al, 2009).…”

“…The Liangwan and Taoyuan plutons, two significant plutons in the northwest of the ore concentration area, are spatially adjacent to numerous large‐ and medium‐sized silver polymetallic deposits, including the Poshan silver deposit, Yindongpo gold deposit and Yindongling silver polymetallic deposit (Zhang et al, 2008, 2009, 2011, 2013). Previous studies (Chai, 2021; Gu, 2017; Jiang, Nie, Fang, & Liu, 2009; Wang, 2014; Zhang, 2021) have investigated the intrusion age, petrogenesis and tectonic setting of the two plutons. However, prior research on the plutons in the Weishancheng ore concentration area has been limited to individual plutons, lacking systematic and comprehensive approaches.…”