Tectonic transition from subduction to retreat of the palaeo-Pacific plate: new geochemical constraints from the late Mesozoic volcanic sequence in eastern Fujian Province, SE China

Abstract

The widespread occurrence of late Mesozoic volcanic rocks in SE China is associated with widespread mineralization. Most geologists have accepted the model of Pacific plate subduction beneath the eastern Asian continent, but there are still controversies, especially the initial timing of the tectonic transition. In order to understand the tectonic evolution of the palaeo-Pacific plate subduction, an integrated study of zircon U–Pb, Lu–Hf isotope compositions and whole-rock geochemistry was carried out for Mesozoic volcanic rocks in eastern Fujian Province. According to the field observations and zircon U–Pb ages, these volcanic rocks can be divided into three phases: an early stage of Late Jurassic volcanic rocks (Phase 1, 159–153 Ma), a late stage of Late Jurassic volcanic rocks (Phase 2, 152–146 Ma) and an early stage of Early Cretaceous volcanic rocks (Phase 3, 143–139 Ma). Overall, these volcanic rocks are composed of intermediate–acid pyroclastic rocks and lava, with high SiO2, Na2O, K2O and Al2O3 contents, belonging to the high-K calc-alkaline and peraluminous series, with enrichment in large ion lithophile and light rare earth elements but depletion in high-field-strength elements and heavy rare earth elements. However, the Phase 1 and 2 volcanic rocks contain different zircon Hf isotopic compositions and whole-rock geochemistry to the Phase 3 volcanic rocks, implying that they have a different petrogenesis. Our study combined with previous research shows that the decreasing zircon ϵHf(t) values of the Middle–Late Jurassic volcanic rocks indicate a decreasing mantle-derived material contribution. On the contrary, the majority of the Early Cretaceous volcanic rocks have variable ϵHf(t) values, requiring varied degrees of involvement of juvenile components in their origin. Thus, we consider that the Late Jurassic volcanic rocks were generated in a compressional tectonic environment during the early stage (> 146 Ma) of palaeo-Pacific subduction. In contrast, the Cretaceous volcanic rocks were formed in an extensional tectonic setting during a later stage (< 143 Ma) of subduction.

Age, geochemistry, mineralization, and tectonic significance of felsic‐intermediate dikes in Shuangqishan Au deposit, Cathaysia block, South China

“…The shadowing area is the Hf isotopic composition of the cathaysian basement from Xu et al (2007). The ε Hf ( t ) of volcanic rocks in the DYY from Cao et al (2020). The ε Hf ( t ) of volcanic rocks in the Southeast Coast of China from Guo et al (2014), Liu et al (2012, 2016), Duan et al (2015), Zhou et al (2006), Fan et al (2017, 2018), Yan et al (2016, 2018), Zhang et al (2018), and Li et al (2020).…”

“…Intrusive rocks, volcanic rocks, and Au deposits represent the products of the tectonic evolution (Cao et al, 2020; Li & Li, 2007; Mao et al, 2008; Qin et al, 2022; Xing et al, 2021). Different kinds of intrusive rocks control the type of mineralization in southern China, Sn mineralization with aluminous A‐type, I‐type, and S‐type granites (Chen et al, 2014; Jiang et al, 2020; Li et al, 2007; Qin et al, 2022), W mineralization with highly differentiated I‐type and S‐type granites (Guo et al, 2014; Jiang et al, 2020; Qin et al, 2022), Cu‐Au‐Pb‐Zn mineralization is related to I‐type granites (Qin et al, 2022; Wang et al, 2016).…”

Zircon U-Pb Dating, Geochemistry, Lu-Hf Isotope Characteristics, and Geological Significance of Volcanic Rocks in Zhenghe Fozi Mountain National Geopark, Fujian, China

“…This geological process results in the formation of a volcanic-intrusive complex belt along the southeastern coastal area. However, different scholars have slightly varying divisions of the time limits for multiple Yanshanian magmatic activities in South China [18][19][20][21][22][23]. According to the characteristics of volcanic assemblage, the temporal and spatial distributions of volcanic rocks, the regional unconformity, the tectonic setting, and the metallogenic types of volcanic rocks, as stated by Yu et al [23], it can be categorized into three cycles: the first cycle (165-145 Ma), the second cycle (145-115 Ma), and the third cycle (115-85 Ma).…”

Early Paleozoic oceanic slab subduction in South China: Evidence from adakite‐like granodiorite and high‐Mg diorite from Puyang pluton in the Wuyi orogenic belt

“…Because of the high closure temperature of the zircon Hf isotopic system, zircon can record the characteristics of different types of source rocks (Cao et al, 2020;Su et al, 2014). Therefore, the zircon Lu-Hf isotope system has become an important tool to constrain the origin of magmas, especially to decipher processes of crustal evolution and mantle-crust interaction (Griffin et al, 2000(Griffin et al, , 2002.…”