Geodynamics of paleo‐Pacific plate subduction constrained by the source lithologies of Late Mesozoic basalts in southeastern China

Abstract

Widespread Late Mesozoic volcanic magmatism in southeastern China is generally thought to represent products in response to the subduction of paleo‐Pacific plate; however, it remains unclear when this process began to affect the mantle and the related magmatism. Here we present a systematic study on the source lithology of Late Mesozoic basalts in this area to highlight a link between lithological variations of mantle and subduction process of paleo‐Pacific plate. Late Mesozoic basalts can be subdivided into four groups based on their erupted ages: 178~172 Ma, approximately 150 Ma, 137~123 Ma, and 109~64 Ma. The primary source lithology of these rocks is pyroxenite rather than peridotite, and this mafic lithology can be formed by either ancient or young recycled crustal components. Notably, the source lithology of the approximately 150 Ma and 137~123 Ma basalts is primarily SiO2‐rich pyroxenite, and the former is carbonated. The discovery of carbonated, SiO2‐rich pyroxenite reflects the influence of a recently recycling event in the mantle. The subduction of paleo‐Pacific plate is the most appropriate candidate and can be responsible for the mantle‐derived magmatism after approximately 150 Ma in southeastern China. Therefore, we suggest a paleo‐Pacific slab rollback with increased dip angle as a possible model to control the lithological variations of Late Mesozoic mantle beneath southeastern China.

Magma Mixing in a Granite and Related Rock Association: Insight From Its Mineralogical, Petrochemical, and “Reversed Isotope” Features

“…All these compositional characteristics apply to the Siling gabbro. Its significant depletions in Nb and Ta is, moreover, a characteristic fingerprint of subduction‐zone magmatism (e.g., Duggen et al, ; Zeng et al, ), and its strong enrichment in Pb relative to Ce, and the resulting positive Pb anomalies and low Ce/Pb ratios (3–6), likely reflects the contribution of pelagic sediment in its source (Plank, ). It is therefore concluded that the mafic magma parent of the Siling gabbro was formed through partial melting of a pyroxenite‐bearing enriched SCLM that was previously modified by Neoproterozoic subduction‐related metasomatism (e.g., Wang et al, ).…”

Lithium Isotopic Compositions of Mesozoic and Cenozoic Basalts From South-Eastern China: Implications for Extremely Low δ7Li of Continental-Type Eclogites

“…The Cenozoic and Mesozoic intraplate basalts are sporadically scattered in the Cathaysia Block. These basalts are spatially and temporally associated with the subduction of the Paleo-Pacific Plate and have mixed enriched-mantle Ⅱ (EM2) and depleted mantle sources (Ho et al, 2003;Chen et al, 2008;Zeng et al, 2016). However, compared to fresh Cenozoic basalts, most Mesozoic basalts underwent varying degrees of chloritization and epidotization (Meng et al, 2012;Cen et al, 2016), thus providing an opportunity to study the Li isotopic behavior during low-temperature alteration processes.…”

Zircon U‐Pb Age, Geochemical, and Sr‐Nd‐Pb‐Hf Isotopic Constraints on the Time Frame and Origin of Early Cretaceous Mafic Dykes in the Wuling Mountain Gravity Lineament, South China

“…2. During both the Middle Jurassic (175-170 Ma) and Early Cretaceous (140 Ma,105 Ma,and 90 Ma), strong lithospheric extension took place, which resulted in the emergence of the large number of rift basins, as well the occurrence of extensive magmatism (e.g., the emplacement of mafic dykes and A-type granite, the eruption of basalt, adakite, bimodal volcanic rock, and the development of complex, metamorphic core complexes); large-scale mineralization in extensional setting is also a key product of these activities found across South China (Guo et al, 2001;Deng et al, 2003;Dai et al, 2005;Yan et al, 2005;Dai, 2007;Shen et al, 2008;Wang et al, 2008;Xu et al, 2009;Duan et al, 2011;Li et al, 2012;Qi et al, 2012;Qi et al, 2012Qi et al, , 2016Liu et al, 2012dLiu et al, , 2013Xia et al, 2015;Cen et al, 2016;Zeng et al, 2016;Wang et al, 2005bWang et al, , 2016Pan et al, 2018). Previous studies have shown that subsequent plate convergence during the Indosinian, South China was affected by oblique subduction-dominated tectonics at about 175 Ma, relating to the paleo-Pacific Plate (Deng et al, 2003).…”