Mesoarchean trondhjemitic continental nucleus and pre-plate tectonic crustal-mantle interactions of the Western Shandong Complex, North China Craton

Abstract

Plate tectonics play an important role in crustal-mantle interactions since late Archean, yet detailed processes of pre-plate tectonic crustal-mantle interactions remain enigmatic. In the Western Shandong Complex of the North China Craton, magmatic rocks recorded successive tectonic transition processes from vertical (plume) to lateral (subduction) during the early Neoarchean. These magmatic records, together with our newly discovered a pre-Neoarchean continental nucleus in the Western Shandong Complex, documented key information on pre-plate tectonic crustal-mantle interactions. In this study, petrology, whole-rock geochemical and Sm–Nd isotopic data, and zircon U–Pb and Lu–Hf isotopes are reported for Neoarchean supracrustal and intrusive rocks for the Western Shandong Complex. Early Neoarchean komatiitic basalts and ultramafic rocks (∼2.77 Ga) were plume-related and generated by crustal contamination of fractional crystallized komatiitic magma. A series of Mesoarchean (∼3.0–2.8 Ga) xenocrystic zircon grains were discovered in the Late Neoarchean charnockites (∼2.56–2.52 Ga), indicating contributions of continental crustal material earlier than regional oldest magmatic records. Based on our new geochronological and geochemical data, a trondhjemitic Mesoarchean (∼3.1–2.8 Ga) continental nucleus was identified and reported for the first time in the Western Shandong Complex. During the early stage of the early Neoarchean, this continental nucleus dismembered during the bottom-up plume processes and the correlated plume-continental nucleus interactions occurred and ubiquitously documented in regional Neoarchean magmatic rocks with different degrees. The plume-continental nucleus interactions consequently resulted in the opening of an oceanic basin and different continental evolutionary processes during the subsequent lateral subduction in the early Neoarchean. The buoyant oceanic plateau was possibly dragged to the trench and blocked subsequent subduction and led to a ∼40 Myr magmatic hiatus between 2.60 Ga and 2.56 Ga.