Middle Paleoproterozoic tectonic evolution of the Trans-North China Orogen, North China Craton: Constraint from the intermediate-acid magmatism in the Lüliang area

The excellent middle-Paleoproterozoic tectono-thermal activities from the Lüliang Complex can provide pivotal constraints on the tectonic evolution of the Trans-North China Orogen between Eastern and Western blocks of North China Craton. LA-ICP-MS zircon dating gives emplacement ages of 2189 ± 16 Ma for gneissic diorite, 2188 ± 11 Ma for gneissic quartz monzonite, 2153 ± 9 Ma for gneissic granite in Chijianling area, respectively. The gneissic diorites have high Al2O3 (15.89–16.69 wt%), MgO (3.35–4.96 wt%), low Sr/Y (11.3–16.6), (La/Yb)N (7.40–8.44), enrichment of LILE and depletion in HFSE, especially Nb, Ta, indicating partial melting of mantle wedge fluxed by the fluids. The gneissic quartz monzonites and gneissic granites belong to high K calc-alkaline and shoshonitic series and show right inclined REE patterns, consisting with I-type granite. Zircon Hf and whole-rock Nd isotopic compositions (εHf(t) = +0.1 to +5.3 and − 7.8 to −1.7; εNd(t) = −0.4 to +0.4 and − 1.8 to −0.6) of the gneissic quartz monzonites and gneissic granites are identical to those of dominant Neoarchean basement materials with addition of Mesoarchean vestiges to a certain extent. The diversity of source material (including continental and volcanic arc materials) resembles to magmatism in normal continental arc margins. The spatial distribution, rock assemblage and decreasing rock formation pressure further hint the tectonic transformation from compression to extension regime in local areas. Taking into account the prevalence magmatic records and contemporaneous deposition of middle-Paleoproterozoic in the Trans-North China Orogen, it suggests an active continental arc setting at ~2.2 Ga and local tectonic extension regime with back-arc basin at ~2.1 Ga for a consequence of the Paleoproterozoic subduction between the Eastern block and Western block of the NCC.