Archean geodynamics in the Central Zone, North China Craton: constraints from geochemistry of two contrasting series of granitoids in the Fuping and Wutai complexes

The Archean to Paleoproterozoic Central Zone of the North China Craton is situated between the Eastern and Western Archean continental blocks and contains two contrasting series of Neoarchean granitoids: the 2523-2486 Ma tonalite-trondhjemite-granodiorite (TTG) gneisses in the Fuping Complex, and the 2555-2525 Ma calc-alkaline granitoids (tonalite, granodiorite, granite and monzogranite) in the Wutai Complex. The Fuping TTG gneisses most likely formed from partial melting of similar to2.7 Ga basalts at >50 km, with an involvement of similar to3.0 Ga crustal material. The Wutai granitoids have higher K2O, LILE and Rb/Sr, but lower Sr/Y and La-N/Yb-N than the Fuping TTG gneisses, are characterized by Nd T-DM from 2.5 to 2.8 Ga and epsilon(Nd(iota)) from 0.49 to 3.34, and are derived from partial melting of a juvenile source at < 37 km. The geochemistry of these two contrasting series of Neoarchean granitoids provides further evidence that the Wutai Complex originated and evolved separately from the Fuping Complex. The Wutai Complex most likely formed as an oceanic island arc with volcanism and synvolcanic granitoid intrusions at 2555-2525 Ma. The Wutai Complex was subsequently accreted onto the Eastem Archean Continental Block, and was probably responsible for crustal thickening and TTG magmatism at 2523-2486 Ma in the Fuping Complex (as part of the Taihangshan-Hengshan block), at the western margin of the Eastern Archean Continental Block. (C) 2004 Elsevier B.V. All rights reserved.