Two linear granite belts in the central-western North China Craton and their implication for Late Neoarchaean-Palaeoproterozoic continental evolution

Precambrian granitoid rocks are widely distributed in the North China Craton (NCC). The dominant granitic rocks in the central-westem NCC are trondbjemitic, tonalitic and granodioritic (TTG) gneisses, as well as some calc-alkaline granitic gneisses and minor charnockites. Two linear granite belts in this area are different from other early Precambrian granitic rocks in the NCC in terms of their occurrence and chemistry; the Liang-Tu (LT) garnet granite belt and the Sanggan (SG) granite belt. The LT belt occurs along two large-scale ductile shear zones in metamorphosed Al-rich sedimentary country rocks (khondalitic series). In the central part of the LT belt are metagabbroic granulite lenses that were originally mafic dykes. In the outer part of the belt, garnet granites grade into khondalitic rocks. LT belt granites have geochemical characteristics of S-type granites. The SG granite belt is similar to400 km long and composed of many deformed gneissic granitic bodies and granitic sills and veins with/without gneissosity. They contain various lenses including high-pressure granulites and retrograded eclogites. The SG granite belt trends east-northeast, parallel to the regional gneissosity of the country rocks. Major and trace element geochemistry of these granites shows characteristics of syn-collisional and post-collisional granite. The country rocks beside the Sanggan granite belt are different, including the Huai'an-Fengzhen terrain (HFT) to the northwest and the Wutai-Fuping terrain (WFT) to the southeast. The LT and SG granite belts formed within an old continental craton and an old orogenic zone between two blocks, respectively. (C) 2003 Elsevier B.V. All rights reserved.