Multistage Formation of Neoarchean Potassic Meta-Granites and Evidence for Crustal Growth on the North Margin of the North China Craton
Xiaowei Zhang, Huafeng Zhang, Ying Tong
Journal of Earth Science ›› 2023, Vol. 34 ›› Issue (3) : 658-673.
Multistage Formation of Neoarchean Potassic Meta-Granites and Evidence for Crustal Growth on the North Margin of the North China Craton
The North China Craton (NCC) is one of the most complex cratons in the world. It underwent a series of tectonothermal events during the Neoarchean–Paleoproterozoic. The petrogenesis of potassic granitoids, the timing, and the style of Archean crustal growth are still debated. Systematic field and petrological stdudies on the potassic meta-granites from the Guyang-Chayouzhongqi region were carried out. New U-Pb ages, zircon Lu-Hf isotopic analyses, and whole-rock geochemical data were obtained. Two groups (∼2.7 Ga and ∼2.5 Ga) of potassic meta-granites were recognized. The ∼2.7 Ga meta-granites are mainly A2-type, with variable ε Hf(t) values (−8.4 to +3.3) and Archean one stage model ages (T DM = ∼3.0 Ga), indicating that their source was derived from ancient anatectic TTG-like granite and depleted mantle, which suggests that thin crust had formed in the Guyang-Chayouzhongqi region by ∼3.0 Ga. Similar to the K-rich granites in the NCC, most of the ∼2.5 Ga potassic meta-granites are typical of A1-type granite, and are enriched in Sm and Gd and depleted in Nb, Ta, P, and Ti. The ages and isotopic data indicate that the ∼2.5 Ga meta-granites were generated from juvenile crustal sources with Neoarchean TTGs. The overall zircon U-Pb and Hf isotopic data furthermore suggested that the ∼2.7 Ga event is the most important stage of magmatic accretion in the NCC, similar to other cratons. In contrast, reworking or metamorphic alteration was the main crustal process in the NCC at ∼2.5 Ga.
zircon / U-Pb age / Lu-Hf isotope / geochemistry / potassic meta-granite / crustal growth / North China Craton
|
|
|
|
|
|
|
|
|
Bureau of Geology and Mineral Resources of Inner Mongolia Autonomous Region (BGMRXUAR) Geological Map of Siziwangqi Region (Scale 1: 200 000), 1965, Beijing: National Geological Data Center (in Chinese)
|
Bureau of Geology and Mineral Resources of Inner Mongolia Autonomous Region (BGMRXUAR) Geological Map of Hohhot Region (Scale 1: 200 000), 1966, Beijing: National Geological Data Center (in Chinese)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/
〈 |
|
〉 |