Early Precambrian geological events in the Zhongtiao Mountain, China: implication for the evolution of Neoarchean to Paleoproterozoic crust in the southern segment of North China Craton
Ruiying Zhang, Yong Sun, Shaohua Zhang
Abstract
Early Precambrian geological events in the Zhongtiao Mountain of China provide important clues for understanding Neoarchean to Paleoproterozoic crustal evolution in the southern segment of North China Craton (NCC). Based on analysis and compare of the component features, spatial and temporal distribution and geochemical features of the crystalline basements in the Zhongtiao Mountain with its surroundings, we identify five distinct episodes of the early Precambrian geological events in the Zhongtiao Mountain as: ca. 2.72–2.61 Ga, ca. 2.56–2.44 Ga, ca. 2.35–2.20 Ga, ca. 2.20–2.0 Ga and ca. 1.97–1.85 Ga. The ca. 2.72–2.61 Ga magmatism mainly involved a significant period of crustal growth with some crustal reworking. These ca. 2.72–2.70 Ga TTG gneisses were produced by partial melting of a subducted oceanic slab, and the ca. 2.62–2.61 Ga granitic rocks were originated from the partial melting of a protolith of juvenile origin (such as the pre-existing ca. 2.72–2.70 Ga TTG suite) together with its intermixing with mantle material. Together with other ca. 2.90–2.61 Ga old rocks in the southern segment of NCC, they made up the ‘Southern Ancient Terrane’. The ca. 2.56–2.44 Ga magmatism represented a major crustal reworking (melting) event with some juvenile addition in the Zhongtiao Mountain, and the formation of TTGs and K-rich granitic rocks during ca. 2.56–2.44 Ga marked a tectono-magmatic event resulting in stabilization of the NCC. The ca. 2.35–2.20 Ga magmatic activities reflected another stage of crustal extension and reworking of the basement rocks. The ca. 2.20–2.0 Ga volcanic-sedimentary rocks, A-type granites, and metamorphic basic volcanic rocks indicated that the stabilized blocks in the NCC still experienced the stage of extension. The ca. 1.97–1.85 Ga magmatic and metamorphic events formed in a phase of compressional deformation and led to the reworking of pre-existed old rocks.