Building the Wutai arc: Insights into the Archean - Paleoproterozoic crustal evolution of the North China Craton

摘要

The Wutai complex is located within the Trans-North China Orogen (TNCO) which marks the collision zone between the Eastern and Western Blocks of the North China Craton (NCC). Here we investigate the timings and mechanisms of Precambrian arc building in Wutai from a suite of newly identified greenstone - felsic tuff - Banded Iron Formation (BIF) - phyllite sequence. Zircon grains from the felsic tuff layer intercalated within the greenstones provide robust constraints on the timing of BIF deposition. Geochemical features of the greenstones and felsic tuff suggest E - MORB and volcanic arc affinity, whereas the BIFs are of submarine hydrothermal origin. Zircon grains in the greenstones define an upper intercept age of 2951 +/- 41 Ma and a lower intercept age of 1845 +/- 190 Ma. Those from the felsic tuff show Pb-207/Pb-206 weighted mean age of 2557 +/- 10 Ma, whereas those from the BIF intercalated with felsic tuff shows an age of 2585 +/- 14 Ma. Metamorphic zircon grains in the BIF define two age populations of ca. 2471 and 1906 Ma. Zircon grains in the phyllite yield an age of 2594 +/- 14 Ma. Kernel density plots define age peaks at 2873 and 2578 Ma marking the major phase of arc building in Wutai. Zircon epsilon Hf (t) values are mostly positive, in the range of 3.15-7.72, suggesting new crustal growth from juvenile/depleted mantle components. Our study provides insights into the Mesoarchean to Neoarchean crust building through subduction-related arc magmatism, followed by Paleoproterozoic metamorphism in the North China Craton.