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Geochemistry of Neoarchean (ca. 2.55–2.50 Ga) volcanic and ophiolitic rocks in the Wutaishan greenstone belt, central orogenic belt, North China craton: Implications for geodynamic setting and continental growth: Discussion

Guochun Zhao^,1 and Alfred Kröner²

¹ Department of Earth Sciences, University of Hong Kong, Pokfulam Road, Hong Kong
² Institut für Geowissenschaften, Universität Mainz, 55099 Mainz, Germany

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We read with interest the contribution by Polat et al. (2005) on the origin of Neoarchean volcanic and ophiolitic rocks in the Wutaishan greenstone belt, northern China, and their geo-dynamic setting. We do not dispute the quality of the authors' data and their interpretations, but we disagree with their tectonic model, which ignores field evidence and a large amount of precise zircon ages recently obtained for the Hengshan–Wutaishan–Taihangshan mountain belt.

In the model shown in their Figure 9, Polat et al. (2005) proposed a Late Archaean continent–arc–continent collision system, in which the high-grade Hengshan and Fuping complexes represent two exotic 2.7–2.6-Ga microcontinental blocks, and the Wutai granite-greenstone represents an intervening island arc, with the final collision at 2.5 Ga. This model is not supported by recent isotopic data obtained by researchers from China, Australia, and Germany (Wilde et al., 1997, 2004, 2005; Guan et al., 2002; Zhao et al., 2002; Kröner et al., 2005a, 2005b, 2006).

First, recent isotopic data do reveal the existence of 2.82–2.66-Ga continental crust in the Hengshan, Wutai, and Fuping complexes, as indicated by ca. 2.7 Ga medium-grained gray biotite gneisses that occur interlayered with the 2520–2480 Ma Hengshan tonalite-trond-hjemite-granodiorite (TTG) gneisses . . . [Full Text of this Article]