Tectonic development of the southern Chinese Altai Range as determined by structural geology, thermobarometry,⁴⁰Ar/³⁹Ar thermochronology, and Th/Pb ion-microprobe monazite geochronology

Revisiting the “Irtish tectonic belt”: Implications for the Paleozoic tectonic evolution of the Altai orogen

“…We note that the age obtained in this study is slightly younger compared with the previously reported age of 277-286 Ma (Gong et al, 2007;Briggs et al, 2009 Table 2) suggesting the fractionation/cumulate of chromite, olivine, and clinopyroxene. Large variations in REE contents ( P REE = 1.1-128 ppm) reflect different abundances and compositions of intercumulus liquids.…”

“…Immediately to the northwest of Fuyun County, Briggs et al (2007Briggs et al ( , 2009) documented a series of imbricated thrust faults (Fig. 9).…”

“…Although many studies have been carried out in the Altai orogen (Dobretsov, 2003;Dobretsov et al, 2003Dobretsov et al, , 2004Xu et al, 2003;Niu et al, 2006;Li, 2006;Xiao et al, 2004Xiao et al, , 2008aXiao et al, , 2008bXiao et al, , 2009bBriggs et al, 2007Briggs et al, , 2009Ao et al, 2010;Glorie et al, 2011;Lei et al, 2011), the tectonic history of this region continues to be a topic of debate, particularly focusing on its accretionary history and continental growth ). The two contrasting models for the growth of the Altai orogen are the duplication of a long-lived, single arc subduction (Sengör et al, 1993) versus multiple arc subduction systems (Mossakovsky et al, 1993;Buslov et al, 2001Buslov et al, , 2003Buslov et al, , 2004Xiao et al, 2004;Briggs et al, 2007;Windley et al, 2007;Rojas-Agramonte et al, 2011).…”

Oceanic lithospheric mantle beneath the continental crust of the Chinese Altai

“…Anderson 1994), and local shear deformation of lithosphere could also induce small degrees of partial melting and generate melt passing through the lithosphere (Asmerom et al 2000). Although we cannot preclude the possibility of the first case, the small volume (,0.1 km 2 ) of the Ashele basalt and synchronous shear deformation in the Chinese Altai (Briggs et al 2009) make the second scenario more possible. We therefore suggest that partial melting of the plagioclase peridotite of the accreted oceanic lithospheric mantle, probably induced by large-scale transpressional movement, may have led to the N-MORB-like Ashele basalt.…”

“…Geochemical studies have revealed that the Altai mountain range, at least the portion in China, consists mainly of juvenile materials accreted during the consumption of the Palaeo-Asian Ocean (Sun et al 2008). The Altaids underwent oroclinal bending after the closure of the Palaeo-Asian Ocean (Sengör & Natal'in 1996), and Late Permian to Jurassic tectonothermal events in the Chinese Altai have been widely interpreted as large-scale translation of terranes (Briggs et al 2009). The Chinese Altai is divided into several units (Xiao et al 2004), and the Ashele basalt covers a small area (,0.1 km 2 ) and is located in the Abagong Unit dominated by an accreted Silurian-early Devonian island arc (Fig.…”