Relative contributions of crust and mantle to the generation of the Tianshan Carboniferous rift-related basic lavas, northwestern China

Metasomatized lithosphere–asthenosphere interaction during slab roll-back: Evidence from Late Carboniferous gabbros in the Luotuogou area, Central Tianshan

“…7a-b and 10) and were probably generated by mixing between asthenospheric and enriched lithospheric mantle melts at a relatively shallow depth, mostly within the spinel stability field. This suggests that they have an upper mantle source, which does not support the plume model proposed by Xia et al (2004aXia et al ( , 2008. An olivine addition calculation can be used to extrapolate back to the composition of the parental magma and minimizes the effects of fractionation (Wang et al, 2002).…”

“…At least three competing mechanisms can be envisaged to account for the fact that Tianshan lithosphere was locally thinned to the extent that decompression melting of the asthenospheric mantle could occur: (1) mantle plume ascent; (2) slab break-off in a post-collisional setting; (3) slab roll-back. Xia et al (2004aXia et al ( , 2008 suggested that Carboniferous magmatic rocks in Tianshan Orogen represent a large igneous province related to a mantle plume. In particular, Xia et al (2008) suggested that the Luotuogou mafic rocks occurred in a rift-related setting and were generated by higher degree (10-30%) partial melting of an asthenospheric OIB-like mantle source in the garnet stability field, probably originating from the plume center.…”

“…Xia et al (2004aXia et al ( , 2008 suggested that Carboniferous magmatic rocks in Tianshan Orogen represent a large igneous province related to a mantle plume. In particular, Xia et al (2008) suggested that the Luotuogou mafic rocks occurred in a rift-related setting and were generated by higher degree (10-30%) partial melting of an asthenospheric OIB-like mantle source in the garnet stability field, probably originating from the plume center. However, our study indicates that the Luotuogou gabbros are dissimilar to OIB (Figs.…”

“…The origin of these mafic rocks has been a matter of debate in three competing models: 1) mantle plume or crustal rifting (Che and Liu, 1996;Xia et al, 2004bXia et al, , 2008, which predicts a dominant role for an upwelling deep-seated mantle plume impinging on the lithosphere (Xia et al, 2004b(Xia et al, , 2008; 2) an island arc model, which suggests a subduction of the Paleo-Tianshan Oceanic Plate Zhou et al, 2004;Zhu et al, 2005Zhu et al, , 2009; or 3) a post-collisional model that invokes slab break-off and subsequent asthenospheric upwelling after the collision between the Junggar plate and the Yili terrane (e.g., Han et al, 2010;Yuan et al, 2010). In this study, we determined plagioclase 40 Ar/ 39 Ar ages and undertook whole rock geochemical and Sr-Nd isotope analyses, electron microprobe analyses of clinopyroxene major element compositions and LA-ICPMS clinopyroxene trace element analyses for the Luotuogou gabbros north of Baluntai town in the Central Tianshan Terrane (Fig.…”

Geochronology and geochemistry of the high Mg dioritic dikes in Eastern Tianshan, NW China: Geochemical features, petrogenesis and tectonic implications

“…It is also unlikely that the dioritic dikes in the Kawabulake Group were formed by low-pressure fractional crystallization (AFC) of parental basaltic magma (Castillo, 2006(Castillo, , 2012, as the assumed parental basalt in the study area is characterized by higher Sr-Nd-Pb isotope values (the eNd(t) of Xiaorequanzi basalt a is mostly >3; Xia et al, 2008). The geochemistry of dioritic dikes in the Kawabulake Group is not consistent with the delamination of over thickened lower crust, as magmas derived from the lower crust are commonly characterized by low MgO and Mg# based on experimental results from metabasalts and eclogites Fig.…”