Early Cretaceous adakitic granites in the Northern Dabie Complex, central China: Implications for partial melting and delamination of thickened lower crust

Petrogenesis of the Early Eocene adakitic rocks in the Napuri area, southern Lhasa: Partial melting of thickened lower crust during slab break-off and implications for crustal thickening in southern Tibet

“…5 and 6). In addition, these samples also show low Mg # values ranging from 36.4 to 49.6, similar to those (Mg # b 50) of adakitic rocks derived by partial melting of the mafic lower crust (e.g., Atherton and Petford, 1993;Wang et al, 2007).…”

“…In view of the above discussion, and the observation that the high K 2 O contents, low MgO, Cr, Ni contents and Mg # values of the Napuri adakitic rocks are similar to those of thickened lower crust-derived adakitic melts ( Fig. 4; Atherton and Petford, 1993;Chung et al, 2003;Wang et al, 2007), we suggest that the Napuri adakitic rocks were most probably generated by partial melting of the continental mafic lower crust.…”

“…Recent studies have shown that adakitic rocks can alternatively be generated by partial melting of mafic lower crust (Atherton and Petford, 1993;Chung et al, 2003Chung et al, , 2009Wang et al, 2007) but the depletion in Y and Yb requires deep crustal melting with garnet as a stable residual phase in their sources (e.g., Atherton and Petford, 1993;Chung et al, 2003Chung et al, , 2009Wang et al, 2007). Thus, such lower crust-derived adakitic rocks have the potential of tracing the presence of anomalously thick continental crust under the Tibetan plateau (e.g., Chung et al, 2003Chung et al, , 2005Chung et al, , 2009Guan et al, 2012;Guo et al, 2007;Hou et al, 2004Hou et al, , 2012Ji et al, 2012 and references therein), and even Cretaceous plateau formation in eastern China (e.g., Zhang et al, 2001).…”

An Early Permian (ca. 280Ma) silicic igneous province in the Alxa Block, NW China: A magmatic flare-up triggered by a mantle-plume?

“…Thus, they should be classed as high Sr/Y granites (Moyen, 2009). Several models have been proposed for the generation of high Sr/Y granitoids, including (a) melting of subducted young and hot oceanic crust (Defant and Drummond, 1990;Kay et al, 1993;Martin et al, 2005;Stern and Kilian, 1996;Tang et al, 2010a;Wang et al, 2007aWang et al, , 2008; (b) assimilation and fractional crystallization (AFC) or fractional crystallization (FC) from parental basaltic magmas (Castillo et al, 1999;Macpherson et al, 2006;Richards and Kerrich, 2007;Rooney et al, 2011); (c) magma mixing between felsic and basaltic magmas (Guo et al, 2007;Streck et al, 2007); and (d) partial melting of thickened lower crust (Atherton and Petford, 1993;Chung et al, 2003;Petford and Atherton, 1996;Wang et al, 2005Wang et al, , 2007b.…”

“…Partial melting of a thickened garnet-bearing mafic lower crust due to heat flux from the mantle (e.g., Atherton and Petford, 1993;Wang et al, 2005Wang et al, , 2007b) is a plausible mechanism for the generation of the high Sr/Y granodiorites. If the high Sr/Y magmas are actually derived from the mafic lower crust, then they should have relatively low MgO contents and be compositionally similar to 1-4.0 GPa experimental melts of metabasalts.…”