Na-rich Partial Melts from Newly Underplated Basaltic Crust: the Cordillera Blanca Batholith, Peru

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

“…In southern Lhasa, the candidates for mantle-derived basaltic and crust-derived felsic end-members are most plausibly represented by the 65-40 Ma Linzizong mafic magmas (e.g., Lee et al, 2012;Mo et al, 2007) and the synchronous (45-53 Ma) Gangdese granites (e.g., Ji et al, 2009Ji et al, , 2012Wen et al, 2008a), respectively. However, the ε Nd (t) and ε Hf (t) values of the Napuri adakitic rocks are lower than those of both the felsic and basaltic end-members, Defant and Drummond (1990) and Petford and Atherton (1996). Crystal fractionation paths of the primary minerals are from Castillo et al (1999).…”

Overlapping Sr–Nd–Hf–O isotopic compositions in Permian mafic enclaves and host granitoids in Alxa Block, NW China: Evidence for crust–mantle interaction and implications for the generation of silicic igneous provinces

“…Studies reporting the generation of related felsic magmas (Atherton and Petford, 1993;Petford and Atherton, 1996) are comparatively rare, although basaltic magma underplating (Annen et al, 2006;Li et al, 2014;Petford and Gallagher, 2001) and partial melting of normal (Bryan et al, 2002) or thickened mafic lower crust (Chung et al, 2003;Johnson et al, 1997;Wang et al, 2005Wang et al, , 2006a have been documented in many cases. The difficulties in identifying magmas sourced from such newly-formed mafic rocks likely occur because the volumes of magma are relatively small in volume and may be masked by the predominance of ancient crust-derived magmas or mantle-derived magmas, and/or due to the lack of isotopic contrast between the mantle and the new crustal sources (Frost 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?

“…Fields of adakites inferred to be derived from subducting oceanic crust is after Wang et al (2006). Melts formed by partial melting of the lower mafic crust are from the following references: Atherton and Petford (1993);Chung et al (2003); Johnson et al (1997); Muir et al (1995); Petford and Atherton (1996);Wang et al (2005). (f) Nd-Sr isotope composition for the Early Permian igneous rocks.…”

“…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.…”