Two subgroups of A-type granites in the coastal area of Zhejiang and Fujian Provinces, SE China: age and geochemical constraints on their petrogenesis

Abstract

Late Cretaceous (90-100 Ma) A-type granites are widespread in the coastal area of the Zhejiang and Fujian Provinces, SE China. According to mineralogical and geochemical characteristics, the A-type granites in this belt can be further divided into aluminous and peralkaline subgroups. The aluminous subgroup often contains aluminous-rich minerals (e.g. spessartine and Mn-rich muscovite), while the peralkaline subgroup usually contains riebeckite, arfvedsonite and aegirine. Geochemically, the aluminous A-type granites show lower Nb, Zr, Ga, Y and REE abundances, and lower FeO*/MgO and Ga/Al than the peralkaline subgroup. When they occur in the same area, the two subgroups of A-type granites display quite similar initial Nd isotopic compositions, which are indicative of mixing of ancient basement crustal rocks with variable amounts of mantle materials. Integrated geological and geochemical investigations indicate that both the aluminous and the peralkaline magmas are highly evolved and reflect the residual liquids left after high degrees of fractional crystallisation in a deep magma chamber. The present authors suggest that the mineralogical and geochemical differences between the aluminous and peralkaline subgroups are likely to have been generated via different differentiation paths controlled by varying fluorine contents of the parent magmas.

Tectonic significance of the Cretaceous granitoids along the south‐east coast of continental China

“…Although previous studies agreed that the petrogenesis of the coastal granitoids involved significant crustal material, different views exist, including that (a) the granitoids were formed by different degrees of fractional crystallization of magmas produced by crust–mantle interaction (Qiu et al, ; Qiu et al, ); (b) these granitoids were crystallized from magmas formed by the partial melting of prior tonalitic to granodioritic rocks (Zhao, Qiu, Liu, & Wang, ); and (c) mantle‐derived mafic magmas mixed with crust‐derived magmas (Zhao et al, ). However, most of these previous studies focused on single plutons or composite granitoid complexes without along‐coast regional comparison.…”

Geochronological, geochemical and Sr–Nd–Hf isotopic constraints on petrogenesis of Late Mesozoic gabbro–granite complexes on the southeast coast of Fujian, South China: insights into a depleted mantle source region and crust–mantle interactions

“…Other Late Mesozoic granitic rocks, which are widely distributed along the coastal region of South China, also have high ε Nd (t) values (−6.8 to −1.5 for Itypes, and −6.3 to −2.5 for A-types; Huang et al 1986;Jahn, Zhou & Li, 1990;Martin et al 1994;Dong et al 1997;Qiu, Wang & McInnes, 1999;Qiu et al 2004Qiu et al , 2008, implying the involvement of mantle material during their petrogenesis. Other Late Mesozoic granitic rocks, which are widely distributed along the coastal region of South China, also have high ε Nd (t) values (−6.8 to −1.5 for Itypes, and −6.3 to −2.5 for A-types; Huang et al 1986;Jahn, Zhou & Li, 1990;Martin et al 1994;Dong et al 1997;Qiu, Wang & McInnes, 1999;Qiu et al 2004Qiu et al , 2008, implying the involvement of mantle material during their petrogenesis.…”

“…(c) Geological sketch map of the HC complex in the northwestern suburbs of Tong'an, Xiamen (modified after the 1:50 000 geological map of Tong'an Sheet). an emphasis on the significance of the underplating of mantle-derived mafic magmas and crust-mantle interactions (e.g. Wu, 1991;Martin et al 1994;Qiu, Wang & McInnes, 1999;Qiu et al 2004Qiu et al , 2008 or the basic rocks (e.g. However, these earlier studies focused separately on either the acidic (e.g.…”

Whole rock major element influences on monazite growth: examples from igneous and metamorphic rocks in the Menderes Massif, western Turkey

“…9). The peralkaline A-type granites with allanite from SE China average 0.5±0.2 wt% CaO, whereas aluminous granites with monazite average 0.6±0.2 wt% (Qiu et al 2004). Monazite may be present in S-type granites with higher CaO contents, but no correlation is found in A-type lithologies.…”

“…For example, we compare our dataset to A-type granites exposed in eastern China ( Fig. 9; Wu et al 2002;Qiu et al 2004;Xie et al 2006). These A-type granites show an opposite relationship to the Turkish samples in a R1 vs. R2 diagram, with allanite found in rocks with lower R2 values than those with monazite only (258±29 vs. 301±26; Fig.…”