Nature and origin of A-type granites with particular reference to southeastern Australia

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

“…Although many~280 Ma granitoids have been reported in the Alxa Block, no A-type granitoids have been identified in previous studies. In general, A-type granites are comparatively enriched in high field strength elements (HFSEs), such as Zr, Nb, Y, REE and Ga (e.g., Collins et al, 1982;Eby, 1992;King et al, 1997King et al, , 2001Sylvester, 1989;Whalen et al, 1987;Yang et al, 2006). In this study, a few granites in the Bayannuoergong batholith have the characteristics of A-type granites.…”

“…The origins of A-type granites have been attributed to: (1) direct fractionation of mantle-derived alkaline basalts (e.g., Mushkin et al, 2003;Turner and Rushmer, 2009;Turner et al, 1992); (2) partial melting of crustal materials at high temperature (e.g., Collins et al, 1982;King et al, 1997;Wang et al, 2010a) and (3) hybridization between anatectic crust-derived felsic and mantle-derived mafic magmas (e.g., Kerr and Fryer, 1993;Mingram et al, 2000;Yang et al, 2006). The absence of any mafic microgranular enclaves in the A-type pluton does not support the generation of these A-type granites by mixing of mantle-derived mafic magma and crustal-derived silicic melts.…”

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

“…Collins et al 1982;Clemens et al 1986;Whalen et al 1987;Creaser et al 1991;Landenberger and Collins 1996). Proposed source compositions that have been favored are lower crust, including tonalite, granodiorite, peraluminous granulite, charnockite and granulitic residuum from melting of I-type granites.…”

“…The elevated contents of alkalis and fluorine in these magmas, as indicated by modal fluorite and high Na 2 O+K 2 O in these rocks, increase the solubility of HFSE by promoting formation of polymeric alkali-silicate complexes and/or alkali-fluoride complexes Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, Saudi Arabia 277 with these metals (Watson 1979;Collerson 1982;Collins et al 1982). The effects of fluorine in granites is well known and it is suggested that the F-rich fluid could produce HREE and HFSE enrichment in the late stages of evolution of granitic melt due to F complexing (Dingwell 1988;Rogers and Satterfield 1994).…”

Petrogenesis of the Early Cretaceous Tiantangshan A‐type Granite in northwestern Guangdong province, SE China and tectonic implications

“…Collins et al, 1982;Eby, 1992;Jiang et al, 2002;Whalen et al, 1987). The Tiantangshan quartz porphyries also show similar geochemical characteristics of A-type granites affinity.…”