https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26273 Hf(t) (-21.2 to 10.5) and δ¹⁸O (4.4‰ to 13.6‰) values. A general negative correlation between them suggests the reworking of old supracrustal materials (average crustal residence age of ca. 2.0Ga) by juvenile mantle-derived magmas. The progression of increasing ε_Hf(t) and decreasing δ¹⁸O values of zircons from the Triassic to the Cretaceous suggests progressive crustal growth during the Mesozoic. The results are consistent with hybridization at an active continental margin. We briefly review tectonic models for the Indosinian orogeny and suggest that the petrologic evidence indicates that Mesozoic magmatism was part of the circum-Pacific accretionary orogens that formed along the continental margin of East Asia no later than ca. 250Ma and continued at least to the late Cretaceous.]]> Sat 24 Mar 2018 07:40:16 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26259 zircon=ca. 11‰; ε_Hf(t)_zircon=ca. -10; Δlog FMQ≤0; Mn in apatite oxybarometer) with rare material input from the mantle. The variation in δ¹⁸O (7.8‰-12.9‰) is more likely a result of hybridization, whereas that in ε_Hf(t) (-31.9 to -1.8) is a result of both hybridization and disequilibrium melting. The variation in mineralogy and geochemistry may be interpreted as a result of entrainment of peritectic garnets from biotite-dehydration melting. Nevertheless, heat input from mantle through basaltic intrusion/underplating is considered to play a major role in high-temperature (>850°C) melting at mid-crustal levels (i.e. the cordierite stable field) for generation of the granitic complex. We interpret that the granites were intruded in a back-arc setting and basaltic magmatism was directly associated with slab roll-back and tearing during the latest Permian and early Triassic times.]]> Sat 24 Mar 2018 07:40:15 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26786 18O=6.8⁰/₀₀-9.4⁰/₀₀) suggest that the Jiufeng pluton was mainly derived from melting of a common metasedimentary source, possibly with a minor basaltic contribution. We consider the geochemical variations of the Jiufeng pluton are primarily a result of incremental assembly of magma batches produced from rapid step-like transition from fluid-saturated to fluid-absent melting of the source. The muscovite granodiorite, with high Na₂O (>3.80wt.%; K₂O/Na₂O=~1), is interpreted to have been produced by fluid-saturated melting at low temperature (~650°C). High P₂O₅ (0.09-0.17wt.%), zircon saturation temperature (T_Zr=769-816°C) and La/Yb ratios (8.4-55.8) of the stage II two-mica granite support its formation from high-temperature (>800°C) biotite-dehydration melting, whereas lower P₂O₅ (<0.02wt.%), T_Zr (685-742°C) and La/Yb (<3) of the stage I two-mica granite suggest its generation at lower temperature, likely by muscovite-dehydration melting. We propose that extensive emplacement of basaltic melts in the lower crust most likely drove the rapid increase of mid-crustal (~20km) temperature (~50°C/m.y.) and widespread crustal melting for the formation of the Jurassic South China LGP. Therefore, formation of the LGP signifies prominent crustal growth as well as crustal reworking in an intraplate setting and was likely a response to flat-slab delamination and foundering.]]> Sat 24 Mar 2018 07:36:22 AEDT ]]>