Formation of high δ18O fayalite-bearing A-type granite by high temperature melting of granulitic metasedimentary rocks, southern China
Access Status
Authors
Date
2011Type
Metadata
Show full item recordCitation
Source Title
DOI
ISSN
School
Collection
Abstract
The genesis of A-type granites has been controversial. Fayalite granite is a member of the most reduced A-type granites, commonly thought to have been primarily sourced from tholeiitic rocks. In this paper we report petrography, whole-rock geochemistry, Sr-Nd isotope, and in situ zircon Hf-O isotope results for a fayalite-bearing A-type granite suite at Jiuyishan in southern China. High zircon δ18O (8.0‰–9.8‰), negative zircon εHf(t) (–6.2 to –2.3), and evolved whole-rock Sr-Nd isotopes (ISr = 0.7151–0.7181; εNd(t) = –7.4 to –6.6) indicate the reworking of old supracrustal rocks. Isotopic and geochemical results, particularly downward inflections of Zr and Ba at ~70 wt% SiO2, point to fractional crystallization rather than magma mixing as the controlling process for the evolution of the igneous suite. Integrated petrological, geochemical, and isotopic studies present the first convincing case that reduced A-type granites can also be generated by high-temperature (>960 °C) melting of granulitic metasedimentary rocks, likely related to the upwelling of the asthenosphere and/or underplating and intrusion of basaltic melts. We emphasize that key factors for the genesis of this unique rock type are low oxygen fugacity (fO2 ), low fH2O, and high temperature.
Related items
Showing items related by title, author, creator and subject.
-
Huang, Hui-Qing (2012)High-K granites have become volumetrically important since at least Proterozoic. Their study bears important implications to crustal and tectonic evolutions. Despite of intensive research, sources and conditions for the ...
-
Wang, Q.; Wyman, D.; Li, Zheng-Xiang; Bao, Z.; Zhao, Z.; Wang, Y.; Jian, P.; Yang, Y.; Chen, L. (2010)There are widespread Neoproterozoic (830–740 Ma) calc-alkaline intrusive rocks in the South China Block, which has been considered a part of the Precambrian supercontinent Rodinia. The tectonic setting of these rocks, ...
-
Tallarico, F.; Figueiredo, B.; Groves, D.; Kositcin, N.; McNaughton, Neal; Fletcher, Ian; Rego, J. (2005)A striking feature of the Carajs region, Brazil, is the clustering of a variety of different types of Cu-Au deposits.The most abundant in the belt are the >200 million metric tons (Mt) of Fe oxide Cu-Au-(U-REE) deposits, ...