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

Published online by Cambridge University Press:  26 July 2007

Jian-Sheng Qiu
Affiliation:
State Key Laboratory for Mineral Deposit Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China. e-mail: jsqiuwyh@public1.ptt.js.cn
De-Zi Wang
Affiliation:
State Key Laboratory for Mineral Deposit Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China. e-mail: editors@public1.ptt.js.cn
Brent I. A. McInnes
Affiliation:
CSIRO Exploration & Mining, Australian Resources Research Centre, Kensington, WA 6151, Australia. e-mail: brent.mcinnes@csiro.au
Shao-Yong Jiang
Affiliation:
State Key Laboratory for Mineral Deposit Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China. e-mail: shyjiang@public1.ptt.js.cn
Ru-Cheng Wang
Affiliation:
State Key Laboratory for Mineral Deposit Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China. e-mail: rcwang@nju.edu.cn
Satoshi Kanisawa
Affiliation:
Institute of Mineralogy, Petrology and Economic Geology, Graduate School of Science, Tohoku University, Sendai 980–8578, Japan. e-mail: kanisawa@mail.tains.tohoku.ac.jp

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.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 2004

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