Role of mantle-derived magma in genesis of early Yanshanian granites in the Nanling Range, South China: in situ zircon Hf-O isotopic constraints

• Published in: Science China. Earth sciences Vol. 52; no. 9; pp. 1262 - 1278
• Main Authors: Li, XianHua, Li, WuXian, Wang, XuanCe, Li, QiuLi, Liu, Yu, Tang, GuoQiang
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science in China Press 01.09.2009; Springer Nature B.V
• Subjects: China, People's Rep; Continental crust; Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Granite; granites; Hf-O; Igneous rocks; Isotopes; Magma; mantle; Q1; Q3; Sediment pollution; Sediments; SIMS; zircon; mantle; SIMS; zircon; Hf-O isotopes; granites
• ISSN: 1674-7313; 1006-9313; 1869-1897; 1862-2801
• DOI: 10.1007/s11430-009-0117-9

Although a number of petrographic observations and isotopic data suggest that magma mixing is common in genesis of many granite plutons, it is still controversial whether the mantle-derived magmas were involved in granites. We carried out in this study a systematic analysis of in situ zircon Hf-O isotopes for three early Yanshanian intrusions dated at ca. 160 Ma from the Nanling Range of Southeast China. The Qinghu monzonite has very homogeneous zircon Hf-O isotopic compositions, εHf(t) =11.6±0.3 and δ18O=5.4‰±0.3‰. In combination with whole-rock geochemical and Sr-Nd isotopic data, the parental magma of the Qinghu monzonite were likely derived from the partial melting of recently-metasomatized, phlogopite-bearing lithospheric mantle without appreciable crustal contamination. The Lisong and Fogang granites and the mafic microgranular enclaves (MME) within the Lisong granites have a wide range of zircon Hf-O isotopic compositions, with Hf and O isotopes being negatively correlated within each pluton. The Lisong MMEs were crystallized from a mantle-derived magma, similar to the parental magma of the Qinghu monzonite, with small amount of crustal assimilation. The Lisong and Fogang granites were formed by reworking of meta-sedimentary materials by mantle-derived magmas and mixing of the mantle-and sediment-derived melts to varying degrees. It is thus concluded that these two Yanshanian granites in the Nanling Range were formed associated with growth and differentiation of continental crust.