Geochronology, geochemistry, and Nd-Hf isotopes of early Palaeozoic-early Mesozoic I-type granites from the Hufang composite pluton, Fujian, South China: crust-mantle interactions and tectonic implications

摘要

The Hufang composite pluton of the Qingliu-Mingxi area of western Fujian is located in the eastern part of the South China Block (SCB). The pluton consists of three granitic intrusions: the Weipu (WP) alkali-feldspar-granite, the Shaxi (SX) biotite-granite, and the Qinxi (QX) alkali-feldspar-granite. Zircon U-Pb ages obtained for the three intrusions are 434 ± 3, 409 ± 3, and 224 ± 2 Ma, respectively, indicating that the Hufang composite pluton is made up of intrusions of both the Caledonian and Indosinian ages. All three intrusive bodies are weakly peraluminous to metaluminous and fall in the high-K calc-alkaline and shoshonite series. They are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and display moderate negative Eu anomalies and roughly flat patterns of heavy rare earth elements (HREEs). Integrated geological and geochemical data suggest that all three granitic intrusions are I-type and were emplaced in post-collisional extensional settings. All of the analysed rocks show homogeneous Nd isotopic compositions, with ϵ_Nd(t) values ranging from −0.25 to +1.32 for the Caledonian SX biotite-granite and from −1.01 to −0.82 for the Indosinian QX alkali-feldspar-granite. However, they display highly variable zircon Hf isotopic compositions, with ϵ_Hf(t) values of −5.9 to +3.8 and −2.4 to +10.2 for the Caledonian WP and SX granites, respectively, and −12.2 to −5.0 for the Indosinian QX granite. These Nd-Hf isotopic characteristics are best explained by binary mixing between juvenile, mantle-derived magma and the evolved crustal components. We suggest that crust-mantle interactions played an important role in the SCB generation of the Caledonian and Indosinian granitoids.View full textDownload full textKeywordsI-type granites, Caledonian, Indosinian, crust-mantle interaction, post-collisional extension, South ChinaRelated var addthis_config = { ui_cobrand: "Taylor & Francis Online", services_compact: "citeulike,netvibes,twitter,technorati,delicious,linkedin,facebook,stumbleupon,digg,google,more", pubid: "ra-4dff56cd6bb1830b" }; Add to shortlist Link Permalink http://dx.doi.org/10.1080/00206814.2010.496542