Geochronology and geochemistry of Permian basalts in western Guangxi Province, Southwest China: Evidence for plume-lithosphere interaction Weiming Fan ⁎ , Chunhong Zhang, Yuejun Wang, Feng Guo, Touping Peng Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China Received 25 October 2006; accepted 24 September 2007 Available online 11 October 2007 Abstract The Emeishan flood basalts are part of an important large igneous province (LIP) along the western margin of the Yangtze Block, Southwest China. Mafic rocks interlayered with Permian sedimentary rocks in western Guangxi Province, on the southeastern margin of the Yangtze Block, have SHRIMP zircon U–Pb weighted mean ages of 259.6 ± 5.9 Ma and 259.1 ± 4.0 Ma, identical to mafic plutons associated with the Emeishan basalts. The basaltic rocks, which are SiO 2 -poor, and FeO-, TiO 2 - and P 2 O 5 -rich, geochemically resemble the Emeishan high-Ti basalts. These rocks are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE), and have (Nb/La) n = 0.75–0.94 and (Hf/Sm) n = 0.78–0.90. They are characterized by moderate 86 Sr/ 87 Sr(i) ratios (0.704922–0.705804), intermediate ɛ Nd (t) values (- 0.23 to 1.50), high 206 Pb/ 204 Pb I ratios (18.77–19.67) and prominent positive Δ8/4 (67.7–82.7) and Δ7/4 (0.96–8.19) values. These geochemical signatures are also comparable to the Emeishan high-Ti basalts and the associated high-Ti intrusions in SW China, and might be attributed to low degrees of melting of a garnet-bearing mantle source. The elemental and isotopic compositions suggest that the magma source reservoir may have involved HIMU- and EM1- components, indicative of plume-lithosphere interaction at the periphery of the plume. We propose that these basalts in western Guangxi Province are spatially and temporally associated with the Emeishan LIP and that the Emeishan flood basalts extend over a broader region than previously thought. © 2007 Elsevier B.V. All rights reserved. Keywords: Basalt; SHRIMP zircon geochronology; Permian; Plume–lithosphere interaction; Emeishan large igneous province; Guangxi Province 1. Introduction The Emeishan flood basalt is part of an important LIP covering an area of more than 500,000 km 2 along the western margin of the Yangtze Block, Southwest China (Fig. 1a). The LIP was formed at the Permian and Triassic boundary at about 260 Ma (Yin et al., 1992; Chung and Jahn, 1995; Song et al., 2001; Xu et al., 2001, 2004; Lo et al., 2002; Zhou et al., 2002a,b, 2006; Ali et al., 2004; Guo et al., 2004; Xiao et al., 2004a,b). He et al. (2003, 2006) divided the LIP spatially into 3 zones (Inner, Intermediate and Outer) on the basis of the bio- stratigraphic, sedimentological and geochemical char- acteristics. Previous studies suggested that the Emeishan Available online at www.sciencedirect.com Lithos 102 (2008) 218 – 236 www.elsevier.com/locate/lithos ⁎ Corresponding author. Current address: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, P.O. Box 1131, Guangzhou 510640, PR China. Tel.: +86 20 85290227; fax: +86 20 85291510. E-mail address: wmfan@gig.ac.cn (W. Fan). 0024-4937/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.lithos.2007.09.019