Petrogenesis and metallogenesis of the Taihe gabbroic intrusion associated with Fe–Ti-oxide ores in the Panxi district, Emeishan Large Igneous Province, southwest China Tong Hou a , Zhaochong Zhang a, ⁎, John Encarnacion b , M. Santosh a, c a State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing, 100083, China b Department of Earth and Atmospheric Sciences, Saint Louis University, 3642 Lindell Boulevard, St. Louis, MO 63108, USA c Division of Interdisciplinary Science, Kochi University, Kochi 780-8520, Japan abstract article info Article history: Received 6 February 2012 Received in revised form 25 June 2012 Accepted 18 September 2012 Available online 25 September 2012 Keywords: Taihe Panxi Emeishan Fe–Ti oxide Geochemistry Petrogenesis Metallogenesis The Taihe layered gabbro intrusion in the northernmost part of the Panxi district in southwest China is part of the 260 million year old Emeishan Large Igneous Province. This intrusion hosts a giant Fe–Ti oxide deposit with 810 million tonnes of ore reserves, which makes it one of the largest deposits in the Panxi district. The intrusion covers an areal extent of ~13 km 2 and has a vertical stratigraphic thickness of ~1400 m. It can be divided into a lower zone (LZ) of coarse-grained gabbro, apatite-bearing gabbro, troctolite and intercalated gabbro and clinopyroxene-bearing troctolite, followed upward by a middle zone (MZ) of gabbro and intercalated clinopyroxenite, plagioclase-bearing clinopyroxenite with major oxide layers, and an upper zone (UZ) of olivine gabbro and layered gabbro including unmineralized leucogabbro and melanogabbro, with some small oxide ore bodies in the lower part. Each of these ‘zones’ contains oxide minerals and relatively similar lithologies. Ore tex- tures and associated mineral assemblages indicate that the ore bodies formed by crystallization of Fe–Ti–V-rich melt under high oxygen fugacity and a volatile-rich environment during the late-stage of magmatic differentia- tion. A general systematic variation of major oxides is seen through the intrusion as reflected by a slight overall decrease in MgO and Fe 2 O 3 (as total iron) and an increase in SiO 2 , Na 2 O, Al 2 O 3 , and CaO upward in the layered sequences. Based on lithology and bulk-rock geochemical features, such as positive Eu anomalies, the Taihe in- trusion is inferred to have been derived from a ferropicritic melt and became more evolved in chemistry upward following a tholeiitic differentiation trend with enrichment in Fe, Ti, and V. The Taihe gabbros define a small range of age-corrected ε Nd (t)(t =260 Ma) from -0.6 to 0.7 and ( 87 Sr/ 86 Sr) t ratios ranging from 0.7040 to 0.7050. The relatively lower ε Nd (t) values and higher ( 87 Sr/ 86 Sr) t ratios compared to those from Lijiang picrite which represents the initial product of Emeishan plume head, combined with the enrichment in light rare earth element (LREE) relative to heavy rare earth element (HREE) as well as negative high field strength element (HFSE; e.g., Nb, Ta, Zr, and Hf) anomalies, suggest that subduction-related material was involved in the source region. We propose that the parental picritic magma was generated from the interaction of the ~260 million year Emeishan mantle plume with the lithospheric mantle, and the picritic magma interacted with an eclogitic component in the lithospheric mantle. In our view, the eclogitic component was derived from the earlier Neoproterozoic subduction. The junction of these subduction-modified lithospheric mantle sources and the Emeishan plume was a possible crucial factor leading to the production of large Fe–Ti oxide deposits in the Panxi area. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Magmatic Fe–Ti oxide ores are commonly associated with, or hosted in, layered mafic intrusions or Proterozoic anorthosite complexes (Bateman, 1951; Cawthorn, 1996; Force, 1991; Lister, 1966; Ram Mohan et al., 2012). However, the mechanisms by which millions of tonnes of Fe, Ti and V become concentrated to form massive Fe–Ti oxide deposits remain poorly understood. For example, although strati- form Fe–Ti oxide ores, such as those of the uppermost part of the Bushveld Complex in South Africa and the Bjerkreim–Sokndal in Norway are generally thought to have formed as a result of magma mixing and/or crustal contamination in a dynamic layered intrusion (Cawthorn, 1996), alternative models proposed include gravitational differentiation (Charlier et al., 2006, 2009; Wager and Brown, 1968), in- creasing oxygen fugacity (Botcharnikov et al., 2008; Toplis and Carroll, 1995) and periodic pressure fluctuation (e.g. Cawthorn and Ashwal, 2009). However, the precise mechanisms by which the oxides crystal- lized and accumulated are poorly known. Ore Geology Reviews 49 (2012) 109–127 ⁎ Corresponding author. Tel.: +86 10 82322195; fax: +86 10 82322176. E-mail address: zczhang@cugb.edu.cn (Z. Zhang). 0169-1368/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.oregeorev.2012.09.004 Contents lists available at SciVerse ScienceDirect Ore Geology Reviews journal homepage: www.elsevier.com/locate/oregeorev