The Baima layered intrusion is located in the central part of the Emeishan Large Igneous Province (ELIP). The N-S striking intrusion is similar to 24 km long and similar to 2 km thick and dips to the west. Based on variations in modal proportions and cumulus mineral assemblages, the intrusion from the base to the top is simply subdivided into a lower zone (12) with most of the economic magnetite layers, and an upper zone (UZ) with apatite-bearing troctolite and gabbro. The rock textures suggest crystallization of the Fe-Ti oxide slightly later than plagioclase (An(67-54)) but relatively earlier than olivine (Fo(74-55)), followed by clinopyroxene and finally apatite. 

Relatively low olivine forsterite content and abundant ilmenite exsolution lamellae in clinopyroxene indicate that the Baima parental magma is a highly evolved Fe-Ti-rich magma. Via MELTS model, it demonstrates that under a closed oxygen system, extensive silicate mineral fractionation of a picritic magma might lead to Fe and Ti enrichment and oxygen fugacity elevation in the residual magma. When such Fe-Ti-rich magma ascends to the shallower Baima intrusion, the Fe-Ti oxides may become an early liquidus phase. Well-matched olivine and plagioclase microprobe data with the results of MELTS calculation, combined with relatively low CaO content in olivine (0.02-0.08 wt.%) indicate that wall-rock contamination probably plays a weak role on oxygen fugacity elevation and the early crystallization of Fe-Ti oxides. Several reversals in whole-rock chromium and plagioclase anorthite contents illustrate that multiple recharges of such Fe-Ti-rich magma mainly occurred along the lower part of the Baima magma chamber. Frequent Fe-Ti-rich magma replenishment and gravitational sorting and settling are crucial for the development of thick Fe-Ti oxide layers at the base of the Baima layered intrusion. (C) 2012 Elsevier B.V. All rights reserved.

Publication name	ORE GEOLOGY REVIEWS　Volume: 49　 Pages: 96-108　 Published: DEC 2012
Author(s)	Zhang, Xiao-Qi; Song, Xie-Yan; Chen, Lie-Meng; Xie, Wei; Yu, Song-Yue; Zheng, Wen-Qin; Deng, Yu-Feng; Zhang, Jia-Fei; Gui, Shu-Guang
Corresponding author	SONG Xieyan songxieyan@vip.gyig.ac.cn Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, 46th Guanshui Rd, Guiyang 550002, Peoples R China.

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