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Liquid immiscibility in the Panzhihua intrusion, SW China: Evidence from ore textures and Fe-Ti oxide-rich globules in gabbros TEXT SIZE: A A A
The Panzhihua intrusion hosts a large Fe-Ti oxide deposit in the Permian Emeishan large igneous province (ELIP), SW China. The mechanism of such massive Fe-Ti oxide accumulation in the layered intrusion is still a matter of debate. In this study, we suggest that the ore formation occurred via density-driven liquid segregation of immiscible Fe-rich liquid, instead of simple mineral sorting of Fe-Ti oxides. Interstitial oxides and kinked plagioclase crystals reveal that the Fe-Ti oxides were crystallized in-situ after their surrounding silicate minerals. Dissolution texture of primocryst plagioclase is ubiquitous in the ores, indicating that the primocryst plagioclase grains were in disequilibrium with the surrounding melt. Fe-Ti oxide-rich globules (similar to 38 wt% FeO) are present in the ore-barren gabbro, and likely represent solidified pockets of the immiscible Fe-rich liquid. Olivine in the Fe-Ti oxide ores occurs as primocrysts (avg. Fo = 68.5) that crystalized before the interstitial Fe-Ti oxides, or as growth rims (avg. Fo = 77.5) that crystalized after interstitial Fe-Ti oxides. The primocryst olivine was likely in equilibrium with the Panzhihua parental magma, and its composition matches well with that of the basalt (Fe2O3T =-16 wt%) exposed near the intrusion. The olivine rim was likely in equilibrium with the residual melt produced from-33% crystallization of the Fe-Ti oxide-rich globule. This study confirms that the ore layers are formed by the sinking of dense immiscible Fe-rich liquid to squeeze out the original silicate melt in the crystal mush, forming the (semi-)massive Fe-Ti oxide layered ores.
 

Publication name

 JOURNAL OF ASIAN EARTH SCIENCES Volume: 209 Article Number: 104683 DOI: 10.1016/j.jseaes.2021.104683 Published: APR 15 2021

Author(s)

 Xiong, Feng; Tao, Yan; Liao, Mingyang; Liao, Yuqi; Ma, Jun

Corresponding author(s) 

 TAO Yan 
 taoyan@vip.gyig.ac.cn  
 Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550081, Guizhou, Peoples R China.

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