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Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe‐Ti‐(V) Oxide Deposit, SW China

Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe‐Ti‐(V) Oxide Deposit,... Dec. 2015 LIU Pingping, ZHOU Meifu, CHEN Weiterry, BOONE Marijn and CNUDDE Veerle, 2015. Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe-Ti-(V) Oxide Deposit, SW China. Acta Geologica Sinica (English Edition), 89(supp. 2): 56. Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe-Ti-(V) Oxide Deposit, SW China LIU Pingping1, ZHOU Meifu1*, CHEN Weiterry1, BOONE Marijn2,3 and CNUDDE Veerle2 1 Department of Earth Sciences,University of Hong Kong, Hong Kong, China 2 Department of Geology and Soil Sciences-UGCT,GHENT University,Krijgslaan 281/S8,900 GHENT,Belgium 3 Unit Sustainable Materials Management,Vito,Mol 2400, Belgium Multiphase solid inclusions within cumulus silicates, particularly olivine, in Fe-Ti oxide ores from the Lower Zone of the Baima intrusion, Emeishan large igneous province, SW China, have been identified for the first time using 2-D scanning electron microscope and 3-D highresolution X-ray computed tomography. These inclusions are spherical to subspherical and range from 100 to 300 μm in diameter. They are composed dominantly of titanomagnetite and ilmenite with minor apatite, hornblende, phlogopite and pyrrhotite. The titanomagnetite in the inclusions has low Cr contents (<700 ppm) similar to the interstitial titanomagnetite, suggesting that these inclusions cannot be early crystallized mineral aggregates. In contrast, the spherical shape of these inclusions provides evidence of early trapped liquids from which these minerals were crystallized. Based on the composition and modal proportions of the daughter mineral phases within the inclusions, the trapped liquids are estimated to have 82.1 to 59.6 wt% FeOT, 11.4 to 18.5 wt% TiO2, 2.69 to 6.12 wt% Al2O3, 1.40 to 4.47 wt% MgO, 0.87 to 4.93 wt% SiO2 and ~1 wt% volatiles including F, S, Cl, P and H2O. Such a liquid composition deviates far from those of the slightly evolved ferrobasaltic magmas parental to Fe-Ti-(V) oxidebearing mafic-ultramafic intrusions of the Emeishan large igneous province. It is thus speculated that these trapped liquids are immiscible Fe-Ti oxide melts formed upon cooling of the ferrobasaltic magmas. The net-textured/ disseminated oxide ores have titanomagnetite compositions similar to those in the inclusions, suggesting that the oxide ores of the Baima intrusion have also formed from the FeTi oxide melts immiscibly separated from the ferrobasaltic magmas. We propose that the immiscible Fe-Ti oxide liquids with high density percolated down through crystalbearing silicate magma and crystallized interconnected FeTi oxide network interstitial to olivine, plagioclase and clinopyroxene. This study highlights that immiscible separation of Fe-Ti oxide liquids from ferrobasaltic magmas is an important mechanism for the formation of magmatic Fe-Ti-(V) oxide deposits hosted in maficultramafic layered intrusions. * Corresponding author. E-mail: mfzhou@hkucc.hku.hk http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Acta Geologica Sinica (English Edition) Wiley

Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe‐Ti‐(V) Oxide Deposit, SW China

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Publisher
Wiley
Copyright
© 2015 Geological Society of China
ISSN
1000-9515
eISSN
1755-6724
DOI
10.1111/1755-6724.12308_35
Publisher site
See Article on Publisher Site

Abstract

Dec. 2015 LIU Pingping, ZHOU Meifu, CHEN Weiterry, BOONE Marijn and CNUDDE Veerle, 2015. Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe-Ti-(V) Oxide Deposit, SW China. Acta Geologica Sinica (English Edition), 89(supp. 2): 56. Using Multiphase Solid Inclusions to Constrain the Origin of the Baima Fe-Ti-(V) Oxide Deposit, SW China LIU Pingping1, ZHOU Meifu1*, CHEN Weiterry1, BOONE Marijn2,3 and CNUDDE Veerle2 1 Department of Earth Sciences,University of Hong Kong, Hong Kong, China 2 Department of Geology and Soil Sciences-UGCT,GHENT University,Krijgslaan 281/S8,900 GHENT,Belgium 3 Unit Sustainable Materials Management,Vito,Mol 2400, Belgium Multiphase solid inclusions within cumulus silicates, particularly olivine, in Fe-Ti oxide ores from the Lower Zone of the Baima intrusion, Emeishan large igneous province, SW China, have been identified for the first time using 2-D scanning electron microscope and 3-D highresolution X-ray computed tomography. These inclusions are spherical to subspherical and range from 100 to 300 μm in diameter. They are composed dominantly of titanomagnetite and ilmenite with minor apatite, hornblende, phlogopite and pyrrhotite. The titanomagnetite in the inclusions has low Cr contents (<700 ppm) similar to the interstitial titanomagnetite, suggesting that these inclusions cannot be early crystallized mineral aggregates. In contrast, the spherical shape of these inclusions provides evidence of early trapped liquids from which these minerals were crystallized. Based on the composition and modal proportions of the daughter mineral phases within the inclusions, the trapped liquids are estimated to have 82.1 to 59.6 wt% FeOT, 11.4 to 18.5 wt% TiO2, 2.69 to 6.12 wt% Al2O3, 1.40 to 4.47 wt% MgO, 0.87 to 4.93 wt% SiO2 and ~1 wt% volatiles including F, S, Cl, P and H2O. Such a liquid composition deviates far from those of the slightly evolved ferrobasaltic magmas parental to Fe-Ti-(V) oxidebearing mafic-ultramafic intrusions of the Emeishan large igneous province. It is thus speculated that these trapped liquids are immiscible Fe-Ti oxide melts formed upon cooling of the ferrobasaltic magmas. The net-textured/ disseminated oxide ores have titanomagnetite compositions similar to those in the inclusions, suggesting that the oxide ores of the Baima intrusion have also formed from the FeTi oxide melts immiscibly separated from the ferrobasaltic magmas. We propose that the immiscible Fe-Ti oxide liquids with high density percolated down through crystalbearing silicate magma and crystallized interconnected FeTi oxide network interstitial to olivine, plagioclase and clinopyroxene. This study highlights that immiscible separation of Fe-Ti oxide liquids from ferrobasaltic magmas is an important mechanism for the formation of magmatic Fe-Ti-(V) oxide deposits hosted in maficultramafic layered intrusions. * Corresponding author. E-mail: mfzhou@hkucc.hku.hk

Journal

Acta Geologica Sinica (English Edition)Wiley

Published: Dec 1, 2015

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