Immiscible hydrous Fe-Ca-P melt and the origin of iron oxide-apatite ore deposits

[en] The origin of iron oxide-apatite deposits is controversial. Silicate liquid immiscibility and separation of an iron-rich melt has been invoked, but Fe-Ca-P-rich and Si-poor melts similar in composition to the ore have never been observed in natural or synthetic magmatic systems. Here we report experiments on intermediate magmas that develop liquid immiscibility at 100 MPa, 1000-1040°C, and oxygen fugacity conditions (fO2) of ΔFMQ = 0.5-3.3 (FMQ = fayalite-magnetite-quartz equilibrium). Some of the immiscible melts are highly enriched in iron and phosphorous ± calcium, and strongly depleted in silicon (<5 wt.% SiO2). These Si-poor melts are in equilibrium with a rhyolitic conjugate and are produced under oxidized conditions (∼FMQ + 3.3), high water activity (aH2O ≥ 0.7), and in fluorine-bearing systems (1 wt.%). Our results show that increasing aH2O and fO2 enlarges the two-liquid field thus allowing the Fe-Ca-P melt to separate easily from host silicic magma and produce iron oxide-apatite ores. © 2018 The Author(s).

Disciplines :

Earth sciences & physical geography

Author, co-author :

Hou, T.; Institute of Mineralogy, Leibniz Universtät Hannover, Hannover, 30167, Germany, State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing, 100083, China

Charlier, Bernard ; Université de Liège - ULiège > Département de géologie > Pétrologie, géochimie endogènes et pétrophysique

Holtz, F.; Institute of Mineralogy, Leibniz Universtät Hannover, Hannover, 30167, Germany

Veksler, I.; GFZ German Research Center for Geosciences, Telegrafenberg, Potsdam, 14473, Germany, Geological Department, Perm State University, Bukireva 15, Perm, 614990, Russian Federation

Zhang, Z.; State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing, 100083, China

Thomas, R.; GFZ German Research Center for Geosciences, Telegrafenberg, Potsdam, 14473, Germany

Namur, Olivier ; Université de Liège - ULiège > Département de géologie > Pétrologie, géochimie endogènes et pétrophysique

Language :

English

Title :

Immiscible hydrous Fe-Ca-P melt and the origin of iron oxide-apatite ore deposits

Publication date :

2018

Journal title :

Nature Communications

eISSN :

2041-1723

Publisher :

Nature Publishing Group, United Kingdom

Volume :

Issue :

Peer reviewed :

Peer Reviewed verified by ORBi

Available on ORBi :

since 15 October 2019

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