Geological settings and metallogenesis of high-grade iron deposits in China

Modified magnetite and hydrothermal apatite in banded iron-formations and implications for high-grade Fe mineralization during retrogressive metamorphism

“…Some previous studies have confirmed that the high-grade Fe ores attributed to hypogene hydrothermal enrichment of BIFs (Li et al 2019(Li et al , 2020Sun et al 2020). The two contentious models proposed for the detailed process of high-grade Fe mineralisation by hydrothermal and metamorphic events in the North China are: (1) remobilisation and re-precipitation of iron, i.e., iron is dissolved and migrated by hydrothermal fluids and then precipitated under favourable conditions (Yang et al 2019;Zhang et al 2021); and (2) desiliconization and iron enrichment, i.e., silica is removed from the BIFs by fluids and the residual magnetite remains in situ to form high-grade Fe ores (Zhang et al 2014a(Zhang et al , 2014b(Zhang et al , 2021Li et al 2015a). Furthermore, in situ U-Pb geochronology on monazite and xenotime intergrown with magnetite and hematite has been attempted to date the high-grade BIFhosted mineralisation (Li et al 2015(Li et al , 2016(Li et al , 2019Zi et al 2015Zi et al , 2018.…”

“…The banded iron-formations (BIFs)-hosted iron deposits are one of the important iron resources, with the quantity of both exploitation and resource reserve ranking as the first in the world (Zhang et al 2014a(Zhang et al , 2014b(Zhang et al , 2021Li et al 2015a). The high-grade Fe ores in China only account for less than 2%, which is significantly different from other countries where the high-grade ores are mainly BIFs-type iron ores (Zhang et al 2014a(Zhang et al , 2014b(Zhang et al , 2021Li et al 2015a;2016.…”

“…The banded iron-formations (BIFs)-hosted iron deposits are one of the important iron resources, with the quantity of both exploitation and resource reserve ranking as the first in the world (Zhang et al 2014a(Zhang et al , 2014b(Zhang et al , 2021Li et al 2015a). The high-grade Fe ores in China only account for less than 2%, which is significantly different from other countries where the high-grade ores are mainly BIFs-type iron ores (Zhang et al 2014a(Zhang et al , 2014b(Zhang et al , 2021Li et al 2015a;2016. Most of them are high-grade hematite deposits, with multistage fluids moved downward and leached the BIFs along deformation structures, including the Hamersley Province in Australia and the Quadrilátero Ferrífero region in Brazil (Hagemann et al, 2016;Sheppard et al 2017aSheppard et al , 2017bRasmussen and Muhling 2018;Li et al 2019).…”

“…The different geochemical compositions of the altered and non-altered apatite zones confirm that the Huogezhuang BIFhosted iron deposit has undergone extensive metasomatism, during which some of the apatite grains have been hydrothermally altered.Magnetite-Li et al 2008; Shi et al 2019a Shi et al , 2019bYang et al 2019). The common proposed source of iron is from continents, sites of submarine hydrothermal fluids, and then precipitated under favourable conditions(Yang et al 2019;Zhang et al 2021); and (2) silica is removed from the BIFs by fluids, and the residual magnetite remains in situ to form high-grade Fe ores(Zhang et al 2014a(Zhang et al , 2014b(Zhang et al , 2021Li et al 2015a). An analogy of the deformation of the BIFs in the NCB may help explain whether what is seen in this area is similar to the BIFs in Western Australia Egglseder et al (2017).…”

Characterizing a new type of nelsonite recognized in the Damiao anorthosite complex, North China Craton, with implications for the genesis of giant magmatic Fe-Ti oxide deposits

“…The liquid immiscibility model is supported by the vein/lense-like occurrence, net-texture and simple mineral assemblage of the nelsonite (Chen et al 2013;He et al 2016), but subsequent melting experiments have questioned the existence of silica-free immiscible Ca-Fe-Ti-P nelsonitic melt (Wang et al 2017). Fractional crystallization is generally accepted to have contributed to the formation of large-scale nelsonite bodies, but this process cannot adequately explain the observation that apatite is separated from clinopyroxene that has similar density, but coexists with Fe-Ti oxides that have distinctly different densities (Zhang et al 2021). The role of fractional crystallization and liquid immiscibility in Fe-Ti mineralization remains unclear.…”