Experimental constraints on the evolution of iron and phosphorus-rich melts: experiments in the system CaO-MgO-Fe2O3-P2O5-SiO2-H2O-CO2

Klemme, Stephan

doi:10.2465/jmps.090311

Cited by 12 publications

(4 citation statements)

References 30 publications

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“…Phosphorus in silicate melts also forms separate clusters that confine iron within stable complexes Fe 3+ (PO 4 ) [86]. It seems likely that structure of the phoscorite melt was constituted by interconnected subnetworks of SiO 4 -tetrahedra and CO 3 -triangles with local domains of PO 4 -tetrahedra and Fe 3+ (PO 4 )-clusters, without a liquid immiscibility [92]. Interaction of this melt with silicate rock launched forsterite crystallization, sometimes with grains of primary "peridotitic" forsterite as seed crystals (Figure 12a).…”

Section: Discussionmentioning

confidence: 99%

Three-D Mineralogical Mapping of the Kovdor Phoscorite–Carbonatite Complex, NW Russia: I. Forsterite

et al. 2018

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The Kovdor alkaline-ultrabasic massif (NW Russia) is formed by three consequent intrusions: peridotite, foidolite-melilitolite and phoscorite-carbonatite. Forsterite is the earliest mineral of both peridotite and phoscorite-carbonatite, and its crystallization governed evolution of magmatic systems. Crystallization of forsterite from CaFe rich peridotite melt produced Si-Al-Na-K-rich residual melt-I corresponding to foidolite-melilitolite. In turn, consolidation of foidolite and melilitolite resulted in Fe-Ca-C-P-F-rich residual melt-II that emplaced in silicate rocks as a phoscorite-carbonatite pipe. Crystallization of phoscorite began from forsterite, which launched destruction of silicate-carbonate-ferri-phosphate subnetworks of melt-II, and further precipitation of apatite and magnetite from the pipe wall to its axis with formation of carbonatite melt-III in the pipe axial zone. This petrogenetic model is based on petrography, mineral chemistry, crystal size distribution and crystallochemistry of forsterite. Marginal forsterite-rich phoscorite consists of Fe 2+-Mn-Ni-Ti-rich forsterite similar to olivine from peridotite, intermediate low-carbonate magnetite-rich phoscorite includes Mg-Fe 3+-rich forsterite, and axial carbonate-rich phoscorite and carbonatites contain Fe 2+-Mn-rich forsterite. Incorporation of trivalent iron in the octahedral M1 and M2 sites reduced volume of these polyhedra; while volume of tetrahedral set has not changed. Thus, trivalent iron incorporates into forsterite by schema (3Fe 2+) oct → (2Fe 3+ +) oct that reflects redox conditions of the rock formation resulting in good agreement between compositions of apatite, magnetite, calcite and forsterite.

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Section: Discussionmentioning

confidence: 99%

Three-D Mineralogical Mapping of the Kovdor Phoscorite–Carbonatite Complex, NW Russia: I. Forsterite

et al. 2018

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“…Formation of phoscorites is a contentious subject with the two leading models suggesting either cumulates from fractional crystallization from carbonatite melts or phoscorite-carbonatite liquid immiscibility. Experiments by Klemme (2010) indicate that an Fe-P-rich melt can crystallize a phoscorite mineral assemblage with the residual liquid resembling carbonatite melts, supporting the fractional crystallization model. However, this model does not explain how an Fe-P-rich melt forms in the first place.…”

Section: Phoscoritesmentioning

confidence: 56%

Introduction

Jeanloz¹

2013

Annu. Rev. Earth Planet. Sci.

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Carbonatites are igneous rocks formed in the crust by fractional crystallization of carbonate-rich parental melts that are mostly mantle derived. They dominantly consist of carbonate minerals such as calcite, dolomite, and ankerite, as well as minor phosphates, oxides, and silicates. They are emplaced in continental intraplate settings such as cratonic interiors and margins, as well as rift zones, and rarely on oceanic islands. Carbonatites are cumulate rocks, which are formed by physical separation and accumulation of crystals that crystallize from a melt, and their parental melts form by either (a) direct partial melting of carbonate-bearing, metasomatized, lithospheric mantle producing alkali-bearing calciodolomitic melts or (b) silicate-carbonate liquid immiscibility following fractional crystallization of carbonate-bearing, silica-undersaturated magmas such as nephelinites, melilitites, or lamprophyres. Their emplacement into the crust is usually accompanied by fenitization, alkali metasomatism of wallrock caused by fluids expelled from the crystallizing carbonatite. Rare earth elements (REE): yttrium and the 14 naturally occurring lanthanides from La to Lu; scandium is not considered a REE Carbonatite system: all igneous and metasomatic rocks, melts, and fluids and their mutual interaction processes and products at any particular carbonatite occurrence Ankerite: in the carbonatite literature, an informal term for any dolomite with substantial Fe contents, including compositions with Mg# > 0.5 [Mg# = Mg/(Mg + Fe)] Natrocarbonatite: an evolved carbonatite melt or rock comprising dominantly alkali carbonates (nyerereite and gregoryite) with halogen enrichmentCarbonatites are major hosts of deposits of the rare earth elements and niobium, and the vast majority of the global production of these commodities is from carbonatites.Carbonatites are igneous rocks formed from carbonate-rich magmas, which ultimately formed in Earth's upper mantle. Carbonatites are associated with economic deposits of metals such as the rare earth elements and niobium, which are essential in high-tech applications. There are more than 600 carbonatites in the geological record but only one currently active carbonatite volcano, Oldoinyo Lengai in Tanzania.

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“…Phoscorites crystallized from mantle-derived melts, and processes such as cumulation, fractional crystallization and liquid immiscibility may play important roles during their formation and evolution. The limited experimental data available are insufficient to establish whether phoscorites formed via fractional crystallization or liquid immiscibility (Klemme, 2010), and future studies are clearly needed to fully understand these exotic rock types.…”

Section: Origin Of Kola Phoscorites and Carbonatitesmentioning

confidence: 99%

"Rare earth elements in phoscorites and carbonatites of the Devonian Kola Alkaline Province, Russia: Examples from Kovdor, Khibina, Vuoriyarvi and Turiy Mys complexes"

Zaitsev

Williams

Jeffries

et al. 2015

Ore Geology Reviews

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The Devonian (ca. 385-360 Ma) Kola Alkaline Province includes 22 plutonic ultrabasic-alkaline complexes, some of which also contain carbonatites and rarely phoscorites. The latter are composite silicate-oxide-phosphate-carbonate rocks, occurring in close space-time genetic relations with various carbonatites. Several carbonatites types are recognized at Kola, including abundant calcite carbonatites (early-and late-stage), with subordinate amounts of late-stage dolomite carbonatites, and rarely magnesite, siderite and rhodochrosite carbonatites. In phoscorites and early-stage carbonatites the rare earth elements (REE) are distributed among the major minerals including calcite (up to 490 ppm), apatite (up to 4400 ppm in Kovdor and 3.5 wt.% REE 2 O 3 in Khibina), and dolomite (up to 77 ppm), as well as accessory pyrochlore (up to 9.1 wt.% REE 2 O 3 ) and zirconolite (up to 17.8 wt.% REE 2 O 3 ). Late-stage carbonatites, at some localities, are strongly enriched in REE (up to 5.2 wt.% REE 2 O 3 in Khibina) and the REE are major components in diverse major and minor minerals such as burbankite, carbocernaite, Ca-and Ba-fluocarbonates, ancylite and others. The rare earth minerals form two distinct mineral assemblages: primary (crystallized from a melt or carbohydrothermal fluid) and secondary (formed during metasomatic replacement). Stable (C-O) and radiogenic (Sr-Nd) isotopes data indicate that the REE minerals and their host calcite and/or dolomite have crystallized from a melt derived from the same mantle source and are co-genetic.

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Experimental constraints on the evolution of iron and phosphorus-rich melts: experiments in the system CaO-MgO-Fe2O3-P2O5-SiO2-H2O-CO2

Cited by 12 publications

References 30 publications

Three-D Mineralogical Mapping of the Kovdor Phoscorite–Carbonatite Complex, NW Russia: I. Forsterite

Three-D Mineralogical Mapping of the Kovdor Phoscorite–Carbonatite Complex, NW Russia: I. Forsterite

Introduction

"Rare earth elements in phoscorites and carbonatites of the Devonian Kola Alkaline Province, Russia: Examples from Kovdor, Khibina, Vuoriyarvi and Turiy Mys complexes"

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