Petrogenesis of a Mid-Proterozoic Anorthosite-Mangerite-Charnockite-Granite (AMCG) Complex: Isotopic and Chemical Evidence from the Nain Plutonic Suite

Emslie, R F; Hamilton, Michael A.; Thériault, R. J.

doi:10.1086/629697

Cited by 233 publications

(142 citation statements)

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“…Massif-type anorthosite plutons and associated mangerite, charnockite and (rapakivi) granite (AMCG suite; Emslie, 1978;Emslie et al, 1994) occur in various terranes but are restricted to the Proterozoic ( Fig. 1; Ashwal, 1993Ashwal, , 2010.…”

Section: Spatial and Temporal Distributionmentioning

confidence: 99%

“…1070 Ma. The Nain Plutonic Suite of Labrador, Canada (Emslie, 1978;Emslie et al, 1994;Ryan, 2000;Myers et al, 2008) has no Fe-Ti deposits but hosts the giant Ni-Cu-Co deposit of the Voisey's Bay intrusion (Li et al, 2000). Two important cupriferous deposits related to anorthosites are found in the Koperberg Suite in South Africa (Conradie and Schoch, 1986;Gibson et al, 1996;Clifford et al, 2004;Duchesne et al, 2007) and the Caraiba complex in Brazil (Oliveira and Tarney, 1995;Barnes, 1996, 1999).…”

Section: Spatial and Temporal Distributionmentioning

confidence: 99%

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Fe–Ti–V–P ore deposits associated with Proterozoic massif-type anorthosites and related rocks

Charlier

Namur

Bolle

et al. 2015

Earth-Science Reviews

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a b s t r a c t a r t i c l e i n f oMagmatic rocks containing economic concentrations of iron, titanium, vanadium and phosphorous are commonly associated with massif-type anorthosites and related rocks. This rock association is part of the anorthositemangerite-charnockite-(rapakivi-)granite suites that are restricted to the Proterozoic. Understanding the geochemistry and emplacement mechanisms of ilmenite, magnetite and apatite ore deposits is crucial for exploration, efficient mining operations and ore processing. This review discusses the controlling factors on the grade of an ore, its mineralogy, and its major and trace element distribution. We present petrogenetic models of currently mined deposits (Lac Tio, Tellnes, Damiao) and discuss the characteristics of minor ore bodies from anorthosite provinces worldwide (Grenville, North China Craton, East European Craton, Rogaland, Laramie). Models of formation of anorthosite and related rocks are presented, as well as the nature of the possible parental magmas of the suite. A mineralogical classification of Fe-Ti ores is proposed: (1) Gabbro-noritic ilmenite ore ± apatite ± magnetite; (2) Ti-magnetite-dominated ore; (3) Nelsonite (Fe-Ti oxides + apatite); and (4) Rutile-ilmenite ore. The stability of ilmenite and magnetite is then critically reviewed and the influence of various factors, particularly oxygen fugacity and crystallization pressure, is examined. We discuss liquidus compositions of Fe-Ti oxides and the behavior of important trace elements such as Cr and V, both of which are sensitive to fO 2 variations. Postcumulus evolution of both oxides can occur due to re-equilibration with trapped liquid, re-equilibration with ferromagnesian silicates, exsolution, oxidation, reaction between ilmenite and magnetite, and metamorphic overprinting. These various processes are described and their effects on the oxide geochemistry are emphasized. Several potential ore-forming processes have been invoked and can explain the formation of huge concentration of ilmenite, ±magnetite, ±apatite. Fractional crystallization can be combined with crystal sorting and plagioclase buoyancy to produce relative enrichment of dense ore minerals. Silicate liquid immiscibility can segregate conjugate Si-rich and Fe-rich melts, the latter being enriched in Fe-Ti-P. Magma mixing can produce hybrid magmas located in a single-phase field of the phase diagram and precipitate a pure ilmenite cumulate. Alternative processes are also described, such as ejection of Fe-Ti-enriched residual melts by filter-pressing and compaction, solidstate remobilization of ilmenite in veins, and hydrothermal transport of Fe and Ti from the host anorthosite followed by concentration in veins and lenticular ore bodies. The magnetic properties of Fe-Ti ore deposits present contrasting signatures, depending on whether the natural remanent magnetization is dominated by hemo-ilmenite or multi-domain magnetite. Micro-and macro-scale deformation features of ore rocks are intimately correlated with magma emplacement, and...

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Section: Spatial and Temporal Distributionmentioning

confidence: 99%

Section: Spatial and Temporal Distributionmentioning

confidence: 99%

Fe–Ti–V–P ore deposits associated with Proterozoic massif-type anorthosites and related rocks

Charlier

Namur

Bolle

et al. 2015

Earth-Science Reviews

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“…These or similar reactions explain not only the noritic character of the rock but also an increased content of plagioclase leading to the formation of leucogabbro and anorthosite. Emslie & Hegner (1993), Emslie, Hamilton & Thériault (1994) and Dempster, Preston & Bell (1999) among others have suggested continental crust as a contaminant in anorthosite genesis. Dempster, Preston & Bell (1999) concluded that 'underplating basalts and juvenile undifferentiated lower crustal rocks are the key to the anorthosite problem'.…”

Section: B Constraints From the Major Element Compositionsmentioning

confidence: 99%

“…Emslie, Hamilton & Thériault, 1994;Andersson, 1997b). Lindh & Johansson (1996) noted that the rapakivi granite is low in alumina leading to the formation of clinopyroxene and hornblende instead of biotite as mafic phases.…”

Section: C Constraints From the Trace Element Compositionmentioning

confidence: 99%

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Evidence of crustal contamination of mafic rocks associated with rapakivi rocks: an example from the Nordingrå complex, Central Sweden

Lindh¹,

Andersson

Lundqvist

et al. 2001

Geol. Mag.

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Gabbro and leucogabbro are volumetrically important rocks in the Nordingrå rapakivi complex, East Central Sweden. Plagioclase, ortho- and clinopyroxenes, and olivine dominate the gabbro. Perthitic orthoclase and quartz are interstitial in relation to the major minerals. The present work is based on 232 major-element and a large number of trace element analyses together with 15 whole rock Sm–Nd isotope analyses of the Nordingrå gabbroic rocks. εNd(T) values are negative, −1.1 to −3.2; the most negative values come from the gabbro. Most rocks are enriched in iron, some extremely enriched; none represent primitive mantle melts. The range of Mg-numbers is the same in the gabbro and the leucogabbro. Plots of the Ni-content vs. the Mg-number are scattered, but there is a positive correlation between these two parameters. The primary mantle-normalized ratios between similar trace elements are normally strongly different from one. Values larger as well as smaller than one are found for the same ratio in different rocks. The rare earth elements are only weakly fractionated with small Eu anomalies, negative for the gabbros and positive for the leucogabbros. The primary magma of the Nordingrå gabbro-anorthosite is thought to have been derived from a mildly depleted mantle source. Variations in the degree of partial melting of a reasonably homogeneous enriched mantle do not explain the observed chemical evolution. Crystal differentiation can account for some geochemical features, especially the Fe-enrichment. Crustal contamination is required by other characteristics as, for example, the negative εNd(T) values and the irregular and sometimes high primary-mantle normalized incompatible trace-element ratios. Al-rich relic material from the formation of the rapakivi granite melt is another source of assimilation. Most probably contaminants are heterogeneous, including undepleted crust (represented, for example, by early Svecofennian and Archaean granitoids), depleted crust (restitic after rapakivi magma extraction), and to some degree the associated rapakivi magma itself. Significant parts of this crust should be Archaean in age.

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An investigation of Fe‐Ti, V in the north‐east Karbi Hills, Shillong Plateau, north‐east India: Implication for mineralization

2021

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The Kulamati gabbro-anorthosite complex in the Karbi Hills of the Shillong Plateau, north-east India is a newly discovered stratified Fe-Ti-V-bearing magmatic body that has been classified as a titano-magnetite ore. The host gabbro-anorthosite is found intruded into the Mesoproterozoic Shillong Group. The stratified Fe-Ti-V oxide body consists mostly of magnetite-rich and magnetite-poor layers. The magnetite-rich bands are composed of titanomagnetite, haematite, ilmenite, and coulsonite with minor Alspinel, while the mineral constituents of silicate bands contain plagioclase, clinopyroxene, olivine, apatite, and chlorite. Titaniferous magnetites display a wide variety of subsolvus features, including Al-spinel-magnetite-ulvöspinel exsolutions and crystallographically oriented ilmenite exsolutions, but magnetites are exclusively vanadiferous. Comprehensive chemical analyses show that the ore is rich in TiO 2 (10.98-12.78 wt%) and V 2 O 5 (1.32-1.47 wt%). Ti is attributed by the presence of rutile, titanite, and ilmenite, while V is attributed by coulsonite as a solid solution component in the titanomagnetite. It records moderate to high Al 2 O 3 (4.51-5.46 wt%), with enrichment of FeO and Fe 2 O 3 (26.22-28.32 wt% and 39.34-42.86 wt%, respectively), which can be attributed to the presence of magnetite-spinel-ulvospinel. Higher Fe 2 O 3 and lower FeO are indicative of oxidizing conditions of the ore-forming environment. The rare earth element (REE) patterns have (La/Yb) N and (Ce/Yb) N ratios comparable to an evolved basaltic melt, with light REE being enriched compared to heavy REE and a positive Eu anomaly. The electron probe micro analyser data of magnetite is conformable with the bulk chemistry, and shows consistently high FeO (70.87-88.06 wt%), Cr 2 O 3 (1.02-2.44 wt%), TiO 2 (0.16-6.20 wt%), and V 2 O 3 (1.47-2.26 wt %), with trace amounts of Al, Si, Mg, Mn, and PGE. As per targeted parameters, the ore occurrence distinctly belongs to a stratified Fe-Ti-V class, where alternate thick (>1.0 m) and thin (<20 cm) strata resulted from the late magmatic crystallization of the original tholeiitic composition.

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Petrogenesis of a Mid-Proterozoic Anorthosite-Mangerite-Charnockite-Granite (AMCG) Complex: Isotopic and Chemical Evidence from the Nain Plutonic Suite

Cited by 233 publications

References 29 publications

Fe–Ti–V–P ore deposits associated with Proterozoic massif-type anorthosites and related rocks

Fe–Ti–V–P ore deposits associated with Proterozoic massif-type anorthosites and related rocks

Evidence of crustal contamination of mafic rocks associated with rapakivi rocks: an example from the Nordingrå complex, Central Sweden

An investigation of Fe‐Ti, V in the north‐east Karbi Hills, Shillong Plateau, north‐east India: Implication for mineralization

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