Mafic layered intrusions

The Sept Iles layered intrusion (Canada)

 

The Sept Iles layered intrusion (564 Ma) is located along the St Lawrence rift system and is thought to have been fed by a mantle plume related to the opening of the Iapetus Ocean. With a diameter of 80 km and an estimated volume of 20,000 km3, Sept Iles is considered to be the third largest layered intrusion on Earth. The intrusion is subdivided into three series: (1) the troctolite-gabbro Layered Series; (2) the anorthositic Upper Border Series and (3) the mostly granitic Upper Series. The intrusion results from the crystallization of several pulses of ferrobasaltic magma. The granitic Upper Series has been shown to represent the most evolved residual liquids of the ferrobasaltic differentiation,  while the Upper Border Series was formed by plagioclase flotation to the top of the magma chamber.

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The Skaergaard layered intrusion (Greenland)

 

The Skaergaard Intrusion is one of several Tertiary layered intrusions along the eastern coast of Greenland. It was formed during the formation of the northern Atlantic approximately 60 million years ago, and represents a single pulse of magma injected into the upper crust and stored there. It is unusual in this respect: most other layered intrusions around the World received several different injections of magma over time, which make them more complicated to understand.

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The Bushveld Complex (South Africa)

 

The ~6.5 km thick sequence of ultramafic and mafic rocks of the Bushveld Complex is the largest layered mafic intrusion known on Earth and it crops out in three major areas (limbs) in northern South Africa. Moreover, interpretation of gravity data suggests that the eastern and western limbs are connected over at least 65,000 km2; thus the intrusion can be considered as a large igneous province in its own right. The intrusion was emplaced into the upper crust about 2 billion years ago in several major magma recharge events and it hosts some of the world’s largest and richest orthomagmatic metal deposits.
 

The Panzhihua intrusion (China)

 

Mafic-ultramafic intrusions in the Pan-Xi region (China) include the Panzhihua, Hongge, Baima, Taihe, and Xinjie intrusions. They commonly contain stratiform Fe-Ti oxide ore bodies in the lower parts of the intrusions, or as cyclic units within the intrusions. The Xinjie and Hongge intrusions contain ultramafic portions, whereas the Panzhihua, Baima, andTaihe intrusions are mafic throughout.

These intrusions represent an important Fe-Ti-V resource in China.The total estimated reserve exceeds 6000 Mt of ore with 27-45 wt.% FeO, 11-12 wt.% TiO2, and 0.2-0.3 wt.% V2O5.

 

The Panzhihua layered gabbroic intrusion is a 19 km long sill. The exposed gabbroic cumulates have a maximum thickness of 2 km. The footwall of the intrusion consists of Neoproterozoic dolomitic limestone (Dengying Formation), locally transformed to marble as a result of contact metamorphism. Abundant marble xenoliths close to the basal contact suggest that the Pankhihuamagma was directly emplaced into the carbonate country rocks.

 

The intrusion hosts significant magmatic Fe–Ti–(V) oxide ores in its lower part. The Panzhihua intrusion has been mined for Fe-Ti oxides for more than 30 years and mining activity is still continuing at present.

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Publications

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• Charlier B., Namur O., Latypov R., Tegner C. (2015) Layered intrusions. Springer, 748p

• Namur O., Higgins M.D., Vander Auwera J. (2015) The Sept Iles Intrusive Suite. In: Charlier et al. (Ed). Layered intrusions. Springer, 465-516

• Namur O., Abily B., Boudreau A., Blanchette F., Bush J.W.M., Ceuleneer G., Charlier B., Donaldson C.H., Duchesne J.C., Higgins M.D., Morata D., Nielsen T.F.D., O’Driscoll B., Pang K.N., Peacock T., Spandler C., Toramaru A., Veksler I.V. (2015) Igneous layering in basaltic magma chambers. In: Charlier et al. (Ed). Layered intrusions. Springer, 75-152

• Keevil H., Namur O., Holness M. (2020). Microstructures and Late-Stage Magmatic Processes in Layered Mafic Intrusions: Symplectites from the Sept Iles Intrusion, Quebec, Canada. Journal of Petrology

• Latypov R., Chistyakova S., Gostin G., Namur O., Barnes S., Kruger W. (2020). Monomineralic anorthosite in layered intrusions are indicators of the magma chamber replenishment by plagioclase-only-saturated melts. Scientific Reports.

• Namur O., Humphreys M. (2018). Trace element constraints on the differentiation and crystal mush solidification in the Skaergaard intrusion, Greenland. Journal of Petrology 59, 387-418

• Yuan Q., Namur O., Fischer L.A., Roberts J., Lu X., Holtz F., Charlier B. (2017). Pulses of plagioclase laden magmas and stratigraphic evolution in the Upper Zone of the Bushveld Complex, South Africa. Journal of Petrology 58, 1619-1643

• Fischer L.A., Wang M., Charlier B., Namur O., Roberts J.R., Veksler I.V., Cawthorn R.G., Holtz F. (2016) Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex. Earth and Planetary Science Letters 443, 108-117

• Holness M.B., Tegner C., Namur O., Pilbeam L. (2015) The earliest history of the Skaergaard magma chamber: a textural and geochemical study of the Cambridge drill core. Journal of Petrology 56, 1199-1227

• Latypov R., Morse T., Robins R., Wilson R., Cawthorn G., Tegner C., Holness M., Lesher C., Barnes S. O’Driscoll B. Veksler I., Higgins M., Wilson A., Namur O., Chistyakova S., Naslund R., Thy P. (2015) A fundamental dispute: A discussion of ’On some fundamentals of igneous petrology’ by Bruce D. Marsh, Contributions to Mineralogy and Petrology (2013) 166: 665-690 Contributions to Mineralogy and Petrology 169, 1-10

• Charlier B., Namur O., Bolle O., Latypov R., Duchesne J.C. (2015) Fe-Ti-V-P ore deposits associated with Proterozoic massif-type anorthosites and related rocks. Earth-Science Reviews 141, 56-81

• Namur O., Humphreys M., Holness M. (2014) Crystallization of interstitial liquid and latent heat buffering in solidifying gabbros: Skaergaard intrusion, Greenland. Journal of Petrology 55, 1389-1427

• Holness M., Namur O., Cawthorn R.G. (2013) Disequilibrium dihedral angles in layered intrusions: the microstructural record of fractionation. Journal of Petrology 54, 2067-2093

• Namur O., Humphreys M., Holness M. (2013) Lateral reactive infiltration in a vertical gabbroic crystal mush, Skaergaard intrusion, East Greenland. Journal of Petrology 54, 985-1016

• Namur O., Charlier B., Holness M.B. (2012) Dual origin of Fe-Ti-P gabbros by immiscibility and fractional crystallization of evolved tholeiitic basalts in the Sept Iles layered intrusion. Lithos 154, 100-114

• Namur O., Charlier B (2012) Efficiency of compaction and compositional convection during mafic crystal mush solidification: the Sept Iles layered intrusion, Canada. Contributions to Mineralogy and Petrology 163, 1049-1068

• Charlier B., Namur O., Toplis M.J., Schiano P., Cluzel N., Higgins M.D., Vander Auwera J. (2011) Large-scale silicate liquid immiscibility during differentiation of tholeiitic basalt to granite and the origin of the Daly gap. Geology 39, 907-910

• Namur O., Charlier B., Pirard C., Hermann J., Liegeois J.P., Vander Auwera J. (2011) Anorthosite formation by plagioclase flotation in ferrobasalt and implications for the lunar crust. Geochimica et Cosmochimica Acta 75, 4998-5018

• Namur O., Charlier B., Toplis M.J., Higgins M.D., Hounsell V., Liegeois J.P., Vander Auwera J. (2011) Evolution of a tholeiitic basalt to A-type granite in the Sept Iles layered intrusion, Canada. Journal of Petrology 52, 487-539