El Laco

El Laco is a volcanic complex in the Antofagasta Region of Chile. It is directly south of the Cordón de Puntas Negras volcanic chain. Part of the Central Volcanic Zone of the Andes, it is a group of seven stratovolcanoes and a caldera. It is about two million years old. The main summit of the volcano is a lava dome called Pico Laco, which is variously reported to be 5,325 metres (17,470 ft) or 5,472 metres (17,953 ft) high. The edifice has been affected by glaciation, and some reports indicate that it is still fumarolically active.

El Laco
The conical summit to the right is named Pico El Laco. The black zones to the left of it are Cerro Laco Sur and Cerro Laco Norte. The image shows only about half of the volcanic complex.
Highest point
Elevation5,325 m (17,470 ft)
Coordinates23°50′29.6″S 67°29′24.6″W[1]
Geography
El Laco is located in Chile
El Laco
El Laco
Location of El Laco

The volcano is known for its magnetite-containing lava flows of enigmatic origin. In total, there are four lava flows and two dykes, as well as a formation of uncertain nature. In addition to lava flow structures, pyroclastics containing iron oxide are also found within the complex. The magmas formed within a magma chamber with a volume of about 30 cubic kilometres (7.2 cu mi);[2] whether the iron-rich lavas are native magnetite lavas or were formed by hydrothermal processes acting on regular rock is under debate. After their discovery in 1958, these iron deposits have been mined. Similar deposits of volcanic iron oxide exist in Australia, Chile, and Iran.

Geography

El Laco is part of the Cordón de Puntas Negras sector of the Central Volcanic Zone,[3]: 681,682  directly south of that volcanic chain.[4] It sits atop a quartzite and sandstone basement that was lifted from the seaground during the Acadian orogeny and is of Ordovician age. Later, Mesozoic and Cenozoic sedimentation occurred, which was then buried by Tertiary rhyolites.[3]: 681,682  Two major volcanic lineaments cross in the El Laco area,[5] including the so-called Calama-Olacapato-El Toro lineament.[6] El Hueso volcano to the north is 5,028 metres (16,496 ft)[7]-5,029 metres (16,499 ft) high and has a basement diameter of 2.5 kilometres (1.6 mi). It has a crater with a diameter of 1 kilometre (0.62 mi).[8]

The city of Antofagasta is located 320 kilometres (200 mi) west of El Laco.[3]: 681  Other close towns are Calama and San Pedro de Atacama. The international road through Sico Pass[9] connecting Salta in Argentina with Calama in Chile runs close to El Laco. A number of tourist sites are found in the Atacama Desert adjacent to El Laco, and the dry climate also makes the area suitable for astronomy facilities.[10]

Geology
Geological map of El Laco

The El Laco volcanic complex is formed by about seven minor stratovolcanoes and lava domes.[11] The complex started its activity in the Miocene-Pliocene, when porphyric andesites formed a stratovolcano. During the Pliocene, ash and pyroclastic eruptions formed a caldera with a diameter of 4–5 kilometres (2.5–3.1 mi), which also contains a central lava dome that formed 6.5 million years ago. Finally, probably during the Pleistocene, five iron-rich magmas were extruded, named Laco Sur, Laco Norte and Rodados Negros. Laquito and Cristales Grandes, two abyssal iron magma structures, date back to that era.[3]: 682–684  The volcanic complex is located an altitude of 4,300–5,470 metres (14,110–17,950 ft) and covers a surface area of 7 by 5 kilometres (4.3 mi × 3.1 mi)[12] with a minimum volume of 14 cubic kilometres (3.4 cu mi) of volcanic rock.[13]

The main summit, Pico Laco[10] or Pitón El Laco,[13] has an altitude of 5,325 metres (17,470 ft),[10] although a maximum height of 5,472 metres (17,953 ft) has also been reported.[14] Pico Laco is an andesitic lava dome with a height of 400 metres (1,300 ft) above the surrounding terrain. The dome, with dimensions of 1.5 by 1 kilometre (0.93 mi × 0.62 mi), has two summits: the higher eastern one and a 5,166-metre (16,949 ft) western summit,[8] and has also been described as a volcanic plug.[13] Pico Laco has been described as a resurgent volcano within a caldera, that is surrounded by secondary vents.[6]

Other summits include the northwestern Hueso Chico, a cone with a height of 120 metres (390 ft) above its surroundings and a crater 250 metres (820 ft) wide. This cone is of dacitic composition. "Volcano 5009" is heavily eroded, and its core of lava and hyaloclastite has been exposed. It has a diameter of 2.5 kilometres (1.6 mi). Eruptive activity here probably coincided with glacier activity during the Pliocene, as evidenced by moraines in the area.[8]

Ages of 10.5[9] to 1.6 mya have been estimated via potassium-argon dating of the andesite lavas and subvolcanic rocks. An age of 5.3±1.9 mya on lavas in the northern part of the volcanic complex is the oldest obtained date. Other dating has resulted in ages of 3.9±1.3 mya for Pico Laco's dome, 3.8±0.9 mya for lavas beneath San Vicente Bayo, 3.7±0.9 mya for a lava front next to Laco Norte, 2.6±0.6 for Crystales Grandes, 2.1±0.4 for Hueso Chico, and 1.6±0.5 for "Volcano 5009". Cordon de Puntas Negras has younger dates.[8] Another date from Pico Laco is 2.0±0.3 mya;[15] one study suggested four separate episodes of volcano development.[13] Volcanic activity continued after the emplacement of the magnetite bodies.[9] Later alteration included hydrothermal alteration and glacial erosion; the former has left bleached rocks and exhalation deposits. Some minor metasomatic alteration occurred at the contact sites between andesites and iron-containing rocks.[16][3]: 684  Hydrothermal alteration has also been described for lower portions of the volcanic pile and probably occurred because of gases escaping from intruded magma. Moraines found west of El Laco were generated by glaciation both on El Laco and Puntas Negras. Surface exposure dating has indicated ages of 226 and 287 ka for some ice-affected lavas[11] and argon-argon dating produced a youngest age of about 120,000 years.[9] Further, andesitic volcanism in neighbouring volcanoes has blanketed El Laco.[3]: 684  Reports exist of continuing fumarolic activity and hot springs with the deposition of clay and other minerals.[11]

Iron-rich deposits

On the flank of the volcano, apatite, hematite, and magnetite deposits are found[17] at altitudes of 4,600–5,200 metres (15,100–17,100 ft).[18] The volcano is mainly known for these flows,[19] but such material is also found in the form of tephra.[20] The deposits lie on top of flat lava flows of andesitic composition,[21] concentrically around Pico Laco.[12] They are named Laco Norte, Laco Sur, San Vicente Alto, San Vicente Bajo, and Rodados Negros.[18] The deposits consist of dykes, hydrothermal deposits, lava flows, pyroclastics, and subvolcanic structures and were erupted from parasitic vents and fissures.[11][16] The magnetite is classified as porphyry-like.[2] Apatite is present as an accessory mineral in the lavas and is abundant in the intrusions.[16] Iron-rich zones also formed in tuffs and lavas.[22] Magnetite in the subvolcanic bodies exists in more massive crystals.[3]: 684  The iron-containing rocks include lava flows, ash, and lapilli,[23] as well as ore breccias. The El Laco magnetite lava flows are unique in the world[10] and formed during active subduction.[21]

Individual deposits

Of these deposits, Laco Norte is the largest and was probably separated from neighbouring Laquito by erosion. It is 60–90 metres (200–300 ft) thick and covers a surface area of 1,000 by 1,500 metres (3,300 ft × 4,900 ft). It was erupted from feeder dykes on its southern and eastern end and forms a table-shaped body on a spur, in the shape of a mesa.[18] At Laco Norte, a structure of five layers is found: a basal andesite, ore in pyroclastic form, magnetite lava, pyroclastics which contain ore, and andesite at the top.[15] Laco Sur has a similar morphology and dimensions of 30–70 by 600 by 750 metres (98 ft–230 ft × 1,969 ft × 2,461 ft); it has been mined. San Vicente Alto is a lava flow on the upper parts of the volcano (30 by 320 by 480 metres (98 ft × 1,050 ft × 1,575 ft)), and San Vicente Bajo is probably a lava dome (250 by 390 metres (820 ft × 1,280 ft)). Laquito (150 metres (490 ft) long and 50 metres (160 ft) wide) and Rodados Negros (500 by 600 metres (1,600 ft × 2,000 ft)) appear to be dykes, while Cristales Grandes (80–100 metres (260–330 ft) long and up to 30 metres (98 ft) wide) is more likely a vein and generally shows signs of hydrothermal formation.[18] A magnetic layer of rock spreads north from the volcano,[24] and a large magnetite body has been modelled beneath Pasos Blancos.[11]

Structure and appearance

The magnetite lavas are primarily aa lava, but other surface features are also found,[10] including pahoehoe features.[24] Columnar morphologies are found on the magnetite, implying that they cooled quickly.[25] There is only one other place in the world where columnar magnetite has been found – Kiirunavaara, in Sweden.[26] Centimeter-sized vesicles to meter-sized tubes coated on the inside by euhedral magnetite were formed in the lava by escaping volcanic gas. Both before and after the magnetite lavas, layers of magnetite-containing pyroclastics were erupted. A 0.5–2-metre (1 ft 8 in – 6 ft 7 in) aureole separates the magnetite rocks from the host rocks. The magnetite lava flows are 50 metres (160 ft) thick, the pyroclastics 30 metres (98 ft) and 20 metres (66 ft) respectively.[3]: 684–685  The pyroclastic-like deposits are porous and fragile and show traces of stratification.[10] The pyroclastics at Laco Sur contain spherules of magnetite as well as some blebs of destinezite.[27][28] An age of 2.1±0.1 million years has been found for ore by fission track dating.[10] The lavas contain veins likely generated by hydrothermal activity.[25]

Origin

Temperatures estimated for the erupted rocks cover a wide range, with some exceeding 800 °C (1,470 °F).[2][29] These rocks are of enigmatic origin,[30] which may be magmatic-hydrothermal or magmatic,[17][29] with the presence of lava bombs of magnetite lava[31] and other evidence supporting the magmatic origin theory.[32][33] According to the magmatic genetic hypothesis magma would have separated from a precursor magma due to spontaneous unmixing of an Fe-rich melt from an andesitic parent magma in a shallow magma reservoir beneath the volcano.[7][34] Other viewpoints consider the texture and chemical composition of the rocks as evidence that metasomatism or hydrothermal replacement of andesitic rocks formed the magnetite "lavas".[35][36] A third hypothesis envisages the crystallization of magnetite within a silicic magma and its subsequent extraction through flotation attached to volatile bubbles.[7] The role of a post-magmatic fluid phase, which was inferred from inclusions in crystals,[36] or of a combination of magmatic and hydrothermal mechanisms has also been suggested.[9]

Some magnetite was oxidized to hematite,[3]: 681  probably under the influence of rainwater as indicated by isotope analysis. Only a minor amount of hematite is primary.[18][29] Isotope data indicate that the formation of this magnetite magma was accompanied by the segregation of plagioclase. This plagioclase may have generated the rhyodacite lava dome. An iron-phosphate-rich magma generated the magnetite lava flows after release of volatile substances. The magma was probably bordering on forming a two-phase melt containing nelsonite and rhyolite. A favourable tectonic context associated with the compression of the magma chamber and the presence of faults helped with the eruption of the magnetite.[3]: 688–689 [23][37] The magma formation probably occurred in a magma chamber.[11] During the cooling of the magma, the ores formed.[24] This process was probably not directed by water-rich phases, and the segregation occurred at a shallow depth.[5] High phosphorus and volatile content may have lowered the melting point of the magma and facilitated its eruption,[21] as well as overcoming density-based constraints on the eruption of iron-rich magmas;[38] the magma would later have forcefully degassed within the volcano.[20] Suggestions that anatexis of iron-rich sediments generated the iron-rich magmas appear implausible.[21] The ultimate origin of the El Laco iron may be subducted metal-containing sediment.[39]

Human history and exploitation

These iron oxide deposits were found in 1958 and first described in 1961.[40][41] Mining in Laco Sur removed about two million tons of magnetite between the 1970s and 1990s, leaving an open pit exposing 30 metres (98 ft) of rock.[1] In 2009, these mineral reserves were mined by Cia Minera del Pacifico S.A.[42] It is estimated that the deposit contains 733.9 million tons of ore,[6] consisting of 50% iron.[3]: 684  The geological interest in these kinds of mineral deposits is enhanced by their frequent association with other minerals, as has been noted at Olympic Dam, Australia.[38] Other magnetite-apatite ore deposits in the Andes are Incahuasi (10.3±0.8 mya), 26 kilometres (16 mi) south of El Laco, and Magnetita Pedernales (Tertiary), about 300 kilometres (190 mi) south-southwest of Laco.[24]

Comparable deposits

The Kiruna magnetites in Sweden resemble the El Laco ones in terms of manganese and vanadium content,[43] and their titanium content is comparably low.[5] The deposits at Kiruna and El Laco have been classified as "Iron oxide-apatite" ore deposits,[33][44] and El Laco is the best preserved and youngest such deposit on Earth.[7] Other deposits of volcanic iron ore are the Chilean Iron Belt, the Tertiary Cerro el Mercado deposit in Mexico, the Eocambrian Bafq district in Iran, and the Proterozoic Kiruna field in Sweden. Of these, Sierra Bandera in the Chilean iron belt may be another example of surface volcanic iron ore rather than subvolcanic ore as is commonly assumed of these deposits.[45]

Petrology

The main rocks of the volcano are andesite and dacite, which contain biotite and pyroxene as well as blebs containing iron oxide. The iron-containing rocks are a less important component.[23] The whole rock falls into the calc-alkaline class of volcanic rocks,[35] similar to these erupted by the neighbouring volcanoes Lascar and Llullaillaco.[13] The andesites contain plagioclase clinopyroxene, orthopyroxene, and phenocrysts of magnetite.[3]: 681–682  Magnetite, and in lesser measure hematite, are the most abundant iron minerals;[3]: 685  anhydrite,[46] diopside,[47] goethite, limonite, maghemite, pyrite,[3]: 685  scapolite[7] and diadochite are also found.[23] Erupted magma was probably gas-rich, as the magnetite lavas would otherwise have melting points of over 1,500 °C (2,730 °F). The lavas lost most of their sulfur and phosphorus after their eruption.[23] High oxygen-18 amounts in the Laco magmas indicate either crustal contamination or isotopic effects during fractional crystallization.[24] Some atmospheric water influence has been inferred from isotope data as well.[36]

Hydrothermal alteration of the central lava dome and iron-bearing deposits has generated alunite, anatase, bassanite, chlorite, copper veinlets, gypsum, illite, jarosite, kaolinite, labradorite, quartz, rutile, sanidine, smectite, sulfur and tridymite. Some of these minerals forms veins inside the rock.[12][7][3]: 684 [18] Silification is prominent and has formed cristobalite and tridymite. Elemental sulfur is also found.[2] Vast regions of the volcano have been altered hydrothermally at temperatures of 200–250 °C (392–482 °F), giving the rock a clear appearance. Minor exhalation deposits are also found in the form of sulfates that sometimes conserve conduits. Red-coloured alteration halos occur in andesites adjacent to iron deposits, probably due to iron input.[12] It is possible that the formation of the iron-rich magma was accompanied by the production of large amounts of hydrothermal fluids which then triggered the hydrothermal alteration.[32]

Environment

The vegetation in the area is primarily low bushland.[10] Short-tailed chinchillas can be found at El Laco,[48] one of the few occurrences of this threatened species in Chile.[49]

El Laco has a classical cold mountain climate at the line between the dry Altiplano with summer precipitation and the hyper-arid Atacama Desert climate.[10] A nearby weather station (23°45′S 67°20′W) at 4,500 metres (14,800 ft) altitude showed an average temperature of 2.3 °C (36.1 °F) in 1991, with strong short-term variability. The majority of precipitation falls during southern hemisphere summer; winter snowfall has been recorded. Air humidity recorded in 1991 was 10–30%.[50]

References
  1. Sillitoe, R. H.; Burrows, D. R. (1 August 2002). "New Field Evidence Bearing on the Origin of the El Laco Magnetite Deposit, Northern Chile". Economic Geology. 97 (5): 1101–1109. doi:10.2113/gsecongeo.97.5.1101.
  2. Knipping, Jaayke L.; Bilenker, Laura D.; Simon, Adam C.; Reich, Martin; Barra, Fernando; Deditius, Artur P.; Wӓlle, Markus; Heinrich, Christoph A.; Holtz, François; Munizaga, Rodrigo (December 2015). "Trace elements in magnetite from massive iron oxide-apatite deposits indicate a combined formation by igneous and magmatic-hydrothermal processes". Geochimica et Cosmochimica Acta. 171: 15–38. Bibcode:2015GeCoA.171...15K. doi:10.1016/j.gca.2015.08.010.
  3. Frutos, J.; Oyarzun, J.; Shiga, Y.; Alfaro, G. (1990). "The El Laco Magnetite Lava Flow Deposits, Northern Chile: An Up-To-Date Review and New Data". Stratabound Ore Deposits in the Andes (8th ed.). Berlin, Heidelberg: Springer Berlin Heidelberg. p. 681. doi:10.1007/978-3-642-88282-1_54. ISBN 978-3-642-88282-1.
  4. Henderson, S. T.; Pritchard, M. E. (May 2013). "Decadal volcanic deformation in the Central Andes Volcanic Zone revealed by InSAR time series". Geochemistry, Geophysics, Geosystems. 14 (5): 1358–1374. Bibcode:2013GGG....14.1358H. doi:10.1002/ggge.20074.
  5. Oyarzun, Jorge; Frutos, Jose (1984). "Tectonic and Petrological Frame of the Cretaceous Iron Deposits of North Chile". Mining Geology. 34 (183): 21–31. doi:10.11456/shigenchishitsu1951.34.21.
  6. Ovalle, J. Tomás; La Cruz, Nikita L.; Reich, Martin; Barra, Fernando; Simon, Adam C.; Konecke, Brian A.; Rodriguez-Mustafa, María A.; Deditius, Artur P.; Childress, Tristan M.; Morata, Diego (5 October 2018). "Formation of massive iron deposits linked to explosive volcanic eruptions". Scientific Reports. 8 (1): 14855. Bibcode:2018NatSR...814855O. doi:10.1038/s41598-018-33206-3. ISSN 2045-2322. PMC 6173703. PMID 30291283.
  7. Cruz, Nikita L. La; Ovalle, J. Tomás; Simon, Adam C.; Konecke, Brian A.; Barra, Fernando; Reich, Martin; Leisen, Mathieu; Childress, Tristan M. (1 November 2020). "The Geochemistry of Magnetite and Apatite from the El Laco Iron Oxide-Apatite Deposit, Chile: Implications for Ore Genesis". Economic Geology. 115 (7): 1461–1491. doi:10.5382/econgeo.4753. ISSN 0361-0128. S2CID 224945826.
  8. Naranjo, J. A.; Henríquez, F. (November 2009). "Geocronología K-Ar y antecedentes paleoambientales del volcanismo de óxido de fierro de El Laco" (PDF). biblioserver.sernageomin.cl (in Spanish). Santiago: XII Congreso Geológico Chileno. Archived from the original (PDF) on 25 November 2015. Retrieved 27 March 2016.
  9. Brown, Laurie; Singer, Brad S.; Barquero-Molina, Miriam (1 March 2021). "Paleomagnetism and 40Ar/39Ar chronology of ignimbrites and lava flows, Central Volcanic Zone, Northern Chile". Journal of South American Earth Sciences. 106: 103037. Bibcode:2021JSAES.10603037B. doi:10.1016/j.jsames.2020.103037. ISSN 0895-9811. S2CID 229462247.
  10. Guijón, Rodrigo; Henríquez, Fernando; Naranjo, José Antonio (12 July 2011). "Geological, Geographical and Legal Considerations for the Conservation of Unique Iron Oxide and Sulphur Flows at El Laco and Lastarria Volcanic Complexes, Central Andes, Northern Chile". Geoheritage. 3 (4): 299–315. doi:10.1007/s12371-011-0045-x. S2CID 129179725.
  11. Naranjo, José A.; Henríquez, Fernando; Nyström, Jan O. (January 2010). "Subvolcanic contact metasomatism at El Laco Volcanic Complex, Central Andes". Andean Geology. 37 (1): 110–120. doi:10.4067/s0718-71062010000100005. ISSN 0718-7106.
  12. Vivallo, W.; Henriquez, F.; Espinoza, S. (1991). "Alteracion hydrothermal en el complejo volcanico El Laco, norte de Chile" (PDF). biblioserver.sernageomin.cl (in Spanish). Congreso Geologico Chileno. Archived from the original (PDF) on 28 March 2016. Retrieved 28 March 2016.
  13. Velasco, Francisco; Tornos, Fernando; Hanchar, John M. (December 2016). "Immiscible iron- and silica-rich melts and magnetite geochemistry at the El Laco volcano (northern Chile): Evidence for a magmatic origin for the magnetite deposits". Ore Geology Reviews. 79: 346–366. doi:10.1016/j.oregeorev.2016.06.007. ISSN 0169-1368.
  14. "Laco". Global Volcanism Program. Smithsonian Institution.
  15. Nystroem, J. O.; Henriquez, F. (1 July 1994). "Magmatic features of iron ores of the Kiruna type in Chile and Sweden; ore textures and magnetite geochemistry". Economic Geology. 89 (4): 820–839. doi:10.2113/gsecongeo.89.4.820.
  16. Dobbs, F. Michael; B., Fernando Henriquez; Vivallo, Waldo (1997). "Caracterizacion de la alteracion hidrothermal de El Laco mediante analisis estadistico de factores" (PDF). biblioserver.sernageomin.cl (in Spanish). VIII Congreso Geologico Chileno. Archived from the original (PDF) on 28 March 2016. Retrieved 28 March 2016.
  17. Kuepouo, Gilbert; Sato, Hiroaki; Tchouankoue, Jean-Pierre; Murata, Mamoru (March 2009). "FeO*-Al2O3-TiO2-Rich Rocks of the Tertiary Bana Igneous Complex, West Cameroon". Resource Geology. 59 (1): 69–86. doi:10.1111/j.1751-3928.2008.00080.x. S2CID 130524930.
  18. Broman, Curt; Nyström, Jan Olov; Henríquez, Fernando; Elfman, Mikael (September 1999). "Fluid inclusions in magnetite-apatite ore from a cooling magmatic system at El Laco, Chile". GFF. 121 (3): 253–267. doi:10.1080/11035899901213253.
  19. Hutchison, Charles S. (1983). "Proterozoic-style mineralization". Economic Deposits and their Tectonic Setting. Macmillan Education UK. p. 219. doi:10.1007/978-1-349-17039-5_10. ISBN 978-1-349-17039-5.
  20. Mungall, J.E.; Long, K.; Brenan, J.M.; Smythe, D.; Naslund, H.R. (17 January 2018). "Immiscible shoshonitic and Fe-P-oxide melts preserved in unconsolidated tephra at El Laco volcano, Chile". Geology. 46 (3): 255. Bibcode:2018Geo....46..255M. doi:10.1130/G39707.1.
  21. Sillitoe, R. H. (1 January 1977). "Metallic mineralization affiliated to subaerial volcanism: a review". Geological Society, London, Special Publications. 7 (1): 99–116. Bibcode:1977GSLSP...7...99S. doi:10.1144/GSL.SP.1977.007.01.13. S2CID 129854767.
  22. Karimzadeh Somarin, A. (October 2004). "Marano volcanic rocks, East Azarbaijan Province, Iran, and associated Fe mineralisation". Journal of Asian Earth Sciences. 24 (1): 11–23. Bibcode:2004JAESc..24...11K. doi:10.1016/S1367-9120(03)00152-4.
  23. Naslund, H.; Mungall, J.; Henríquez, F.; Nyström, J.; Lledó, H.; Lester, G.; Aguirre, R. (November 2009). "Melt inclusions in silicate lava s and iron-oxide tephra of the El Laco volcano, Chile" (PDF). biblioserver.sernageomin.cl. Santiago: XII Congreso Geológico Chileno. Archived from the original (PDF) on 27 March 2016. Retrieved 27 March 2016.
  24. Nyström, Jan Olov; Billström, Kjell; Henríquez, Fernando; Fallick, Anthony E.; Naslund, H. Richard (December 2008). "Oxygen isotope composition of magnetite in iron ores of the Kiruna type in Chile and Sweden". GFF. 130 (4): 177–188. doi:10.1080/11035890809452771. hdl:10533/142602. S2CID 129299865.
  25. Nyström, Jan Olov (4 January 2010). "Apatite iron ores of the Kiruna Field, northern Sweden: Magmatic textures and carbonatitic affinity". Geologiska Föreningen i Stockholm Förhandlingar. 107 (2): 133–141. doi:10.1080/11035898509452625.
  26. Nyström, Jan Olov; Henriquez, Fernando (March 1989). "Dendritic magnetite and miniature diapir-like concentrations of apatite: Two magmatic features of the Kiirunavaara iron ore". Geologiska Föreningen i Stockholm Förhandlingar. 111 (1): 53–64. doi:10.1080/11035898909454759.
  27. Nyström, Jan Olov; Henríquez, Fernando; Naranjo, José A.; Naslund, H. Richard (1 March 2016). "Magnetite spherules in pyroclastic iron ore at El Laco, Chile". American Mineralogist. 101 (3): 587–595. Bibcode:2016AmMin.101..587N. doi:10.2138/am-2016-5505. S2CID 73624204.
  28. Velasco, Francisco; Pinta, Noelia de la; Tornos, Fernando; Briezewski, Thomas; Larrañaga, Aitor (2020-06-01). "The relationship of destinezite to the acid sulfate alteration at the El Laco magnetite deposit, Chile". American Mineralogist. 105 (6): 860–872. doi:10.2138/am-2020-7122. ISSN 1945-3027.
  29. Jami, M.; Dunlop, A. C.; Cohen, D. R. (1 September 2007). "Fluid Inclusion and Stable Isotope Study of the Esfordi Apatite-Magnetite Deposit, Central Iran". Economic Geology. 102 (6): 1111–1128. doi:10.2113/gsecongeo.102.6.1111.
  30. Veksler, Ilya V.; Dorfman, Alexander M.; Danyushevsky, Leonid V.; Jakobsen, Jakob K.; Dingwell, Donald B. (10 August 2006). "Immiscible silicate liquid partition coefficients: implications for crystal-melt element partitioning and basalt petrogenesis" (PDF). Contributions to Mineralogy and Petrology. 152 (6): 685–702. Bibcode:2006CoMP..152..685V. doi:10.1007/s00410-006-0127-y. S2CID 55543949.
  31. Henríquez, Fernando; Nyström, Jan Olov (September 1998). "Magnetite bombs at El Laco volcano, Chile". GFF. 120 (3): 269–271. doi:10.1080/11035899809453216.
  32. Tornos, Fernando; Velasco, Francisco; Hanchar, John M. (1 June 2016). "Iron-rich melts, magmatic magnetite, and superheated hydrothermal systems: The El Laco deposit, Chile". Geology. 44 (6): 427. Bibcode:2016Geo....44..427T. doi:10.1130/G37705.1. ISSN 0091-7613. S2CID 131003403.
  33. Troll, Valentin R.; Weis, Franz A.; Jonsson, Erik; Andersson, Ulf B.; Majidi, Seyed Afshin; Högdahl, Karin; Harris, Chris; Millet, Marc-Alban; Chinnasamy, Sakthi Saravanan; Kooijman, Ellen; Nilsson, Katarina P. (2019-04-12). "Global Fe–O isotope correlation reveals magmatic origin of Kiruna-type apatite-iron-oxide ores". Nature Communications. 10 (1): 1712. Bibcode:2019NatCo..10.1712T. doi:10.1038/s41467-019-09244-4. ISSN 2041-1723. PMC 6461606. PMID 30979878.
  34. Keller, Tobias; Tornos, Fernando; Hanchar, John M.; Pietruszka, Dorota K.; Soldati, Arianna; Dingwell, Donald B.; Suckale, Jenny (2022-10-17). "Genetic model of the El Laco magnetite-apatite deposits by extrusion of iron-rich melt". Nature Communications. 13 (1): 6114. doi:10.1038/s41467-022-33302-z. ISSN 2041-1723. PMC 9576724. PMID 36253366.
  35. Dare, Sarah A. S.; Barnes, Sarah-Jane; Beaudoin, Georges (29 October 2014). "Did the massive magnetite 'lava flows' of El Laco (Chile) form by magmatic or hydrothermal processes? New constraints from magnetite composition by LA-ICP-MS". Mineralium Deposita. 50 (5): 607–617. doi:10.1007/s00126-014-0560-1. S2CID 129783571.
  36. Nabatian, Ghasem; Ghaderi, Majid (March 2013). "Oxygen isotope and fluid inclusion study of the Sorkhe-Dizaj iron oxide-apatite deposit, NW Iran". International Geology Review. 55 (4): 397–410. Bibcode:2013IGRv...55..397N. doi:10.1080/00206814.2012.713547. S2CID 128956228.
  37. Mungall, J. E.; Maslund, H. R. (May 2009). "Melt inclusions in Fe oxide and phosphate tephra of El Laco volcano, Chile". AGU Spring Meeting Abstracts. 12: V12A–04. Bibcode:2009AGUSM.V12A..04M.
  38. Kesler, Stephen E (December 1997). "Metallogenic evolution of convergent margins: Selected ore deposit models". Ore Geology Reviews. 12 (3): 153–171. doi:10.1016/S0169-1368(97)00007-3.
  39. Loberg, B. E. H.; Horndahl, A.-K. (October 1983). "Ferride geochemistry of Swedish precambrian iron ores". Mineralium Deposita. 18 (3): 487–504. Bibcode:1983MinDe..18..487L. doi:10.1007/BF00204493. S2CID 128544097.
  40. Zeil, Werner (December 1964). "Die Verbreitung des jungen Vulkanismus in der Hochkordillere Nordchiles". Geologische Rundschau (in German). 53 (2): 731–757. Bibcode:1964GeoRu..53..731Z. doi:10.1007/BF02054561. S2CID 128979648.
  41. Park, Charles F. (1961-03-01). "A magnetite "flow" in northern Chile". Economic Geology. 56 (2): 431–436. doi:10.2113/gsecongeo.56.2.431. ISSN 1554-0774.
  42. Geological Survey (US) (2011). Minerals Yearbook: Area Reports: International 2009 Latin America and Canada, Band 3. Government Printing Office. pp. 7–19. ISBN 978-1-4113-2976-8. Retrieved 22 March 2016.
  43. Müller, Barbara; Axelsson, Mikael D.; Öhlander, Björn (March 2003). "Trace elements in magnetite from Kiruna, northern Sweden, as determined by LA-ICP-MS". GFF. 125 (1): 1. doi:10.1080/11035890301251001. S2CID 129437314.
  44. Verdugo-Ihl, Max R.; Ciobanu, Cristiana L.; Cook, Nigel J.; Ehrig, Kathy J.; Courtney-Davies, Liam (1 March 2020). "Defining early stages of IOCG systems: evidence from iron oxides in the outer shell of the Olympic Dam deposit, South Australia". Mineralium Deposita. 55 (3): 429. doi:10.1007/s00126-019-00896-2. ISSN 1432-1866. S2CID 189829439.
  45. Nyström, J. O.; Henríquez, F.; Travisany, V. (October 1996). "Volcanic iron ores of the Kiruna type". GFF. 118 (sup004): 45–46. doi:10.1080/11035899609546321.
  46. MATTHEWS, S. J.; JONES, A. P.; BEARD, A. D. (1 October 1994). "Buffering of melt oxygen fugacity by sulphur redox reactions in calc-alkaline magmas". Journal of the Geological Society. 151 (5): 815–823. Bibcode:1994JGSoc.151..815M. doi:10.1144/gsjgs.151.5.0815. S2CID 128416319.
  47. Hawkins, T.; Smith, M. P.; Herrington, R. J.; Maslennikov, V.; Boyce, A. J.; Jeffries, T.; Creaser, R. A. (October 2015). "The geology and genesis of the iron skarns of the Turgai belt, northwestern Kazakhstan" (PDF). Ore Geology Reviews. 85: 216–246. doi:10.1016/j.oregeorev.2015.10.016.
  48. Valladares, Pablo F.; Espinosa, Martín; Torres, Mauricio; Diaz, Eric; Zeller, Nicolai; de La Riva, Jorge; Grimberg, Moisés; Spotorno, Ángel (June 2012). "Nuevo registro de Chinchilla chinchilla (Rodentia, Chinchillidae) para la región de Atacama, Chile. Implicancias paea su estado de conservación". Mastozoología Neotropical (in Spanish). 19 (1). ISSN 0327-9383. Retrieved 22 March 2016.
  49. Valladares F, Pablo; Spotorno, Ángel E; Cortes M, Arturo; Zuleta R, Carlos (20 August 2018). "Chinchilla chinchilla (Rodentia: Chinchillidae)". Mammalian Species. 50 (960): 53. doi:10.1093/mspecies/sey007.
  50. Messerli, Bruno; Grosjean, Martin; Graf, Kurt; Schotterer, Ueli; Schreier, Hans; Vuille, Mathias (1992). "Die Veränderungen Von Klima Und Umwelt in Der Region Atacama Seit Der Letzten Kaltzeit" (PDF). Erdkunde (in German). 46 (3/4). doi:10.3112/erdkunde.1992.03.09. Retrieved 27 March 2016.
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