Experiments on silicate melt immiscibility in the system Fe2SiO4–KAlSi3O8–SiO2–CaO–MgO–TiO2–P2O5 and implications for natural magmas

Bogaerts, Michel; Schmidt, Max W.

doi:10.1007/s00410-006-0111-6

Cited by 59 publications

(20 citation statements)

References 49 publications

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“…Although we cannot exclude that some melt inclusions represent an emulsion of unsegregated immiscible melts, we suggest that most of the compositional range that we observe is controlled by a temperature-dependent evolution of element partitioning between immiscible melts. This is confirmed by experimental data showing that CaO partitioning between the Fe-and Si-rich liquids is indeed strongly dependent on temperature, melt composition, and melt structure (Bogaerts and Schmidt, 2006;Charlier and Grove, 2012), which results in a non-linear CaO vs. SiO 2 trend of immiscible pairs (Fig. 5C).…”

Section: Trapping Of Melt Inclusions and Compositional Evolution Durisupporting

confidence: 80%

Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex

Fischer

Wang

Charlier

et al. 2016

Earth and Planetary Science Letters

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The Bushveld Complex (South Africa) is the largest layered intrusion on Earth and plays a considerable role in our understanding of magmatic differentiation and ore-forming processes. In this study, we present new geochemical data for apatite-hosted multiphase inclusions in gabbroic cumulates from the Bushveld Upper Zone. Inclusions re-homogenized at high-temperature (1060-1100 • C) display a range of compositions in each rock sample, from iron-rich (35 wt.% FeO tot ; 28 wt.% SiO 2 ) to silica-rich (5 wt.% FeO tot ; 65 wt.% SiO 2 ). This trend is best explained by an immiscible process and trapping of contrasted melts in apatite crystals during progressive cooling along the binodal of a two-liquid field. The coexistence of both Si-rich and Fe-rich immiscible melts in single apatite grains is used to discuss the ability of immiscible melts to segregate from each other, and the implications for mineral and bulk cumulate compositions. We argue that complete separation of immiscible liquids did not occur, resulting in crystallization of similar phases from both melts but in different proportions. However, partial segregation in a crystal mush and the production of contrasting phase proportions from the Fe-rich melt and the Si-rich melt can be responsible for the cyclic evolution from melanocratic (Fe-Ti-P-rich) to leucocratic (plagioclase-rich) gabbros which is commonly observed in the Upper Zone of the Bushveld Complex where it occurs at a vertical scale of 50 to 200 m.

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Section: Trapping Of Melt Inclusions and Compositional Evolution Durisupporting

confidence: 80%

Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex

Fischer

Wang

Charlier

et al. 2016

Earth and Planetary Science Letters

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“…6a-b). Two diagrams are used, with and without TiO 2 , because, although TiO 2 is important for the development of immiscibility (Visser and Koster van Groos 1979b;Bogaerts and Schmidt 2006), our experiments do not discriminate its role as they all have similar TiO 2 content at the onset of immiscibility. Alkalis reduce the liquidus temperature, as well as P 2 O 5 and TiO 2 , which also expand the immiscibility field .…”

Section: 4mentioning

confidence: 99%

“…augite (Grove et al 1992), which is at a higher temperature compared to the binodal. Experiments on liquid immiscibility have mainly been performed on simplified systems (e.g., Roedder 1978;Bogaerts and Schmidt 2006). Consequently, even though phase relations in the system K 2 O-FeO-Al 2 O 3 -SiO 2 are well known (Roedder 1978;Visser and Koster van Groos 1979a;Freestone and Powell 1983) and the effects of other elements such as P 2 O 5 , TiO 2 , CaO, and MgO in reducing or expanding the immiscibility field have been experimentally identified (Watson 1976;Visser and Koster van Groos 1979b;Naslund 1983;Bogaerts and Schmidt 2006), direct application of these results to complex natural basaltic systems is not straightforward.…”

Section: Introductionmentioning

confidence: 99%

Experiments on liquid immiscibility along tholeiitic liquid lines of descent

Charlier

Grove

2012

Contrib Mineral Petrol

199

165

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Crystallization experiments have been conducted on compositions along tholeiitic liquid lines of descent to define the compositional space for the development of silicate liquid immiscibility. Starting materials have 46-56 wt% SiO 2 , 11.7-17.7 wt% FeO tot , and Mgnumber between 0.29 and 0.36. These melts fall on the basaltic trends relevant for Mull, Iceland, Snake River Plain lavas and for the Sept Iles layered intrusion, where large-scale liquid immiscibility has been recognized. At one atmosphere under anhydrous conditions, immiscibility develops below 1,000-1,020°C in all of these compositionally diverse lavas. Extreme iron enrichment is not necessary; immiscibility also develops during iron depletion and silica enrichment. Variations in melt composition control the development of silicate liquid immiscibility along the tholeiitic trend. Elevation of Na 2 O ? K 2 O ? P 2 O 5 ? TiO 2 promotes the development of two immiscible liquids. Increasing melt CaO and Al 2 O 3 stabilizes a singleliquid field. New data and published phase equilibria show that anhydrous, low-pressure fractional crystallization is the most favorable condition for unmixing during differentiation. Pressure inhibits immiscibility because it expands the stability field of high-Ca clinopyroxene, which reduces the proportion of plagioclase in the crystallizing assemblage, thus enhancing early iron depletion. Magma mixing between primitive basalt and Fe-Ti-P-rich ferrobasalts can serve to elevate phosphorous and alkali contents and thereby promote unmixing. Water might decrease the temperature and size of the two-liquid field, potentially shifting the binodal (solvus) below the liquidus, leading the system to evolve as a single-melt phase.

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“…Nevertheless, experiments also showed that other elements such as TiO 2 and alkalis (Na 2 O+K 2 O) either enlarge the two-liquid field or decrease the liquidus temperature, favoring liquid-liquid unmixing (Watson 1976;Visser and Koster van Groos 1979;Bogaerts and Schmidt 2006;Charlier and Grove 2012). Charlier and Grove (2012) have experimentally shown that silicate liquid immiscibility may develop below 1,000-1,020°C in compositionally diverse tholeiitic lavas at one atmosphere under anhydrous conditions.…”

Section: Cr-rich Titanomagnetite and Cr-poor Titanomagnetitementioning

confidence: 99%

New textural and mineralogical constraints on the origin of the Hongge Fe-Ti-V oxide deposit, SW China

Wang

Zhou

2013

Miner Deposita

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The Hongge magmatic Fe-Ti-Voxide deposit in the Panxi region, SW China, is hosted in a layered mafic-ultramafic intrusion. This 2.7-km-thick, lopolith-like intrusion consists of the lower, middle, and upper zones, which are composed of olivine clinopyroxenite, clinopyroxenite, and gabbro, respectively. Abundant Fe-Ti oxide layers mainly occur in the middle zone and the lower part of the upper zone. Fe-Ti oxides include Cr-rich and Cr-poor titanomagnetite and granular ilmenite. Cr-rich titanomagnetite is commonly disseminated in the olivine clinopyroxenite of the lower parts of the lower and middle zones and contains 1.89 to 14.9 wt% Cr 2 O 3 and 3.20 to 16.2 wt% TiO 2 , whereas Cr-poor titanomagnetite typically occurs as net-textured and massive ores in the upper middle and upper zones and contains much lower Cr 2 O 3 (<0.4 wt%) but more variable TiO 2 (0.11 to 18.2 wt%). Disseminated Cr-rich titanomagnetite in the ultramafic rocks is commonly enclosed in either olivine or clinopyroxene, whereas Cr-poor titanomangetite of the net-textured and massive ores is mainly interstitial to clinopyroxene and plagioclase. The lithology of the Hongge intrusion is consistent with multiple injections of magmas, the lower zone being derived from a single pulse of less differentiated ferrobasaltic magma and the middle and upper zones from multiple pulses of more differentiated magmas. Cr-rich titanomagnetite in the disseminated ores of the lower and middle zones is interpreted to represent an early crystallization phase whereas clusters of Cr-poor titanomagnetite, granular ilmenite, and apatite in the nettextured ores of the middle and upper zones are thought to have formed from an Fe-Ti-(P)-rich melt segregated from a differentiated ferrobasaltic magma as a result of liquid immiscibility. The dense Fe-Ti-(P)-rich melt percolated downward through the underlying silicate crystal mush to form net-textured and massive Fe-Ti oxide ores, whereas the coexisting Si-rich melt formed the overlying plagioclase-rich rocks in the intrusion.

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Experiments on silicate melt immiscibility in the system Fe2SiO4–KAlSi3O8–SiO2–CaO–MgO–TiO2–P2O5 and implications for natural magmas

Cited by 59 publications

References 49 publications

Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex

Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex

Experiments on liquid immiscibility along tholeiitic liquid lines of descent

New textural and mineralogical constraints on the origin of the Hongge Fe-Ti-V oxide deposit, SW China

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