Phosphate minerals in LL chondrites: A record of the action of fluids during metamorphism on ordinary chondrite parent bodies

Jones, R. H.; McCubbin, F. M.; Dreeland, L.; Guan, Yunbin; Burger, P. V.; Shearer, C. K.

doi:10.1016/j.gca.2014.01.027

Cited by 86 publications

(132 citation statements)

References 75 publications

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“…The apatites also had trace to minor abundances of SiO 2 , MnO, and Na 2 O, with 0.33 to 0.89 wt% SiO 2 , 0.22 to 0.41 wt% MnO, and 0.07 to 0.32 wt% Na 2 O. These apatite compositions are similar to the ranges observed in many natural apatites from terrestrial worlds across the Solar System, including, Earth, Moon, Mars, Vesta, and ordinary chondrite parent bodies (e.g., Harlov et al 2006;Jones et al 2014;McCubbin et al 2011McCubbin et al , 2013Sarafian et al 2013).…”

Section: Cation Composition Of Apatite and Melt From Each Experimentssupporting

confidence: 73%

Experimental investigation of F, Cl, and OH partitioning between apatite and Fe-rich basaltic melt at 1.0–1.2 GPa and 950–1000 °C

McCubbin

Kaaden

Tartèse

et al. 2015

American Mineralogist

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131

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Apatite-melt partitioning experiments were conducted in a piston-cylinder press at 1.0-1.2 GPa and 950-1000 °C using an Fe-rich basaltic starting composition and an oxygen fugacity within the range of DIW-1 to DIW+2. Each experiment had a unique F:Cl:OH ratio to assess the partitioning as a function of the volatile content of apatite and melt. The quenched melt and apatite were analyzed by electron probe microanalysis and secondary ion mass spectrometry techniques. The mineral-melt partition coefficients (D values) determined in this study are as follows: D F Ap-Melt = 4.4-19, D Cl Ap-Melt = 1.1-5, D OH Ap-Melt = 0.07-0.24. This large range in values indicates that a linear relationship does not exist between the concentrations of F, Cl, or OH in apatite and F, Cl, or OH in melt, respectively. This nonNernstian behavior is a direct consequence of F, Cl, and OH being essential structural constituents in apatite and minor to trace components in the melt. Therefore mineral-melt D values for F, Cl, and OH in apatite should not be used to directly determine the volatile abundances of coexisting silicate melts. However, the apatite-melt D values for F, Cl, and OH are necessarily interdependent given that F, Cl, and OH all mix on the same crystallographic site in apatite. Consequently, we examined the ratio of D values (exchange coefficients) for each volatile pair (OH-F, Cl-F, and OH-Cl) and observed that they display much less variability: K d Cl-F Ap-Melt = 0.21± 0.03, K d OH-F Ap-Melt = 0.014 ± 0.002, and K d OH-Cl Ap-Melt = 0.06 ± 0.02. However, variations with apatite composition, specifically when mole fractions of F in the apatite X-site were low (X F < 0.18), were observed and warrant additional study. To implement the exchange coefficient to determine the H 2 O content of a silicate melt at the time of apatite crystallization (apatitebased melt hygrometry), the H 2 O abundance of the apatite, an apatite-melt exchange K d that includes OH (either OH-F or OH-Cl), and the abundance of F or Cl in the apatite and F or Cl in the melt at the time of apatite crystallization are needed (F if using the OH-F K d and Cl if using the OH-Cl K d ). To determine the H 2 O content of the parental melt, the F or Cl abundance of the parental melt is needed in place of the F or Cl abundance of the melt at the time of apatite crystallization. Importantly, however, exchange coefficients may vary as a function of temperature, pressure, melt composition, apatite composition, and/or oxygen fugacity, so the combined effects of these parameters must be investigated further before exchange coefficients are applied broadly to determine volatile abundances of coexisting melt from apatite volatile abundances.

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Section: Cation Composition Of Apatite and Melt From Each Experimentssupporting

confidence: 73%

Experimental investigation of F, Cl, and OH partitioning between apatite and Fe-rich basaltic melt at 1.0–1.2 GPa and 950–1000 °C

McCubbin

Kaaden

Tartèse

et al. 2015

American Mineralogist

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131

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“…However, because of the similarities between merrillite and whitlockite, few analytical methods can distinguish between the two phases and, as such, during routine meteorite analyses the merrillite endmember is typically just assumed23. Previous work by McCubbin et al 30.…”

Section: Discussionmentioning

confidence: 99%

“…The mineral occurs in most meteorite types including chondrites, achondrites, pallasites and both Martian and lunar meteorites where it is a major carrier of REEs171819202122. Natural merrillite is generally igneous, although it can occur as a metamorphic product in chondritic meteorites171823. Along with chlorapatite (Ca 5 [PO 4 ] 3 [Cl]), merrillite is one of the two most commonly occurring phosphates in meteorites17202324.…”

mentioning

confidence: 99%

“…Natural merrillite is generally igneous, although it can occur as a metamorphic product in chondritic meteorites171823. Along with chlorapatite (Ca 5 [PO 4 ] 3 [Cl]), merrillite is one of the two most commonly occurring phosphates in meteorites17202324. In fact, the mineral is typically the dominant phosphate phase in shergottite Martian meteorites, the most common type of Martian meteorites, where it is two to three times more abundant than chlorapatite, suggesting merrillite may be the dominant igneous phosphate on Mars as well1202526.…”

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confidence: 99%

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Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate

et al. 2017

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Meteorites represent the only samples available for study on Earth of a number of planetary bodies. The minerals within meteorites therefore hold the key to addressing numerous questions about our solar system. Of particular interest is the Ca-phosphate mineral merrillite, the anhydrous end-member of the merrillite–whitlockite solid solution series. For example, the anhydrous nature of merrillite in Martian meteorites has been interpreted as evidence of water-limited late-stage Martian melts. However, recent research on apatite in the same meteorites suggests higher water content in melts. One complication of using meteorites rather than direct samples is the shock compression all meteorites have experienced, which can alter meteorite mineralogy. Here we show whitlockite transformation into merrillite by shock-compression levels relevant to meteorites, including Martian meteorites. The results open the possibility that at least part of meteoritic merrillite may have originally been H+-bearing whitlockite with implications for interpreting meteorites and the need for future sample return.

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“…Additionally, it is an important component of planetary materials (Piccoli and Candela 2002;Spear and Pyle 2002;Knudsen and Gunter 2002;Patiño Douce and Roden 2006;Jones et al 2014), having been used to estimate H 2 O abundances in the interiors of the Moon and Mars (McCubbin et al 2010a, 2010b, 2012Gross et al 2013). Apatite is the main hard part of the human anatomy, the source of phosphorous in fertilizer, and an important potential material for the storage of nuclear waste (Ewing and Wang 2002).…”

Section: Introductionmentioning

confidence: 99%

Thermal expansion of F-Cl apatite crystalline solutions

Hovis

Abraham

Hudacek

et al. 2015

American Mineralogist

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We have studied the thermal expansion of 15 synthetic and two natural F-Cl apatite solid solutions through the calculation of unit-cell dimensions at elevated temperatures based on X-ray powder diffraction data collected from room temperature to ~900 °C at 50 to 100 °C intervals. Coefficients of thermal expansion for the a and c unit-cell axes show sensitivity to composition, with α a increasing by about 50% and α c decreasing by a third from chlorapatite to fluorapatite. Despite the relationships observed for a and c, the thermal expansion coefficient for unit-cell volume shows little sensitivity to composition, which can be explained only by a mutually compensating structural adjustment along the latter axes as temperature rises. Results of this study also imply that the thermodynamically ideal volumes of mixing for F-Cl apatite solid solutions observed at ambient conditions continue to at least 900 °C.

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Phosphate minerals in LL chondrites: A record of the action of fluids during metamorphism on ordinary chondrite parent bodies

Cited by 86 publications

References 75 publications

Experimental investigation of F, Cl, and OH partitioning between apatite and Fe-rich basaltic melt at 1.0–1.2 GPa and 950–1000 °C

Experimental investigation of F, Cl, and OH partitioning between apatite and Fe-rich basaltic melt at 1.0–1.2 GPa and 950–1000 °C

Shock-transformation of whitlockite to merrillite and the implications for meteoritic phosphate

Thermal expansion of F-Cl apatite crystalline solutions

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