Astromaterials and Oxide-Silicate Interaction:

Martian basaltic meteoritesLunar picritic glasses

Microgabbros: Plag, Px, & minor phases (Fe-Ti Ox, Fa, FeS, phosphates)

Olivine microgabbros: Ol phenocrysts in gabbroic groundmass

Oxidized or reduced materials?Products of wet or dry crystallization?Primary or differentiated magmas?

Martian basaltic Martian basaltic meteoritesmeteorites

Martian basaltic Martian basaltic meteoritesmeteorites

Chemical zoning in Plag (e.g., Ga, Chemical zoning in Plag (e.g., Ga, Al, Sr) & Px (Fe/Mg, Ca, minor Al, Sr) & Px (Fe/Mg, Ca, minor elements)elements)

Late appearance of Fe-Ti Spl (Ti-Mt)Late appearance of Fe-Ti Spl (Ti-Mt)Oxide-silicate reactionsOxide-silicate reactionsLate SiOLate SiO22 polymorph crystallization polymorph crystallizationWhole rock Fe-Ti-P enrichmentWhole rock Fe-Ti-P enrichmentImpact-related featuresImpact-related features

Fe2Si2O6, Fe2SiO4

CaMgSi2O6

CaMgSiO4

0.0

0.1

0.2

0.3

0.4

0.0

0.1

0.2

0.3

0.4

Mg2Si2O6, Mg2SiO4

0.00.10.20.30.40.50.60.70.80.91.0

0.00.10.20.30.40.5

Px isotherms (calc.)Pyroxene compositions (obs.)Olivine compositions (obs.)Exsolved Px (obs.) near and in oxide-silicate clusters

Ol (calc.) in equilibrium with oxides+pyroxene(s)Px (calc.) in equilibrium with oxides+olivineBest Px-like bulk symplectite CaFeSi2O6

CaFeSiO4

1250

1150 1050

950

900 850[OAQ]

Late stage oxide-silicate reactions

A

BC

T (oC)

600 700 800 900 1000 1100 1200

logfO

2FM

Q

-4

-2

0

2

Los Angeles meteoriteA: TiMt crystallizationAB: Pig + TiMt = Ol + IlmB: Cpx = Pig + AugBC: Pig + TiMt = Ol + Aug + IlmIlm+TiMt or TiMt only (QUE94201)Ol-Px-Spl3Fe2SiO4 + O2 = 2Fe3O4 + 3SiO2

Zagami

Shergotty

QUE94201

EET7

9001

AEET79001B

Usp100

Fe + Ilm100

Dhofar 019

SAU

005

Usp60

Usp70

Usp80

Usp90

Ilm94

Ilm96

Ilm98

NWA 1110

Los Angeles

MgO (wt% )

0 20 40 60 80 100

FeOT (wt% )

0

20

40

60

80

100

Na2O + K2O (wt% )

0

20

40

60

80

100

Microgabbros (330-575 Ma)Microgabbros (age unknown)Microgabbros (175 Ma)Model mantle compositions

Mars Pathfinder rocks

MgO (wt% )

0 20 40 60 80 100

FeOT (wt% )

0

20

40

60

80

100

Na2O + K2O (wt% )

0

20

40

60

80

100

Pyroxenite (4.5 Ma)Pyroxenites & Dunite (1.3 Ga)Microgabbros (330-575 Ma)Microgabbros (age unknown)Lherzolites (180 Ma)Microgabbros (175 Ma)Model mantle compositions

Mars Pathfinder rocksThingmuli (Iceland)Santorini (Aegean Arc)

Summary: Martian basaltic meteorites

Differentiated basaltic magmas

Crystallized under reducing (FMQ-1 to FMQ-3.5) and H2O-poor conditions (<<1 wt%)

Regolith material(s) added

To better constrain parental melts, crystal fractionation conditions, and residual liquids

To quantify regolith contributions in order to evaluate assimilation models

To establish genetic, temporal, and spatial relations through mineralogical and chemical affinities

Summary: Martian basaltic meteoritesSummary: Martian basaltic meteorites

Lunar picritic glasses

TiO2 variability and enrichment (0.3-16.4 wt%)

Primary mantle melts?

Potential relation to the mare basalts?

(“It’s orange!” Harrison

Schimtt, Moon, Dec 1972)

Model recipe(s) for hi-Ti picritic glasses

Ilm (FeTiO3) is the chief source of TiO2

Melting of mixed, Ilm-bearing, mantle sources

Assimilation of shallow level Ilm-rich materials by ascending low-Ti mantle melts

Limitations

Late-stage lunar magma ocean (LMO) Ilm+Cpx cumulates cannot sink

Partial melting of LMO Ilm+Cpx cumulates does not produce melts with the observed compositions

Partial melting of hybrid mantle sources produced by mixing of descending hi-Ti melts and Ol+Opx cumulates do not reproduce the picritic glasses

Limitations

Assimilation of shallow level Ilm-rich LMO cumulates or Ilm by ascending low-Ti mantle melts does not reproduce the picritic glass compositions

Trace element and isotope systematics favor small degree partial melting over assimilation

Alternative recipe for hi-Ti glasses

Ilmenite (FeTiO3) is neither the sole nor the dominant Ti oxide, e.g., pseudobrookite oxide (armalcolite: RTi2O5-R2TiO5)

Ti oxides are not introduced late to the deep lunar mantle but coexist with lunar mantle silicate minerals

Oxide-silicate interaction at different levels in the lunar interior

T (oC)

600 900 1200 1500 1800 2100 2400

P (

GPa)

0

1

2

3

4

5

6

Gk

Kar

En Fo

TiO2

SiO2 Kar+Fo

Gk+EnMgOEn Fo

RtRt

Kar

Gk

MgTi2O5: Kar (Psd ox)MgTiO3: Gk (Ilm)TiO2: RtMg2Si2O6: En (Opx)Mg2SiO4: Fo (Ol)

Projection (mol%) from CaAl2Si2O8, Ca2Si2O6, and FeO on the Per (MgO) – Rt (TiO2) – Qz (SiO2) ternary

Summary: Lunar hi-Ti picritic glasses

Ti oxides (Psd, Rt, Ilm), Ol, and Opx can coexist in planetary interiors, including that of the Earth’s Moon

Models of melt segregation from depths that are characterized by Ol+Opx co-precipitation from melt may not be applicable

If picritic glasses are partial melts then their sources may be Ti oxide-bearing pyroxenites and/or harzburgites

Summary: Lunar hi-Ti picritic glasses

Better understanding of high-pressure oxide-silicate phase relations, especially at reducing conditions

Establish mineral and melt compositions (major and trace elements)

Grain-scale distribution of Ti-enriched melts in a peridotitic matrix