magma evolution of poikilitic shergottite nwa 7397 from ... · magma evolution of poikilitic...
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RESEARCH POSTER PRESENTATION DESIGN © 2015
www.PosterPresentations.com
NWA 7397
• Poikilitic shergottite
• Discovered in Morocco in June, 2012 [1]
• 2.13 kg, partially covered in fusion crust
• 3rd REE-enriched permafic (after RBT 04262 and GRV 020090) [2]
• Crystallization age: ??
• Comprised of 2 lithologies [2] :
Poikilitic: olivine, pyroxene, chromite
Non-poikilitic: olivine, pyroxene, maskelynite, minor spinel, phosphate, sulfide, Fe-oxide
• Olivine of both lithologies contain melt inclusions (MIs)
Introduction
• Determine the melt inclusion (MI)-source magmas and their progressivedifferentiation using textural observations
• Understand the evolution of shergottite magmatic systems
Objectives
7 MIs of a thick section of NWA 7397 (Fig. 3) were studied by-
• EDX-elemental maps and BSE-images JEOL-SEM 7600F @ NASA-JSC
• Major oxide analysis of host olivines and MIs Cameca SX-100 electronmicroprobe @ NASA-JSC
• Modal composition (in wt.%) calculation of MIs ImageJ software
• Post-entrapment Fe-Mg re-equilibration correction PETROLOG3 software
Methods
Melt Inclusions (MIs)
References
[1] Meteoritical Bulletin Database. [2] Howarth et al. (2014) MAPS, 49, 1812-1830. [3] Danyushevsky et al. (2002) Chem Geo, 183, 5-24. [4] Potter et al. (2015) LPSC XLVI, Abstr. #2945. [5] Basu Sarbadhikari et al. (2011) GCA, 75, 6803-6820. [6] Basu Sarbadhikari et al. (2016) MAPS, 1-17. [7] Agee et al. (2013) Science, 339, 780-785. [8] Filiberto & Dasgupta (2011) EPSL, 304, 527-537. [9] McSween et al. (2009) Science, 324, 736-739. [10] McSween et al. (2006) JGR, 111, E02S10. [11] Schmidt et al. (2014) JGR, 119, 64-81.
Compared to RBT 04262
1University of Houston, Houston TX 77204, USA, [email protected], 2Jacobs, NASA-Johnson Space Center, Mail Code X13, Houston TX 77058, USA
J. Ferdous1, A. D. Brandon1 and A. H. Peslier2
Magma Evolution of Poikilitic Shergottite NWA 7397
from its Olivine-hosted Melt Inclusions
Figure 1: NWA 7397. block is 1 cm.
Source: www.meteoritemarket.com
Figure 3: Energy Dispersive X-ray (EDX) map of NWA 7397 thick section showing major phaseswith the poikilitic (P) and non-poikilitic (nP) lithologies outlined by the black line. The analyzedmelt inclusion (MI) locations are marked by red boxes.
Figure 5: Compositional diagram of primarypyroxenes [2] and MI-pyroxenes (MI PX) ofNWA 7397.
Melt Compositions
Figure 2: Major phases and modalabundances of NWA 7397 [2].
Host OlivineMI Ca-poor PXMI Ca-rich PX
a)Host OlivineMI Ca-poor PXMI Ca-rich PX
b)
Host OlivineMI-1 Mg-rich PX rimMI-1,2 K-Na-rich GlassMI-2 Ca-rich PX rim
c)
MI-1
MI-2
Host OlivineMI-1,2 PXMI-1,2 K-Na-rich Glass
d)
MI-1
MI-2
Host OlivineMI Mg-rich PX rimMI Ca-rich PX rimMI Plag-rich GlassMI K-feld-rich Glass
e) f)Host OlivineMI Ca-P-rich PXMI Plag-rich Glass
Figure 4: Compositional maps of NWA7397 melt inclusions generated usingImageJ software. Poikilitic MIs (a-b) andNon-poikilitc MIs (c-g). PX= pyroxene,Plag= plagioclase, K-feld= K-feldspar.
Host OlivineMI Plag-rich GlassMI K-feld-rich GlassMI SulfideMI Phosphate
g)
Primary PXMI PX
Figure 6: MgO/FeO ratios of NWA 7397 MIs andcorrected for Fe-Mg exchange with host olivinevs. forsterite content (Fo) of host olivine. Blackarrow= equilibrium conditions between olivineand basaltic melt [3].
Figure 8: SiO2 vs. (a) FeO/MgO ratio and (b) Na2O+K2O- diagrams of MI-trapped magma
compositions (MC) of NWA 7397, RBT 04262 [4], LAR 06319 [5] and Tissint [6] with other
Martian surface rocks [7,8] and Martian mantle average [8]. Blue arrows= fractionation trends in
terrestrial magmas [9]. Blue shaded area= SNC-bulk composition field, Pink shaded area= Gusev
crater rock composition field [10], Green shaded area= Gale crater rock composition field [11].
Figure 7: Molar Mg# vs. (a) SiO2, (b) Al2O3, (c) CaO and (d) CaO/Al2O3 contents of MIs of NWA7397 and another olivine-phyric shergottite RBT 04262 [4] before and after the post-entrapmentcorrections [3]. P= Poikilitic MI, nP= Non-poikilitic MI, PBC= Present Bulk Composition, MC=Trapped Magma Composition.
Compared to Other Meteorites and Rover data
0
5
10
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25
0 10 20 30 40 50 60 70 80
Al 2
O3
(wt
%)
(b)
0
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0 10 20 30 40 50 60 70 80
CaO
(w
t %
)
Molar Mg#
(c)
0
0.4
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0 10 20 30 40 50 60 70 80
CaO
/Al 2
O3
Molar Mg#
(d)
(a)
(b)
Conclusions
• MI of NWA 7397 and RBT 04262 have higher SiO2 and distinct alkali-contentscompared to SNC bulk-rock and Bounce rock. Their compositions can be linkedby fractional crystallization processes.
• Some MI of NWA 7397 and RBT 04262 have compositions resembling that ofrocks analyzed by the Pathfinder rover.
• One MI from NWA 7397 has a composition similar to those of Gale craterrocks.
45
55
65
75
0 10 20 30 40 50 60 70 80
SiO
2(w
t%)
NWA-P-PBC NWA-P-MC NWA-nP-PBC
NWA-nP-MC RBT-P-PBC RBT-P-MC
RBT-nP-PBC RBT-nP-MC(a)