Martian meteorites (SNC and others)

Shergottite, Nakhlite, Chassignite, Orthopyroxenite, Augite Basalts, Basaltic Breccias

Norbert Brügge, Germany

Last update:
17.01.2015

The SNC-meteorites are a group of Achondrite meteorites, by them is assumed, that they originate from the Mars. They own an in comparison with other meteorite low old (about a billion years) and must originate thus from a celestial object, which had still a relatively young geological activity. Besides they includes gases, which correspond to in their composition of the Mars-atmosphere, as they are determined also by measurements of the Viking-probes.

SNC-Meteorites are often made of small mineral grains that can't be seen clearly without a microscope. To see these small grains, scientists grind and polish rock samples very thin (0.03 millimeters) so light can pass through them. This picture is a microscopic view, about 2.3 millimeters across, of a martian meteorite. The brown areas are grains of the mineral pyroxene and the clear white areas are the mineral plagioclase. These are the two most abundant minerals in basalt, both on Earth and Mars. The black areas are magnetite, an iron-oxide mineral.

The following meteorites are identified as stones from Mars
(compare:  Météorites martiennes  and  imca: List of Martian Meteorites  and  meteoris: List of Martian Meteorites )

 SNC-Group

 

 Name  Location

Date

Type

1

Chassigny

France, Haute-Marne province, village of Chassigny

1815

Chassignite

Dunite

2

Shergotty

India, Bihar State, town Shergahti

1865

Shergottite

Enriched mafic diabasic

3

Zagami

Nigeria, Katsina Province, Zagami Rock

1962

Shergottite

Enriched mafic

4

Los Angeles 001

United States, California, Los Angeles County
(probably Mojave Desert)

?

Shergottite

Enriched mafic diabasic

Los Angeles 002

?

Shergottite

Enriched mafic diabasic

5

Lafayette

United States, Indiana, Lafayette

1931

Nakhlite

Clinopyroxenite

6

Governador Valadares

Brazil, state Minas Gerais, city Governador Valadares

1958

Nakhlite

Clinopyroxenite

7

Nakhla

Egypt, El-Nakhla village, Gov. Alexandria

1911

Nakhlite

Clinopyroxenite

   

 Saudi Arabia

 

 

8

Sayh al Uhaymir 005

Oman, Sayh al Uhaymir

1999

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 008

1999

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 051

2000

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 060

2001

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 090

2002

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 094

2001

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 120

2002

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 125

2003

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 130

2004

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir 150

2002

Shergottite

Depleted permafic olivine-phyric

Sayh al Uhaymir xxxx

2003

Shergottite

Depleted permafic olivine-phyric

9

Dhofar 019

Oman, Dhofar

2000

Shergottite

Depleted permafic olivine-phyric

Dhofar 1668

2010

Shergottite

Depleted permafic olivine-phyric

Dhofar 1674

2010

Shergottite

Depleted permafic olivine-phyric

10

Dhofar 378

2000

Shergottite

Enriched mafic

Dhofar xxxx

2001

Shergottite

Enriched mafic

11

Jiddat al Harasis 479

Oman

2008

Shergottite

Enriched mafic diabasic

   

 Antartica

 

 

12

ALHA 77005

Antarctica, Victoria Land, Allan Hills

1977

Shergottite

Intermediate ultramafic poikilitic

13

EETA 79001A

Antarctica, Victoria Land, Elephant Moraine

1980

Shergottite

Intermediate permafic olivine-phyric

14

EETA 79001B

1980

Shergottite

Mafic

15

LEW 88516

Antarctica, Victoria Land, Lewis Cliff

1988

Shergottite

Intermediate ultramafic poikilitic

16

QUE 94201

Antarctica, Victoria Land, Queen Alexandra Range

1994

Shergottite

Depleted mafic diabasic

17

A

Yamato 000027

Antarctica, Victoria Land, Yamato Mountains

2000

Shergottite

Intermediate ultramafic poikilitic

Yamato 000047

2000

Shergottite

Intermediate ultramafic poikilitic

Yamato 000097

2000

Shergottite

Intermediate ultramafic poikilitic

B

Yamato 793605

1979

Shergottite

Intermediate ultramafic poikilitic

C

Yamato 984028

1998

Shergottite

Intermediate ultramafic poikilitic

YA 1075 (Yanai)

1999

Shergottite

Intermediate ultramafic poikilitic

18

Yamato 000593

2000

Nakhlite

Clinopyroxenite

Yamato 000749

2000

Nakhlite

Clinopyroxenite

Yamato 000802

2000

Nakhlite

Clinopyroxenite

19

Yamato 980459

1998

Shergottite

Depleted permafic olivine-phyric

Yamato 980497

1998

Shergottite

Depleted permafic olivine-phyric

20

GRV 99027

Antarctica, Grove Hill

2000

Shergottite

Intermediate ultramafic poikilitic

GRV 020090

2002

Shergottite

Intermediate ultramafic poikilitic

21

MIL 03346

Antarctica, Transantarctic Mountains, Miller Range

2003

Nakhlite

Clinopyroxenite

MIL 090030

2009

Nakhlite

Clinopyroxenite

MIL 090032

2009

Nakhlite

Clinopyroxenite

MIL 090136

2009

Nakhlite

Clinopyroxenite

22

RBT 04261

Antarctica, Roberts Massiv

2004

Shergottite

Enriched permafic poikilitic

RBT 04262

2004

Shergottite

Enriched permafic poikilitic

23

LAR 06319

Antarctica, Larkman Nunatak

2006

Shergottite

Enriched permafic olivine-phyric

LAR 12011

2012

Shergottite

Enriched permafic olivine-phyric

24

LAR 12095

2012

Shergottite

Depleted permafic olivine-phyric

LAR 12240

2012

Shergottite

Depleted permafic olivine-phyric

   

 North Africa

 

 

25

Dar al Gani 476

Libya

1998

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 489

1997

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 670

1999

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 735

1997

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 876

1998

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 975

1999

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 1037

1999

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani xxxx

1999

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

Dar al Gani 1051

2000

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

26

Ksar Ghilane 002

Tunisia, Quibili

2010

Shergottite

Enriched mafic diabasic

27

NWA 817

Western Sahara

2000

Nakhlite

Clinopyroxenite

28

NWA 1950

Marocco, Atlas mountains

2001

Shergottite

Intermediate permafic poikilitic

NWA 7721

2012

Shergottite

Intermediate permafic poikilitic

29

NWA 4797

Marocco, Missour

2001

Shergottite

Intermediate ultramafic poikilitic

30

NWA 1195

Marocco, Safsaf

2002

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

31

A

NWA 1068

Marocco, Maarir

2001

Shergottite

Enriched permafic olivine-phyric

NWA 1110

2001

Shergottite

Enriched permafic olivine-phyric

NWA 1183

2002

Shergottite

Enriched permafic olivine-phyric

NWA 1775

2002

Shergottite

Enriched permafic olivine-phyric

NWA 2373

2004

Shergottite

Enriched permafic olivine-phyric

NWA 2969

2004

Shergottite

Enriched permafic olivine-phyric

B

NWA 2646

NW-Africa

2004

Shergottite

? Enriched permafic olivine-phyric

C

NWA 3186

Marocco ?

2005

Shergottite

Enriched permafic olivine-phyric

32 A

NWA 4222

NW-Africa

2006

 Shergottite

Depleted permafic olivine-phyric

B

NWA 5789

Marocco

2009

Shergottite

Depleted permafic olivine-phyric

C

NWA 6162

Marocco, Lbirat

2010

Shergottite

Depleted permafic olivine-phyric

D

Tissint

Marocco, Qued Draa

2011

Shergottite

Depleted permafic olivine-phyric

33 A

NWA 856

Western Sahara

2001

Shergottite

Enriched mafic

B

NWA 1669

Marocco

2001

Shergottite

Enriched mafic

C

NWA 5718

NW-Africa

2006

Shergottite

Enriched mafic

NWA xxxx

2009

Shergottite

Enriched mafic

D

NWA 6963

Marocco, Tan Tan

2011

Shergottite

Enriched mafic

NWA 7258

2011

Shergottite

Enriched mafic

E

NWA 7257

Marocco

2011

Shergottite

Enriched mafic

F

NWA 7500

Mali, Taoudenni

2012

Shergottite

Enriched mafic

34

NWA 7032

Marocco

2011

Shergottite

Depleted permafic microgabbroic

NWA 7272

2011

Shergottite

Depleted permafic microgabbroic

35

NWA 7042

Marocco

2011

Shergottite

 Intermediate permafic intersertal

36

NWA 7320

Western Sahara ?

2011

Shergottite

Enriched mafic gabbroic

37

NWA 480

Marocco

2000

Shergottite

Intermediate mafic diabasic

NWA 1460

2001

Shergottite

Intermediate mafic diabasic

NWA 5029

2003

Shergottite

Intermediate mafic diabasic

38 A

NWA 2800

NW-Africa

2007

Shergottite

Enriched mafic diabasic

B

NWA 5298

Mauritania, southern of Bir Gandous

2008

Shergottite

Enriched mafic diabasic

C

NWA 7944

Marocco, Al Mahbas

2013

Shergottite

Enriched mafic diabasic

39

NWA 4480

NW-Africa

2006

Shergottite

Intermediate mafic

40

NWA 5990

Marocco, Hamada du Draa

2009

Shergottite

Depleted permafic diabasic

41

NWA 7635

Western Sahara

2012

Shergottite

Depleted mafic olivine-plagioclase-phyric

42

NWA 2737

Western Sahara

2000

Chassignite

Dunite

43

NWA 4468

Western Sahara, El Aiun

2006

Shergottite

Enriched permafic poikilitic

44

NWA 7387

Western Sahara, Smara

2012

Shergottite

Enriched permafic poikilitic

NWA 7397

2012

Shergottite

Enriched permafic poikilitic

NWA 7755

2012

Shergottite

Enriched permafic poikilitic

NWA 7937

2012

Shergottite

Enriched permafic poikilitic

NWA 8161

2013

Shergottite

Enriched permafic poikilitic

45

NWA 998

Algeria

2001

Nakhlite

Clinopyroxenite

46

A

NWA 2046

Algeria, Lakhbi

2003

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

B

NWA 2626

Algeria

2004

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

C

NWA 4925

2006

Shergottite

Depleted permafic olivine-orthopyroxene-phyric

47 NWA 4527

Algeria

2006

Shergottite

Depleted permafic olivine-phyric

48

NWA 2975

Algeria

2005

Shergottite

Enriched mafic

NWA 2986

2006

Shergottite

Enriched mafic

NWA 2987

2007

Shergottite

Enriched mafic

NWA 3171

2004

Shergottite

Enriched mafic

NWA 4766

2006

Shergottite

Enriched mafic

NWA 4783

2007

Shergottite

Enriched mafic

NWA 4857

2007

Shergottite

Enriched mafic

NWA 4864

2007

Shergottite

Enriched mafic

NWA 4878

2007

Shergottite

Enriched mafic

NWA 4880

2007

Shergottite

Enriched mafic

NWA 4930

2007

Shergottite

Enriched mafic

NWA 5140

2007

Shergottite

Enriched mafic

NWA 5214

2007

Shergottite

Enriched mafic

NWA 5219

2007

Shergottite

Enriched mafic

NWA 5313

2008

Shergottite

Enriched mafic

NWA 5366

2007

Shergottite

Enriched mafic

NWA 7182

2006

Shergottite

Enriched mafic

NWA 7890

2010

Shergottite

Enriched mafic

NWA 8116

2010

Shergottite

Enriched mafic

49

NWA 6342

Algeria

2010

Shergottite

Enriched ultramafic

50

NWA 2990

NW-Africa (Western Sahara ?)

2007

Shergottite

Intermediate permafic olivine-phyric

51

NWA 5960

Mauritania or Western Sahara

2009

Shergottite

Intermediate permafic olivine-phyric

NWA 6234

2010

Shergottite

Intermediate permafic olivine-phyric

NWA 6710

2011

Shergottite

Intermediate permafic olivine-phyric

52

NWA 5790

Mauritania

2008

Nakhlite

Clinopyroxenite

NWA 6148

2009

Nakhlite

Clinopyroxenite

 

 Orthopyroxenite

 

ALH 84001

Antarctica, Victoria Land, Allan Hills

1984

 Enriched ultramafic phaneritic

 

 Augite Basalts

 

NWA 8159

Marocco ?

?

Depleted mafic

 

 Mafic Breccia

 

NWA 7034

Western Sahara, Ghredad Sabti

2011

Strewnfield with
Mafic polymict breccia
(with content of water)

NWA 7475  

NWA 7533

2012
NWA 7906 2013
NWA 7907  2013
NWA 8114 2013
NWA 8171  

 

 Ungrouped

Mercury ?

NWA 7325

Marocco ??

2012 new ungrouped Achondrite
with greenish crystalls (chromium diopside)

NWA 8014

Algeria, Bir el Abbes

2013

NWA-8409

 NW-Africa 2013

 

The most abundant group of SNC meteorites are called the basaltic shergottites. Their composition is similar to that of rocks analysed at the Opportunity landing site and the basaltic component that forms much of the martian surface regolith and underlying geology in terms of Fe enrichment. However, the Spirit rocks are picritic and also more alkali-rich than the basaltic shergottites. Olivine-phyric shergottites form another recognizable group of the shergottites, which accumulated phenocryst or xenocryst olivine grains from a separate olivine-saturated basaltic melt. These large olivine grains were not derived by disruption of peridotite shergottite sources because the olivine-phyric shergottites generally have a more highly depleted geochemistry than the peridotitic shergottites. Peridotite shergottites have the clearest cumulate textures of the SNCs and differ from the other shergottites in their low proportion of feldspathic material and high proportions of olivine. The cores of pyroxene in basaltic shergottites crystallized slowly at depth from melts that at least in some cases were H2O-bearing followed by more rapid crystallization of the Fe-rich rims in a near-surface intrusive or extrusive setting.
Pyroxenite nakhlites formed as cumulates in a thick lava flow from the accumulation of augite followed by olivine. Trapping of varying amounts (5-20%) of basaltic, interstitial melt (the nakhlites in the upper parts of the parental lava flow having the higher proportions of trapped melt) has given the nakhlites their LREE-enriched geochemical signature. The dunite Chassigny, which has near-identical ejection and crystallization ages to the nakhlites, may also be associated with them.
The martian mantle source region has over twice the FeO contents of the terrestrial mantle and the SNC compositions reflect this in their Fe enrichment compared with analogous terrestrial and lunar rocks. Another compositional feature of the SNCs is their low Al contents, which reflect depletion of source regions, perhaps as a result of the formation of a magma ocean. However, discordance between Mg-number and Al2O3 contents of the nakhlite and other SNC groups shows that the SNC melts were derived from mantle source regions with differing depletion histories. The modelled martian magma ocean would have a lower proportion of plagioclase and lower density than the lunar one. Inferred noble metal contents in the martian mantle calculated from the SNCs suggest that, like the Earth, Mars underwent a later accretion of chondritic material.
In addition to petrographic classification, we suggest that the basaltic, olivine-phyric and peridotitic shergottites can also be subclassified geochemically on the basis of their LREE depletion into HD (highly depleted), MD (moderately depleted) and SD (slightly depleted). The SD shergottites mainly correspond to the basaltic shergottites, the MD to peridotitic shergottites and the HD correspond to olivine-phyric shergottites.
The melt compositions of the SNCs, either known directly from the whole-rock composition or calculated from melt inclusions within cumulate phases, do not show any clear evidence for an andesitic component. The best data available from the Pathfinder rock analyses suggest that those rocks may be basaltic andesites; that is, with slightly higher SiO 2 and Na2O + K2O than the basaltic shergottites (although it is possible that this chemistry reflects contamination of the Pathfinder analyses by alteration rinds). Spectroscopic data in support of the geochemical evidence for an andesitic component in the northern lowlands of Mars are not yet conclusive. However, the existence of a K- and Fe-enriched component in parts of the northern lowlands distinct from the basaltic signature in the remaining northern lowlands and southern highlands is established. The formation mechanism for such large-scale magmatic heterogeneities is not clear but might involve fractionation of basaltic magmas trapped in magma ocean rocks or the fractionation of shergottitic compositions under hydrous conditions.
The absence of an andesitic-like chemical signature in the SNCs suggests that they were derived from areas in the northern lowlands where the K-rich 'andesitic' spectral signature is absent or in low abundance. Two likely regions are the Tharsis region of shield volcanoes and the Elysium-Amazonis volcanic plains. These regions also contain young volcanic rocks compatible with the relatively young ages of the SNCs. The crystallization ages fall within five groups. ALH84001 is the oldest at 4.5 Ga, the nakhlites and Chassigny have ages of 1.3 Ga, peridotitic shergottites 180 Ma and basaltic shergottites 165-475 Ma. On the basis of these ages it is clear that only the ALH84001 orthopyroxenite is derived from the ancient highlands. The SNCs were ejected from Mars in between four and seven impact events but uncertainties in the calculation of ejection ages means that the grouping of samples with ejection events is not always clear. However, the ejection of the nakhlites and chassigny in one event at 11 Ma is well established.

This summary is results from a meeting held at the Geological Society of London in 2003 about Volcanism on Mars.


 

An interesting question is this:
Have the recently diagnosed organic cellules and carbonat globules in the meteorites ALH 84001 a relevance ?