Pecora Escarpment 82506 meteorite, Pecora Escarpment, Transantarctic Mountains, Eastern Antarctica, Antarcticai
Regional Level Types | |
---|---|
Pecora Escarpment 82506 meteorite | Meteorite Fall Location |
Pecora Escarpment | - not defined - |
Transantarctic Mountains | Mountain Range |
Eastern Antarctica | Region |
Antarctica | Continent |
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Latitude & Longitude (WGS84):
85° 41' 27'' South , 67° 42' 47'' West
Latitude & Longitude (decimal):
Locality type:
Meteorite Class:
Meteoritical Society Class:
Köppen climate type:
Other/historical names associated with this locality:
PCA 82506
Ureilite (olivine-pigeonite subgroup)
(Find, 1982; 5.32 kg)
When discovered on the Antarctic ice, the moderately large Pecora Escarpment 82506 (PCA 82506) meteorite [dimensions, 22 x 16 x 9 cm] retained a patchy fusion crust covering ~75% of the surface. Beneath the surface small grains of olivine (Fa21) and pigeonite (Wo6Fs18En76) of uniform composition dominated the meteorite's volume. Many individual grains were rimmed by carbonaceous material — primary graphite accompanied by Fe-rich metal, troilite, occasional cohenite, and other phases. The olivine is Ca-rich as is characteristic for ureilites with some grains exhibiting shock-produced undulose extinction (albeit, for a ureilite, relatively mild). The very small amounts of original metal have largely been converted into limonite during the meteorite's ~12,000 year residence on (or under?) the Antarctic ice. Sm-Nd model ages suggest that most of the meteorite's components were accumulated ~4.55 billion years ago. During this epoch of aggregation, the pigeonite was produced during a short period of very rapid cooling. In the main PCA 82506's general characteristics conform to those of most ureilites, but the presence of magmatic carbon has generated perhaps the most sustained topic of inquiry.
Ureilites are olivine-pyroxene cumulates that contain interstitial carbon. Ureilites are the second largest group of achondrites or differentiated stony meteorites (only the HED meteorites, largely derived from Vesta are more numerous). PCA 82506 is among the more massive of theses unusual meteorites, ranking 8th out of the 400+ ureilite specimens listed at the 'Meteoritical Bulletin Database' as of mid-July 2015. Indeed, PCA 82506 was the second largest ureilite recovered before 2000 (6 larger ones, 5 from African deserts have since been recovered). It is somewhat surprising that such a large meteorite has not been given more attention than it has. It may be that untangling the details of an early episode(s) of reduction found on the rims of some grains has been obscured by the slow, but relentless oxidation produced by twelve millennia of exposure to the earth's air and ice.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsMineral List
6 valid minerals.
Meteorite/Rock Types Recorded
Note: data is currently VERY limited. Please bear with us while we work towards adding this information!
Select Rock List Type
Alphabetical List Tree DiagramDetailed Mineral List:
ⓘ 'Clinopyroxene Subgroup' Reference: Berkley, J. L. (1986) Four antarctic ureilites: Petrology and observations on ureilite petrogenesis. Meteoritics 24(2): 169-189. (June 1986). |
ⓘ Cohenite Formula: Fe3C Reference: Berkley, J. L. (1986) Four antarctic ureilites: Petrology and observations on ureilite petrogenesis. Meteoritics 24(2): 169-189. (June 1986). |
ⓘ Enstatite Formula: Mg2Si2O6 Description: Attached to the thin reduced olivine rim. Reference: Miyamoto, M., Toyoda, H. & Takeda, H. (1985) Thermal History of Ureilite as Inferred from Mineralogy of Pecora Escarpment 82506 (abstract). Lunar and Planetary Science XVI, pp. 567-568. (Mar 1985). |
ⓘ 'Fayalite-Forsterite Series' Reference: Antarctic Meteorite Working Group (1984) Antarctic Meteorite Newsletter 7(1). (Feb 1984).; Miyamoto, M., Toyoda, H. & Takeda, H. (1985) Thermal History of Ureilite as Inferred from Mineralogy of Pecora Escarpment 82506 (abstract). Lunar and Planetary Science XVI, pp. 567-568. (Mar 1985).; Berkley, J. L. (1986) Four antarctic ureilites: Petrology and observations on ureilite petrogenesis. Meteoritics 24(2): 169-189. (June 1986). |
ⓘ Graphite Formula: C Description: As tiny grains. Reference: Berkley, J. L. (1986) Four antarctic ureilites: Petrology and observations on ureilite petrogenesis. Meteoritics 24(2): 169-189. (June 1986). |
ⓘ Iron Formula: Fe Description: Iron (Ni 2.7wt%) in at least one instance. Reference: Berkley, J. L. (1986) Four antarctic ureilites: Petrology and observations on ureilite petrogenesis. Meteoritics 24(2): 169-189. (June 1986). |
ⓘ 'Limonite' Reference: Antarctic Meteorite Working Group (1984) Antarctic Meteorite Newsletter 7(1). (Feb 1984). |
ⓘ Pigeonite Formula: (CaxMgyFez)(Mgy1Fez1)Si2O6 Reference: Antarctic Meteorite Working Group (1984) Antarctic Meteorite Newsletter 7(1). (Feb 1984).; Miyamoto, M., Toyoda, H. & Takeda, H. (1985) Thermal History of Ureilite as Inferred from Mineralogy of Pecora Escarpment 82506 (abstract). Lunar and Planetary Science XVI, pp. 567-568. (Mar 1985). |
ⓘ Troilite Formula: FeS Reference: Antarctic Meteorite Working Group (1984) Antarctic Meteorite Newsletter 7(1). (Feb 1984). |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
Group 1 - Elements | |||
---|---|---|---|
ⓘ | Cohenite | 1.BA.05 | Fe3C |
ⓘ | Graphite | 1.CB.05a | C |
ⓘ | Iron | 1.AE.05 | Fe |
Group 2 - Sulphides and Sulfosalts | |||
ⓘ | Troilite | 2.CC.10 | FeS |
Group 9 - Silicates | |||
ⓘ | Enstatite | 9.DA.05 | Mg2Si2O6 |
ⓘ | Pigeonite | 9.DA.10 | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
Unclassified Minerals, Rocks, etc. | |||
ⓘ | 'Clinopyroxene Subgroup' | - | |
ⓘ | 'Fayalite-Forsterite Series' | - | |
ⓘ | 'Limonite' | - |
List of minerals for each chemical element
C | Carbon | |
---|---|---|
C | ⓘ Cohenite | Fe3C |
C | ⓘ Graphite | C |
O | Oxygen | |
O | ⓘ Pigeonite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
O | ⓘ Enstatite | Mg2Si2O6 |
Mg | Magnesium | |
Mg | ⓘ Pigeonite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
Mg | ⓘ Enstatite | Mg2Si2O6 |
Si | Silicon | |
Si | ⓘ Pigeonite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
Si | ⓘ Enstatite | Mg2Si2O6 |
S | Sulfur | |
S | ⓘ Troilite | FeS |
Ca | Calcium | |
Ca | ⓘ Pigeonite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
Fe | Iron | |
Fe | ⓘ Pigeonite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
Fe | ⓘ Troilite | FeS |
Fe | ⓘ Cohenite | Fe3C |
Fe | ⓘ Iron | Fe |
References
Sort by
Year (asc) Year (desc) Author (A-Z) Author (Z-A)Antarctic Meteorite Working Group (1984) Antarctic Meteorite Newsletter 7(1). (Feb 1984).
Miyamoto, M., Toyoda, H. & Takeda, H. (1985) Thermal History of Ureilite as Inferred from Mineralogy of Pecora Escarpment 82506 (abstract). Lunar and Planetary Science XVI, pp. 567-568. (Mar 1985)
Berkley, J. L. (1986) Four antarctic ureilites: Petrology and observations on ureilite petrogenesis. Meteoritics 24(2): 169-189. (June 1986).
Goodrich, C. A. & Lugmair, G. W. (1991) PCA 82506: A Ureilite with LREE-enriched Component and a Whole Rock Sm-Nd Model Age of 4.55 Ga (abstract). Lunar and Planetary Science Conference XXII: 467-468. (March 1991).
Mittlefehldt, D. W., McCoy, T. J., Goodrich, C. A. & Kracher, A. (1998). Non-chondritic meteorites from asteroidal bodies. In: Planetary Materials (Papike, J. J., Editor): Chapter 4, 195 pages. Mineralogical Society of America: Washington, DC, USA. (1998).
Molin, G. M., Pasqual, D., Tribaudino, M. & Goodrich, C. A. (1999) Thermometric and Microtextural Study of P21/c Pigeonite from Ureilite PCA82506 (En 76) and an Fe-rich Terrestrial Pigeonite (En 47). 30th Annual Lunar and Planetary Science Conference, abstract no. 1140 (Mar 1999) .
Grady, M. M. (2000). Catalogue of Meteorites (5/e). Cambridge University Press: Cambridge; New York; Oakleigh; Madrid; Cape Town. 689 pages.
Grady, M. M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.
Other Regions, Features and Areas containing this locality
Antarctic PlateTectonic Plate
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