Fezzou 002 ( 2,051 g )

Endstück mit Kruste, auf Hochglanz poliert !
 
Endcut with crust, highly polished !
 
 
Angrite, benannt nach Angra dos Reis, Brasilien, im Herbst 1869, sind eine relativ seltene Art von basaltischem Achondrit mit niedrigem Alkaligehalt, hohem Ca/Al-Verhältnis und einer charakteristischen Mineralzusammensetzung, die im Allgemeinen Al-Ca-Ti-reiches Pyroxen, Ca-reichen Plagioklas und Ca-reichen Olivin umfasst, aus dem möglicherweise das Mineral Kirschsteinit freigesetzt wurde.
 
Angrites, named after the Angra dos Reis, Brazil, fall of 1869, are a relatively rare type of basaltic achondrite with low alkali contents, high Ca/Al ratios, and a distinctive mineral assemblage, generally including Al-Ca-Ti-rich pyroxene, Ca-rich plagioclase, and Ca-rich olivine that may have exsolved the mineral kirschsteinite.
 
 
Fezzou 002        30.794°N, 4.861°W
Centre-South, Morocco
Find: 2023 Sep
Classification: Angrite
History: Found in September 2023 in eastern Morocco near the village of Lahfira at 30.794°N, 4.861°W and subsequently purchased from the finder by Mark Lyon.
Physical characteristics: A single broken stone in two pieces (11340 and 1028 g) with a thin coating of vesicular black fusion crust.
Petrography: (A. Irving, UWS, and P. Carpenter, WUSL) The specimen is an aggregate (mean grainsize ~350 µm) of interlocking anhedral grains exhibiting an allotriomorphic-granular texture. Composed predominantly of Al-Ti-augite (pink in thin section), Ca-bearing olivine, kirschsteinite and almost pure anorthite together with accessory hercynitic spinel (pleonaste), troilite and rare Fe metal. Blades or lamellae of kirschsteinite are present within some olivine grains. Some polycrystalline pyroxene-rich clusters and clusters of kirschsteinite+olivine up to ~3 mm in size are present. Vesicles are absent.
Geochemistry: Al-Ti-augite (Fs16.3-17.9Wo56.2-57.8, FeO/MnO = 77-101, Al2O3 10.1-11.4 wt.%, TiO2 1.5-2.8 wt.%, N = 5), olivine (Fa59.4-60.5Ln2.4-3.2, FeO/MnO = 61-68, N = 4), kirschsteinite (Fa37.7-39.3Ln45.0-48.1, FeO/MnO = 59-65, N = 4), anorthite (An99.9-100.0Or0.0, N = 4), pleonaste [Fe0.78Mg0.30Al1.88 Ti0.02Cr0.04O4]. Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed subsamples by laser fluorination gave, respectively δ17O 2.217, 2.194, 2.137; δ18O 4.444, 4.350, 4.239; Δ17O -0.130, -0.103, -0.101 per mil (all data linearized, TFL slope = 0.528).
Classification: Angrite (allotriomorphic-granular).
Specimens: 34.5 g including one polished thin section at UWB; 40 g at Ministry of Energy Transition and Sustainable Development, Rabat, Morocco; remainder with Mr M. Lyon.
 
State/Prov/County:
Centre-South
Place of purchase:
Morocco
Date:
2023 Sep
Latitude:
30.794°N
Longitude:
4.861°W
Mass (g):
12368
Pieces:
2
Class:
Angrite
Shock stage:
low
Weathering grade:
low
Fayalite (mol%):
59.4-60.5
Ferrosilite (mol%):
16.3-17.9
Wollastonite (mol%):
56.2-57.8
Classifier:
A. Irving, UWS, and P. Carpenter, WUSL
Type spec mass (g):
34.5
Type spec location:
UWB
Main mass:
M. Lyon
Comments:
Work name JC23-8; submitted by A. Irving