76315 (94) Impact Melt Breccia
We would like to thank the following for the use of this sample:
76315 is a micropoikilitic impact melt breccia whose matrix has finely-divided flow banding. The modal mineralogy of the matrix is about 50% plagioclase and 40% low-Ca pyroxene with minor amounts of augite, olivine, ilmenite, armalcolite and metallic iron. Clasts seen in 20 thin sections include poikilitic 70-80% plagioclase fragments, granulitic 70-80% plagioclase fragments, crushed feldspar or anorthositic fragments (rotation 1), intersertal plagioclase-pyroxene-olivine fragments, crushed spinel-olivine fragments, crushed troctolite fragments and aphanitic feldspathic fragments. Surprisingly, in our thin section there is an almost perfectly euhedral pyroxene clast (rotation 2).
The sample weighed 671 grams before analysis and has been broadly dated at 3.9 billion years (Ar/Ar).
Further details of this and other Apollo samples are here: http://curator.jsc.nasa.gov/lunar/
Ma = Millions of years ago
Rock forming mineral:
- metallic iron,