Feldspathic granulite 79215 - Limitations on T-fo2 conditions and time of metamorphismFeldspathic granulite 79215, an annealed polymict breccia which has a bulk composition between anorthositic gabbro and gabbroic anorthosite, contains numerous oxide complexes in the matrix. An Ar-39-Ar-40 stepwise heating experiment gives a well-defined plateau corresponding to an age of 4.03 + or - 0.02 AE. The polmict character of this breccia and the variability of the complexes suggest that they formed as a consequence of reactions between spinel-rich clasts and matrix under the high-T low-P conditions of an ejecta blanket. The duration of annealing is estimated to have been less than 10 million yr; the absence of a KREEP component may indicate an inhomogeneous distribution of this component at the lunar surface at 4.0 AE.
Document ID
19790055129
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Mcgee, J. J. (State Univ. of New York Stony Brook, NY, United States)
Bence, A. E. (State Univ. of New York Stony Brook, NY, United States)
Eichhorn, G. (State Univ. of New York Stony Brook, NY, United States)
Schaeffer, O. A. (New York, State University Stony Brook, N.Y., United States)