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Lunar highland rock types: Their implications for impact-induced fractionationLunar rocks may be classified into three major groups: (1) coarse-grained igneous rocks, (2) fine-grained igneous rocks, and (3) breccias. Group 1 is interpreted as primitive lunar crustal rocks that display various degrees of crushing and/or annealing. Group 2 is interpreted as volcanic rocks. Group 3 is interpreted as resulting from impacts on the lunar surface and is subdivided on the basis of matrix textures into fragmental breccias, crystalline breccias that have been annealed, and crystalline breccias with igneous matrices. A synthesis of the data concerning lunar highlands polymict breccias compels the prediction that the breccias should have homogeneous matrices from rock to rock within regions of the highlands of limited size where impact mixing has been efficient and extensive. But the returned breccias, even from one landing site, display a wide range in composition. This incompatibility between prediction and observation is a paradox that may be resolved by a process that acts after impact mixing to cause a differentiation of the breccia compositions. Partial melting of the local average crustal composition (as modeled by the average soil composition for each site) and separation of melt and residue in ejecta and/or fall-back blankets are compatible with the reviewed data and may resolve the paradox.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Phinney, W. C.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Warner, J. L.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Simonds, C. H.
(Lunar Science Inst.)
Date Acquired
August 9, 2013
Publication Date
January 1, 1977
Publication Information
Publication: The Soviet-Am. Conf. on Cosmochem. of the Moon and Planets, pt. 1
Subject Category
Report/Patent Number
Accession Number
Funding Number(s)
Distribution Limits
Work of the US Gov. Public Use Permitted.
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