Deformation of Silicates from the Sea of Tranquillity

Carter, N. L.; Leung, I. S.; AvéLallemant, Hans G.

doi:10.1126/science.167.3918.666

Cited by 6 publications

(2 citation statements)

References 4 publications

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“…It thus appears that strain in chondrule pyroxene often originated in a process other than shock. A similar conclusion was reached for lunar pigeonites and augites in Apollo II basalts (Carter et al, 1970;Sclar, 1970;Chao et al, 1970). As discussed below, low-Ca pyroxene in Chainpur chondrules was probably strained by polytype transformations (protoenstatite --+ CLENI OREN and CLEN --+ OREN) that arose during the crystallization and annealing of the chondrules.…”

Section: Significance Of Strain In Low-ca Pyroxenesupporting

confidence: 55%

Deformation and thermal histories of chondrules in the Chainpur (LL3.4) chondrite

Ruzicka

1990

Meteoritics

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Transmission-electron-microscopy (TEM) and optical data suggest that chondrules in the Chainpur (LL3.4) chondrite experienced varied thermal and deformation histories prior to the final agglomeration ofthe meteorite. Chainpur may be regarded as an agglomerate or breccia that experienced little deformation or heating during and after the final accumulation and compaction of its constituents.One chondrule in Chainpur was impact-shocked to high pressures (-20-50 GPa), almost certainly prior to final agglomeration, either while it was an independent entity in space or while it was in the regolith of a parent body. However, most (>85%) of the chondrules in Chainpur were evidently not significantly shock-metamorphosed subsequent to their formation. The dearth of shock effects implies that most chondrules in Chain pur did not form by shock melting, although some chondrules may have formed by this process.Dusty-metal-bearing olivine grains, which are widely interpreted to have escaped melting during chondrule formation, contain moderate densities of dislocations (-10' em -2). The dislocations in these grains were introduced before or during the last episode ofmelting in at least one chondrule. This observation can be explained if olivine was impact-deformed before or during chondrule formation, or if olivine was strained by reduction or thermally-induced processes during chondrule formation.Low-Ca pyroxene grains in chondrules are often strained. In most cases this strain probably arose as a by-product of polytype transformations (protoenstatite~clinoenstatite/orthoenstatite and clinoenstatite~orthoenstatite) that occurred during the igneous crystallization and static annealing of chondrules.Droplet chondrules with glassy mesostases were minimally annealed, consistent with an origin as relatively rapidly cooled objects in an unconfined, cold environment. Some irregular chondrules and at least one droplet chondrule were thermally metamorphosed prior to final agglomeration, either as a result of moderately slow cooling (-100°C/hr) from melt temperatures (during auto metamorphism) or as a result of reheating episodes. Two ofthe most annealed chondrules contain relatively abundant plagioclase feldspar, and one of these has a uniform olivine composition appropriate to that of an LlA chondrite.

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Section: Significance Of Strain In Low-ca Pyroxenesupporting

confidence: 55%

Deformation and thermal histories of chondrules in the Chainpur (LL3.4) chondrite

Ruzicka

1990

Meteoritics

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“…Compositional variations, both within and between grains, are extremely complex. The grains are strongly zoned and they contain inhomogeneities that are not related to zoning, probably produced by rapid crystallization[Carter et al, 1970]; in addition, they contain inhomogeneities resulting frown subsolidus unmixing[Ross et al, 1970]. Most of the pyroxene is augire and subcalcic augire.…”

mentioning

confidence: 99%

Petrology of the Apollo 11 ilmenite basalts

James¹,

Jackson²

1970

J. Geophys. Res.

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Most of the crystalline rock fragments in the sample of lunar regolith returned by Apollo 11 are ilmenite basalts. The mineralogy of all these rocks is similar; major minerals are clinopyroxene, calcic plagioclase, and ilmenite, and olivine is a common minor constituent. But they differ considerably in textures, bulk chemical compositions, sequence of crystallization, and mineral compositions. Two textural variants make up the bulk of the fragments: intersertal basalts (most type A rocks); and ophitic basalts (all type B rocks). Ophitic basalts may be subdivided into fine-and medium-grained types, and their textures, wholerock compositions, mineral proportions, and mineral compositions vary systematically with grain size. The textural variations and compositional trends are similar to those of terrestrial basalts from partly differentiated sills or thick lava flows; the ophitic basalts are probably derived from one or more thick lunar lava flows or sills that fractionated slightly on cooling. Intersertal basalts have more uniform whole-rock compositions, mineral proportions, and mineral compositions than do ophitic basalts, and it appears that the samples are derived from the same or closely related magmas that did not fractionate appreciably during crystallization. These rocks have textures indicating that their parent magma was extruded onto the lunar surface and cooled rapidly. Hornfels textures in many samples suggest that they have been thermally metamorphosed, but this process did not greatly modify vesicularity, mineral proportions, whole-rock compositions, or mineral compositions. Textures of both primary volcanic and annealed basalts are identical to those of basalts from terrestrial lava lakes; it seems likely that the intersertal basalts crystallized in one or more lunar lava lakes. No reasonable process of fractional crystallization can link the parent magmas of the intersertal and ophitic ilmenite basalts, and it is likely that both formed independenfiy by fractional melting in the lunar interior. Other types of basalt occur as sparse small fragments in the regolith and in breccias. Most common among these minor types are ilmenite basalt vitrophyres that have the same mineral assemblage as the two major types but have much more variable textures and mineral proportions. The general geology of the landing site suggests that the intersertal and ophitic rocks are fragments of local bedrock, and that the mare filling beneath the landing site consists largely of basaltic lava. flows. Age-dating studies of the surface debris indicate that the regolith has an apparent age at least a half billion years older than the ilmenite basalt fragments it contains. There is some evidence to suggest that the regolith, in addition to fragmented basalt, contains 15-30% of very fine plagioclaserich material that. has a very old apparent age, and that may be derived from the lunar highlands.The surface of the moon at the landing site of the Apollo 11 lunar module is a layer of fragmental debris, the lunar regolith, estimat...

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A martini-glass clinopyroxene from the moon

Bence

Papike

1971

Earth and Planetary Science Letters

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Deformation of Silicates from the Sea of Tranquillity

Cited by 6 publications

References 4 publications

Deformation and thermal histories of chondrules in the Chainpur (LL3.4) chondrite

Deformation and thermal histories of chondrules in the Chainpur (LL3.4) chondrite

Petrology of the Apollo 11 ilmenite basalts

A martini-glass clinopyroxene from the moon

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