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At least 1,009 records · Page 56
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NASA NTRS1977

Orientale and Caloris

Based on revised stratigraphy, structural interpretation, explosion-crater data, and a genetic model for Orientale, it is suggested that Orientale and Caloris have much in common. It is noted that: (1) although the basin fill in Caloris is different from that seen in Orientale, the materials between the most prominent scarp and the weakly-developed outer scarp may be degraded equivalents of the massifs and knobs associated with the Montes Rook, (2) the Montes Rook and the main Caloris scarp have similar stratigraphic and structural features, (3) the lineated ejecta derived from shallower horizons are found near and beyond the weakly-developed outer Caloris scarp which is the counterpart of the Orientale scarp, (4) a well developed field of secondary craters is observed beyond 1 basin diameter at Caloris, (5) the observed textural differences between the material around the main Caloris scarp and the lineated material beyond suggest that Mercury is layered and that Caloris crater excavated coherent materials from one or more of these layers at depth, and (6) the difference in spacing between the Caloris rings is not related to internal layering effects.

Mccauley, J. F.↗
NASA NTRS1977

Interpretations of optical observations of Mercury and the moon

Optical, thermal and radar remote-sensing measurements indicate that Mercury is covered with a relatively thick layer of soil similar in texture and thickness to lunar regolith. Photometric limb profiles measured by Mariner 10 imply that the small-scale slopes on Mercury are about half those on the moon, probably because of differing gravity. The differential photometric functions of Mercury and the moon have a latitudinal dependence which can be completely accounted for by shadowing in craters. The lack of polar darkening on Mercury in spite of the presence of a magnetic field implies that the dominant soil-darkening process on Mercury, and by extension, on the moon is not dependent on the solar wind, but probably is deposition of material evaporated by meteorite impacts. Recent measurements of Mercury's spectral reflectivity in the IR and vacuum UV are both consistent with the surface rocks of Mercury being lower in FeO than those of the moon. Based on laboratory experiments the average FeO content on the surface of Mercury is estimated to be between 3 and 6%.

Hapke, B.↗
NASA NTRS1977

Mineralogy, petrology and chemistry of ANT-suite rocks from the lunar highlands

Anorthositic-noritic-troctolitic (ANT) rocks are the oldest and most abundant rocks of the lunar surface, and comprise about 90% of the suite of the lunar highlands. Consideration is given to the mineralogy, petrology, bulk chemistry, and origin of ANT-suite rocks. Problems associated in classifying and labeling lunar highland rocks because of textural complexities occurring from impact modifications are discussed. The mineralogy of ANT-suite rocks, dominated by plagioclase, olivine and pyrozene, and containing various minor minerals, is outlined. The petrology of ANT-suite rocks is reviewed along with the major element bulk composition of these rocks, noting that they are extremely depleted in K2O and P2O5. Various models describing the origin of ANT-suite rocks are summarized, and it is suggested that this origin involves a parental liquid of high-alumina basalt with low Fe/Fe+Mg.

Prinz, M.↗
NASA NTRS1977

Petrology, mineralogy and chemistry of KREEP basalt

KREEP basalt is an important lunar material that was formed in large quantities early in the evolutionary history of the moon. Fragments of KREEP basalt were returned from all landing sites and make up most of the material of the Apollo 14 collection. These fragments have a wide variety of textures caused by various secondary processes but they are all characterized by a large and distinctive trace-element content. They are also characterized by a general basaltic composition that is similar to the olivine-plagioclase-pyroxene peritectic in the system silica-anorthite-olivine (Fe/Fe + Mg = 0.3).

Meyer, C., Jr.↗
NASA NTRS1978

Investigation of the Manicouagan impact crater, Quebec - An introduction

An interdisciplinary study of the 65-km diameter Manicouagan ring structure in Quebec was undertaken to gain insight into the integrated effects of impacts on terrestrial planetary bodies. The paper serves as an introduction to several companion papers and summarizes major conclusions. Studies of the 214 m.y. old structure show that the melt rocks are texturally inhomogeneous but chemically homogeneous and can be modeled as a mixture of target lithologies. The melt rocks have a Sr-87/Sr-86 ratio compatible with the melting of crustal rocks. The melt had a two-stage cooling history with clast-melt interactions indicative of mixing superheated silicate liquid with cold clasts. Grain size, clast reactions, and thermal equilibration of clasts and melts are described.

Phinney, W. C.↗
NASA NTRS1977

Coarse-grained basalt 71597 - A product of partial olivine accumulation

Rock 71597, a coarse-grained plagioclase-poikilitic basalt that contains 15.8% MgO and 19.3% modal olivine, is described. Olivine and ilmenite crystals occur in two size generations, and large subequant olivine crystals, small 'matrix' olivines, and large ilmenite crystals are characterized. Since large olivine and ilmenite crystals with skeletal habits suggestive of crystallization under relatively rapid cooling are found in a rock whose texture is consonant with slower cooling, it is suggested that the large skeletal crystals formed toward the more rapidly cooled margin of a flow and accumulated by gravitational crystal settling toward the flow's interior. In support of this hypothesis, calculations indicate that the observed olivine compositions are approximately 10 mol% too Fe-rich to have crystallized from a melt of composition corresponding to that of 71597.

Warner, R. D.↗
NASA NTRS1977

Cooling histories of Apollo 15 quartz-normative basalts

Controlled cooling rate studies of vitrophyre 15597 are used to calculate the physical properties of a quartz-normative magma as well as cooling histories of Apollo 15 quartz-normative basalts (QNB). Pyroxene phenocrysts of a QNB magma do not settle appreciably during the cooling of the flow unit; this behavior is consistent with the small degree of chemical differentiation that occurred between members of the suite. Two types of cooling histories for QNB are discerned. The vitrophyres experienced initial slow cooling followed by rapid cooling, and the coarse-grained microgabbros underwent slow nearly linear cooling histories. Textural evidence suggests that lunar vitrophyres crystallized near the top of the flow. It is suggested that the pattern of cooling may have been caused by the chilling of liquids that inherited early crystals in the interior of the flow.

Grove, T. L.↗
NASA NTRS1977

Compositional variation in late-stage differentiates in mare lavas, as indicated by silicate melt inclusions

Questions regarding an interpretation of data from silicate melt inclusions are considered, taking into account the fragmental nature of the record, the possible effects of cooling rate on late-stage melt composition, and the crystallization of the trapped melt. New data related to 484 new analyses are provided in a separate table. Textural and mineralogical features and bulk chemical composition for an overall characterization of late-stage differentiates are discussed. A description is presented of a grouping and recognition of rock types on the basis of late-stage inclusion analyses. Attention is given to the bimodality of potassium values and the delineation of differentiation trends. It is found that many of the problems in interpretation and much of the scatter found in the composition of silicate melt inclusions in lunar samples can be attributed to the incomplete nature of the record and to crystallization after trapping.

Roedder, E.↗
NASA NTRS1977

Feldspathic granulitic impactites and pre-final bombardment lunar evolution

It is suggested that feldspathic granulitic impactites, which are characterized by a high model plagioclase content of between 70 and 80%, all formed in the period after consolidation of the lunar crust and before the final bombardment. The granulitic impactites contain essentially no KREEP component, which suggests that KREEP appeared on the lunar surface mostly after the formation of the granulitic impactites, at about the start of the final bombardment. The granulite metamorphism indicated by the matrix textures of these samples requires 1000 C temperatures for prolonged periods of time. The apparent sequence of formation is granulitic impactites before the final bombardment, crystalline-matrix breccias during the final bombardment, and vitric-matrix breccias after the final bombardment. The sequence is consistent with a described thermal model of breccia lithification and with characteristics of the decay of the meteorite flux rate.

Warner, J. L.↗
NASA NTRS1977

Chemical compositions and possible immiscibility of two silicate melts in 12013

The lunar sample 12013, a complex mixture of gray breccia and black breccia, is described. The gray breccia consists of mostly basaltic and gabbroic lithic clasts as well as plagioclase and pyroxene mineral clasts set in a matrix of smaller clasts and a felsite of granitic composition, while the black breccia is comprised of mostly mineral clasts, some lithic clasts, and felsite blebs enclosed in an aphanitic groundmass of basaltic composition. Textural relationships indicate that the felsite and the black breccia groundmass crystallized from melts which coexisted prior to the final lithification of 12013 but failed to mix. Both the felsite and the black breccia groundmass have extreme enrichments of incompatible elements. The critical feature of their compositions is a 'splitting up' of incompatible element associations so that the highest REE and P concentrations are in the black breccia groundmass, and the highest K, Ba, and Rb concentrations are in the felsite.

Quick, J. E.↗
NASA NTRS1977

Pristine nonmare rocks and the nature of the lunar crust

It is shown that the interdisciplinary study of the nonmare lunar rocks based on trace element, major element, and isotopic data plus petrographic evidence can succeed in amassing a large suite of demonstrably pristine rocks, and that the relative numbers of these rocks are not in accord with statistics amassed on soil fragments and glasses. The term 'pristine' is taken to mean rocks with primary compositions (albeit not necessarily textures) produced by lunar endogenous igneous processes. Melt rocks and crystalline matrix breccias produced by impact processes are excluded. A petrographic synonym for pristine would be 'unremelted, monomict'. It is found that anorthositic norites and noritic anorthosites were rare as primary nonmare rocks. Mechanical mixing appears to have been the dominant petrogenetic process on the highlands.

Warren, P. H.↗
NASA NTRS1977

Petrology of four clasts from consortium breccia 73215

One felsite ('granite') and three ANT-suite anorthositic gabbro clasts extracted from breccia 73215 are described. The felsite clast has two components - fragments of crystalline felsite and veins and patches of felsic glass. The crystalline felsite, which consists largely of a vermicular intergrowth of quartz and Ba-K-feldspar, crystallized from a highly differentiated melt between 3.90 and 4.05 b.y. The felsic glass component consists of crystallized brown and colorless glasses and uncrystallized colorless glass which are all K and Si rich. The relation of glass features to past heating and the breccia-forming event is considered. In the three anorthositic gabbros, which have similar mineralogies and gradational textures, plagioclase is dominant, and olivine and orthopyroxene are the major mafic minerals. The petrologic data suggest that the gabbros formed as heated, partly melted, and/or recrystallized polymict breccias. It is possible that the approximately 4.25 b.y. age obtained for the three rocks is the date of the melting/recrystallization event.

James, O. B.↗
NASA NTRS1977

Effects of thermal metamorphism on compositions of lunar spinels

The reported study represents an attempt to evaluate experimentally the compositional and textural changes that are likely to be observed in the Fe-Ti-Cr spinels of lunar igneous rocks by subsequent thermal metamorphism. The Apollo 12 igneous rock, 12018,43, was chosen for this investigation because an earlier study of another fraction of this rock by El Goresy et al. (1971) has reported an almost continuous trend of spinel compositions between Cr-Ulvoespinel and Ti-chromite. The nature of the compositional changes in the heated spinels (and ilmenites) is found to be such that the changes cannot be explained by intragranular adjustments alone. In the heated sample, pyroxene grains adjacent to the high-Ti spinels show a decrease in FeO, and an increase in MgO and Al2O3 at the interface. This may account for the MgO depletion and a part of the FeO enrichment in the high-Ti spinels. It is believed that the heating experiment demonstrates that thermal metamorphism of lunar basalts is likely to modify the compositions of their preexisting spinels (and ilmenites).

Misra, K. C.↗
NASA NTRS1977

Geology of the Imbrium Basin Apennine Mountains and relation to the Apollo 15 landing site

Detailed mapping of the Imbrium Basin Apennine Mountains has emphasized several important factors in the geologic evolution of this region. Pre-Imbrian topography was composed of two types of landforms: (1) the nearby Serenitatis, South Imbrium, Aestuum, and Vaporum basins which produced widely spaced regional lows and a sequence of basin deposits; (2) pre-Imbrian craters that reworked existing basin deposits and produced local topographic lows. The sequence of events during the Imbrium impact can be summarized as follows: intensive structural uplift along the Apennine Front occurred prior to the emplacement of ballistic ejecta. Ejecta became more discontinuous toward the backslope and produced radial texture by sedimentary erosional and depositional processes. Post-ejecta-emplacement downfaulting exposed pre-Imbrian deposits along the front and caused severe seismic disturbances that reworked many of the previous units and accentuated pre-basin structures. Tectonic mapping and orbital geophysical data support the idea that little structural modification has occurred in the Apennines since their formation 3.9 b.y. ago.

Spudis, P.↗
NASA NTRS1977

Chemical characterization of lunar core 60010

Twenty-eight major, minor, and trace-element abundances have been determined in nine fines fractions of core 60010 by instrumental thermal and 14 MeV neutron activation analysis. With the exception of the elements Fe, Co, and Ni, core section 60010 exhibits a much more uniform composition than the lower section (60009) of the double drive tube collected at the Apollo 16 LM site. The siderophilic meteorite indicator elements Fe, Co, and Ni are significantly enriched in subsample 40, which is located 3.0-4.5 cm below the lunar surface, and are highly variable throughout the 60010 core section. Microscopic examination of subsample 40 revealed the presence of numerous metallic fragments including an approximately 1-mm metal fragment exhibiting only Fe, Co, Ni, and Ir gamma-ray peaks and having a composition typical of a coarse octahedrite. Composition profiles of 60010 exhibit small variations in lithophilic element abundances which can be related to most of the seven stratigraphic units of Duke and Nagle (1976). Although the basal portion of 60010 has been described as texturally similar to the upper unit of 60009, the present chemical studies show a marked compositional difference at this interface.

Ali, M. Z.↗
NASA NTRS1977

Apollo 17 ropy glasses

Ropy glasses are a major soil component in the Apollo 17 gray soils 74240 and 74260. These particles form a distinct morphological type characterized by a wide range of dynamic shapes with a diagnostic sorted and welded fine-grained debris coating. Apollo 17 ropy glasses show abundant evidence for shock. Shocked lithic and mineral inclusions, lack of any igneous textures, and lechatelierite, all indicate an impact origin. A striking similarity is observed between the lunar ropy glasses and the glass impact bombs (Flaedle) of the Ries Crater in Germany. A highland basaltic composition was observed for the Apollo 17 ropy glasses in contrast to the KREEP composition of ropy glasses from the Apollo 12 and Apollo 14 landing sites. Other workers have presented convincing evidence that ejecta from Tycho reached the Taurus-Littrow Valley, and these ropy glasses may represent Tycho ejecta. However, the close stratigraphic association of the ropy glasses with the greater than 3.5 b.y. old orange glass suggests the ropy glasses may be too old to be Tycho ejecta, which should be only about 100 m.y. old. If this is the case, the ropy glasses represent impact glasses from a very old impact in an unknown highlands source area.

Fruland, R. M.↗
NASA NTRS1975

Magma genesis by in situ melting within the lunar crust

Blue-gray breccia 73217 represents a brecciated and partially melted assemblage of plutonic rock fragments. The textural and chemical evidence leads to the conclusion that the melt was generated within the lunar crust and that subsequent cooling and crystallization occurred prior to the transportation of this rock to the surface. The melt generated in this fashion, by in situ melting at depth, of moderately Mg-rich rocks, produced a liquid enriched in Fe, Ti, K, and P which could produce sodic ferrogabbro and granitic rocks similar to the light portion of 12013, but not KREEP.

Crawford, M. L.↗
NASA NTRS1975

Origin of the Station 7 boulder - A note

The origin of the matrix types from the Apollo 17 Station 7 boulder is considered along with the origin of boulder material from Station 2, Boulder 1, and 73215. It is pointed out that the formation of the matrix rocks in this boulder and in the other Apollo 17 boulders in a single impact event is consistent with the isotopic evidence, ages, major-element chemistry, large ion lithophile (LIL) trace-element abundances, and textures. It had been suggested by Winzer et al. (1974), based on calculations from crystal-liquid partition coefficients for LIL trace elements, that target rocks corresponding in trace-element composition to the matrix types could have been produced by partial fusion of rocks similar to 77215. Using the same type of calculation, liquids quite similar in trace-element composition to the Station 7 boulder matrix types can be produced.

Winzer, S. R.↗