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NASA NTRS1982

Petrologic and age relations of the Apollo 16 rocks - Implications for subsurface geology and the age of the Nectaris basin

In connection with its proximity to the Nectaris basin, the Apollo 16 site is the prime lunar sampling site for dating the Nectaris impact. It is found that the Ar-40/Ar-39 data set upper limits on the time of formation of the major types of breccia at the Apollo 16 site. These are 3.92 b.y. for the feldspathic fragmental breccias, and 3.92 b.y. for the dimict breccias. The data establish that the major subsurface units at the site were deposited no longer than 3.92 b.y. ago. Recent developments indicate that the bulk of the material at the site probably has Nectarian or pre-Nectarian ages. An age of 3.9 b.y. must be a rough upper limit to the age of the Nectaris impact. This limit must be verified by additional studies.

James, O. B.↗
NASA NTRS1982

Geochemical studies of rocks from North Ray Crater, Apollo 16

The samples included in the study were all collected as individual specimens from Station 11 near the rim of North Ray Crater. Samples were selected to cover the entire range of rock types from anorthosites to subophitic impact melts, giving particular attention to the feldspathic breccias which predominate at the site. The chemical composition of North Ray Crater rocks is discussed along with the compositional variations among North Ray Crater samples, and the relationships between North Ray Crater and other Apollo 16 stations. It is pointed out that the primary objective in sampling the Apollo 16 site was to characterize materials from the Cayley Plains and Descartes Highlands.

Lindstrom, M. M.↗
NASA NTRS1982

Regolith maturation on the earth and the moon with an example from Apollo 15

Petrographic data on twelve Apollo 15 surface samples and on twelve samples from the double drive tube 15010/011 are presented in the form of triangular AML (agglutinate-monomineralic fragments-lithic fragments) plots. The triangular AML plots for different grain sizes show smoothly varying contour lines only for the solids derived mainly from mare basalts. These contour lines are interpreted as lines of isomaturity. The AML plots with isomature contours are somewhat similar to QFR (quartz-feldspar-rock fragments) triangular plots used for terrestrial clastic sediments. Both kinds of plots are sensitive to maturity and both may be used to predict evolution paths. Soils from predominantly highland areas and from other mixed terrains at Apollo 15 sites do not make smooth contours on AML diagrams. By analogy with QFR diagrams, the lack of smooth contours may be due to mixed source rock families, or to recent mixing, or both.

Basu, A.↗
NASA NTRS1982

The Apollo 15 yellow impact glasses - Chemistry, petrology, and exotic origin

The Apollo 15 yellow impact glasses are characterized by moderate TiO2 (about 4.8%) and high abundances of the large ion lithophile elements (e.g., K, P, Hf, Th, REE). Since the chemistry of these glasses cannot be duplicated by any combination of local components presently known to occur at the Apollo 15 landing site, these yellow glasses seem to be exotic to that area. Chemical and petrologic constraints suggest that these samples were produced by impact melting of an immature mare regolith developed upon an unusual variety of mare basalt. It is speculated that the target basalts were the youngest lava flows known to exist on the moon (i.e., Eratosthenian-age lavas in Oceanus Procellarum and Mare Imbrium). Specific tests are proposed for evaluating this provocative hypothesis.

Delano, J. W.↗
NASA NTRS1982

Petrologic variations in Apollo 16 surface soils

Source rock, maturation history and intrasite variation data are derived for the Apollo 16 regolith by comparing modal analyses of 15 surface soils with rake and rock sample data. Triangular source rock component plots show that Apollo 16 soils have similar source rocks that are well homogenized throughout the site. The site can be divided into three soil petrographic provinces. Central site soils are mature, well homogenized, and enriched in glass. They are probably the most typical Cayley Plains materials present. North Ray soils are immature to submature, containing North Ray ejecta. South Ray soils are mature, but contain small amounts of fresh impact melts and plagioclase, due perhaps to the breakdown of blocky South Ray ejecta. The different compositions and physical properties of North and South Ray ejecta support the hypothesis that the latter event excavated Cayley material, while the former excavated Descartes materials.

Houck, K. J.↗
NASA NTRS1983

Mare glasses from Apollo 17 - Constraints on the moon's bulk composition

Two previously unreported varieties of mare volcanic glass have been discovered in Apollo 17 samples. Twenty-three chemical types of volcanic glass have now been analyzed from the six Apollo landing sites. These volcanic glasses, which may be samples of primary magmas derived from the differentiated lunar mantle, define two linear arrays that seem to reflect regional, if not global, regularities among the source regions of these melts. Additional systematics among these glasses have been used to estimate the bulk composition of the moon. The results suggest that the refractory lithophile elements are present at abundances of 1.7 x chondrites. The silicate portion of the moon appears to have a major-element composition similar to a volatile (Si, Na, K)-depleted, earth's upper mantle. The theory involving an earth-fission origin of the moon can be tested further through trace element analyses on the volcanic glasses, and through determination of the N/Ar-36 ratio and noble gas isotopes from primordial lunar gas trapped within vesicles associated with mare volcanic glass.

Delano, J. W.↗
NASA NTRS1983

Chemistry of the Apollo 11 highland component

Thirty-eight Apollo 11 lunar highland fragments from coarse fines 10085 have been subjected to petrologic and chemical study. Six major chemical groups are identified: (a) high-K KREEP; (b) anorthosite with a 10X chondrite positive Eu anomaly and anorthosite with 30X positive Eu anomaly; (c) ANT; (d) LKFM; (e) anorthositic gabbro with no Eu anomaly, with a positive Eu anomaly, and with a negative Eu anomaly; and (f) dominant Highland component, 2X-10X chondrite with a positive 10X-14X Eu anomaly. Newly recognized groups are presented based on the REE patterns: (a) ANT group with 5X La and a 22X positive Eu anomaly; (b) 10X flat with 14X positive Eu anomaly; and (c) 2-3X flat with a 10X positive Eu anomaly. The highland suite is very low in K and REE, and is overall quite similar to the Apollo 16 suite.

Laul, J. C.↗
NASA NTRS1983

Mn-53 profiles in four Apollo surface cores

Mn-53 data are presented for four Apollo cores with an emphasis on the past 10-to-the-7th-year history of these samples: (1) Core 15011 has excess Mn-53 down to a depth of at least 9 cm, which is probably due to the continuous addition of near-surface irradiated material. (2) The Mn-53 profile for 64002 above 12 cm is relatively flat and in excess of that calculated for a static core, which suggests that the upper part of this core was deposited rapidly about 2 m.y. ago. (3) Results for the Apollo 17 drill stem show a large excess of Mn-53 from at least 3 cm downwards. Some magnetic separates obtained from this core have very high Mn-53 activities, probably due to the presence of agglutinates that were recently irradiated very near the surface. (4) The Mn-53 content of the upper part of 74002 is similar to that of trench samples collected nearby and indicates that the gray, orange, and black soils at this site have been exposed together near the surface for at least the last 10 m.y.

Nishiizumi, K.↗
NASA NTRS1984

Apollo 16 - Impact melt sheets, contrasting nature of the Cayley plains and Descartes mountains, and geologic history

Apollo 16 stations four and five rake samples have been examined petrographically and by electron microprobe and INAA. Lithologic abundances support the idea (Korontev, 1981) that the variation of soil composition at Apollo 16 results from mixing between a component represented by station five and components much like either the dimict breccias or feldspathic fragmental breccias in composition. Pyroxene, olivine, and coexisting plagioclase compositions from within the anorthosite portions of dimict breccias bridge the gap between the Mg-rich and ferroan anorthosite fields. Analyses from associated cumulate and granulitic clasts indicate that they are the source of the intermediate material. Dimict breccias formed about 3.92 b.y. ago, the nectaris event occurred 3.84-3.92 b.y. ago, and the Cayley plains were deposited as a result of the Imbrium event sometime later than 3.84 b.y.

Mckinley, J. P.↗
NASA NTRS1984

Petrologic comparisons of Cayley and Descartes on the basis of Apollo 16 soils from stations 4 and 11

Petrologic aspects of the Cayley and Descartes formations are reviewed in the light of new data on Apollo 16 soils. Specific comparison of the modal abundances of lithic fragments in drive tube sample 64001/2 from the slopes of Stone Mountain (station 4) and in soil 67941 from the North Ray Crater rim (station 11) shows that melt rocks, especially poikilitic rocks, are more abundant at station 4 than at station 11; the reverse is true for fragmental breccias. Such lithologic differences suggest that stations 4 and 11 do not belong to the same geologic formation. Metamorphosed breccias are pervasive in both the formations and may represent a local component that has been reworked and diluted as fresh materials were added. Lithologic compositions inferred from the study of soil samples are different from lithologic compositions inferred from the study of rake samples or breccia clasts. This difference may be related to a mixing of material of different grain size distributions. The petrology of soils at the Apollo 16 site may not accurately reflect original material associated with either the Descartes or the Cayley formation because of extensive mixing with local material.

Basu, A.↗
NASA NTRS1985

Quenching Effects on Iron Site Partitioning in the Apollo 17 Orange Glass Composition

Mare petrogenesis and the structure of the lunar interior were studied. Analyses of the spectral signatures of glasses was useful to remote sensing applications in areas of the moon where glass is in significant proportions in the lunar soil. The studies provided information on Fe site occupancies in glasses, which are used to construe oxygen fugacities at the lunar surface. Data were obtained through work on synthetic analogues of lunar glasses. However, recent Mossbauer studies of an Apollo 15 green glass composition have shown that synthetic glasses are extremely sensitive to variations in quenching media. Glass structure and Fe(3+)/Fe(2+) ratios are strongly controlled by quenching conditions, which may mask the effects of the original glass' formation temperature or oxygen partial pressure. Synthetic glasses were often run at low fugacities on Pt wires. The effects of quench media on the Apollo 17 orange glass composition are considered.

Dyar, M. D.↗
NASA NTRS1984

Apollo 16 site geology and impact melts - Implications for the geologic history of the lunar highlands

The geology of the Apollo 16 site is reconsidered on the basis of data from photogeology, geochemical remote sensing, and lunar samples. The site possesses an upper surface of anorthositic gabbro and related rocks. Mafic components were deposited as basin ejecta. The events involved in its geological evolution were the Nectaris impact and the Imbrium impact. The role of large, local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta. The most abundant melt composition at Apollo 16 is an aluminous variety of LKFM basalt supplied by the Nectaris impact as ejected basin impact melt. The mafic LKFM melt may have been supplied by the Imbrium impact. More aluminous melt groups are probably derived from local, small craters. The remainder of the deposits in the region are composed of anorthositic clastic debris derived from the Nectaris basin, the local crustal substrate, and Imbrium and other basins.

Spudis, P. D.↗
NASA NTRS1985

Isotope analysis of crystalline impact melt rocks from Apollo 16 stations 11 and 13, North Ray Crater

The North Ray Crater Target Rock Consortium was formed to study a large number of rake samples collected at Apollo 16 stations 11 and 13 with comparative chemical, mineralogical, and chronological techniques in order to provide a larger data base for the discussion of lunar highland evolution in the vicinity of the Apollo 16 landing region. The present investigation is concerned with Rb-Sr and Sm-Nd isotopic analyses of a number of whole-rock samples of feldspathic microporhyritic (FM) impact melt, a sample type especially abundant among the North Ray crater (station 11) sample collection. Aspects of sample mineralogy and analytical procedures are discussed, taking into account FM impact melt rocks 6715 and 63538, intergranular impact melt rock 67775, subophitic impact melt rock 67747, subophitic impact melt rock 67559, and studies based on the utilization of electron microscopy and mass spectroscopy.

Reimold, W. U.↗
NASA NTRS1985

Apollo 15 mare units and their petrogenesis

Samples from 12 different mare sites were identified and classified among the Apollo 15 samples. The genesis of the Apollo 15 mare units is summarized given the general model of mare basalt source regions and of more basalt genesis derived from a synthesis of the major oxide/major mineral, compatible siderophile, and incompatible trace element data and isotopic ratios of the Rb/Sr and Sm/Nd systems.

Binder, A. A.↗
NASA NTRS1985

Hadley Rille, lava tubes and mare volcanism at the Apollo 15 site

Hadley Rille appears to be a collapsed lava tube/channel, whose formation history may be more intimately related to the mare units sampled at 15 than was previously thought. More work is needed relating samples and observations from Apollo 15 to the rille and its geologic evolution. As the only sinuous rille visited during the Apollo missions, Hadley Rille represents a data source that is directly applicable to the deciphering of processes involved in lunar mare volcanism.

Greeley, R.↗
NASA NTRS1985

Apollo 15 mare basalts: A diverse suite or two distinct groups?

The literature geochemical data for 60 Apollo 15 mare basalts were compiled in order to evaluate possible intra-group relationships of the Apollo 15 mare basalts. The effects of olivine or pigeonite fractionation were discussed. Models were developed to explain the trace element characteristics of the samples.

Salpas, P. A.↗
NASA NTRS1986

Chronology and isotopic geochemistry of apollo 14 basalts and Skaergard Gabbro, Eastern Greenland

Work completed on Apollo 14 basalts has been published. The two dates obtained from these rocks comprised the oldest and two of the three oldest ages (4.1 and 4.3 billion years) known for lunar maria basalts; thus their ages are important in understanding the moon's earliest history. Owing to the antiquity of these rocks, two more fragments have been dated as part of a second ASEE/NASA SFF program. The new ages are 3.95 and 4.12 billion years, thus further establishing and amplifying the earlier results. This work, although perhaps more interesting for its chronologic information, was begun as a test of chemical and petrographic models. Fragments of Apollo basalt were placed into five categories, based on petrologic and chemical, especially rare-earth element, composition. Isotopic studies were begun in an attempt to determine if the five groups of basalts were related by age or initial isotopic composition (isotopic composition of lava at time of extrusion). Although a few of the representatives of the five groups have the same age and/or initial strontium-isotopic composition, within the analtytical uncertainties, most apparently are unrelated. Petrologic implications of these data will be published in an appropriate journal.

Dasch, E. J.↗
NASA NTRS1986

Geochronology and petrogenesis of Apollo 14 very high potassium mare basalts

Rb-Sr, K-Ar, and Sm-Nd isotopic studies were undertaken for two Apollo 14 very high potassium (VHK) highly radiogenic mare basaltic clasts from breccias 14305 and 14168. Rb-Sr data indicate ages of 3.83 + or - 0.08 b.y., and 3.82 + or - 0.12 b.y. for samples 14305 and 14168 respectively, for lambda(Rb-87) = 0.0 139/b.y. Their corresponding initial Sr-87/Sr-86 ratios are nearly identical, as well as their Ar-39 to Ar-40 age spectra, and it is proposed that they were derived from the same flow. The Sm-Nd isotopic data of whole rock and mineral separates for the two VHK basalts define an internal isochrone age of 3.94 + or - 0.16 b.y. for lambda (Sm-147) = 0.00654/b.y. and an initial Nd-143/Nd-144 of 0.50673 + or - 21. The similarity in isotopic ages suggests that VHK basalts crystallized from a melt about 3.85 b.y. ago. VHK basalts show very large Rb/Sr fractionation but no significant Sm/Nd fractionation at the time of crystallization. The source material had a Rb/Sr ratio similar to those of Apollo 14 high-Al mare basalts and a nearly chrondritic Sm/Nd ratio. Basalt/granite interaction was found to be responsible for the extreme enrichments of Rb/Sr and K/La during the formation of VHK basalts. It is concluded that K, Rb-rich components of granitic wall rocks in the highland crust were selectively introduced into ascending hot high-Al mare basaltic magma upon contact.

Shih, C.-Y.↗