Standing on the Shoulders of Apollo: MEMS seismometers for the Lunar Geophysical Network
UNKNOWN
Panning, Mark P.↗
Engineering topics
Neal, Clive R.
Publications and source records attributed to Neal, Clive R..
Advancing Science of the Moon: Progress Toward Achieving the Goals of the Scientific Context for Exploration of the Moon Report
No abstract available
Denevi, Brett W.↗
A Synthesis of Experimental Data Describing the Partitioning of Moderately Volatile Elements in Major Rock Forming Minerals: Implications for the Moon
Highly volatile elements [condensation temperatures below about 700 K] and water are highly informative about lunar bulk composition (hence origin), differentiation and magmatic evolution, and the role of impacts in delivering volatiles to the Moon. Fractionation of volatile elements compared to moderately volatile and refractory elements are informative about high-temperature conditions that operated in the proto-lunar disk. Existing data show clearly that the Moon is depleted in volatile elements compared to the bulk silicate Earth. For example, K/Th is ~400-700 in the Moon compared to 2800-3000 in Earth. A complicating factor is that the abundances of the highly volatile elements in major lunar lithologies vary by approximately two orders of magnitude. Perhaps most interesting, H2O is not correlated with the concentration of volatile elements, indicating a decoupling of highly volatile elements from the even more volatile H2O. We contend that this decoupling could be a significant tracer of processes operating during lunar formation, differentiation, and bombardment, and the combination of analyzing both volatile elements and water is likely to provide significant insight into lunar geochemical history. This variation and lack of correlation raises the question: what were the relative contributions of crystallization in the magma ocean, subsequent mantle overturn, production of secondary magmas, and addition of volatiles by large impacts in producing this apparently large range in volatile abundances? This current study will produce new partitioning data relevant to the role and distribution of the volatile and non-volatile, yet geochemically significant elements (Co, Ni, Zn, Se, Rb, Sr, Mo, Ag, Cd, In, Sb, Ce, Yb, Tl, Pb, Bi) during the thermal and magmatic evolution of the Moon.
Vander Kaaden, Kathleen E.↗
Sims Analysis of Water Abundance and Hydrogen Isotope in Lunar Highland Plagioclase
The detection of indigenous water in mare basaltic glass beads has challenged the view established since the Apollo era of a "dry" Moon. Since this discovery, measurements of water in lunar apatite, olivine-hosted melt inclusions, agglutinates, and nominally anhydrous minerals have confirmed that lunar igneous materials contain water, implying that some parts of lunar mantle may have as much water as Earth's upper mantle. The interpretation of hydrogen (H) isotopes in lunar samples, however, is controversial. The large variation of H isotope ratios in lunar apatite (delta Deuterium = -202 to +1010 per mille) has been taken as evidence that water in the lunar interior comes from the lunar mantle, solar wind protons, and/or comets. The very low deuterium/H ratios in lunar agglutinates indicate that solar wind protons have contributed to their hydrogen content. Conversely, H isotopes in lunar volcanic glass beads and olivine-hosted melt inclusions being similar to those of common terrestrial igneous rocks, suggest a common origin for water in both Earth and Moon. Lunar water could be inherited from carbonaceous chondrites, consistent with the model of late accretion of chondrite-type materials to the Moon as proposed by. One complication about the sources of lunar water, is that geologic processes (e.g., late accretion and magmatic degassing) may have modified the H isotope signatures of lunar materials. Recent FTIR analyses have shown that plagioclases in lunar ferroan anorthosite contain approximately 6 ppm H2O. So far, ferroan anorthosite is the only available lithology that is believed to be a primary product of the lunar magma ocean (LMO). A possible consequence is that the LMO could have contained up to approximately 320 ppm H2O. Here we examine the possible sources of water in the LMO through measurements of water abundances and H isotopes in plagioclase of two ferroan anorthosites and one troctolite from lunar highlands.
Hui, Hejiu↗
Evidence for a "Wet" Early Moon
The Moon was thought to have lost its volatiles during impact(s) of a Mars-size planetesimal with the proto Earth [1] and during degassing of an early planet-wide magma ocean [2]. This view of an anhydrous Moon, however, has been challenged by recent discoveries of water on its surface [3-5] and in lunar volcanics [6-10] and regoliths [11]. Indigenous water is suggested to be heterogeneously distributed in the lunar interior and some parts of lunar mantle may contain as much water as Earth's upper mantle [6,10]. This water is thought to have been brought in part through solar wind implantation [3-5,8,11] and meteorite/cometary impacts [3,4,8,12] after the formation of the primary crust. Here we measured water in primary products of the Lunar Magma Ocean (LMO) thereby by-passing the processes of later addition of water to the Moon through impact events or during mantle overturn as suggested by previous studies (e.g., [8,12]). So far, ferroan anorthosite (FAN) is the only available lithology that is believed to be a primary product of the LMO [2]. It is generally accepted that plagioclase, after crystallization, floated in the LMO and formed FAN as the original crust [2]. Therefore, any indigenous water preserved in FAN was partitioned from the LMO. These data can be used to estimate the water content of the magma ocean at the time of plagioclase crystallization, as well as that of the mare magma source regions.
Hui, Hejiu↗
Processes involved in the formation of magnesian-suite plutonic rocks from the highlands of the Earth's Moon
The earliest evolution of the Moon likely included the formation of a magma ocean and the subsequent development of anorthositic flotation cumulates. This primary anorthositic crust was then intruded by mafic magmas which crystallized to form the lunar highlands magnesian suite. The present study is a compilation of petrologic, mineral-chemical, and geochemical information on all pristine magnesian-suite plutonic rocks and the interpretation of this data in light of 18 'new' samples. Of these 18 clasts taken from Apollo 14 breccias, 12 are probably pristine and include four dunites, two norites, four troctolites, and two anorthosites. Radiogenic isotopic whole rock data also are reported for one of the 'probably pristine' anorthositic troctolites, sample 14303,347. The relatively low Rb content and high Sm and Nd abundances of 14303,347 suggest that this cumulate rock was derived from a parental magma which had these chemical characteristics. Trace element, isotopic, and mineral-chemical data are used to interpret the total highlands magnesian suite as crustal precipitates of a primitive KREEP (possessing a K-, rare earth element (REE)-, and P-enriched chemical signature) basalt magma. This KREEP basalt was created by the mixing of ascending ultramafic melts from the lunar interior with urKREEP (the late, K-, REE-, and P-enriched residuum of the lunar magma ocean). A few samples of the magnesian suite with extremely elevated large-ion lithophile elements (5-10x other magnesian-suite rocks) cannot be explained by this model or any other model of autometasomatism, equilibrium crystallization, or 'local melt-pocket equilibrium' without recourse to an extremely large-ion lithophile element-enriched parent liquid. It is difficult to generate parental liquids which are 2-4 x higher in the REE than average lunar KREEP, unless the liquids are the basic complement of a liquid-liquid pair, i.e., the so-called 'REEP-fraction,' from the silicate liquid immiscibility of urKREEP. Scarce age information on lunar rocks suggests that magnesian-suite magmatism was initiated at progressively more recent time from the northeast to the southwest on the lunar nearside from 4.45 to 4.25 Ga.
Snyder, Gregory A.↗
Basalt generation at the Apollo 12 site. Part 1: New data, classification, and re-evaluation
New data are reported from five previously unanalyzed Apollo 12 mare basalts that are incorporated into an evaluation of previous petrogenetic models and classification schemes for these basalts. This paper proposes a classification for Apollo 12 mare basalts on the basis of whole-rock Mg# (molar 100*(Mg/(Mg+Fe))) and Rb/Sr ratio (analyzed by isotope dilution), whereby the ilmenite, olivine, and pigeonite basalt groups are readily distinguished from each other. Scrutiny of the Apollo 12 feldspathic 'suite' demonstrates that two of the three basalts previously assigned to this group (12031, 12038, 12072) can be reclassified: 12031 is a plagioclase-rich pigeonite basalt; and 12072 is an olivine basalt. Only basalt 12038 stands out as a unique sample to the Apollo 12 site, but whether this represents a single sample from another flow at the Apollo 12 site or is exotic to this site is equivocal. The question of whether the olivine and pigeonite basalt suites are co-magmatic is addressed by incompatible trace-element chemistry: the trends defined by these two suites when Co/Sm and Sm/Eu ratios are plotted against Rb/Sr ratio demonstrate that these two basaltic types cannot be co-magmatic. Crystal fractionation/accumulation paths have been calculated and show that neither the pigeonite, olivine, or ilmenite basalts are related by this process. Each suite requires a distinct and separate source region. This study also examines sample heterogeneity and the degree to which whole-rock analyses are representative, which is critical when petrogenetic interpretation is undertaken. Sample heterogeneity has been investigated petrographically (inhomogeneous mineral distribution) with consideration of duplicate analyses, and whether a specific sample (using average data) plots consistently upon a fractionation trend when a number of different compostional parameters are considered. Using these criteria, four basalts have been identified where reported analyses are not representative of the whole-rock composition: 12005, an ilmenite basalt; 12006 and 12036, olivine basalts; and 12031 previously classified as a feldspathic basalt, but reclassified as part of the pigeonite suite.
Neal, Clive R.↗
Basalt generation at the Apollo 12 site. Part 2: Source heterogeneity, multiple melts, and crustal contamination
The petrogenesis of Apollo 12 mare basalts has been examined with emphasis on trace-element ratios and abundances. Vitrophyric basalts were used as parental compositions for the modeling, and proportions of fractionating phases were determined using the MAGFOX prograqm of Longhi (1991). Crystal fractionation processes within crustal and sub-crustal magma chambers are evaluated as a function of pressure. Knowledge of the fractionating phases allows trace-element variations to be considered as either source related or as a product of post-magma-generation processes. For the ilmenite and olivine basalts, trace-element variations are inherited from the source, but the pigeonite basalt data have been interpreted with open-system evolution processes through crustal assimilation. Three groups of basalts have been examined: (1) Pigeonite basalts-produced by the assimilation of lunar crustal material by a parental melt (up to 3% assimilation and 10% crystal fractionation, with an 'r' value of 0.3). (2) Ilmenite basalts-produced by variable degrees of partial melting (4-8%) of a source of olivine, pigeonite, augite, and plagioclase, brought together by overturn of the Lunar Magma Ocean (LMO) cumulate pile. After generation, which did not exhaust any of the minerals in the source, these melts experienced closed-system crystal fractionation/accumulation. (3) Olivine basalts-produced by variable degrees of partial melting (5-10%) of a source of olivine, pigeonite, and augite. After generation, again without exhausting any of the minerals in the source, these melts evolved through crystal accumulation. The evolved liquid counterparts of these cumulates have not been sampled. The source compositions for the ilmenite and olivine basalts were calculated by assuming that the vitrophyric compositions were primary and the magmas were produced by non-modal batch melting. Although the magnitude is unclear, evaluation of these source regions indicates that both be composed of early- and late-stage Lunar Magma Ocean (LMO) cumulates, requiring an overturn of the cumulate pile.
Neal, Clive R.↗
Petrogenesis of Apollo 12 mare basalts. Part 1: Multiple melts and fractional crystallization to explain olivine and ilmenite basalt compositions
Mare basalts returned by the Apollo 12 mission have been divided into 4 groups on the basis of mineralogy and whole-rock chemistry: olivine basalts; pigeonite basalts; ilmenite basalts; and feldspathic basalts. James and Wright and Rhodes et al. concluded that the olivine and pigeonite groups were co-magmatic and that the within group variations are due to fractional crystallization of olivine and minor Cr-spinel, with pigeonite replacing olivine in the pigeonite basalts. Rhodes et al. concluded that the parental compositions for these suites were probably represented by the vitrophyres, and the olivine basalts are comprised essentially of cumulates and the pigeonites of evolved end-members. However, Neal et al. have demonstrated, using trace-element considerations, that the Apollo 12 olivine and pigeonite suites are not related. The ilmenite basalts were studied extensively by Dungan and Brown who noted that both cumulates and evolved fractionates were present within this group. In their modeling, Dungan and Brown used the vitrophyre compositions as parents. Neal et al. demonstrated that the feldspathic suite was probably comprised of only one member - 12038. Herein, the ilmenite and olivine basalts are demonstrated to be the products of several non-modal partial melting events of a single source followed by closed-system fractional crystallization.
Neal, Clive R.↗
Petrogenesis of Apollo 12 mare basalts. Part 2: An open system model to explain the pigeonite basalt compositions
Original petrogenetic models suggested that the pigeonite basalts were the evolved equivalents of the olivine basalts. Rhodes et al. concluded that the olivine and pigeonite basalts were co-magmatic, but Neal et al. have demonstrated that these two basaltic groups are distinct and unrelated. The pigeonite suite is comprised of porphyritic basalts with a fine-grained ground mass and range continuously to coarse-grained microgabbros with ophitic to graphic textures. Although it was generally recognized that the pigeonite basalts were derived from the olivine basalts by olivine + minor Cr-spinel fractionation, the compositional gap between these groups is difficult to reconcile with such a model. Indeed, Baldridge et al. concluded that these two basaltic groups could not have been co-magmatic. In this paper, we suggest an open system AFC model for pigeonite basalt petrogenesis. The assimilant is lunar anorthositic crust and the r value used is 0.6. While the choice of assimilant composition is difficult to constrain, the modeling demonstrates the feasibility of this model.
Neal, Clive R.↗
The Apollo 17 mare basalts: Serenely sampling Taurus-Littrow
As we are all aware, the Apollo 17 mission marked the final manned lunar landing of the Apollo program. The lunar module (LM) landed approximately 0.7 km due east of Camelot Crater in the Taurus-Littrow region on the southwestern edge of Mare Serenitatis. Three extravehicular activities (EVA's) were performed, the first concentrating around the LM and including station 1 approximately 1.1 km south-southeast of the LM at the northwestern edge of Steno Crater. The second traversed approximately 8 km west of the LM to include stations 2, 3, 4, and 5, and the third EVA traversed approximately 4.5 km to the northwest of the LM to include stations 6, 7, 8, and 9. This final manned mission returned the largest quantity of lunar rock samples, 110.5 kg/243.7 lb, and included soils, breccias, highland samples, and mare basalts. This abstract concentrates upon the Apollo 17 mare basalt samples.
Neal, Clive R.↗
Using Apollo 17 high-Ti mare basalts as windows to the lunar mantle
The Apollo 17 high-Ti mare basalts are derived from source regions containing plagioclase that was not retained in the residue. Ilmenite appears to remain as a residual phase, but plagioclase is exhausted. The open-system behavior of the type B2 basalts results in slightly higher Yb/Hf and La/Sm ratios. The nature of the added component is not clear, but may be a KREEP derivative or residue. The recognition of plagioclase in the source(s) of these basalts suggests that the location of the source region(s) would be more likely to be less than 150 km (i.e., closer to the plagioclase-rich crust), which would allow incorporation of plagioclase into the source through incomplete separation of crustal feldspar.
Neal, Clive R.↗
A chemical model for generating the sources of mare basalts - Combined equilibrium and fractional crystallization of the lunar magmasphere
A chemical model for simulating the sources of the lunar mare basalts was developed by considering a modified mafic cumulate source formed during the combined equilibrium and fractional crystallization of a lunar magma ocean (LMO). The parameters which influence the initial LMO and its subsequent crystallization are examined, and both trace and major elements are modeled. It is shown that major elements tightly constrain the composition of mare basalt sources and the pathways to their creation. The ability of this LMO model to generate viable mare basalt source regions was tested through a case study involving the high-Ti basalts.
Snyder, Gregory A.↗
Petrogenesis of mare basalts - A record of lunar volcanism
The classification, sources, and overall petrogenesis of mare basalts are reviewed. All mare basalt analyses are used to define a sixfold classification scheme using TiO2 contents as the primary division. A secondary division is made using Al2O3 contents, and a tertiary division is defined using K contents. Such divisions and subdivisions yield a classification containing 12 categories, of which six are accounted for by the existing Apollo and Luna collections. A variety of postmagma-generation such as fractional crystallization, either alone or combined with wallrock assimilation, are invoked to explain the compositional ranges of the various mare basalt suites. High-Ti mare basalts are found at Apollo 1 and Apollo 17 sites; the A-11 basalts contain lower TiO2 abundances, a considerably larger range in trace-element contents, and the only occurrence of high-Ti/high-K mare basalts. The low-Ti basalts exhibit a wide range of major-and trace-element compositions and require source heterogeneity, fractional crystallization, and some assimilation.
Neal, Clive R.↗
Paired lunar meteorites MAC88104 and MAC88105 - A new 'FAN' of lunar petrology
To determine the chemical characteristics of the MAC88104/5 meteorite six thin sections and three bulk samples were analyzed by electron microprobe and instrumental neutron activation. It is concluded that this meteorite is dominated by lithologies of the ferroan anorthosite suite and contains abundant granulitized highland clasts, devitrified glass beads of impact origin, and two small clasts of basaltic origin. It is suggested that one of these basaltic clasts, clast E, is mesostasis material, and clast G is similar to the very low-Ti or low-Ti/high-alumina mare basalts. Impact melt clasts MAC88105, 69, and 72 have major and trace element compositions similar to the bulk meteorite.
Neal, Clive R.↗
Evidence for metasomatism of the lunar highlands and the origin of whitlockite
The origin of whitlockite, a REE-rich mineral present in lunar highlands, is investigated using available experimental results of elemental partitioning between whitlockite and melt and between two immiscible liquids. A comparison with occurrences in mare basalt mesostasis assemblages demonstrated that whitlockite in the lunar highlands has not resulted from crystallization from the residual interstitial melt, and the nature of REE partition coefficients for whitlockite showed that they cannot have crystallized from KREEP melts. The only lunar melt which contains REE abundances compatible with whitlockite composition is the basic immiscible melt derived from a KREEPy liquid. It is suggested that whitlockite found in the lunar highlands is a post-cumulus metasomatic phase that precipitated from a melt formed when the urKREEP underwent silicate liquid immiscibility.
Neal, Clive R.↗
A strontium and neodymium isotopic study of Apollo 17 high-Ti mare basalts - Resolution of ages, evolution of magmas, and origins of source heterogeneities
The geochronological and compositional differences between previously identified magma types (A, B1, B2, and C) were investigated using high-precision Rb-Sr and Sm-Nd isotopic data for a set of Apollo 17 high-Ti mare basalt samples chosen to span the range of each of the magma types. These data, combined with previously reported geochemical ages, suggest that Apollo 17 volcanism was initially dominated by an eruption of Type B basalts. Data obtained from new whole-rock Sr and Nd isotopic analyses exhibited distinct differences in initial Sr and Nd isotopic compositions between Types A, B1, B2, and C basalts and were found to be consistent with existing petrogenetic models.
Paces, James B.↗
Wanted: Lunar detectives to unravel the mysteries of the Moon! Crime to be solved: Mass extinctions on the Moon by meteorite impact!
The criteria and clues for identifying meteorite contamination are outlined to aid in the quest for more knowledge regarding the evolution of the Moon and the early Earth. The Warren and Wasson seven criteria for establishing the pristine nature of highland rocks are presented. Other topics covered include iron/nickel metals, monomict nature, and lunar glasses. The major conclusion is that pristinity should not be the primary consideration in the study of lunar rocks. The most important criterion to establish is whether or not the lunar sample contains more than one lunar rock type. Even if a sample is non-pristine, as long as only one lunar rock type is present, petrogenetic interpretation can still be carried out.
Neal, Clive R.↗