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Taylor, Lawrence A.

Publications and source records attributed to Taylor, Lawrence A..

62 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Continental growth through time by underplating of subducted oceanic crust: Evidence from kimberlites in South Africa and SW Pacific

In the dynamic model of plate tectonics, it is evident that crustal components are returned to the mantle by subduction. Chemical signatures of these subducted components were identified in ocean island volcanics and in island arc volcanics. Indeed, an origin involving a subducted protolith was postulated for certain types of xenoliths in kimberlite, including diamonds. Recent studies of eclogite xenoliths in kimberlite from southern Africa and megacrysts form the Malaitan alnoite, Solomon islands, indicate that lithospheric underplating by subducted oceanic crust has occurred in these two contrasting areas. The results of new eclogite studies from the Bellsbank kimberlite, South Africa, and isotopic data from the Malaitan alnoite megacryst suite. This forms the basis for discerning the role of lithospheric underplating in the growth of cratons and in the evolution of mantle-derived magma.

Taylor, Lawrence A.↗
NASA NTRS1988

Highland materials at Apollo 17 - Contributions from 72275

A set of Apollo 17 feldspathic highland clasts from polymict breccia 72275 have been studied. The clasts include six granulites and a rare Apollo 17 ferroan anorthosite (FAN). The composition of these clasts is discussed in detail. It is suggested that there are three possibilities regarding the petrogenesis of Apollo 17 FAN: (1) the rocks are products of late-stage crystallization from their parent magma, (2) the rocks solidified with a high amount of trapped liquid relative to FANs from other sites, or (3) the highlands rocks that formed at this site crystallized from a parent magma with a composition distinct from that of other lunar highland sites.

Salpas, Peter A.↗
NASA NTRS1988

Olivine vitrophyres - A nonpristine high-Mg component in lunar breccia 14321

The presence of olivine vitrophyres in breccia 14321 is discussed, suggesting that olivine vitrophyres could account for the high-Mg component of soils and breccias in the lunar highlands. The olivine vitrophyre clasts from 14321 have high bulk MgO and the Mg/(Mg+Fe) ratio is 78 percent. The olivine vitrophyres are impact melt rocks and are rich in KREEP. The high MgO concentration is manifest by skeletal quench crystals of olivine that constitute about 30 percent of the mode.

Shervais, John W.↗
NASA NTRS1988

Importance of lunar granite and KREEP in very high potassium (VHK) basalt petrogenesis

Analysis of five very high potassium (VHK) basalts from Apollo 14 breccia 14303 shows the presence of a KREEP component. An assimilation and fractional crystallization model is presented to describe the basalt evolution. The influence of granite assimilation on the basalt evolution is discussed. The presence of VHK basalts containing only a granite signature and those with both granite and KREEP signatures suggests that there are at least two different VHK basalt flows at the Apollo 14 site.

Neal, Clive R.↗
NASA NTRS1988

Apollo 14 mare basalt petrogenesis - Assimilation of KREEP-like components by a fractionating magma

Based on analysis of whole rock and mineral data from 22 samples, it is shown that the trace element characteristics of 14321 high-AL mare basalts exhibit variations that cannot be related to short-range mixing alone. It is suggested that the five groups defined for Apollo 14 high-Al basalts are due to sampling. It is found that the addition of new data results in a continuum of compositions. Detailed trace element modeling demonstrates that a primitive parental magma evolves by assimilation and fractional crystallization (AFC) with KREEP. The ratio of mass assimilated to mass crystallized is found to be 0.22. It is suggested that this AFC process occurs within the lunar crust and that the fractionating phases are effectively removed from the system.

Neal, Clive R.↗
NASA NTRS1988

Generation of native Fe in lunar soil

A study of lunar samples indicatesa that the lunar soil contains up to a magnitude more native Fe than do the rocks from which it was derived. This is due to the abundant Fe in the agglutinates of the soil. The Fe in these agglutinates formed by the reduction of Fe(2+) in the micrometeorite impact-produced melt due to the presence of solar-wind implanted H and C. The amount of agglutinates is a function of the maturity of a given soil. The FMR signature, Is/FeO, measures the amount of agglutinates, which increase as maturity increases. Thus, the Is/FeO signature is indicative of the relative amounts of solar-wind implanted elements, notably He and H, in the lunar soil.

Taylor, Lawrence A.↗
NASA NTRS1987

Apollo 17 KREEPy basalts - Evidence for nonuniformity of KREEP

Breccia 72275 contains pristine KREEPy basalt clasts that are not found among other samples collected at Apollo 17. These basalts occur as discrete clasts and as clasts enclosed within basaltic microbreccias. Mineral and whole-rock chemical analyses reveal that the microbreccias are compositionally indistinguishable from the basalt clasts. Samples of the 72275 matrix also have the same compositions as the basalts and the basaltic microbreccias. 72275 was assembled in situ from a single flow or series of closely related flows of Apollo 17 KREEPy basalt before it was transported to the Apollo 17 site. As a rock type, Apollo 17 KREEPy basalts are distinct from Apollo 15 KREEP basalts. The Apollo 17 samples have lower REE concentrations, steeper negative slopes of the HREE, and are less magnesian than the Apollo 15 samples. The two basalt types cannot be related by fractional crystallization, partial melting, or assimilation. This is evidence for the compositional nonuniformity of KREEP as a function of geography.

Salpas, Peter A.↗