P. H. Warren's research while affiliated with University of California, Los Angeles and other places

Publications (232)

Article
The 14321 lunar granite (14321g) has recently been reinterpreted (Bellucci et al., 2019) as a piece of the Hadean Earth, impact-transported to the Moon. In principle, samples of such derivation may afford important insights into the nature of Earth's Hadean crust. We have tested the terrestrial provenance hypothesis by comparing trace-element data...
Article
The unique occurrence of abundant (~1 vol%) near-pure-Fe metal in the Camel Donga eucrite is more complicated than previously believed. In addition to that component of groundmass metal, scattered within the meteorite are discrete nodules of much higher kamacite abundance. We have studied the petrology and composition of two of these nodules in the...
Article
The last liquids of the lunar magma ocean, known as urKREEP, should be highly enriched in volatiles, such as water, fluorine, and chlorine. We find chlorine-rich glasses in two pristine KREEP basalts from the Moon and calculate the volatile contents of the urKREEP component, and use this to estimate the fluorine and chlorine content of the lunar ma...
Article
Results of whole-rock ⁴⁰Ar/³⁹Ar step-heating analyses of extra-terrestrial materials have been used to constrain the timing of impacts in the inner solar system, solidification of the lunar magma ocean, and development of planetary magnetic fields. Despite the importance of understanding these events, the samples we have in hand are non-ideal due t...
Article
Earth and the Moon are shown here to have indistinguishable oxygen isotope ratios, with a difference in Δ′17O of −1 ± 5 parts per million (2 standard error). On the basis of these data and our new planet formation simulations that include a realistic model for primordial oxygen isotopic reservoirs, our results favor vigorous mixing during the giant...
Article
The secondary alteration of Camel Donga was more complex than previously realized. Ni-rich metals show some of its Fe component was derived as impact debris.
Article
Full-text available
Geochemical evidence suggests that the material accreted by the Earth did not change in nature during Earth's accretion, presumably because the inner protoplanetary disc had uniform isotopic composition similar to enstatite chondrites, aubrites and ungrouped achondrite NWA 5363/5400. Enstatite meteorites and the Earth were derived from the same neb...
Article
The Northwest Africa 5738 eucrite contains a record of unprecedented geochemical complexity for a sample from the HED asteroid. It originated with a uniquely evolved (Stannern Trend) primary igneous composition, combining ultra-high bulk incompatible element and Na2O concentrations with a relatively low mg. Its bulk oxygen-isotopic composition (Δ′1...
Article
A revised estimation of the bulk-Moon composition, based on new interior-density constraints from GRAIL and recent seismic studies, has a higher-than-Earth FeO.
Article
Modeling of 40Ar/39Ar age spectra from Jilin and Apollo samples reveal serious problems with prior efforts to constrain impact ages in the inner solar system.
Article
We have discovered widespread 48Ca isotope anomalies in chondrites and achondrites that provide important constraints on the nature of Earth’s building blocks.
Article
We discuss the enigmatic fluid-metasomatic melange, including Fe-metals, in the NWA 5738 eucrite, and a search for analogous stuff in ancient lunar rocks.
Article
Secondary veins in the NWA 5738 eucrite include spinels whose compositions suggest origin at high fO_2. Pyroxenes adjacent to the rock's remarkably elongate Fe-metals have lost Ca, and have slightly anomalous mg inherited from the original pigeonite.
Article
Northwest Africa 6693 is a new type of achondrite, with a unique combination of oxygen-isotopic composition (low Δ¹⁷O: −1.08‰; also δ¹⁷O = 1.19‰) and FeO-rich, low mg bulk composition. A mode (in vol%) shows 70% pyroxene, 16% olivine and 13% feldspar, along with 0.6% Cr-spinel, and 0.4% NiFe metal (awaruite). Its coarse-poikilitic texture, with pig...
Article
We report the petrology and geochemistry of a suite of 30 Apollo 16 North Ray Crater rocklets, some of which will be used for thermochronology.
Article
The evidence for a wet Moon continues with water- and hydrogen-isotope data from apatite in all four suites of Apollo 12 basalts.
Article
The extremely evolved NWA 5738 eucrite has diverse late alteration products, offering unprecedented insights into fluid-driven alteration processes on Vesta.
Article
Determining the age of Nectaris is key for constraining the lunar cataclysm hypothesis and the Nice Model of Solar System evolution. Some of our Apollo 16 North Ray Crater rocklets combine Nectaris-like low K (etc.) with impact-melt textures.
Article
Little-weathered NWA 7258 resembles Shergotty, but has low Al2O3 (5 wt%) and very high incompatible levels, up to 21 xCI (Hf). The concave shape of the REE pattern (15xCI for La, 19x for Tb), albeit typical of 'enriched' shergottites, is enigmatic.
Article
Full-text available
Eucrite NWA 5738, which is essentially unweathered, is exceptionally rich in Na2O (0.67 wt%) and REE (7.7 µg/g La). Its plagioclase is mostly An73-78. It also has a relatively low bulk mg (34 mol%) and NWA 049-like annealed aqueous-alteration veins.
Article
MIL 090340 and MIL 090206 were originally classified as ureilites. From petrography, mineral compositions, oxygen isotopes and bulk compositions, we show that they are brachinite-like instead. The reason for the mis-identification is intriguing.
Article
New results on water and D/H of lunar apatite are presented. Implications of high volatile abundances of lunar apatite for the water inventory of the Moon are considered in light of degassing of molecular hydrogen and low oxygen fugacities.
Article
Mineralogical data show that MIL 090340, originally classed as a dunitic and uniquely ferroan ureilite, is more likely a brachinite, and certainly not a ureilite. Carbon is absent. Olivine Cr and Ca contents are vastly lower than the ureilite range.
Article
Full-text available
The final stage of terrestrial planet formation consists of the cleanup of residual planetesimals after the giant impact phase. Dynamically, a residual planetesimal population is needed to damp the high eccentricities of the terrestrial planets after the giant impact stage. Geochemically, highly siderophile element (HSE) abundance patterns inferred...
Article
Abstract– New analyses of mafic silicates from 14 ureilite meteorites further constrain a strong correlation (Singletary and Grove 2003) between olivine-core Fo ratio and the temperature of equilibration (TE) recorded by the composition of pigeonite. This correlation may be compared with relationships implied by various postulated combinations of F...
Article
Plots such as ε54Cr vs. ε50Ti and ε54Cr vs. Δ17O reveal a fundamental dichotomy among planetary materials. The “carbonaceous” chondrites, by virtue of high ε50Ti and high ε62Ni, as well as, especially for any given Δ17O, high ε54Cr, are separated by a wide margin from all other materials. The significance of the bimodality is further manifested by...
Article
The abundant, diverse ureilite meteorites are peridotitic asteroidal mantle restites that have remarkably high bulk carbon contents (average 3 wt%) and have long been linked to the so-called carbonaceous chondrites (although this term is potentially misleading, because the high petrologic type "carbonaceous" chondrites are, if anything, C-poor comp...
Article
We present new results on the D/H and water content of lunar apatites in support of a wet Moon and an elevated D/H.
Article
Abstract–Megaregolith accumulation can have important thermal consequences for bodies that lose heat by conduction, as vacuous porosity of the kind observed in the lunar megaregolith lowers thermal conductivity by a factor of 10. I have modeled global average ejecta accumulation as a function of the largest impact size, with no explicit modeling of...
Article
Water plays a critical role in the evolution of planetary bodies, and determination of the amount and sources of lunar water has profound implications for our understanding of the history of the Earth-Moon system. During the Apollo programme, the lunar samples were found to be devoid of indigenous water. The severe depletion of volatiles, including...
Article
A characteristic feature of ureilite meteorites is reduction of FeO. But the reduction is usually confined to the rims of olivine. In the LAR 04315, LAP 03587 and Almahata Sitta ureilites, pyroxene was extensively reduced by impact smelting. In LAR 04315, the impact caused nearly all of the original pigeonite to melt or otherwise become sufficientl...
Article
Hydrogen isotopes of lunar water in apatite are measured in Apollo rock samples for the first time. The Moon has a unique D/H.
Article
Abstract— A popular model for ureilites assumes that during anatexis in an asteroidal mantle, pressure-buffered equilibrium smelting (partial reduction coincident with partial melting) engendered their conspicuous mafic-silicate-core mg diversity (75–96 mol%). Several mass-balance problems arise from this hypothesis. Smelting inevitably consumes a...
Article
Abstract— New data for lunar meteorites and a synthesis of literature data have significant implications for the interpretation of global Th data and for the Moon's bulk composition. As presently calibrated (Prettyman et al. 2002), the Lunar Prospector gamma-ray data imply that the average global surface Th = 1.58 μg/g. However, that calibration yi...
Article
Abstract— The Elephant Moraine (EET) 96001 ureilite contains a remarkable diversity of feldspars, which occur as tiny (no more than 60 μm maximum dimension) grains within a few Fe,S-rich (now weathered to mostly Fe oxide) veins. Molar S: Fe ratio in the veins averages 0.08 ± 0.02. The veins meander and feature large fluctuations in apparent width;...
Article
We have used neutron activation and electron-probe fused-bead techniques to analyze the bulk major and trace-element compositions of 104 named HED meteorites (about 100–102 distinct meteorites, depending upon pairings), including 32 polymict eucrites, 30 howardites and six diogenites. Most were not previously analyzed for siderophile trace elements...
Article
NWA5415 is unusual among HEDs for its clear manifestation of origin by large-scale impact melting. Our section's five relict olivines display reaction textures (pyroxene coronas) formed by immersion in melt on the Si-rich side of the ol-px liquidus.
Article
Apollo 14 regolith breccia 14076, long known to be uniquely endowed with high-alumina, silica-poor (HASP) material of evaporation-residue origin, has been found to contain a diverse suite of complementary condensates, dubbed GASP (gas-associated spheroidal precipitates). GASP occurs in two forms: as glassy or extremely fine grained quenched-melt sp...
Article
Full-text available
Manuscript consists of text (37 pages), 2 tables, and 10 figures.
Article
It has long been customary to assume that in the bulk composition of the Earth, all refractory-lithophile elements (including major oxides Al2O3 and CaO, all of the REE, and the heat-producing elements Th and U) occur in chondritic, bulk solar system, proportion to one another. Recently, however, Nd-isotopic studies (most notably Boyet M. and Carls...
Article
Full-text available
Lunar breccia 73217 consists largely of a uniformly granitic (7.5% K2O) mesostasis glass, which imparts high alkalis, including 2% K2O, to the bulk-rock. The origin of this breccia is enigmatic. The mesostasis may not in the strictest sense be impact melt.
Article
Apollo 14 breccia 14076 contains diverse silicate impact-vapor condensates: quenched-melt spheroids mostly <5 μm across, clasts up to 200 μm; all extremely low in refractory oxides. Spheroids have mg from 7-84 mol%, and FeO/SiO2 (wt.) from 0.002-0.67.
Article
New bulk-compositional data, including trace siderophile elements such as Ir, Os, Au, and Ni, are presented for 25 ureilites. Without exception, ureilites have siderophile abundances too high to plausibly have formed as cumulates. Ureilites undoubtedly underwent a variety of “smelting,” by which C was oxidized to CO gas while olivine FeO was reduce...
Article
Impacts have been important in the evolution of the Moon's crust and regolith, and impact melt products (breccias, glasses, and "highland basalts") account for a huge fraction of all sampled nonmare materials. As we endeavor to unravel the history of the Moon using these materials, it is important to understand that three fundamentally distinct typ...
Article
Abstract— We have analyzed nine highland lunar meteorites (lunaites) using mainly INAA. Several of these rocks are difficult to classify. Dhofar 081 is basically a fragmental breccia, but much of its groundmass features a glassy-fluidized texture that is indicative of localized shock melting. Also, much of the matrix glass is swirly-brown, suggesti...
Article
New data for lunar meteorites and a synthesis of literature data have significant implications for the interpretation of global Th data and for the Moon's bulk composition. As presently calibrated (Prettyman et al. 2002), the Lunar Prospector gamma-ray data imply that the average global surface Th = 1.58 mu g/g. However, that calibration yields imp...
Article
We have measured Mg isotopes in a highland breccia, four Ap-12 mare basalts, mare volcanic spheroids (Ap-15 green and Ap-17 black) and highland regolith spheroids. The Ap-15 green spheroids are significantly heavier than the Ap-17 black spheroids.
Article
Full-text available
We present much new data for ureilites. The average ureilite composition can be modeled by assuming that the major yet not exhaustive siderophile depletions of typical ureilites formed by down-seepage of small proportions of S-rich metallic melt.
Article
Abstract— We compare and contrast the mineralogy and petrology of the 2 stones of the extremely ferroan and Cr-poor martian meteorite, Los Angeles. The 2 stones are similar in many characteristics, strongly suggesting that they originated from a single flow or shallow intrusion. However, stone 2 is more ferroan and enriched in late-stage materials...
Article
We integrated Lunar Prospector-GRS data, as calibrated by Lawrence et al. [2000], for 38 regions defined by the Apollo GRS team. For Th-poor (farside+limb) highland regions, the LP-GRS Th calibration is systematically higher by 0.88±0.11 µg/g.
Article
Lunar Prospector gamma-ray spectrometer data for surface thorium indicate that craters greater than about 60 km in diameter tend to excavate into materials less Th-rich than the surface regolith. For the largest 12 craters and basins amenable to this type of analysis (diameters between 90 and 930 km), the ratio of crater (or basin) Th concentration...
Article
Porosity has been directly measured for eight lunar meteorite breccias and calculated for two more on the basis of literature density measurements. Lunar meteorite regolith breccias display systematically low porosity in comparison to otherwise analogous Apollo regolith breccias. Among seven meteoritic regolith breccias, porosity ranges from 1 to 1...
Article
The major- and trace-element composition of highlands meteorites Dh25 and Dh26 show that both are dominated by a FAN component. Incompatible element depletion and low Ti abundances suggest a farside origin. O-isotopes are typical for lunar meteorites.
Article
Full-text available
We report the first bulk compositional data for a new eucrite with the proposed name of Bluewing 001 [1]. A 0.174 g fragment was powdered for bulk analysis by a combination of INAA and fused bead electron-probe analysis. Our study only commenced at the end of November, so unfortunately our data are still somewhat preliminary. Results for diagnos-ti...
Article
We report the first data and description for a eucrite found by one of the authors (PG) on 14 June 2000 as a single stone of 6.1 g, in the Bluewing Flat area of Pershing County, Nevada. The name Bluew-ing 001 has been approved by the Nomenclature Committee of the Meteoritical Society. A 0.46 g sawn end piece was used to produce a 9×9 mm thin sectio...
Article
Full-text available
The bulk chemistry of three new lunar meteorites is presented and placed within the context of each meteorite's petrographic texture. Unusual PGEs for D-26 is not explainable by contamination, but may reflect the presence of siderophile-rich nuggets.
Article
Los Angeles is a new martian meteorite that expands the compositional range of basaltic shergottites. Compared to Shergotty, Zagami, QUE94201, and EET79001-B, Los Angeles is more differentiated, with higher concentrations of incompatible elements (e.g., La) and a higher abundance of late-stage phases such as phosphates and K-rich feldspathic glass....
Article
Full-text available
The martian atmospheric D/H value of 5.2 times terrestrial is significantly higher than any found on Earth, and has been ascribed to preferential loss of H relative to D from the atmosphere through Jeans escape over time. Here, based on ion microprobe analyses of apatite grains from martian meteorite QUE94201, it is shown that the pre-Jeans escape...
Article
The Lunar Prospector gamma-ray spectrometer (LP-GRS) recently provided a wealth of new data for the global distribution of thorium in the lunar regolith [1]. Geochemically, Th is the exemplar of a large suite of refractory-incompatible elements, including e.g., all of the REE except Eu. It is generally assumed that all these elements, and even the...
Article
We present new bulk compositional data for 6 martian meteorites, including highly siderophile elements Ni, Re, Os, Ir and Au. These and literature data are utilized for comparison versus the siderophile systematics of igneous rocks from Earth, the Moon, and the HED asteroid. The siderophile composition of ALH84001 is clearly anomalous. Whether this...
Article
Lunar meteorite QUE94281 is remarkably similar to Y-793274. Pairing in the conventional Earth-entry sense is difficult to reconcile with the 2500 km separation between the find locations for these two samples. Nonetheless, both of these regolith breccias are dominated by VLT mare basalt, the pyroxenes of which feature exsolution lamellae on a remar...
Article
High-temperature models for origin of the carbonates in Martian meteorite ALH84001 are implausible. The impact metasomatism model, invoking reaction between CO2 rich fluid and the host orthopyroxenite, requires conversion of olivine into orthopyroxene, yet olivine in ALH84001 shows no depletion in carbonate-rich areas; or else conversion of orthopy...
Article
The strongest evidence for the lunar magmasphere hypothesis is still the pronounced geochemical bimodality among pristine nonmare rocks. Magnesium-suite (MgS) rocks have a distinctly higher mg ratio than ferroan anorthositic suite (FAS) cumulates of otherwise similar geochemistry (e.g., Na/Ca, REE, and especially Eu/AI). Well-sampled FAS rocks are...
Article
We present new bulk compositional data for six martian meteorites, including the highly siderophile elements Ni, Re, Os, Ir, and Au. These and literature data are compared with the siderophile systematics of igneous rocks from Earth, the Moon, and the HED asteroid. The composition of ALH 84001 is anomalously siderophile-poor. Whether this reflects...
Article
New bulk compositional data for six martian meteorites, including highly siderophile elements Ni, Re, Os, Ir, and Au [ I ], are utilized along with literature data for comparison with the siderophile systematics of igneous rocks from Earth, the Moon, and the HED asteroid. Queen Alexandra Range 94201 and EET 79001-B are both depleted in the "noblest...
Article
Abstract— According to a currently popular model for petrogenesis on the howardite, eucrite, and diogenite (HED) parent asteroid, the diogenites are not comagmatic with most eucrites but instead formed in separate orthopyroxenite-dominated plutons. This model can be tested for consistency with mass balance for MgO and FeO, assuming the overall diog...
Article
Full-text available
The high-Al mare basalts from Apollo 14 include most of the oldest individual mare samples known, with Rb-Sr ages in several cases between 4.1 and 4.3 Ga. However, the Nd isotopic systematics for the same samples are generally disturbed, even though under most circumstances Nd isotopes probably tend to be more resistant to disturbance than Sr isoto...
Article
Evidence is presented for source-crater pairing of lunar meteorites Y-793274 and QUE94281 on the basis of analyses of low-Ti mare glass spherules from the matrices of these breccias. It is argued that these meteorites are source-crater paired, but that EET87521 is most likely the product of a separate launch event. Site averages of pure mare basalt...