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G Ryder - One of the best experts on this subject based on the ideXlab platform.
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chemical variation of the large apollo 15 olivine normative Mare Basalt rock samples
Journal of Geophysical Research, 2001Co-Authors: G Ryder, Benjamin C SchuraytzAbstract:Most chemical analyses of Apollo 15 olivine-normative Mare Basalts have been conducted on subsamples of 4 g) to obtain greater whole-rock representivity. These subsamples were individually ground and homogenized, and splits were taken for analysis. Furthermore, we used both X-ray fluorescence and neutron activation techniques to analyze for a comprehensive set of elements suitable for petrogenetic interpretation. The analyses show that the samples form a single coherent suite with almost all of the variation corresponding with olivine control (15% range). A few of the coarser rocks are not quite represented even at this sampling size. The analyses show that the rocks are individually distinct and that analyses are not merely of unrepresentative pieces of a single rock, undifferentiated rock unit, or rocks differing only by short-range unmixing of residual fluids. The petrographic features, including the low abundance of olivine and its small size, and the vesicularity of even some of the coarser samples, show that the olivine that controlled the chemical variation is not accumulated in any of the rocks. The Apollo 15 olivine-normative Mare Basalts were extruded as a series of magmas from a shallow but not locally surficial, olivine-accumulating magma system and formed a sequence of thin flows. A greater understanding of the relationships within and among other Mare Basalt sequences would be obtained by obtaining comprehensive chemical analyses on splits taken from subsamples of 5 g of all rocks large enough to obtain such subsamples.
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old age of formation for a distinct variety of a17 high titanium Mare Basalt
LPI, 1998Co-Authors: J Dasch, C Y Shih, Y Reese, H Wiesmann, G Ryder, L E NyquistAbstract:High-titanium Mare Basalts and volcanic glasses collected at the Apollo 17 landing site that have been analyzed chemically probably are not part of a single eruptive event. They constitute at least three Basaltic groups (e.g. [1]) which have been interpreted as being related through partial melting or fractionation processes, or both, of a primary magma, melts of heterogeneous provenance, or some mix of these possibilities. Ryder [2] described a possible new type (D) of hightitanium Mare Basalt (79001, 2161) from an A17 drive tube which sampled the rim of Van Serg crater, a young impact crater. Ryder based his conclusion on the rock’s more primitive bulk chemistry, its subophitic texture, the order of appearance of minerals formed, and their grain sizes and textures. We report Rb-Sr and Sm-Nd isotopic analyses which show that 79001, 2175 is the oldest high-titanium Basalt reported from the moon, and which support Ryder’s conclusion that this rock constitutes a distinct variety of A17 high-titanium Mare Basalts.
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a glass spherule of questionable impact origin from the apollo 15 landing site unique target Mare Basalt
Geochimica et Cosmochimica Acta, 1996Co-Authors: G Ryder, Paul H. Warren, Gregory W. Kallemeyn, J W Delano, Brent G DalrympleAbstract:A 6 mm-diameter dark spherule, 15434,28, from the regolith on the Apennine Front at the Apollo 15 landing site has a homogeneous glass interior with a 200 μm-thick rind of devitrified or crystallized melt. The rind contains abundant small fragments of Apollo 15 olivine-normative Mare Basalt and rare volcanic Apollo 15 green glass. The glass interior of the spherule has the chemical composition, including a high FeO content and high CaO/Al2O3, of a Mare Basalt. Whereas the major element and Sc, Ni, and Co abundances are similar to those of low-Ti Mare Basalts, the incompatible elements and Sr abundances are similar to those of high-Ti Mare Basalts. The relative abundance patterns of the incompatible trace elements are distinct from any other lunar Mare Basalts or KREEP; among these distinctions are a much steeper slope of the heavy rare earth elements. The 15434,28 glass has abundances of the volatile element Zn consistent with both impact glasses and crystalline Mare Basalts, but much lower than in glasses of Mare volcanic origin. The glass contains siderophile elements such as Ir in abundances only slightly higher than accepted lunar indigenous levels, and some, such as Au, are just below such upper limits. The age of the glass, determined by the 40Ar/39Ar laser incremental heating technique, is 1647 ±11 Ma (2 δ); it is expressed as an age spectrum of seventeen steps over 96% of the 39Ar released, unusual for an impact glass. Trapped argon is negligible. The undamaged nature of the sphere demonstrates that it must have spent most of its life buried in regolith; 38Ar cosmic ray exposure data suggest that it was buried at less than 2m but more than a few centimeters if a single depth is appropriate. That the spherule solidified to a glass is surprising; for such a Mare composition, cooling at about 50 °C s−1 is required to avoid crystallization, and barely attainable in such a large spherule. The low volatile abundances, slightly high siderophile abundances, and the young age are perhaps all most consistent with an impact origin, but nonetheless not absolutely definitive. The 15434,28 glass is distinct from the common yellow impact glasses at the Apollo 15 landing site, in particular in its lower abundances of incompatible elements and much younger age. If we accept an impact origin, then the trace element relative abundances preclude both typical KREEP and the common Apollo 15 yellow impact glass from contributing more than a few percent of the incompatible elements to potential mixtures. The melted part of any target must have consisted almost entirely of a variety (or varieties) of Mare Basalt or glass distinct from any known Mare Basalts or glasses, including Apollo 15 yellow volcanic glass, or mixtures of them. However, the rind inclusions, similar to materials of local origin, do suggest a source near the Apollo 15 landing site. An impact melt cannot have dissolved much, if any, of such inclusions. A lack of regolith materials in the rind and in the melt component suggest an immature source terrain. Thus, even for an impact origin, there is the possibility (though not requirement) that the volcanic target is younger than most Mare plains. The crater Hadley C, 25 km away, is a potential source. If the 15434,28 glass is instead directly of volcanic origin, it represents an extremely young Mare magma of a type previously undiscovered on the Moon.
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a glass spherule of questionable impact origin from the apollo 15 landing site unique target Mare Basalt
Geochimica et Cosmochimica Acta, 1996Co-Authors: G Ryder, Paul H. Warren, Gregory W. Kallemeyn, J W Delano, Brent G DalrympleAbstract:A 6 mm-diameter dark spherule, 15434,28, from the regolith on the Apennine Front at the Apollo 15 landing site has a homogeneous glass interior with a 200 microns-thick rind of devitrified or crystallized melt. The rind contains abundant small fragments of Apollo 15 olivine-normative Mare Basalt and rare volcanic Apollo 15 green glass. The glass interior of the spherule has the chemical composition, including a high FeO content and high CaO/Al2O3, of a Mare Basalt. Whereas the major element and Sc, Ni, and Co abundances are similar to those of low-Ti Mare Basalts, the incompatible elements and Sr abundances are similar to those of high-Ti Mare basaits. The relative abundance patterns of the incompatible trace elements are distinct from any other lunar Mare Basalts or KREEP; among these distinctions are a much steeper slope of the heavy rare earth elements. The 15434,28 glass has abundances of the volatile element Zn consistent with both impact glasses and crystalline Mare Basalts, but much lower than in glasses of Mare volcanic origin. The glass contains siderophile elements such as Ir in abundances only slightly higher than accepted lunar indigenous levels, and some, such as Au, are just below such upper limits. The age of the glass, determined by the Ar-40/Ar-39 laser incremental heating technique, is 1647 +/- 11 Ma (2 sigma); it is expressed as an age spectrum of seventeen steps over 96% of the Ar-38 released, unusual for an impact glass. Trapped argon is negligible. The undamaged nature of the sphere demonstrates that it must have spent most of its life buried in regolith; Ar-38 cosmic ray exposure data suggest that it was buried at less than 2m but more than a few centimeters if a single depth is appropriate. That the spherule solidified to a glass is surprising; for such a Mare composition, cooling at about 50 C/s is required to avoid crystallization, and barely attainable in such a large spherule. The low volatile abundances, slightly high siderophile abundances, and the young age are perhaps all most consistent with an impact origin, but nonetheless not absolutely definitive.
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an apollo 15 Mare Basalt fragment and lunar Mare provinces
Meteoritics & Planetary Science, 1996Co-Authors: G Ryder, Trina Cox BurlingAbstract:Lunar sample 15474,4 is a tiny fragment of olivine-augite vitrophyre that is a Mare Basalt. Although petroraphically distinct from all other Apollo 15 samples, it has been ignored since its first brief description. Our new petrographic and mineral chemical data show that the olivines and pyroxenes are distinct from those in other Basalts. The Basalt cooled and solidified extremely rapidly; some of the olivine might be cumulate or crystallized prior to extrusion. Bulk-chemical data show that the sample is probably similar to an evolved Apollo 15 olivine-normative Basalt in major elements but is distinct in its rare earth element pattern. Its chemical composition and petrography both show that 15474,4 cannot be derived from other Apollo 15 Mare Basalts by shallow-level crystal fractionation. It represents a distinct extrusion of magma. Nonetheless, the chemical features that 15474,4 has in common with other Apollo 15 Mare Basalts, including the high FeO/Sc, the general similarity of the rare earth element pattern, and the common (and chondritic) TiO2/Sm ratio, emphasize the concept of a geochemical province at the Apollo 15 site that is distinct from Basalts and provinces elsewhere. In making a consistent picture for the derivation of all of the Apollo 15 Basalts, both the commonalities and the differences among the Basalts must be explained. The Apollo 15 commonalities and differences suggest that the sources must have consisted of major silicate phases with the same composition but with varied amounts of a magma trapped from a contemporary magma ocean. They probably had a high olivine/pyroxene ratio and underwent small and reasonably consistent degrees of partial melting to produce the Basalts. These inferences may be inconsistent with models that suggest greatly different depths of melting among Basalts, primitive sources for the green glasses, or extensive olivine fractionation during ascent. An integrated approach to lunar Mare provinces, of which the Apollo 15 Mare Basalts constitute only one, offers advances in our understanding of the physical and chemical processes of source formation and Mare production but has so far not been utilized.
L. A. Taylor - One of the best experts on this subject based on the ideXlab platform.
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evidence for high temperature fractionation of lithium isotopes during differentiation of the moon
Meteoritics & Planetary Science, 2016Co-Authors: William F Mcdonough, Fangzhen Teng, Roberta L Rudnick, L. A. TaylorAbstract:Lithium isotope and abundance data are reported for Apollo 15 and 17 Mare Basalts and the LaPaz low-Ti Mare Basalt meteorites, along with lithium isotope data for carbonaceous, ordinary, and enstatite chondrites, and chondrules from the Allende CV3 meteorite. Apollo 15 low-Ti Mare Basalts have lower Li contents and lower δ7Li (3.8 ± 1.2‰; all uncertainties are 2 standard deviations) than Apollo 17 high-Ti Mare Basalts (δ7Li = 5.2 ± 1.2‰), with evolved LaPaz Mare Basalts having high Li contents, but similar low δ7Li (3.7 ± 0.5‰) to Apollo 15 Mare Basalts. In low-Ti Mare Basalt 15555, the highest concentrations of Li occur in late-stage tridymite (>20 ppm) and plagioclase (11 ± 3 ppm), with olivine (6.1 ± 3.8 ppm), pyroxene (4.2 ± 1.6 ppm), and ilmenite (0.8 ± 0.7 ppm) having lower Li concentrations. Values of δ7Li in low- and high-Ti Mare Basalt sources broadly correlate negatively with 18O/16O and positively with 56Fe/54Fe (low-Ti: δ7Li ≤4‰; δ56Fe ≤0.04‰; δ18O ≥5.7‰; high-Ti: δ7Li >6‰; δ56Fe >0.18‰; δ18O <5.4‰). Lithium does not appear to have acted as a volatile element during planetary formation, with subequal Li contents in Mare Basalts compared with terrestrial, martian, or vestan Basaltic rocks. Observed Li isotopic fractionations in Mare Basalts can potentially be explained through large-degree, high-temperature igneous differentiation of their source regions. Progressive magma ocean crystallization led to enrichment in Li and δ7Li in late-stage liquids, probably as a consequence of preferential retention of 7Li and Li in the melt relative to crystallizing solids. Lithium isotopic fractionation has not been observed during extensive differentiation in terrestrial magmatic systems and may only be recognizable during extensive planetary magmatic differentiation under volatile-poor conditions, as expected for the lunar magma ocean. Our new analyses of chondrites show that they have δ7Li ranging between −2.5‰ and 4‰. The higher δ7Li in planetary Basalts than in the compilation of chondrites (2.1 ± 1.3‰) demonstrates that differentiated planetary Basalts are, on average, isotopically heavier than most chondrites.
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oxygen and iron isotope constraints on near surface fractionation effects and the composition of lunar Mare Basalt source regions
Geochimica et Cosmochimica Acta, 2010Co-Authors: Yang Liu, James M D Day, Michael J Spicuzza, Paul R Craddock, John W Valley, Nicolas Dauphas, L. A. TaylorAbstract:Oxygen and iron isotope analyses of low-Ti and high-Ti Mare Basalts are presented to constrain their petrogenesis and to assess stable isotope variations within lunar mantle sources. An internally-consistent dataset of oxygen isotope compositions of Mare Basalts encompasses five types of low-Ti Basalts from the Apollo 12 and 15 missions and eight types of high-Ti Basalts from the Apollo 11 and 17 missions. High-precision whole-rock d 18 O values (referenced to VSMOW) of low-Ti and high-Ti Basalts correlate with major-element compositions (Mg#, TiO2 ,A l 2O3). The observed oxygen isotope variations within low-Ti and high-Ti Basalts are consistent with crystal fractionation and match the results of mass-balance models assuming equilibrium crystallization. Whole-rock d 56 Fe values (referenced to IRMM-014) of high-Ti and low-Ti Basalts range from 0.134& to 0.217& and 0.038& to 0.104&, respectively. Iron isotope compositions of both low-Ti and high-Ti Basalts do not correlate with indices of crystal fractionation, possibly owing to small mineral-melt iron fractionation factors anticipated under lunar reducing conditions. The d 18 O and d 56 Fe values of low-Ti and the least differentiated high-Ti Mare Basalts are negatively correlated, which reflects their different mantle source characteristics (e.g., the presence or absence of ilmenite). The average d 56 Fe values of low-Ti Basalts (0.073 ± 0.018&, n = 8) and high-Ti Basalts (0.191 ± 0.020&, n = 7) may directly record that of their parent mantle sources. Oxygen isotope compositions of mantle sources of low-Ti and high-Ti Basalts are calculated using existing models of lunar magma ocean crystallization and mixing, the estimated equilibrium mantle olivine d 18 O value, and equilibrium oxygen-fractionation between olivine and other mineral phases. The differences between the calculated whole-rock d 18 O values for source regions, 5.57& for low-Ti and 5.30& for high-Ti Mare Basalt mantle source regions, are solely a function of the assumed source mineralogy. The oxygen and iron isotope compositions of lunar upper mantle can be approximated using these mantle source values. The d 18 O and d 56 Fe values of the lunar upper mantle are estimated to be 5.5 ± 0.2& (2r) and 0.085 ± 0.040& (2r), respectively. The oxygen isotope composition of lunar upper mantle is identical to the current estimate of Earth’s upper mantle (5.5 ± 0.2&), and the iron isotope composition of the lunar upper mantle overlaps within uncertainty of estimates for the terrestrial upper mantle (0.044 ± 0.030&).
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petrogenesis of lunar Mare Basalt meteorite miller range 05035
Meteoritics & Planetary Science, 2009Co-Authors: Yang Liu, Christine Floss, E Hill, James M D Day, L. A. TaylorAbstract:Miller Range (MIL) 05035 is a low-Ti Mare Basalt that consists predominantly of pyroxene (62.3 vol%) and plagioclase (26.4 vol%). Pyroxenes are strongly shocked and complexly zoned from augite (Wo33) and pigeonite (Wo17) cores with Mg# = 50-54 to hedenbergite rims. Coexisting pyroxene core compositions reflect crystallization temperatures of 1000 to 1100 °C. Plagioclase has been completely converted to maskelynite with signs of recrystallization. Maskelynite is relatively uniform in composition (An94Ab6-An91Ab9), except at contacts with late-stage mesostasis areas (elevated K contents, An82Ab15Or3). Symplectites (intergrowth of Fe-augite, fayalite, and silica) of different textures and bulk compositions in MIL 05035 suggest formation by decomposition of ferro-pyroxene during shock-induced heating, which is supported by the total maskelynitization of plagioclase, melt pockets, and the presence of a relict pyroxferroite grain. Petrography and mineral chemistry imply that crystallization of MIL 05035 occurred in the sequence of Fe-poor pyroxenes (Mg# = 50-54), followed by plagioclase and Fe-rich pyroxenes (Mg# = 20-50), and finally hedenbergite, Fe-Ti oxides, and minor late-stage phases. Petrography, bulk chemistry, mineral compositions, and the age of MIL 05035 suggest it is possibly source crater-paired with Asuka (A-) 881757 and Yamato (Y-) 793169, and may also be launch-paired with Meteorite Hills (MET) 01210. MIL 05035 represents an old (~3.8-3.9 Ga), incompatible element-depleted low-Ti Basalt that was not sampled during the Apollo or Luna missions. The light-REE depleted nature and lack of Eu anomalies for this meteorite are consistent with an origin distant from the Procellarum KREEP Terrane, and genesis from an early cumulate mantle-source region generated by extensive differentiation of the Moon.
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lunar meteorite lapaz icefield 04841 petrology texture and impact shock effects of a low ti Mare Basalt
Meteoritics & Planetary Science, 2009Co-Authors: L. A. Taylor, Christine Floss, E Hill, Yang LiuAbstract:Found during the 2004 U.S. Antarctic Search for Meteorites season, LaPaz Icefield (LAP) 04841 represents an addition to the LaPaz lunar Basalts suite and brings the total mass collected to 1.93 kg. The presence of FeNi grains, troilite, and the anorthositic composition of plagioclase are evidence for the lunar origin of this meteorite. Pyroxene and olivine Mn/Fe values plot along the trend set for lunar Basalts. Analyses of chromite grains provide a V/(Al + Cr) ratio of 1.33 ± 13, translating to an fO2 one log unit below the IW buffer, in accordance with previous fO2 estimates for lunar Basalts. Application of the Zr-cooling speedometer, for ilmenite and ulvospinel pairs, gives a cooling rate of 5.2 °C/day, matching previous estimates of cooling rates for the LaPaz lunar meteorites and Apollo Mare Basalts. Mineral modes and chemistries, as well as trace-element patterns, provide compelling evidence for pairing of this meteorite to others in the LaPaz lunar Basalt suite.
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lapaz 04841 comparative petrology and textural study of a new lunar Mare Basalt meteorite
Lunar and Planetary Science Conference, 2007Co-Authors: E Hill, L. A. Taylor, Yang LiuAbstract:Introduction: Lunar Mare Basalt meteorites found in Antarctica and the hot deserts of Earth provide samples of the Moon that extend our knowledge beyond that gained during the Apollo and Luna missions. Through their study, we obtain a broader view of lunar magmatism and source rock composition. As impactexcavated samples, meteorites also offer the potential for the study of deeper regions of the Moon. To date, 20 Mare Basalt finds are catalogued on the List of Lunar Meteorites [1], of which 6 were found on the LaPaz Ice Field in Antarctica. Previous work (e.g., [2,3]) has presented strong arguments for 5 of these (LAP 02205, LAP 02224, LAP 02226, LAP 02436, and LAP 03632) to have originated from the same flow. The 2004 Antarctic search for meteorites season saw the addition of a 6 LaPaz lunar Basalt to the collection. This find of LAP 04841 measured 5 x 2.5 x 2.5 cm and weighed 0.06 kg, bringing the total mass of LaPaz lunar Basalts to 1.93 kg. Preliminary reports suggest that this new find is paired to the other 5 LaPaz meteorites [4], and is most similar to LAP 02205. We present here the first textural description, mineralogy, and mineral chemistry of LAP 04841 (thin sections LAP 04841,14 & 5, and thick section LAP 04841,18). We also confirm similarities between this meteorite and the other 5 LaPaz lunar Basalts. Petrography and Textures: LAP 04841 is a coarse-grained Basalt with subophitic texture. The major mineralogy consists of pyroxene and plagioclase, with interstitial ilmenite. Minor phases include olivine, Ti-chromite, and ulvospinel. Also present are shockinduced melt veins and a mesostasis, consisting of fayalite, SiO2, K-rich glass, and with trace amounts of FeNi, troilite, ilmenite, ulvospinel, phosphates, and baddeleyite. The order of crystallization, inferred from mineral associations, is believed to be Ti-chromite + olivine, pyroxene + ulvospinel, pyroxene + plagioclase + ilmenite, and mesostasis. The level of shock-induced deformations varies from slide to slide with the most-intense affected being LAP 04841,14, in which all plagioclases have been fully or partially converted to diaplectic glass, i.e., maskelynite. However, section 18 contains both plagioclase and maskelynite, and section 5 contains no maskelynite, only plagioclase. Mineralogy: Pyroxene is the most abundant phase and accounts for 56.2 vol% of the samples. Grains are anhedral and range in size up to ~0.5 mm. Pyroxenes have cores of augite, sometimes pigeonite (Wo14-20). Grain compositions grade continuously from core to rim with progressive Fe enrichment to high-Fe augite (Fs59Wo39), and pyroxferroite (Fs86Wo13).
Paul H. Warren - One of the best experts on this subject based on the ideXlab platform.
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lunar meteorite queen alexandra range 94281 glass compositions and other evidence for launch pairing with yamato 793274
Meteoritics & Planetary Science, 1999Co-Authors: Paul H. Warren, Tomoko AraiAbstract:Abstract— Lunar meteorite Queen Alexandra Range 94281 is remarkably similar to Yamato 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 very-low-Ti (VLT) Mare Basalt, the pyroxenes of which feature exsolution lamellae on a remarkably coarse scale (typical lamella width = 0.5–1 μm) by Mare standards. The pyroxenes also show similar compositional variations (e.g., Fe# vs. Ti# trends, which confirm parentage from VLT Mare Basalt). Plots using Al2O3 or FeO as a tracer of the highland component indicate indistinguishable internal Mare-highland geochemical mixing trends. The same two distinctive glass types dominate the Mare glass populations of both breccias. Glass type YQ1 features 0.37–0.63 wt% TiO2, 10–17 wt% MgO, and 9–11 wt% Al2O3. Glass type YQ2 features higher TiO2 (0.99–1.22 wt%), which is inversely correlated with MgO (12.6–13.8 wt%), and nearly constant (8.8 wt%) Al2O3. All of these similarities suggest that Y-793274 and QUE 94281 are a launch pair, which we designate YQ. Most of these similarities also extend to another Mare-breccia meteorite, Elephant Moraine 87521. However, the EET 87521 Mare Basalt is unusually V-poor (∼88 μg/g), whereas the YQ Mare component contains ∼166 μg/g. Queen Alexandra Range 94281 features a variety of textural domains. Discrete patches of dark matrix material appear to represent clods of mature regolith that have been mixed with a coarser, relatively immature material. Interior to a frothy fusion crust are areas of massive glass that probably formed as a splash coating on QUE 94281 when it was still on the Moon. The coarse YQ and EET 87521 pyroxene exsolution features imply relatively slow cooling in either a very shallow sill or an unusually thick (ponded) lava and/or later annealing within a cryptoMare. Mare pyroclastic glasses, including the two YQ varieties, are systematically MgO-rich compared to crystalline Mare Basalts. This disparity may be a consequence of limited survival of graphite—the main fuel for explosive volcanism—during formation of the Mare source regions as magma ocean cumulates. Graphite (2.2 g/cm3) survived preferentially in regions that avoided extensive early melting and thus remained MgO-rich. An apparent bimodality in the TiO2 contents of Mare volcanics, especially the pyroclastic glasses, also seems a plausible consequence of petrogenesis by remelting of magma ocean cumulates. Cumulates deposited after the magma ocean evolved to ilmenite saturation had vastly higher TiO2 contents than cumulates deposited shortly before. The YQ regolith's subequal proportions of Mare and highland matter are consistent with derivation from a terrain close to a Mare-highland boundary. However, a similar mixture might also develop through vertical mixing in a cryptoMare or a region of thin Mare coverage. Thus, unfortunately, the YQ bulk composition is not a very useful clue to the identity of the source crater.
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a glass spherule of questionable impact origin from the apollo 15 landing site unique target Mare Basalt
Geochimica et Cosmochimica Acta, 1996Co-Authors: G Ryder, Paul H. Warren, Gregory W. Kallemeyn, J W Delano, Brent G DalrympleAbstract:A 6 mm-diameter dark spherule, 15434,28, from the regolith on the Apennine Front at the Apollo 15 landing site has a homogeneous glass interior with a 200 μm-thick rind of devitrified or crystallized melt. The rind contains abundant small fragments of Apollo 15 olivine-normative Mare Basalt and rare volcanic Apollo 15 green glass. The glass interior of the spherule has the chemical composition, including a high FeO content and high CaO/Al2O3, of a Mare Basalt. Whereas the major element and Sc, Ni, and Co abundances are similar to those of low-Ti Mare Basalts, the incompatible elements and Sr abundances are similar to those of high-Ti Mare Basalts. The relative abundance patterns of the incompatible trace elements are distinct from any other lunar Mare Basalts or KREEP; among these distinctions are a much steeper slope of the heavy rare earth elements. The 15434,28 glass has abundances of the volatile element Zn consistent with both impact glasses and crystalline Mare Basalts, but much lower than in glasses of Mare volcanic origin. The glass contains siderophile elements such as Ir in abundances only slightly higher than accepted lunar indigenous levels, and some, such as Au, are just below such upper limits. The age of the glass, determined by the 40Ar/39Ar laser incremental heating technique, is 1647 ±11 Ma (2 δ); it is expressed as an age spectrum of seventeen steps over 96% of the 39Ar released, unusual for an impact glass. Trapped argon is negligible. The undamaged nature of the sphere demonstrates that it must have spent most of its life buried in regolith; 38Ar cosmic ray exposure data suggest that it was buried at less than 2m but more than a few centimeters if a single depth is appropriate. That the spherule solidified to a glass is surprising; for such a Mare composition, cooling at about 50 °C s−1 is required to avoid crystallization, and barely attainable in such a large spherule. The low volatile abundances, slightly high siderophile abundances, and the young age are perhaps all most consistent with an impact origin, but nonetheless not absolutely definitive. The 15434,28 glass is distinct from the common yellow impact glasses at the Apollo 15 landing site, in particular in its lower abundances of incompatible elements and much younger age. If we accept an impact origin, then the trace element relative abundances preclude both typical KREEP and the common Apollo 15 yellow impact glass from contributing more than a few percent of the incompatible elements to potential mixtures. The melted part of any target must have consisted almost entirely of a variety (or varieties) of Mare Basalt or glass distinct from any known Mare Basalts or glasses, including Apollo 15 yellow volcanic glass, or mixtures of them. However, the rind inclusions, similar to materials of local origin, do suggest a source near the Apollo 15 landing site. An impact melt cannot have dissolved much, if any, of such inclusions. A lack of regolith materials in the rind and in the melt component suggest an immature source terrain. Thus, even for an impact origin, there is the possibility (though not requirement) that the volcanic target is younger than most Mare plains. The crater Hadley C, 25 km away, is a potential source. If the 15434,28 glass is instead directly of volcanic origin, it represents an extremely young Mare magma of a type previously undiscovered on the Moon.
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a glass spherule of questionable impact origin from the apollo 15 landing site unique target Mare Basalt
Geochimica et Cosmochimica Acta, 1996Co-Authors: G Ryder, Paul H. Warren, Gregory W. Kallemeyn, J W Delano, Brent G DalrympleAbstract:A 6 mm-diameter dark spherule, 15434,28, from the regolith on the Apennine Front at the Apollo 15 landing site has a homogeneous glass interior with a 200 microns-thick rind of devitrified or crystallized melt. The rind contains abundant small fragments of Apollo 15 olivine-normative Mare Basalt and rare volcanic Apollo 15 green glass. The glass interior of the spherule has the chemical composition, including a high FeO content and high CaO/Al2O3, of a Mare Basalt. Whereas the major element and Sc, Ni, and Co abundances are similar to those of low-Ti Mare Basalts, the incompatible elements and Sr abundances are similar to those of high-Ti Mare basaits. The relative abundance patterns of the incompatible trace elements are distinct from any other lunar Mare Basalts or KREEP; among these distinctions are a much steeper slope of the heavy rare earth elements. The 15434,28 glass has abundances of the volatile element Zn consistent with both impact glasses and crystalline Mare Basalts, but much lower than in glasses of Mare volcanic origin. The glass contains siderophile elements such as Ir in abundances only slightly higher than accepted lunar indigenous levels, and some, such as Au, are just below such upper limits. The age of the glass, determined by the Ar-40/Ar-39 laser incremental heating technique, is 1647 +/- 11 Ma (2 sigma); it is expressed as an age spectrum of seventeen steps over 96% of the Ar-38 released, unusual for an impact glass. Trapped argon is negligible. The undamaged nature of the sphere demonstrates that it must have spent most of its life buried in regolith; Ar-38 cosmic ray exposure data suggest that it was buried at less than 2m but more than a few centimeters if a single depth is appropriate. That the spherule solidified to a glass is surprising; for such a Mare composition, cooling at about 50 C/s is required to avoid crystallization, and barely attainable in such a large spherule. The low volatile abundances, slightly high siderophile abundances, and the young age are perhaps all most consistent with an impact origin, but nonetheless not absolutely definitive.
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consortium reports on lunar meteorites yamato 793169 and asuka 881757 a new type of Mare Basalt
Lunar and Planetary Inst. Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z, 1993Co-Authors: Keizo Yanai, Paul H. Warren, Christian Koeberl, Hiroshi Takeda, M M Lindstrom, Mitsunobu Tatsumoto, N Torigoe, Keiji Misawa, G W Kallemeyn, Hideyasu KojimaAbstract:Consortium studies on lunar meteorites Yamato 793169 and Asuka 881757 (formerly Asuka-31) were performed to characterize these new samples from unknown locations in the lunar Mare. Both meteorites are coarse-grained Mare rocks having low Mg/Fe ratios (bulk mg'=30-35) and low TiO2 (1.5-2.5 percent in homogenized bulk samples). They are intermediate between VLT and low-Ti Mare Basalts. Although these meteorites are not identical to each other, their mineral and bulk compositions, isotopic systematics, and crystallization ages are remarkably similar and distinct from those of all other Mare Basalts. They appear to represent a new type of low-Ti Mare Basalt that crystallized at about 3.9Ga. These meteorites are inconsistent with the canonical correlation between the TiO2 contents and ages of Mare Basalts and suggest that our knowledge of lunar volcanism is far from complete.
M Anand - One of the best experts on this subject based on the ideXlab platform.
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trace element modelling of Mare Basalt parental melts implications for a heterogeneous lunar mantle
Geochimica et Cosmochimica Acta, 2014Co-Authors: M Anand, L J Hallis, Stanislav StrekopytovAbstract:The heterogeneous-source model of Mare Basalt formation indicates that Lunar Magma Ocean (LMO) overturn produced an uneven mixture of early-formed olivine and pyroxene, and late-formed, ilmenite-rich cumulates, which subsequently partially melted to give rise to Mare magmas. These heterogeneous cumulate source regions would not only have been characterised by different mineral modal abundances, but also by different trace element compositions. The aim of this work was to investigate the petrology and geochemistry of a diverse suite of Apollo Mare Basalts, and utilise trace-element modelling in order to understand their petrogenetic history. Chemical modelling confirms that the Mare Basalts were produced by relatively small degrees of partial melting (<10%) of the LMO cumulates, and that the dominant melting type (batch vs. fractional) varies among different Basalt groups. Similarly, single-source mineralogy cannot be applied to all Mare Basalt types, confirming that the lunar mantle was heterogeneous at the time of generation of Mare magmas. Plagioclase is not required in the source of most Mare Basalts, with the notable exception of the Apollo 14 high-Al Basalts. Addition of more than 1% plagioclase to the source of other Basalts produces weaker negative Eu anomalies than those observed in the samples. AFC calculations demonstrate the compositional differences between materials assimilated into the Apollo 14 high-Al and Apollo 11 high-K Mare Basalt partial melts, highlighting the complexities of Mare Basalt petrogenesis.
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timing and duration of Mare Basalt magmatism constraints from lunar samples
Lunar and Planetary Science Conference, 2008Co-Authors: M Anand, Kentaro TeradaAbstract:One of the important issues in lunar science relates to the understanding of the timing and duration of Mare magmatism which has significant implications for the thermal evolution of the lunar interior through time. Remote sensing studies of the Moon have indicated existence of Mare regions as old as 4 Ga and as young as 1 Ga. In contrast, most lab-based studies involving direct age dating of “returned” Basaltic lunar samples (from Apollo and Luna missions, and lunar meteorites) by radiometric techniques have yielded much narrower age ranges for Mare magmatism, typically in the time interval of 3.9 to 3.1 Ga. However, less attention have been given to some notable examples of ancient Mare magmatism, samples of which exist in terms of 4.2 – 4.3 Ga Basalts. Recently, a number of chronological investigations of Basaltic lunar samples have revealed crystallization ages which are older, as well as, younger, than previously known range for Mare Basalt ages. These new findings have necessitated revisiting the topic of ages and duration of Basalt volcanism on the Moon and the causes and consequences of it for the lunar evolution with implications for post-accretion planetary differentiation processes.
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cryptoMare magmatism 4 35 gyr ago recorded in lunar meteorite kalahari 009
Nature, 2007Co-Authors: Kentaro Terada, M Anand, A K Sokol, A Bischoff, Yuji SanoAbstract:The origin and evolution of the Moon remain controversial, one notable point of controversy being the timing of the beginning and end of Basaltic volcanism in the lunar Mares, or plains. Lunar research over the past three decades has suggested that Mare volcanism occurred mainly after the late heavy bombardment that ended 3.9 billion years ago, because most of known Mare Basalts (lunar meteorites and returned Apollo and Luna samples), and remote sensing data, indicate crystallization ages younger than 3.9 billion years. But a new U–Pb dating of minerals in the lunar meteorite Kalahari 009 gives an age of roughly 4.35 billion years for a lunar Basalt. This suggests that the volcanism started as early as 4.35 billion years ago, relatively soon after lunar formation and differentiation, and that Kalahari 009 is our first sample of a 'cryptoMare' from the Moon. The result of U–Pb dating of minerals in a lunar meteorite, Kalahari 009 is reported. Analyses of five grains associated with Basaltic clasts give an age of 4.35 ± 0.15 billion years. These are thought to represent the crystallization ages of parental Basalt magma, making Kalahari 009 one of the oldest known Mare Basalt. This suggests that Mare Basalt volcanism on the Moon started as early as 4.35 billion years ago. The origin and evolution of the Moon remain controversial1,2, with one of the most important questions for lunar evolution being the timing and duration of Basaltic (Mare) magmatism1,3,4,5,6,7,8. Here we report the result of ion microprobe U–Pb dating of phosphates in a lunar meteorite, Kalahari 009, which is classified as a very-low-Ti Mare-Basalt breccia. In situ analyses of five phosphate grains, associated with Basaltic clasts, give an age of 4.35 ± 0.15 billion years. These ancient phosphate ages are thought to represent the crystallization ages of parental Basalt magma, making Kalahari 009 one of the oldest known Mare Basalts. We suggest that Mare Basalt volcanism on the Moon started as early as 4.35 Gyr ago, relatively soon after its formation and differentiation, and preceding the bulk of lunar volcanism which ensued after the late heavy bombardment around 3.8-3.9 Gyr (refs 7 and 8). Considering the extremely low abundances of incompatible elements such as thorium and the rare earth elements in Kalahari 009 (ref. 9) and recent remote-sensing observations illustrating that the cryptomaria tend to be of very-low-Ti Basalt type10,11,12, we conclude that Kalahari 009 is our first sample of a very-low-Ti cryptoMare from the Moon.
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uranium lead systematics of phosphates in lunar Basaltic regolith breccia meteorite hills 01210
Earth and Planetary Science Letters, 2007Co-Authors: M Anand, Kentaro Terada, K H Joy, Yu Sasaki, Yuji SanoAbstract:Chronological studies of brecciated lunar meteorites have proved difficult, because they are mixtures of materials from various sources and the radiometric “clocks” are sometimes affected by the subsequent impact events on the Moon. Here, we report the in-situ U–Pb dating of phosphates in lunar meteorite, Meteorite Hills (MET) 01210, which is a regolith breccia consisting of low-Ti Mare Basalt clasts and mineral fragments with a minor anorthositic component. In-situ analyses of four merrillite and four apatite grains in MET 01210, which are resistant to secondary events, resulted in a 207Pb/206Pb–204Pb/206Pb isochron age of 3904 ± 85 Ma (95% confidence limit). This phosphate formation age, when considered as the crystallisation age of this low-Ti Basalt, is similar to crystallization ages of 3.8–3.9 Ga for unbrecciated low-Ti Basalt meteorites, Asuka 881757 and Yamato 793169. This result reinforces the hypothesis that all these three meteorites originated from the same area on the Moon and were launched by a single impact event, consistent with the similarity of launch ages, mineralogical and geochemical signatures.
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petrology and geochemistry of lapaz icefield 02205 a new unique low ti Mare Basalt meteorite
Geochimica et Cosmochimica Acta, 2006Co-Authors: L. A. Taylor, Clive R Neal, M Anand, Kentaro Terada, Christine Floss, Shiho TanikawaAbstract:LaPaz Icefield 02205 (LAP 02205) is a new low-Ti Mare-Basalt meteorite that was discovered in the LaPaz Ice Field in Antarctica. This is the first crystalline lunar Basalt in the US Antarctic collection and the only 5th unbrecciated Mare-Basalt meteorite to be discov- ered to date. The rock has a typical Basaltic texture with tabular and elongated pyroxene and plagioclase crystals, and minor olivine grains commonly rimmed by pyroxenes. Core- to rim- zoning in terms of Fe and Mg is present in almost all pyroxene grains. Accessory minerals include ilmenite, chromite, ulvospinel, troilite, and FeNi metal. This rock is highly enriched in late-stage mesostasis. Free silica is also abundant. In terms of texture and mineralogy, LAP 02205 displays features of low-Ti Mare Basalts, with similarities to some low- Ti Apollo 12 and Apollo 15 Basalts. Whole-rock major- and trace-element compositions confirm the highly fractionated nature of this Basalt. The whole-rock REE contents of the meteorite are the highest among all known low-Ti Mare Basalts. The platinum group element (PGE) contents in LAP are also enriched suggesting the possibility of endogenously enriched source regions or the PGEs generally behaved as incompatible elements during crystal fractionation under low fO2 conditions. Trace-element contents of mineral grains in LAP 02205 display wide variations, suggesting extensive non-equilibrium crystallization. The REE concentrations in the earliest-formed minerals provide constraints on the composition of the parental liquid, which is similar to the measured whole-rock composition. Crys- tallization modeling of the LAP 02205 bulk composition yields a reasonable fit between predicted and observed mineral phases and com- positions, except for the high-Mg olivine cores, which are observed in the rock but not predicted by the modeling. An isochron age of 2929 ± 150 Ma for phosphate minerals makes this rock one of the youngest lunar Basalts known to date. The young age and specific geochemical characteristics of LAP distinguish it from those of most other low-Ti Mare Basalts. However, the low-Ti Mare Basalt mete- orite, NWA 032, has a similar young age, and the two meteorites also appear to be closely related from some geochemical perspectives and might have originated from similar source regions on the Moon.
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a glass spherule of questionable impact origin from the apollo 15 landing site unique target Mare Basalt
Geochimica et Cosmochimica Acta, 1996Co-Authors: G Ryder, Paul H. Warren, Gregory W. Kallemeyn, J W Delano, Brent G DalrympleAbstract:A 6 mm-diameter dark spherule, 15434,28, from the regolith on the Apennine Front at the Apollo 15 landing site has a homogeneous glass interior with a 200 μm-thick rind of devitrified or crystallized melt. The rind contains abundant small fragments of Apollo 15 olivine-normative Mare Basalt and rare volcanic Apollo 15 green glass. The glass interior of the spherule has the chemical composition, including a high FeO content and high CaO/Al2O3, of a Mare Basalt. Whereas the major element and Sc, Ni, and Co abundances are similar to those of low-Ti Mare Basalts, the incompatible elements and Sr abundances are similar to those of high-Ti Mare Basalts. The relative abundance patterns of the incompatible trace elements are distinct from any other lunar Mare Basalts or KREEP; among these distinctions are a much steeper slope of the heavy rare earth elements. The 15434,28 glass has abundances of the volatile element Zn consistent with both impact glasses and crystalline Mare Basalts, but much lower than in glasses of Mare volcanic origin. The glass contains siderophile elements such as Ir in abundances only slightly higher than accepted lunar indigenous levels, and some, such as Au, are just below such upper limits. The age of the glass, determined by the 40Ar/39Ar laser incremental heating technique, is 1647 ±11 Ma (2 δ); it is expressed as an age spectrum of seventeen steps over 96% of the 39Ar released, unusual for an impact glass. Trapped argon is negligible. The undamaged nature of the sphere demonstrates that it must have spent most of its life buried in regolith; 38Ar cosmic ray exposure data suggest that it was buried at less than 2m but more than a few centimeters if a single depth is appropriate. That the spherule solidified to a glass is surprising; for such a Mare composition, cooling at about 50 °C s−1 is required to avoid crystallization, and barely attainable in such a large spherule. The low volatile abundances, slightly high siderophile abundances, and the young age are perhaps all most consistent with an impact origin, but nonetheless not absolutely definitive. The 15434,28 glass is distinct from the common yellow impact glasses at the Apollo 15 landing site, in particular in its lower abundances of incompatible elements and much younger age. If we accept an impact origin, then the trace element relative abundances preclude both typical KREEP and the common Apollo 15 yellow impact glass from contributing more than a few percent of the incompatible elements to potential mixtures. The melted part of any target must have consisted almost entirely of a variety (or varieties) of Mare Basalt or glass distinct from any known Mare Basalts or glasses, including Apollo 15 yellow volcanic glass, or mixtures of them. However, the rind inclusions, similar to materials of local origin, do suggest a source near the Apollo 15 landing site. An impact melt cannot have dissolved much, if any, of such inclusions. A lack of regolith materials in the rind and in the melt component suggest an immature source terrain. Thus, even for an impact origin, there is the possibility (though not requirement) that the volcanic target is younger than most Mare plains. The crater Hadley C, 25 km away, is a potential source. If the 15434,28 glass is instead directly of volcanic origin, it represents an extremely young Mare magma of a type previously undiscovered on the Moon.
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a glass spherule of questionable impact origin from the apollo 15 landing site unique target Mare Basalt
Geochimica et Cosmochimica Acta, 1996Co-Authors: G Ryder, Paul H. Warren, Gregory W. Kallemeyn, J W Delano, Brent G DalrympleAbstract:A 6 mm-diameter dark spherule, 15434,28, from the regolith on the Apennine Front at the Apollo 15 landing site has a homogeneous glass interior with a 200 microns-thick rind of devitrified or crystallized melt. The rind contains abundant small fragments of Apollo 15 olivine-normative Mare Basalt and rare volcanic Apollo 15 green glass. The glass interior of the spherule has the chemical composition, including a high FeO content and high CaO/Al2O3, of a Mare Basalt. Whereas the major element and Sc, Ni, and Co abundances are similar to those of low-Ti Mare Basalts, the incompatible elements and Sr abundances are similar to those of high-Ti Mare basaits. The relative abundance patterns of the incompatible trace elements are distinct from any other lunar Mare Basalts or KREEP; among these distinctions are a much steeper slope of the heavy rare earth elements. The 15434,28 glass has abundances of the volatile element Zn consistent with both impact glasses and crystalline Mare Basalts, but much lower than in glasses of Mare volcanic origin. The glass contains siderophile elements such as Ir in abundances only slightly higher than accepted lunar indigenous levels, and some, such as Au, are just below such upper limits. The age of the glass, determined by the Ar-40/Ar-39 laser incremental heating technique, is 1647 +/- 11 Ma (2 sigma); it is expressed as an age spectrum of seventeen steps over 96% of the Ar-38 released, unusual for an impact glass. Trapped argon is negligible. The undamaged nature of the sphere demonstrates that it must have spent most of its life buried in regolith; Ar-38 cosmic ray exposure data suggest that it was buried at less than 2m but more than a few centimeters if a single depth is appropriate. That the spherule solidified to a glass is surprising; for such a Mare composition, cooling at about 50 C/s is required to avoid crystallization, and barely attainable in such a large spherule. The low volatile abundances, slightly high siderophile abundances, and the young age are perhaps all most consistent with an impact origin, but nonetheless not absolutely definitive.