Time and duration of lunar highlands crust formation

All radiometric systems indicate that crust-mantle differentiation on the moon is dominated by events which occurred very early in lunar history. However, due to remaining uncertainties in model parameters and assumptions in the calculation of model ages, it is not yet possible to resolve the precise times of occurrence of these events nor the duration of the formation of the highlands crust. The strongest time constraints are offered by direct radiometric ages of samples formed during this earliest period. Two possible candidates for this material, norites 78236 and 73255,27,45, were examined utilizing the Sm-Nd radiometric system. Sm-Nd systematics of 78236 show post-crystallization disturbance but indicate that this norite crystallized in the lunar crust about 4.34 AE ago. Data for 73255,27,45 define an isochron and yield a crystallization age of 4.23 ± 0.05 AE. The initial Nd isotopic composition of both norites is within uncertainty of a “chondritic” reference reservoir at the time of their respective crystallizations. The implications for lunar crustal formation persisting over a time span of close to 350 m.y. are discussed.     

利用重力地形导纳估计月壳厚度

在频域使用多窗口(Multitaper)方法来计算月球正面四个形成于不同历史时期月海区(Smythii, Crisium, Imbrium, Orientale)的重力地形导纳,然后将其与月球弹性岩石圈的理论导纳模型相比较,由最小二乘法得出四个月海区的月球岩石圈的平均弹性厚度约为8 km,月壳的厚度分别为：Smythii 盆地,72 km; Crisium 盆地 70 km;Orientale 盆地 60 km;Imbrium 盆地57 km.随着月球的演化,月壳厚度呈现变厚的趋势.     

Osmium isotope and highly siderophile element systematics of the lunar crust

Coupled ¹⁸⁷Os/¹⁸⁸Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ± 0.3 pg g^? 1 Os, 1.5 ± 0.6 pg g^? 1 Ir, 6.8 ± 2.7 pg g^? 1 Ru, 16 ± 15 pg g^? 1 Pt, 33 ± 30 pg g^? 1 Pd and 0.29 ± 0.10 pg g^? 1 Re (～ 0.00002 × CI) and Re/Os ratios that were modestly elevated (¹⁸⁷Re/¹⁸⁸Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (～ 0.00007 × CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle–crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments.If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust–mantle concentration ratios (D-values) must be ≤ 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust–mantle HSE partitioning for the Earth and Moon are somewhat surprising. Low HSE abundances in the lunar crust, coupled with estimates of HSE concentrations in the lunar mantle implies there may be a ‘missing component’ of late-accreted materials (as much as 95%) to the Moon if the Earth/Moon mass-flux estimates are correct and terrestrial mantle HSE abundances were established by late accretion.     

60025: relict of primitive lunar crust?

New isotopic analyses are presented for 3 plagioclase-rich fractions and one mafic fraction from ferroan anorthosite 60025. The observed²⁰⁶Pb/²⁰⁴Pb ratios vary between 52.5 and 60.5, all much higher than the ratio for terrestrial contamination. In a²⁰⁷Pb/²⁰⁶Pb²⁰⁴Pb/²⁰⁶Pb correlation diagram, the plagioclase data define a model PbPb age of 4.520 ± 0.007 AE using meteoritic primordial lead for the non-radiogenic component. In the concordia diagram the plagioclase data yield intersections at 4.503 ± 0.007 and 0.28 AE. The meaning of the lower intercept is obscure. The earlier 60025 analysis of Tera and Wasserburg [1], with an observed²⁰⁶Pb/²⁰⁴Pb of 23.0, agrees closely with the new plagioclase data in the isotope correlation and concordia diagrams. Since the apparent age does not correlate with the²⁰⁶Pb/²⁰⁴Pb ratios and U contents of the samples, it does not appear to be controlled by terrestrial lead contamination. The time-averaged μ values for the plagioclase leads are exceptionally low, 16–55, and agree within factors of 2 with the observed μ values in the samples. These are much lower than the values observed for mafic rocks or their sources, showing that the anorthosite lead has never been associated for a substantial length of time with any high μ source. In this way the 60025 data differ substantially from UPb data for two other lunar anorthosites, 15415 and 60015. The results suggest that the averaged model Pb ages of 4.51 ± 0.01 AE closely approximate the crystallization age for the plagioclase fraction of the anorthosite, and that it dates back to an early phase in lunar history. One sample from the mafic fraction of 60025 yields a younger model Pb age of 4.42 AE. The age may have been lowered by post-crystallization disturbances or perhaps this fraction is not coeval with the plagioclase fraction.     

Subsidence history of the Bahama Escarpment and the nature of the crust underlying the Bahamas

Subsidence of the Bahama Escarpment, determined from deep-diving submersible and dredge samples, is used to constrain the nature of crust underlying the Bahamas. Horizontal disposition of the Hauterivian/Barremian (125 Ma) age boundary along the Bahama Escarpment is inconsistent with an underlying oceanic crust (either normal or thickened) here, and suggests that thinned continental crust underlies the Bahamas. Subsidence curves are then fit based on a stretched lithosphere model to a stratigraphic section (2000–4000 m) off Cat Island. This analysis indicates crustal thinning by a factor (β) of 2.0–2.5, resulting in present crustal thicknesses of 10–12 km. We propose that rifting beneath the Bahamas occurred from middle (175–180 Ma) to late (160 Ma) Jurassic time. The pre-extension Bahamas fit between North and South America and Africa in Early Jurassic time, eliminating overlap of the present Bahamas onto Africa in reconstructions of the North Atlantic.     

Creep response of the lunar crust in mare regions from an analysis of crater deformation

The settling trends of 318 lunar mare craters are compared with predictions of numerical finite-element models in order to determine the creep response of the upper lunar mare crust. No settling is evident in craters smaller than 5 km in diameter. Settling rates of larger craters increase as function of crater size in a manner suggesting a non-linear lunar creep response corresponding to the power law $\text{ε}\text{?}\text{= 8.3 · 10}{}^{\mathrm{?34}}\text{σ}{}^2$ where έ is the strain rate and σ is the differential stress. However, the observed nonlinearity is probably an apparent nonlinearity resulting from the temperature induced viscosity decrease with depth due to a lunar crustal temperature gradient of 3° C/km and a creep activation energy of 20 kcal/mole. It is concluded that creep in the lunar medium is essentially Newtonian, and that the effective viscosity of the upper lunar mare crust is (1.6 ± 0.3) · 10²⁵ poise.     

上月壳中的散射引起月震尾波的数值模拟研究

在阿波罗月震记录中普遍存在着强烈持久的尾波信号,这样的波形特征无法用均匀分层月球模型解释.一个普遍被接受的解释是月震尾波由月球浅层结构对月震波的散射引起.我们采用基于交错网格的伪谱和有限差分混合方法模拟研究非均匀上月壳对月震波的散射效应,在此基础上解释月震尾波的形成机制,并估计出上月壳速度扰动的强度.我们发现,在均匀分层模型基础上,进一步考虑上月壳中的非均匀结构对月震波的散射效应,能有效地解释月震信号中强烈持久的尾波.我们认为月震尾波可能是由上月壳中的低波速、低衰减和散射这三个因素的共同作用所引起.采用不同的扰动标准差模拟上月壳的非均匀性,并比较模拟波形与真实月震图的相似程度,我们发现上月壳中速度扰动的标准差应该在3%到5%之间,很可能接近于3%.     

Elastic properties of garnet solid-solution series

The elastic constants of sixteen garnet specimens of wide variety in chemical composition are accurately determined by means of the rectangular parallelpiped resonance method. The dependence of the elastic properties on chemical composition is analyzed using the present data and those for seven garnets investigated by other authors. The property X_i of a garnet solid solution i is given by a linear addition law in terms of the mole fraction n_ij of component j; X_i = Σn_ijX_j where the X_j's are the properties of the end-members j (j = pyrope, almandine, spessartine, grossular and andradite). The X_j's are determined for density ρ, bulk modulus K, and shear moduli C_s = (C₁₁ ? C₁₂)/2 and C₄₄. No systematic deviation is observed from the linear addition law for the elastic moduli nor for other quantities such as the elastic wave velocities. The extrapolated elastic moduli (Mbar) of the end-members are:

     

11.

Methods and some results of investigations of the scattering properties in the crust and mantle     

A.V. Nikolaev 《Physics of the Earth and Planetary Interiors》1981,26(4):285-291

Results derived from analyses of mainly forward-scattered seismic waves are reported. Major findings are that the strongest scattering originates in the crust and upper and lower mantle, while the central parts of the mantle appear relatively homogeneous. In the upper mantle the extent of the heterogeneities exhibits regional variations. Interestingly, scattering observations do not appear to be time-invariant in certain regions, thus being indicative of active evolutionary processes.     

12.

Electrical properties of a synthetic lunar pyroxenite,and the internal temperature of the moon     

H.G. Tolland 《Physics of the Earth and Planetary Interiors》1974,8(3):292-294

     

13.

Elastic properties of eclogite rocks from the Bohemian massif   总被引：1，自引：0，他引：1  

Vladislav Babuška  Jiří Fiala  D. J. Mayson  R. C. Liebermann  Reviewer J. Buben 《Studia Geophysica et Geodaetica》1978,22(4):348-361

Summary Compressional velocity anistropy has been studied in detail at atmospheric pressure for 78 specimens of 23 types of eclogite rocks from the Bohemian massif. For nine of these rock types, compressional and shear velocities were measured as a function of pressure to750 MPa at room temperature. The velocity anisotropy for both compressional and shear waves is less than4% at high pressure. The velocities increase with increasing garnet content and decrease with increasing symplectitization. The Moldanubian eclogites have significantly higher velocities, on the average, than the eclogites from the Kruné hory crystalline complex, although the densities of both groups are comparable.     

14.

Elastic properties from acoustic and volume compression experiments     

Jay D. Bass  Robert C. Liebermann  Donald J. Weidner  Stephen J. Finch 《Physics of the Earth and Planetary Interiors》1981,25(2):140-158

Hydrostatic compression data for a number of high-pressure phases of oxides and silicates, which have been studied independently by acoustic techniques, have been analyzed by least-squares fitting of the Birch-Murnaghan equation of state to determine the zero-pressure bulk modulus K₀ and its pressure derivative K′₀ for each material. The standard deviations of K₀ and K′₀ so determined are generally underestimated unless the experimental errors in the measurements of volume and pressure are explicitly included. When the values of K₀ determined from the acoustic and compression techniques are consistent, test results for quartz and rutile demonstrate that constraining K₀ to be equal to the acoustic value significantly improves both the accuracy and the precision of K′₀ obtained from the compression data. Similar analyses for high-pressure phases (e.g., pyrope garnet and silicate spinels) indicate that by combining the acoustic and P-V data, the standard deviation of K′₀ is typically reduced by a factor of three. Thus, we conclude that this approach does allow precise determinations of K′₀ even when neither technique alone is able to resolve this parameter. For some materials, however, the P-V and acoustic experiments do not define mutually consistent values of K₀, invalidating any combination of these data. The compression data for stishovite clearly exhibit run to run effects, and we infer that systematic errors are present in some of the P-V data which are responsible for many of the interlaboratory inconsistencies. Such systematic biases in the P-V data can at least be partially compensated for by performing several duplicate experimental runs.     

15.

利用GPS观测的时间序列资料反演地壳地幔黏性结构   总被引：9，自引：3，他引：9       下载免费PDF全文

朱守彪  蔡永恩 《地球物理学报》2006,49(3):771-777

地球介质的黏度是地球动力学研究中的重要参数. 在考虑震后震源区介质物性变化的情况下,本文提出利用GPS观测的时间序列资料反演地壳、地幔黏度的方法. 计算中,将遗传算法与Marquardt法相结合,利用遗传算法搜索结果作为Marquardt法反演的初始模型,运用微扰法形成Jacobian矩阵. 根据余震分布及地震波速度变化确定震源区的范围及介质的物性变化情况,利用黏弹性有限单元模型（Maxwell体）及台湾集集地震后GPS观测的时间序列数据,反演了台湾地区地壳、地幔的黏性系数. 反演计算及数值实验表明,该方法反演黏度的效率高,稳定性好. 反演结果初步显示台湾地区的地壳、地幔的黏度分别为1.2×1018Pa·s和3.6×1019 Pa·s.     

16.

On the fluid nature of intermediate conductive layers in the Earth's crust: Evidence from electromagnetic sounding and superdeep well logging     

A. A. Zhamaletdinov 《Izvestiya Physics of the Solid Earth》2011,47(2):127-137

The question whether it is possible to associate the nature of intermediate conducting layers, revealed in the upper crust in the Baltic Shield and other ancient crystalline structures, with the presence of fluids of a surface origin is considered. With this aim in view, the results of frequency electromagnetic sounding with controlled sources have been analyzed, and the geodynamical interpretation of the nature of an intermediate conducting layer was carried out in the context of the dilatant-diffusion theory of the Earth’s crust fracturing, where the superdeep well logging data have been taken into account.     

17.

Ultramafic inclusions in anorthite megacrysts from the Isle of Skye     

Colin H. Donaldson 《Earth and Planetary Science Letters》1975,27(2):251-256

1–15 μm diameter ultramafic inclusions in anorthitic plagioclase megacrysts from Skye were analyzed by electron microprobe and tentatively identified as sub-calcic augite, or sub-calcic augite submicroscopically intergrown with amphibole. The inclusions nucleated in Ca-Al-depleted, Fe-Mg-H₂O-enriched magma adjacent to the interface between plagioclase crystals and basalt and were rapidly enveloped by the growing plagioclase. The inclusions may be important in the fractional crystallization of the Skye alkali olivine basalt suite.     

18.

A note on the magnetic properties of lunar sample 15535,28 and the implications regarding palaeointensity determinations     

A. Stephenson  D.W. Collinson 《Earth and Planetary Science Letters》1975,27(2):360-361

     

19.

基于绕月单卫星和双星测量的月球重力场恢复仿真分析   总被引：5，自引：0，他引：5       下载免费PDF全文

鄢建国  平劲松  李斐  松本晃志  王广利  史弦 《地球物理学报》2007,50(2):425-429

月球重力场是月球科学研究的重要部分,是进一步了解月球内部结构和构造的基础,也是我国探月计划“嫦娥工程”一个重要的科学研究内容.本文针对“嫦娥工程”,利用GSFC/NASA/USA的GEODYNII/SOLVE轨道分析软件,分析计算了利用单星跟踪数据恢复月球重力场的能力,同时模拟计算了双星跟踪数据在恢复月球重力场方面的能力,结合可能的工程环境我们对两种情况分别给出了30天、60天和90天的计算结果.计算表明双星相比于单星对月球重力场的中低阶位系数有比较显著的改善.     

20.

Neutron capture effects in lunar gadolinium and the irradiation histories of some lunar rocks     

G.W. LugmairK. Marti 《Earth and Planetary Science Letters》1971

The Gd isotopic composition in 19 lunar rock and soil samples from three Apollo sites is reported. The analytical techniques and the high precision mass spectrometric measurements are discussed. Enrichments in¹⁵⁸GdO/¹⁵⁷GdO due to neutron capture range up to 0.75%. Integrated ‘thermal’ neutron fluxes derived from the isotopic anomalies of Gd are compared with spallation Kr data from aliquot samples to construct a model which gives both average cosmic-ray irradiation depths and effective neutron exposure ages (T_n) for some rocks. In the case of rock 12053, this yields an average sample location of ∼300 g/cm² below the lunar surface and an effective irradiation age of ∼230 my, compared to 99 my obtained by the⁸¹Kr-Kr method. Rock 14310 is the first lunar sample where Kr anomalies due to resonance neutron capture in Br are observed. A⁸¹Kr-Kr exposure age of 262 ± 7 my is calculated for this rock.     

	Almandine	Pyrope	Spessartine	Grossular	Andradite
$\text{K}$	1.779 ± 0.008	1.730 ± 0.009	1.742 ± 0.009	1.691 ± 0.008	1.379 ± 0.017
$\text{C}{}_{\mathrm{<mtext>s</mtext>}}$	0.981 ± 0.004	0.925 ± 0.004	0.964 ± 0.004	1.106 ± 0.004	0.979 ± 0.007
$\text{C}{}_{\mathrm{<mtext>44</mtext>}}$	0.958 ± 0.005	0.919 ± 0.005	0.937 ± 0.005	1.017 ± 0.006	0.827 ± 0.010

Methods and some results of investigations of the scattering properties in the crust and mantle

Results derived from analyses of mainly forward-scattered seismic waves are reported. Major findings are that the strongest scattering originates in the crust and upper and lower mantle, while the central parts of the mantle appear relatively homogeneous. In the upper mantle the extent of the heterogeneities exhibits regional variations. Interestingly, scattering observations do not appear to be time-invariant in certain regions, thus being indicative of active evolutionary processes.     

Elastic properties of eclogite rocks from the Bohemian massif

Summary Compressional velocity anistropy has been studied in detail at atmospheric pressure for 78 specimens of 23 types of eclogite rocks from the Bohemian massif. For nine of these rock types, compressional and shear velocities were measured as a function of pressure to750 MPa at room temperature. The velocity anisotropy for both compressional and shear waves is less than4% at high pressure. The velocities increase with increasing garnet content and decrease with increasing symplectitization. The Moldanubian eclogites have significantly higher velocities, on the average, than the eclogites from the Kruné hory crystalline complex, although the densities of both groups are comparable.     

Elastic properties from acoustic and volume compression experiments

Hydrostatic compression data for a number of high-pressure phases of oxides and silicates, which have been studied independently by acoustic techniques, have been analyzed by least-squares fitting of the Birch-Murnaghan equation of state to determine the zero-pressure bulk modulus K₀ and its pressure derivative K′₀ for each material. The standard deviations of K₀ and K′₀ so determined are generally underestimated unless the experimental errors in the measurements of volume and pressure are explicitly included. When the values of K₀ determined from the acoustic and compression techniques are consistent, test results for quartz and rutile demonstrate that constraining K₀ to be equal to the acoustic value significantly improves both the accuracy and the precision of K′₀ obtained from the compression data. Similar analyses for high-pressure phases (e.g., pyrope garnet and silicate spinels) indicate that by combining the acoustic and P-V data, the standard deviation of K′₀ is typically reduced by a factor of three. Thus, we conclude that this approach does allow precise determinations of K′₀ even when neither technique alone is able to resolve this parameter. For some materials, however, the P-V and acoustic experiments do not define mutually consistent values of K₀, invalidating any combination of these data. The compression data for stishovite clearly exhibit run to run effects, and we infer that systematic errors are present in some of the P-V data which are responsible for many of the interlaboratory inconsistencies. Such systematic biases in the P-V data can at least be partially compensated for by performing several duplicate experimental runs.     

利用GPS观测的时间序列资料反演地壳地幔黏性结构

地球介质的黏度是地球动力学研究中的重要参数. 在考虑震后震源区介质物性变化的情况下,本文提出利用GPS观测的时间序列资料反演地壳、地幔黏度的方法. 计算中,将遗传算法与Marquardt法相结合,利用遗传算法搜索结果作为Marquardt法反演的初始模型,运用微扰法形成Jacobian矩阵. 根据余震分布及地震波速度变化确定震源区的范围及介质的物性变化情况,利用黏弹性有限单元模型（Maxwell体）及台湾集集地震后GPS观测的时间序列数据,反演了台湾地区地壳、地幔的黏性系数. 反演计算及数值实验表明,该方法反演黏度的效率高,稳定性好. 反演结果初步显示台湾地区的地壳、地幔的黏度分别为1.2×1018Pa·s和3.6×1019 Pa·s.     

On the fluid nature of intermediate conductive layers in the Earth's crust: Evidence from electromagnetic sounding and superdeep well logging

The question whether it is possible to associate the nature of intermediate conducting layers, revealed in the upper crust in the Baltic Shield and other ancient crystalline structures, with the presence of fluids of a surface origin is considered. With this aim in view, the results of frequency electromagnetic sounding with controlled sources have been analyzed, and the geodynamical interpretation of the nature of an intermediate conducting layer was carried out in the context of the dilatant-diffusion theory of the Earth’s crust fracturing, where the superdeep well logging data have been taken into account.     

Ultramafic inclusions in anorthite megacrysts from the Isle of Skye

1–15 μm diameter ultramafic inclusions in anorthitic plagioclase megacrysts from Skye were analyzed by electron microprobe and tentatively identified as sub-calcic augite, or sub-calcic augite submicroscopically intergrown with amphibole. The inclusions nucleated in Ca-Al-depleted, Fe-Mg-H₂O-enriched magma adjacent to the interface between plagioclase crystals and basalt and were rapidly enveloped by the growing plagioclase. The inclusions may be important in the fractional crystallization of the Skye alkali olivine basalt suite.     

基于绕月单卫星和双星测量的月球重力场恢复仿真分析

月球重力场是月球科学研究的重要部分,是进一步了解月球内部结构和构造的基础,也是我国探月计划“嫦娥工程”一个重要的科学研究内容.本文针对“嫦娥工程”,利用GSFC/NASA/USA的GEODYNII/SOLVE轨道分析软件,分析计算了利用单星跟踪数据恢复月球重力场的能力,同时模拟计算了双星跟踪数据在恢复月球重力场方面的能力,结合可能的工程环境我们对两种情况分别给出了30天、60天和90天的计算结果.计算表明双星相比于单星对月球重力场的中低阶位系数有比较显著的改善.     

Neutron capture effects in lunar gadolinium and the irradiation histories of some lunar rocks

The Gd isotopic composition in 19 lunar rock and soil samples from three Apollo sites is reported. The analytical techniques and the high precision mass spectrometric measurements are discussed. Enrichments in¹⁵⁸GdO/¹⁵⁷GdO due to neutron capture range up to 0.75%. Integrated ‘thermal’ neutron fluxes derived from the isotopic anomalies of Gd are compared with spallation Kr data from aliquot samples to construct a model which gives both average cosmic-ray irradiation depths and effective neutron exposure ages (T_n) for some rocks. In the case of rock 12053, this yields an average sample location of ∼300 g/cm² below the lunar surface and an effective irradiation age of ∼230 my, compared to 99 my obtained by the⁸¹Kr-Kr method. Rock 14310 is the first lunar sample where Kr anomalies due to resonance neutron capture in Br are observed. A⁸¹Kr-Kr exposure age of 262 ± 7 my is calculated for this rock.