The mineralogy and petrology of the Luna 20 soil sample

Fragments of igneous rocks, glasses and minerals comprise 25 per cent of the studied sample of the Luna 20 soil. Basalt fragments in the Luna 20 soil are similar to basalts from the mare regions of the Moon—in that they are characterized by the presence of iron-rich olivines and pyroxenes. On the basis of the FeO contents of plagioclases, it appears possible to distinguish between the plagioclase of the mare and highland regions of the Moon. Other igneous rock fragments are anorthosite, gabbroic anorthosite and anorthositic gabbro. The most abundant rock type (75 per cent of the sample) is microbreceia. One third of the fragments of microbreccia have undergone thermal metamorphism resulting in the homogenization of phases and the development of poikioblastic and hornfelsic textures. Excluding the basalt fragments, the dominant minerals in the Luna 20 soil are anorthite (An_93–98), magnesium-rich orthopyroxenes, intermediate clinopyroxenes and olivine (< Fa₅₀). Chemically, the Luna 20 and Apollo 16 soil samples are similar, but the Luna 20 soil is slightly depleted in aluminum and calcium and enriched in iron and magnesium relative to the Apollo 16 soils. The slight difference in bulk chemistry of the two soils may be a result of the presence of a minor amount of mare material in the Luna 20 soil and its apparent absence in the Apollo 16 soils.     

Petrology of some lithic fragments from Luna 20

Microscopic and electron microprobe studies were made of polished thin sections of part of a 30-mg sample of 250–500 μm lunar soil returned by Luna 20 from a point between Mare Fecunditatis and Mare Crisium. Very fine-grained lithic (crystalline) rock fragments, composing about one fifth of the total sample, have mineralogical compositions equivalent to various types of gabbro, anorthositic gabbro, gabbroic anorthosite and troctolite, with minor basalt. The textures now observed in these fragments are in large part metamorphic. Twentyseven electron microprobe analyses of minerals from these fragments are presented, including olivine, plagioclase, pyroxene, spinel, nickel-iron and a Zr-Ti-REE mineral possibly similar to ‘phase B’ of Lovering and Wark (1971). Analyses of seven melt inclusions and twenty-eight defocused beam analyses of lithic fragments are also given. Some of the fragments contain ‘gas’ inclusions which, along with the fine grain size, are believed to indicate final crystallization under low pressure near surface conditions. The almost complete absence of granophyric material in this sample raises the question of whether or not there are at least two distinct magmas for the plagioclase-rich terrae rocks from which this soil sample was derived in part.     

Petrology of Luna 20 regolith from the lunar highlands

The Luna 20 regolith sample contains crystalline lithic fragments of mare basalt, the anorthosite-norite-troctolite group, and feldspathio basalt. Discrete mineral fragments and mineral fragments in regolith breccias can generally be assigned, based on chemical criteria, to one or the other of the first two rock types. A complex history is indicated for the regolith fragments involving repeated metamorphism and melting of the highlands due to impact events. The glass fragments and the feldspathic basalts probably are the result of this melting and their composition may be representative of a large portion of the regolith at this site.     

影响文山三七品质的土壤地质背景因素

应用农业地质学的理论和方法，初步探讨了影响云南文山地区的三七品质的土壤地质背景因素。结果表明：不同类型的土壤地质背景上种植出的三七，具有不同的品质特征。火山岩形成的土壤，种植出的三七，其总皂甙的得率高，碳酸盐形成的红壤，种植出的三七，则总皂甙得率最低，碎屑岩和碳酸岩形成的混合型土壤，种植出的三七，其总皂甙得率则居于二者之间。高钾的火山岩类土壤地质背景和高稀土的碳酸盐类土壤地质背景，是形成不同品质特征三七的根本原因，钾和稀土是形成三七不同品质特征的重要元素。     

Redistribution and fractionation of rare-earth and other elements in a weathering profile

A weathering profile on a uniform Lower Cretaceous volcanogenic sandstone from southern Victoria, Australia is enriched in rare-earth elements (REE), Y and other elements including Ba, Sr and Rb. Enrichments of REE of up to 7 times parent-rock values are associated with Fe-leached members of alteration couplets with little or no enrichment in adjacent Fe-rich members. These alteration couplets are similar in appearance to Liesegang banding. The REE have been fractionated during accumulation, leading to relative enrichment of the light rare earths (LREE).

The formation of an alteration couplet from fresh rock at the weathering front involves redistribution of only Fe (and P) and does not involve redistribution of REE, Y. Ba, Sr and Rb. Breakdown of original minerals in the present soil and degradation of vermiculite in the upper part of the weathering profile releases RE and related elements into solution. This solution moves down and along the profile until it comes into contact with neutral to alkaline conditions at the narrow weathering front. Here REE particularly are absorbed and apparently fixed in vermiculite forming at the expense of biotite and chlorite. (La + Ce + Nd + Y) up to 10.1 wt.% is recorded in degraded biotite grains with similar but lower contents in the degraded diagenetic chlorite cement.

Such accumulation and fractionation have important implications for REE studies involving sedimentary rocks or for that matter outcrop samples of any rock type.     

北秦岭西峡龙王庙石墨矿床地球化学特征及成因

西峡龙王庙石墨矿床位于北秦岭朱阳关—柳泉铺石墨成矿带东部南支,矿体赋存于古元古界秦岭群中深区域变质岩系中,原岩属陆源碎屑岩-碳酸盐岩夹中基性火山岩沉积建造。矿体呈层状、似层状,局部为透镜状产出。矿石构造主要为鳞片状,少量浸染状及块状。矿石主要由含石墨(条带)方解大理岩组成。主量元素整体表现为低Si、低Al、低碱、高CaO、高烧失量的特点,微量元素分析显示大离子亲石元素Rb、U、Th、La、Sm富集,高场强不相容元素Ba、Nb、Ti亏损。Sr/Ba比值为0.55~3.30,平均值2.07。Rb/Sr比值为0.02~1.15,平均值0.28。∑REE含量偏高,REE的分异程度高,轻稀土较重稀土富集,Eu和Ce负异常明显,表明石墨矿变质岩系的原岩可能形成于被动大陆边缘海构造环境。综合分析认为,西峡龙王庙晶质石墨矿床为有机成因的区域变质型晶质石墨矿床,矿床后期叠加热变质及构造改造的特征明显。     

Lunar materials: Their mineralogy,petrology and chemistry

The manned Apollo 11, 12, 14 and 15 and the automated Luna 16 lunar missions have provided us with lunar rock and regolith (soil) samples from a number of geologically distinct sites. The mare regions were sampled by Apollo 11, 12 and Luna 16, whereas Apollo 14 landed on a terrain with more relief, the Fra Mauro Formation which represents an ejecta blanket from the Imbrian Basin, and Apollo 15 touched down near the lunar highlands. The samples collected consist of a mixture, mainly of basalt, breccia and regolith (soil-particulate matter, generally < 1 cm in size). The basalts show considerable variation in texture, mineralogy and chemistry and probably represent fragments from various parts of relatively thin and extensive lava flows in the maria. The breccias represent regolith material which was indurated to varying degrees by impact events. The regolith is a product of the breakdown, again by impact, of coherent rock masses of basalt and breccia.     

Rare earths,other trace elements and iron in Luna 20 samples

The results of the analysis by neutron activation of six samples from the Luna 20 mission and one sample of < 1 mm fines from Apollo 16 are reported. The concentrations of the rare-earth elements (REE) in the samples of fines from Luna 20 and Apollo 16 are less than those found for corresponding materials from the mare areas but a negative Eu anomaly is still present. The concentrations of the REE in fines from Luna 20 are only about two-thirds as great as in the sample of Apollo 16 fines, but the concentrations of Co, Sc and Cr are greater by factors ranging from 1.5 to 2.3.     

滇西梁河—潞西地区新生代英安岩的源区及成因——来自地球化学的证据

报道了滇西梁河—潞西地区新生代英安岩的主量、微量、稀土元素和Nd同位素地球化学研究成果。英安岩富集轻稀土元素、大离子亲石元素（Rb、Th、U、K）,相对亏损重稀土元素和Nb、Ta、Sr、P、Ti,具有Eu负异常和Pb正异常。火山岩的εNd（0）为-10.3~-8.72,Nd同位素模式年龄（tDM）为1.2~1.4Ga。这些地球化学特征表明,研究区英安岩源于区域基底岩系的部分熔融,并与该地区同期幔源玄武质岩浆发生了不同程度的混合。     

Visible and near-infra-red transmission and reflectance measurements of the Luna 20 soil

Visible and near-infra-red spectra of chemically analyzed grains of glass and minerals from the Luna 20 sample were compared with diffuse reflectance spectra of the bulk soil. As in the spectra of soil samples from other localities on the Moon, pyroxene contributes two broad absorption features near 1 μm and 2 μm. The soil has a high integral reflectance (or albedo) arising from plagioclase, which appears to be the dominant mineral in the lunar highlands. The Luna 20 soil curve is most similar to the reflectance curves of the non-rayed soils at Apollo 16, in agreement with the generally similar mineralogy of these samples. The average pyroxene composition in the Luna 20 soil, as determined from the absorption bands in the diffuse reflectance spectra, and analyses of single crystals, is more calcic than in the lithic fragments. Thus, the soil appears to have a few per cent of admixed material derived from mare basalts. Comparison of the soil spectrum with telescopic curves of nearby areas reveals a close similarity; however, the Luna 20 sample is slightly less mature than expected. Luna 20 may have sampled subsurface material that is fresher than the regional surface soil, or alternatively, the Luna 20 area may contain an admixture of relatively recently exposed material from a ray crater.     

Apatite as an indicator mineral for mineral exploration: trace-element compositions and their relationship to host rock type

Over 700 apatite grains from a range of rock types have been analysed by laser-ablation microprobe ICPMS for 28 trace elements, to investigate the potential usefulness of apatite as an indicator mineral in mineral exploration. Apatites derived from different rock types have distinctive absolute and relative abundances of many trace elements (including rare-earth elements (REE), Sr, Y, Mn, Th), and chondrite-normalised trace-element patterns. The slope of chondrite-normalised REE patterns varies systematically from ultramafic through mafic/intermediate to highly fractionated granitoid rock types. (Ce/Yb)_cn is very high in apatites from carbonatites and mantle-derived lherzolites (over 100 and over 200, respectively), while (Ce/Yb)_cn values in apatites from granitic pegmatites are generally less than 1, reflecting both HREE enrichment and LREE depletion. Within a large suite of apatites from granitoid rocks, chemical composition is closely related to both the degree of fractionation and the oxidation state of the magma, two important parameters in determining the mineral potential of the magmatic system. Apatite can accept high levels of transition and chalcophile elements and As, making it feasible to recognise apatite associated with specific types of mineralisation. Multivariate statistical analysis has provided a user-friendly scheme to distinguish apatites from different rock types, based on contents of Sr, Y, Mn and total REE, the degree of LREE enrichment and the size of the Eu anomaly. The scheme can be used for the recognition of apatites from specific rock types or styles of mineralisation, so that the provenance of apatite grains in heavy mineral concentrates can be determined and used in geochemical exploration.     

Chemical composition of Luna 20 rocks and soil and Apollo 16 soils

The abundances of 24 major, minor and trace elements have been measured by INAA in Luna 20 metaigneous rocks 22006,1 and 22007,1, breccia 22004 and soil 22001,9 and in Apollo 16 soils 62281, 66041 and 66081. An additional 12 trace meteoritic and non-meteoritic elements have also been determined in 22001 and 62281 soils by RNAA. The bulk compositions of L 20 and Ap 16 rocks and soils show close similarity between the two highland sites. There are appreciable differences in bulk compositions between the L 20 highland and the L 16 mare site (120 km apart), suggesting little intermixing of rocks and soils from either site. Luna 20 rocks 22006 and 22007 are nearly identical in chemical composition to Ap 16 metaigneous rocks 61156 and 66095. Luna 20 rocks are feldspathic and are similar to low K-type Fra Mauro basalts. Such rocks and anorthositic gabbros appear to be the major components in highland soils. Luna 20 soil can be distinguished from Ap 16 soils by lower abundances of Al₂O₃, CaO and large ion lithophilic elements. Luna 20 breccia 22004 probably is compacted soil. All L 20 samples show negative Eu anomalies with $\text{Sm}\text{Eu}$ ratios of 5.8, 7.2, 3.9 and 3.3 for rocks 22006, 22007, breccia 22004 and soil 22001, respectively. Norite-KREEP is insignificant, ≤1 per cent, at the L 20 highland site. The derivation of the L 20 soil may be explained by ≈33 per cent of L 20 metaigneous rocks and ≈ 65 per cent anorthositic gabbroic breccia rocks like 15418 (with a positive Eu anomaly) and ≈ 2 per cent meteoritic contributions. Interelement correlations observed previously for maria are also found in highland samples. Luna 20 and Ap 16 soils are low in alkalis. Both soils show an apparent Cd-Zn rich component similar to that observed at the mare sites and high 11 abundances relative to mare sites. The Ap 16 (62281) soil contains a fractionated meteoritic component (probably ancient) of ≈ 1.5 per cent in addition to ≈ 1.9 per cent Cl like material. Luna 20 soil may simply contain 1.9 per cent Cl equivalent.     

岩石－土壤－脐橙系统中稀土元素迁聚特征

在赣南稀土高背景区和稀土低背景区不同地质环境脐橙果同,系统采集岩、土、脐橙植物样,用ICP-MS法测定样品中15种稀土元素的含量,并对稀土元素在岩石、土壤和脐橙植物体内的分布、迁移、累积特征进行了研究.结果表明:a.基岩的稀土元素含量影响(决定)土壤各层位的稀土元素含量;b.土壤环境中稀土元素含量高低直接影响脐橙植物体稀土元素含量,但不完全成正比;c.基岩的稀土元素配分模式基本上贯穿土壤各层位、脐橙植物体各器官;d.岩、土、脐橙三大环节稀土无素的百分含量,总的趋势是轻稀土比重逐渐增高,重稀土比重逐渐降低,但重稀土在脐橙植物体末稍器官比例有所增加;e.岩土脐橙生态系统立体刮面中,稀土元素的垂直方向运动呈向量关系;f.由于土壤-植物壁垒作用和脐橙植物体自身的选择性吸收、控制性积累功能,高、低稀土背景区脐橙果肉的稀土含量均低于国家食品卫生限量标准.     

The weathering of norite at Black Hill,South Australia

Black Hill is a boulder‐strewn residual of norite standing 45 m above the Murray Plains about 80 km northeast of Adelaide. Between the boulders, the crystalline rock has weathered to a dark‐brown terra rossa‐rendzina soil with calcite, illite, kaolin, and hematite as the principal secondary minerals. At one site on the smooth lower slopes of the outcrop, the material above the norite consists of partially weathered granular fragments with considerable dolomite and some calcite in nodular form. Below the surface, the rock has been weathered along joints to produce the clay mineral nontronite, and between each corestone and this plastic clay there is a zone of laminated but essentially unaltered rock 10–25 cm thick. Pieces of amorphous silica occur sporadically in some joints and on the surface.

The dark‐brown soil appears to be related to the present environment but the nontronite in the joint weathering, the dolomite, and the amorphous silica are all consistent with the norite having been inundated, possibly during the Miocene marine transgression.

Calculations based on the retention of elements such as aluminium, potassium, titanium, and iron have been used to predict quantitatively the amount of certain minerals such as quartz, calcite, and dolomite introduced to the weathering profiles.     

Geochemical survey of rare earth elements (REEs) in the concealed ore body of Hongcheon,Korea

Because of the risk of diminishing supplies of rare earth elements (REEs) worldwide due to China’s dominance over REE supply, the necessity of developing domestic resources of REE has been realized in other countries. To explore new ore bodies, a geochemical survey was conducted at one existing carbonatite REE deposit in the Hongcheon area of Korea. Proper sampling strategies and baseline data for the interpretation of the results were determined through a pilot study conducted in the area. Enrichment in the concentration of light REE (LREE) over that of heavy REE, which is typical in carbonatite-type deposits, was observed in stream sediments and heavy mineral samples collected during the geochemical survey. Maximum concentrations of LREE were 2,299 and 27,798 mg/kg for stream sediments and heavy minerals, respectively. Among LREEs, La and Ce are the dominant components of all REEs, comprising approximately 68 % of mean concentrations. Considering the distribution pattern of La + Ce contents and the associations with the existing outcropping ore bodies, the zone of prospective REE mineralization was determined to be in the south-western part of the area. A detailed follow-up soil survey of the zone found even higher concentrations of La and Ce (2,450 and 3,100 mg/kg, respectively), and suggested the possible extension of the existing ore bodies. Likewise, a systematic geochemical survey for REE is feasible for locating concealed ore bodies in the area, where the mineralization is mostly covered with soil, and rock outcrops are scarce.     

REE geochemistry of the recent playa sediments from the Thar Desert, India: An implication to playa sediment provenance

The playas (saline lakes) situated in the Thar Desert, north-west India, provide prominent examples of alkaline brine and varying assemblages of detrital and evaporite mineralogy. The eastern margin of the desert is relatively semi-arid, whereas the central to western region is arid to hyper-arid in nature. Rare earth elements (REEs) systematics in the sediments of nine different playas of the Thar Desert were studied to understand the provenance of the sediments and the intensity of chemical weathering in the region. Based on the REE patterns, fractionation of light REE (LREE) (La/Sm)_N and heavy REE (HREE) (Gd/Yb)_N, and Eu anomaly (Eu/Eu*), the upper continental crust normalised playa sediments are divided into two different groups. The eastern margin playa sediments show homogeneous REE contents, relatively positive Eu anomaly and depleted HREE values, whereas the western arid core playa sediments have highly variable REE contents, relatively negative Eu anomaly and similarly fractioned LREE and HREE patterns. The dissimilarity in the degree of HREE fractionations both in the eastern and western playa sediments is attributed to the differential distribution of minerals, depending upon their resistance to chemical weathering. It is believed that the relatively higher abundance of REE bearing heavy minerals and the presence of higher amounts of evaporites influence the large variation of REE distribution and enriched HREE in the western playa sediments. Apart from the relatively higher abundance of heavy minerals, the presence of rock fragments of variable petrographic character and roundness mirror the lower rock–water interaction in the arid western region. The presence of well-rounded metamorphic rock fragments and minerals, sourced from the eastern margin Aravalli mountains, indicates that the playas of the entire desert get the detrital and dissolved material mainly from the Aravalli mountains. Additionally, the western playas receive sediments from their surrounding Proterozoic and Mesozoic formations. This interpretation is supported by the presence of angular rock fragments of basalt, rhyolite and limestone in the western playas.     

含碎石紫色土坡面降雨入渗和产流产沙过程

在室内土槽模拟降雨试验基础上,观测了具有不同碎石体积含量紫色土的降雨入渗地表产流产沙量以及细沟间径流和细沟径流的流速,以期建立碎石含量与土壤流失的定量关系。研究结果表明:土壤中碎石混合对降雨入渗有正负两方面的影响,当碎石含量为20%~30%时,碎石的存在增强土壤入渗能力,当碎石含量提高到30%时,土壤的入渗能力被削弱。土壤中碎石混合通过不同的作用机制对坡面细沟间径流流速和细沟径流流速产生不同的影响,随着碎石含量的增加,细沟间径流平均流速逐渐增加,细沟径流的平均流速逐渐降低。土壤中碎石混合通过改变土壤的物质组成和结构,增强土壤的抗蚀性和抗冲性,随着碎石含量的增加,径流含沙率和土壤流失量显著降低,土壤流失比与碎石含量呈极显著指数负相关关系。     

晓天卢镇关岩群斜长角闪岩类地球化学特征及其与金矿的成因关系

通过斜长角闪岩类岩石学特征,岩石地球化学特征、微量元素、稀土元素数据进行计算与分析,探讨了其成因类型及变质岩原岩恢复,属于中基性—中酸性火山岩。晓天火山沉积洼地中火山岩、火山碎屑岩在稀土元素特征曲线的相似性确定火山岩物源来源于基底岩系卢镇关岩群中基性—中酸性火山岩。根据斜长角闪岩、火山岩、火山碎屑岩含金丰度的研究,认为区内金矿床的成矿物质与卢镇关岩群中斜长角闪岩类岩石存在密切关系,其物源主要为卢镇关岩群中斜长角闪岩类。     

Sedimentary-volcanic tuffs formed during the early Middle Triassic volcanic event in Guizhou Province and their stratigraphic significance

The sedimentary-volcanic tuff (locally called "green-bean rock") formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements (REE), as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.     

Geochemistry of red residua underlying dolomites in karst terrains of Yunnan-Guizhou Plateau: II. The mobility of rare earth elements during weathering

The aim of this study is to characterize the evolution of the rare earth elements (REE) in the Pingba red residua on karst terrain of Yunnan-Guizhou Plateau. The in-situ weathering and the two-stage development of the profile had been inferred from REE criterions. The REE were significantly fractionated, and Ce was less mobilized and separated from the other REEs at the highly enriched top of the profile. This is consistent with the increase of oxidation degree in the regolith. And it is also suggested that the wet/dry climate change during chemical weathering caused Ce alternative change between enrichment and invariance in the upper regolith. Chondrite-normalized REE distribution patterns for samples from dolomites and the lower regolith are characteristic of MREE enrichment and remarkable negative Ce-anomalies patterns (similar to the convex-up REE patterns). The following processes are interpreted for the patterns in this study: (1) the accumulation of MRRE-rich minerals in dolomite dissolution, (2) water–rock interaction in the weathering front, and (3) more leaching MREE from the upper part of the profile. The latter two explanations are considered as the dominant process for the formation of the REE patterns. Samples from the soil horizon exhibit typical REE distribution patterns of the upper crust, i.e., La_N/Yb_N=10 and Eu/Eu*=0.65. All data indicate that the leaching process is very important for pedogenesis in this region. The experiments demonstrating that abnormal enrichment of REE at the upper regolith–bedrock interface is caused by a combination of volume change, accumulation of REE-bearing minerals, leaching of REE from the upper regolith, and water–rock interaction during rock–soil alteration processes. Our results support the conclusion that the weathering profile represents a large, continental elemental storage reservoir, whereas REE enrichment occurs under favorable conditions in terms of stable tectonics, low erosion and rapid weathering over sufficiently long time.