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1.
Geochemistry of soils of King George Island, South Shetland Islands, West Antarctica: Implications for pedogenesis in cold polar regions 总被引：1，自引：0，他引：1
Fine fractions of soils on the Barton Peninsula, King George Island, West Antarctica have been forming during the last 6000 yr since the last deglaciation. Texturally, they are mostly composed of mineral and rock fragments with some volcanic ashes, which are also indicated by geochemical compositions representing for the nonclay silicate minerals and low values of chemical index of alteration. No significant changes are observed in major- and trace element abundances. Such geochemical characteristics suggest that chemical weathering of bedrocks on the Barton Peninsula seems insignificant and that the soils are composed of physically weathered mineral and rock fragments which are mixed with eolian additions of volcanic ashes and Patagonian dusts. Chondrite-normalized rare earth element (REE) distribution patterns of the Barton Peninsula soils are slightly different from those of bedrocks, indicating that the REE abundances and characteristics were influenced by eolian additions. Mixing calculations, which mass-balance the REEs, suggest that volcanic ashes blown from Deception Island were the major eolian contributor, followed by atmospheric dusts sourced from Patagonia, South America. Even in the warmer and humid climatic conditions in the maritime Antarctic region, the chemical weathering of bedrocks appears to be insignificant, probably due to the relatively short duration of weathering since the last deglaciation. 相似文献
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3.
Sabah Yilmaz ahin 《Chemie der Erde / Geochemistry》2008,68(1):81-92
Rocks of the Late Cretaceous Tamdere Quartz Monzonite, constituting a part of the Eastern Pontide plutonism, include mafic microgranular enclaves (MMEs) ranging from spheroidal to ellipsoidal in shape, and from a few centimeters to decimeters in size. The MMEs are composed of diorite, monzodiorite and quartz diorite, whereas the felsic host rocks comprise mainly quartz monzonite, granodiorite and rarely monzogranite on the basis of both mineralogical and chemical compositions. The common texture of felsic host rocks is equigranular. MMEs are characterized by a microgranular texture and also reveal some special types of microscopic textures, e.g. antirapakivi, poikilitic K-feldspar, small lath-shaped plagioclase in large plagioclase, blade-shaped biotite, acicular apatite, spike zones in plagioclase and spongy-cellular plagioclase textures.
The distribution of major, trace and RE elements apparently reflect exchange between the MMEs and the felsic host rocks mainly due to thermal, mechanical and chemical interactions between coeval felsic host magma and mafic magma. The most evident major element transfer from felsic host magma to mafic magma blob is that of alkalis such as Na and K. LILEs such as Rb, Sr, Ba and some HFSEs such as Nb, Y, Zr and Th have been migrated from felsic host magma to MMEs. Apart from these major and trace elements, the other element transfer from felsic host magma to mafic one concerns REE contents. Such a transfer of REEs has evidently increased the LREE contents of MMEs. Enrichments in alkalis, LILEs, HFSEs and REEs could have been achieved by diffusional processes during the solidification of magma sources. The felsic and mafic magma sources behave as Newtonian and visco-plastic materials. In such an interaction, small MMEs behave as a closed system due to immediate rapid cooling, whereas the bigger MMEs suffer greater diffusion from the Newtonian felsic host magma due to slow cooling. 相似文献
4.
新疆乌仑古－斋桑泊构造带晚古生代花岗岩类的稀土元素分布模式 总被引：6，自引：0，他引：6
本文选择新疆北部乌仑古－斋桑泊构造带上６个有代表性的花岗岩体，系统进行了岩体地质、显微岩相学、主量元素与稀土元素地球化学研究．根据岩石副矿物类型与主要造岩矿物组成解释了各种岩石类型的稀土配分，根据主量元素－稀土元素相关性闸明了稀土元素在结晶分异过程中的分镏，按照两阶段、不同结晶分异程度模型对各种岩石类型的稀土配分进行了定量模拟；根据不同岩石类型的时空分布及其与构造环境的对应关系探讨了它们的成因。最后，对碱性花岗岩的成因提出了新的解释。 相似文献
5.
Rare earth element (REE) abundances are reported for ten whole rock and eight mineral samples from the Preacher Creek ultramafic intrusion of southeastern Wyoming. Chondrite-normalized distribution patterns for the whole rocks exhibit a broad maximum between Sm and Gd and reflect the REE pattern of clinopyroxene, the major REE-bearing phase. Alteration of the primary mineral assemblages to actinolite and chlorite, which is generally minor, does not appear to have significantly affected the REE distributions. Absolute abundances of the REE in the rocks and constituent minerals increase as a function of differentiation, and relative abundances suggest an accompanying light REE enrichment. Trapped-liquid phases, which may be relatively enriched in REE, possibly account for some or all of the observed REE trends. The REE data, interpreted in terms of crystal-melt fractionation, suggest derivation of the intrusion by crystallization from a gabbroic magma having a REE distribution pattern similar to the parent magma of the Skaergaard stratiform complex. The results of this study are in accord with and complement a previous proposal that the Preacher Creek body formed in a manner analogous to major stratiform intrusions. 相似文献
6.
HSUWeibiao 《《地质学报》英文版》2004,78(5):1060-1074
Coupled with a petrographical study, I carried out an ion probe study of rare earth element microdistributions in mineral phases of silicate inclusions from the Colomera IIE iron meteorite. Most mineral grains have homogeneous REEs, but show considerable inter-grain variations by a factor of 2 to 100. The whole rock REE abundances for Colomera,estimated by combining REE data with modal abundances, are relatively LREE-enriched with REEs of～10’CI, which suggest that Colomera silicates were highly differentiated and might represent a low degree partial melt (-10%) of a chondritic source. REE geochemistry of Colomera silicate inclusions points to an origin that involves differentiation,dynamic mixing, remelting, reduction, recrystallization, and subsequent rapid cooling near the surface of a planetary body. 相似文献
7.
Titanite occurs as an accessory phase in a variety of igneous rocks, and is known to concentrate geologically important elements
such as U, Th, rare earth element (REE), Y and Nb. The differences in the abundances of the REEs contained in titanite from
granitoid rocks could reflect its response to changes in petrogenetic variables such as temperature of crystallization, pressure,
composition, etc. Widespread migmatization in the granodiorite gneisses occurring to the east of Kolar and Ramagiri schist
belts of the eastern Dharwar craton resulted in the enrichment of the REEs in titanite relative to their respective host rocks.
A compositional influence on the partitioning of REEs between titanite and the host rock/magma is also noticed. The relative
enrichment of REEs in titanite from quartz monzodiorite is lower than that found in the granodioritic gneiss. Depletion of
REE and HFSE (high field-strength elements) abundances in granitic magmas that have equilibrated with titanite during fractional
crystallization or partial melting has been modelled. As little as 1% of titanite present in residual phases during partial
melting or in residual melts during fractional crystallization can significantly lower the abundances of trace elements such
as Nb, Y, Zr and REE which implies the significance of this accessory mineral as a controlling factor in trace element distribution
in granitoid rocks. Sm–Nd isotope studies on titanite, hornblende and whole rock yield isochron ages comparable to the precise
U–Pb titanite ages, invoking the usefulness of Sm–Nd isochron ages involving minerals like titanite. 相似文献
8.
A Geochemical Study of an REE-rich Carbonatite Dyke at Bayan Obo, Inner Mongolia, Northern China 总被引：5，自引：0，他引：5
YANG Xueming ZHENG Yongfei YANG Xiaoyong ZHANG Peishan M.J. LE BAS Department of Earth Space Sciences University of Science Technology of Chin Hefei China Institute of Geology Geophysics Chinese Academy of Sciences Beijing China School of Ocean Earth Science University of Southampton SOI ZH U.K. 《《地质学报》英文版》2000,74(3):605-612
An REE-rich carbonatite dyke was found in Dulahala, close to the Bayan Obo superlarge REE-Nb-Fe mineral deposit in Inner Mongolia, northern China. The REE content in the dyke varies greatly, from 1% up to 20% (wt), which might constitute rich REE ores. Light REEs in the carbonatite are enriched and highly fractionated relative to heavy REEs and there is no Eu anomaly. The REE and trace element distribution patterns of the carbonatite are identical to those of fine-grained dolomite marble which is the host rock of the Bayan Obo REE-Nb-Fe superlarge mineral deposit. This indicates a petrogenetic linkage between the REE-rich carbonatite and the mineralizations in this region. 相似文献
9.
Weibiao Hsu 《Geochimica et cosmochimica acta》2003,67(24):4807-4821
An ion probe study of rare earth element (REE) geochemistry of silicate inclusions in the Miles IIE iron meteorite was carried out. Individual mineral phases among inclusions have distinct REE patterns and abundances. Most silicate grains have homogeneous REE abundances but show considerable intergrain variations between inclusions. A few pyroxene grains display normal igneous REE zoning. Phosphates (whitlockite and apatite) are highly enriched in REEs (50 to 2000 × CI) with a relatively light rare earth element (LREE)-enriched REE pattern. They usually occurred near the interfaces between inclusions and Fe host. In Miles, albitic glasses exhibit two distinctive REE patterns: a highly fractionated LREE-enriched (CI normalized La/Sm ∼15) pattern with a large positive Eu anomaly and a relatively heavy rare earth element (HREE)-enriched pattern (CI-normalized Lu/Gd ∼4) with a positive Eu anomaly and a negative Yb anomaly. The glass is generally depleted in REEs relative to CI chondrites.The bulk REE abundances for each inclusion, calculated from modal abundances, vary widely, from relatively depleted in REEs (0.1 to 3 × CI) with a fractionated HREE-enriched pattern to highly enriched in REEs (10 to 100 × CI) with a relatively LREE-enriched pattern. The estimated whole rock REE abundances for Miles are at ∼ 10 × CI with a relatively LREE-enriched pattern. This implies that Miles silicates could represent the product of a low degree (∼10%) partial melting of a chondritic source. Phenocrysts of pyroxene in pyroxene-glassy inclusions were not in equilibrium with coexisting albitic glass and they could have crystallized from a parental melt with REEs of ∼ 10 × CI. Albitic glass appears to have formed by remelting of preexisting feldspar + pyroxene + tridymite assemblage. Yb anomaly played an important role in differentiation processes of Miles silicate inclusions; however, its origin remains unsolved.The REE data from this study suggest that Miles, like Colomera and Weekeroo Station, formed when a molten Fe ball collided on a differentiated silicate regolith near the surface of an asteroid. Silicate fragments were mixed with molten Fe by the impact. Heat from molten Fe caused localized melting of feldspar + pyroxene + tridymite assemblage. The inclusions remained isolated from one another during subsequent rapid cooling. 相似文献
10.
The geochemical patterns of major and trace elements in zonal garnets and the mineral inclusions in them formed by progressive and regressive metamorphism of pelites are established. It is shown that an increase in temperature and pressure led to a decrease in the Y and HREE contents in garnets, and the increase in their contents is related to a decrease in the PT-parameters of their formation. A negative correlation between the CaO and REE contents in garnet indicates their isomorphism. The main reason for the sharp increase in the CaO content in garnets during collision metamorphism is mass transfer between the garnet and the plagioclase. The deviations from this situaiton, which are expressed in simultaneous increase in the grossular component in garnet and the anorthite component in plagioclase, are caused by metamorphic reactions related to the epidote decomposition. The mass transfer of major and trace elements between the reacting phases in metamorphic reactions mostly occurred with preservation of the balance of matter. The mirror shape and the character of the REE patterns of the rock-forming minerals relative to the composition of the rock indicate the equilibration of the HREE and Y contents between garnet, the major concentrator of these elements in the rock, and other phases. The balance between the LREEs and HREEs in the rock is achieved by the presence of variable amounts of monazite. 相似文献
11.
N. A. Ekimova P. A. Serov T. B. Bayanova I. R. Elizarova F. P. Mitrofanov 《Doklady Earth Sciences》2011,436(1):28-31
This paper presents data on the distribution of REEs in sulfide minerals from ore-bearing gabbronorites in the Penikat layered
intrusion and the results of their isotopic-geochronological Sm-Nd study. A new procedure for determination of REEs in the
samples without preliminary separating and concentrating was tested on standard samples to be further used for analysis of
sulfide minerals. Analysis of the spectra of the REE distribution in sulfides represents a distribution trend that is similar
to the already studied bulk rock and allows deducing that the character of the REE distribution in sulfide minerals from gabbronorites
in the Penikat layered intrusion was inherited from the parent magma melt; while the formation of sulfides took place at the
stage of rock crystallization. The performed complex studies allow considering that sulfides can be successfully used together
with the rock-forming minerals in Sm-Nd dating of ore-bearing mafite-ultramafite intrusions. 相似文献
12.
REE geochemistry of the Zhoutan Group metasedimentary rocks in central Jiangxi Province,Southeast China 总被引：1，自引：0，他引：1
Detailed REE and trace elements geochemical studies of the Zhoutan Group metasedimentary rocks in central Jiangxi Province,
China, and rock-forming minerals such as garnet were conducted and the results showed that the REEs are partly present in
the rock-forming minerals and are dominantly contained in the lattice of accessory minerals. In the process of metamorphism
the REEs between garnet porphyroblast and rock and the partitioning of REEs between garnet and the host rock is obviously
controlled by the chemical composition of the system. The REEs compositions of metamorphic veins and their minerals display
remarked lanthanide tetrad effects and the element pairs Zr-Hf, Y-Ho, Pb-Nd and U-Th have also experienced a certain degree
of fractionation with respect to the metasedimentary rocks and they can be used as discriminating indicators to some extent
for the occurrence of fluid processes in the process of metamorphism of the Zhoutan Group. 相似文献
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14.
《International Geology Review》2012,54(2):95-119
Eclogites are often the only tangible high-pressure evidence we have from a paleosubduction zone, and they potentially preserve important geochemical information from the descending slab. Selected Group B/C eclogites and metapelites from the Trescolmen locality in the Adula nappe in the central Swiss Alps were chosen for a detailed investigation to determine oxygen isotope ratios and major- and trace-element compositions of the main rock-forming minerals. Complex major-element zonation patterns in garnet porphyroblasts indicate a pre-Alpine, medium-pressure growth history coupled with a high-pressure modification during the Alpine orogeny. Garnet REE patterns are notably HREE depleted in rim regions, with high overall REE content, particularly in the cores of grains. Omphacites are relatively homogenous in major elements, and show LREE- and HREE-depleted patterns, but with overall abundances of REEs lower than in garnets. These patterns are best explained by partitioning of the HREEs into garnet and the LREEs into zoisite. Oxygen-isotope systematics indicate limited fluid flow in eclogites and surrounding metapelites. δ18O values of quartz and garnet at the interface between eclogites and metapelites are indistinguishable and point to fluid exchange. Oxygen equilibrium conditions among rock-forming minerals, particularly between quartz and garnet in eclogites and metapelites, were reached, and fractionation indicates temperatures of ～600°C. The δ18O of unaltered eclogites (5.5 to 7.5 ‰) suggests a basaltic, MORB-type protolith. 相似文献
15.
Archean sedimentary rocks of very limited lateral extent from horizons within basaltic and ultramafic volcanic sequences at Kambalda, Western Australia, are extremely variable in major elements, LIL and ferromagnesian trace element compositions. The REE patterns are uniform and do not have negative Eu anomalies. Two samples have very low total REE abundances and positive Eu anomalies attributed to a very much greater proportion of chemically deposited siliceous material. Apart from these two samples, the Kambalda data are similar to REE abundances and patterns from Archean sedimentary rocks from Kalgoorlie, Western Australia and to average Archean sedimentary rock REE patterns. These show a fundamental distinction from post-Archean sedimentary rock REE patterns which have higher ratios and a distinct negative Eu anomaly. 相似文献
16.
Very few studies deal with the biogeochemical behaviors of rare earth elements (REEs) in goldfields. This paper presents the
geochemical and biogeochemical characteristics of REEs within the soil–plant system in the Hetai goldfield, Guangdong, China.
The samples from the goldfield region show anomalies in distribution patterns and behavioral characteristics of REES as compared
with those from the background areas. The REEs in rocks, soils, and plants prove to be much higher than those in the surrounding
regions. The distribution patterns of REEs are characterized by LREE-enrichment and HREE-depletion, with the REE concentrations
in Layer A being the highest. Differentiations between LREEs and HREEs may lead to some extent of negative Eu anomaly in the
soils. Research results demonstrate that the REEs in a soil profile can be transferred and accumulated during the mineral
formation and supergenic geochemical processes, and the anomalies are obviously related to the geological settings for the
REE-bearing ore-forming processes and to the geochemical characteristics of the habitats for the REE-bearing plants. For Dicranopteris dichotoma, the total amount of REEs in the tissues shows an order of leaf > root > stem, while for Pinus massoniana the order becomes root > leaf > stem. The distribution patterns of REEs in Pinus massoniana leaves are similar to those in soils where the plants grow up in the mineralization area. However, in the background areas
the REE distribution patterns for Pinus massoniana stems are similar to those for soils where the plants grow up. Parameters such as biological absorption coefficients and
biological transfer coefficients show the differences in REE absorption features among plants and indicate that REEs can be
transferred among plant organs. The two coefficients can reveal the different survival mechanisms for the two plant species,
which are subject to long-term REE-affected stress conditions in the gold mineralization zone. 相似文献
17.
Geochemistry and origin of rare earth elements (REEs) in the Shengli River oil shale, northern Tibet, China 总被引：4，自引：0，他引：4
Xiugen Fu Jian Wang Yuhong Zeng Fuwen Tan Jianglin He 《Chemie der Erde / Geochemistry》2011,(1):21-30
The Shengli River-Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. Twenty-eight samples including oil shale, micritic limestone and marl were collected from the Shengli River area to determine the contents and distribution patterns of rare earth elements (REEs) in marine oil shale. Oil shale samples from the Shengli River area have high ash yield (61.86–67.48%) and TOC content (8.02–13.67%) with low total sulfur (St,d) content (0.76–1.39%) and intermediate shale oil content (3.60–16.30%). The total rare earth element (ΣREE) content in oil shale samples is notably depleted (46.79–67.90 μg/g), approximately one third of the mean value of the North American Shale Composite (NASC), and lower than that of world-wide black shales and Chinese coals, but higher than that of world-wide coals and micritic limestone samples (29.21 μg/g) from the Shengli River area. The oil shale samples from the Shengli River area exhibit shale-like Chondrite or NASC-normalized REE patterns similar to those of micritic limestone and marl samples from this area, indicating that REEs of these different lithological samples may have been derived from a similar terrigenous source.REE contents of oil shale samples are highly positive correlated with ash yield and show a positive correlation with Fe and a weakly positive correlation with organic sulfur, and the vertical variations of REEs mainly follow those of Si, Al, K and Ti. All these facts indicate that the REE contents in oil shale seams are mainly controlled by clay minerals and, to a lesser extent, by pyrite, as well as partly associated with oil shale organic constituents. Rare earth elements in the Shengli River oil shale have originated from two sources: a felsic volcanic rock source and a clastic or/and limestone source. 相似文献
18.
C.A.R. de Albuquerque 《Lithos》1978,11(3):219-229
Rare earth elements (REE) were determined in two suites of Hercynian ‘Younger’ granodiorites and granites, one massive and the other porphyritic. Within each suite, the REE abundances decrease towards the more felsic granite while the REE patterns are almost identical. The patterns of the porphyritic types are only slightly more fractionated than those of the massive rocks. Negative Eu-anomalies are observed in all rocks although those of the granodiorites are smaller than those of the granites. Modeling of the data indicates that the granitic magmas may be derived, by partial melting, from the greywackes and pelites of the orogenic belt, the melts being in equilibrium with a residuum composed of quartz, plagioclase, garnet, orthopyroxene or cordierite, and, possibly, biotite. 相似文献
19.
Barry L. Weaver John Tarney Brian F. Windley Bernard E. Leake 《Geochimica et cosmochimica acta》1982,46(11):2203-2215
The meta-volcanic amphibolites closely associated with the Fiskenaesset anorthosite complex can be subdivided on the basis of trace element patterns or mineral chemistry; by far the most abundant type has light rare-earth element (LREE) depleted REE patterns and displays a wide range in trace element abundances. Chemically comparable amphibolites can be recognised throughout the ca. 2800 M.yr. West Greenland terrain.The geochemistry of the basaltic amphibolites is dominantly controlled by fractional crystallisation processes, although variable degrees of partial melting may also be important. The required crystal extract (plagioclase dominated) in the proposed fractionation scheme is very similar to the primary mineralogy of cumulates of the Fiskenaesset complex and trace element models support a genetic relationship between the anorthosite complex and enclosing host amphibolites.The application of trace element discrimination to assign tectonic environment in the Archaean is arguable. However, details of the trace element chemistry (especially chondritic La/Ta ratios) are taken to suggest, out of a range of likely tectonic environments, an ocean floor, rather than island arc, affinity for the Fiskenaesset amphibolites. The large ion lithophile (LIL) elements display erratic distribution patterns, but are generally enriched relative to the REE. This appears not to be related to high-grade metamorphism but may be a relict feature of seafloor alteration. The association of the cumulate sequence with meta-volcanic amphibolites and metasediments probably represents an ocean floor assemblage emplaced into the lower crust during crustal accretion. 相似文献
20.
Jon Steen Petersen 《Contributions to Mineralogy and Petrology》1980,73(2):161-172
Quantitative analysis of REE distribution in differentiated, clearly intrusive charnockites from southwest Norway, reveal extreme variation in both absolute abundances and fractionation patterns. The pyroxene-bearing, charnockitic facies show uniform REE patterns with slight enrichment of the light-REE (about 150x chondrites) and positive, neutral or negative Eu-anomalies. Subsequent amphibole-bearing, adamellitic facies show progressive, preferential enrichment of light-REE, reaching La-values higher than 500x chondrites, and increasingly negative Euanomalies. Finally, highly differentiated biotite-granites show a marked depletion of ight-REE, ending with chondrite-normalized La/Lu ratios about 1 and Eu/ Eu* ratios less than 0.2.Using geochemical model calculation, relating major element variations between three main stages of differentiation in terms of refractory mineral assemblages, stepwise quantitative modelling of the REE distributions reproduces the observed changes, and support an origin of the charnockite series as progressively fractionated residual liquids.Close similarity with the REE patterns of charnockite-rapakivi suites elsewhere implies that these may constitute a series of co-magmatic rocks, derived from related more basic source magmas. The fact that the least differentiated members of the series, the charnockites, generally display remarkably uniform REE-patterns, suggests that they equilibrated with a refractory crystal fraction that produces a uniform, bulk partition coefficient. The present analysis suggests that this would be plagioclase and orthopyroxene in a ratio of about 41 and including minor apatite, which in turn points towards affinity with potentially plagioclase-rich cumulates. 相似文献