检索结果-南通市图书馆

Magmatic systems of large continental igneous provinces

Geoscience Frontiers 2017年第4期8卷 621-640页

作者： E.Sharkov M.Bogina A.Chistyakov institute of Geology of Ore Deposits PetrographyMineralogy and Geochemistry RAS

Large igneous provinces（LIPs） formed by mantle superplume events have irreversibly changed their composition in the geological evolution of the Earth from high-Mg melts（during Archean and early Paleoproterozoic） to Phanerozoic-type geochemically enriched Fe-Ti basalts and picrites at 2.3 *** propose that this upheaval could be related to the change in the source and nature of the mantle superplumes of different *** first generation plumes were derived from the depleted mantle,whereas the second generation（thermochemical） originated from the core-mantle boundary（CMB）.This study mainly focuses on the second（Phanerozoic） type of LIPs,as exemplified by the midPaleoproterozoic Jatulian-Ludicovian LIP in the Fennoscandian Shield,the Permian-Triassic Siberian LIP,and the late Cenozoic flood basalts of *** latter LIP contains mantle xenoliths represented by green and black *** xenoliths are fragments of cooled upper margins of the mantle plume heads,above zones of adiabatic melting,and provide information about composition of the plume material and processes in the plume *** on the previous studies on the composition of the mantle xenoliths in within-plate basalts around the world,it is inferred that the heads of the mantle（thermochemical） plumes are made up of moderately depleted spinel peridotites（mainly lherzolites）and geochemically-enriched intergranular fluid/***,it is presumed that the plume heads intrude the mafic lower crust and reach up to the bottom of the upper crust at depths-20 *** generation of two major types of mantle-derived magmas（alkali and tholeiitic basalts） was previously attributed to the processes related to different PT-parameters in the adiabatic melting zone whereas this study relates to the fluid regime in the plume *** is also suggested that a newly-formed melt can occur on different sides of a critical plane of silica undersaturation and can acquire either alkalic or tholeiitic composition de

关键词： Magmatic systems LIP Mantle plume Paleoproterozoic Mantle xenoliths Basalts

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Gold mineralisation and orogenic metamorphism in the Lena province of Siberia as assessed from Chertovo Koryto and Sukhoi Log deposits

引用

Geoscience Frontiers 2016年第3期7卷 453-481页

作者： Marina A.Yudovskaya Vadim V.Distler Vsevolod Yu.Prokofiev Nickolay N.Akinfiev institute of Geology of Ore Deposits PetrographyMineralogy and Geochemistry RAS EGRI University of the Witwatersrand

The Chertovo Koryto gold deposit（80 t Au at 1.84 g/t） in the Lena world-class province,Siberia,is hosted in a metamorphosed sequence of the Paleoproterozoic Mikhailovsk Formation that comprises the oldest black shale strata of the Baikal-Patom *** mineralisation is confined to the thrust zone complicated with a conjugate anticline fold,zones of shearing and *** struaural position of the mineralisation is similar to that at the giant Sukhoi Log deposit in the neighbouring Mama-Bodaibo *** the latter,the isotope age data suggest that Khomolkho black shales,hosts to Sukhoi Log mineralisation,are of Ediacaran age and underwent prograde metamorphism during early *** geochemical composition of the terrigenous rocks that host Sukhoi Log,Chertovo Koryto,and a number of other deposits at the various stratigraphic levels throughout the Proterozoic sequence have much in *** do not show elevated metal contents above the common black shale abundances,except for Au and As,which is at variance with the accepted view on diagenetic enrichment of black shales in the Lena *** occurrence of sagenitic rutile in quartz and chlorite pseudomorphs after biotite and other petrographic observations provide evidence on a retrograde nature of the metamorphic mineral assemblages in the Mikhailovsk *** sulphides are pyrrhotite and arsenopyrite with very minor pyrite at Chertovo Koryto,whereas pyrite is the predominant sulphide in the Sukhoi Log *** inclusion data on both deposits emphasise a high-temperature nature of the mineralisation albeit revealing great contrast in the fluid *** Log mineralisation was formed at mixing between low-salinity aqueous solutions and dense gaseous carbonic fluids,which facilitated effective gold scavenging and precipitation,as demonstrated by thermodynamic *** precursory devolatilisation of the Mikhailovsk sediments at the prograde stage results in the paucity of gaseous carbon

关键词： Gold Black shales Orogenic metamorphism Orogenic fluid Sukhoi Log Chertovo Koryto

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Were Late Cretaceous extinctions of gastropods selective by generic longevity?

引用

Geoscience Frontiers 2013年第1期4卷 87-93页

作者： Dmitry A.Ruban Division of mineralogy and petrography Geology and Geography FacultySouthern Federal University

Many gastropod taxa went extinct during the Late Cretaceous. The stratigraphic ranges of 268 genera permit to establish the longevity of extinction victims for each stage of this epoch. ＂Young＂ taxa （originated within B epochs before the extinction） prevailed among victims of the extinctions in all stages. The proportion of ＂old＂ taxa （originated before the Cretaceous） that went extinct was the highest in the Cenomanian, and it was the lowest in the Coniacian and the Maastrichtian. It appears that the end-Cretaceous mass extinction affected chiefly ＂young＂ taxa. However, the comparison with the earlier time intervals suggests that this pattern of selectivity by generic longevity was not specific for the noted catastrophe, but, in contrast, it was typical for the entire Late Cretaceous. The latest Cenomanian environmental perturbation （OAE2） caused a stronger extinction of＂old＂ taxa, and thus, this biotic crisis was less selective by generic longevity. This hypothesis, however, is not proven by the statistical test.

关键词： Gastropods Extinction Longevity Selectivity Late Cretaceous

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

U-Blacks Mineralization in Sandstone Uranium Deposits

引用

Journal of Earth Science 2022年第2期33卷 308-316页

作者： Olga A.Doynikova institute of Ore Deposits Geology PetrographyMineralogy and Geochemistry Russian Academy of ScienceMoscow 119017Russia

Ores of infiltration sandstone-hosted uranium deposits in the sedimentary cover are ubiquitous composed of dispersed soot powder mineralization of black,brownish-black *** studies of such loose U-ores by analytical transmission electron microscopy(ATEM)proved their polymineral *** blacks are composed by at least three different U-mineral forms:oxide(uraninite),silicate(coffinite)and phosphate(ningyoite)which are present in various proportions of ore *** high dispersed friable uranium formations are difficult to diagnose by traditional mineralogical methods(optical,XRD,IR and X-ray spectroscopy,etc.)which analyze total sample composition(phases mixture);their results characterize the dominant sample phase,omitting both sharply subordinate and X-ray amorphous *** research results are based on ATEM methods(SAED+EDS),which are optimal for crystallochemical diagnostics in the mineralogical study of such uranium *** article presents the diagnostic characteristics under electron microscope(EM)of uranous minerals from different sandstone deposits with their origin being discussed.

关键词： uranous minerals uraninite coffinite ningyoite biogenic nature U-deposit ore deposit geology

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Uranium Isotope Variations(234U/238U and 238U/235U)and Behavior of U-Pb Isotope System in the Vershinnoe Sandstone-Type Uranium Deposit,Vitim Uranium Ore District,Russia

引用

Journal of Earth Science 2022年第2期33卷 317-324页

作者： V.N.Golubev I.V.Chernyshev B.T.Kochkin N.N.Tarasov G.V.Ochirova A.V.Chugaev institute of Geology of Ore Deposits PetrographyMineralogy and GeochemistryRussian Academy of SciencesMoscow 119017Russia

The U-Pb isotope system and uranium isotope composition(235U/238U and 234U/238U)were studied in a number of samples from the vertical section of the uranium ore body at the Vershinnoe sandstone-type deposit,Vitim uranium ore district,*** parameters were determined to broadly *** of the 234U/238U ratio from the equilibrium value indicate that the uranium ore was not completely conserved during the postore stage,and uranium was determined to continue migrating at the *** of the U-Pb isotope age value and 234U/238U isotope ratio provides an insight into the migrate direction of uranium in the ore *** broad variations(137.377–137.772)in the 238U/235U ratio over the vertical section of the ore body can be explained by the different settings of the samples relative to the ore deposition front and changes in the redox conditions when this front *** fact that theδ238U and K234/238 values are correlated indicates that the transfer of the 234U isotope into the aqueous phase may have been coupled with isotope fractionation in the 238U-235U system during the postformation uranium migration within the orebody.

关键词： sandstone-type uranium deposit U-Pb age uranium isotope composition ore deposit geology

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Central Asia—A Global Model for the Formation of Epigenetic Deposits in a Platform Sedimentary Cover

引用

Journal of Earth Science 2022年第2期33卷 278-288页

作者： Igor Pechenkin Vladislav Petrov FSBI All-Russian Scientific-Research institute of Mineral Resources MoscowRussia institute of Geology of Ore Deposits petrography mineralogy and Geochemistry RAS MoscowRussia

Metallogenic specialization of sedimentary cover in Central Asia is determined by its tectonic setting that governs the hydrodynamic regime(exfiltrational or infiltrational)and as a consequence,the hydrogeochemical zonality(type of water and its gaseous and microcomponent composition).Hydrodynamic conditions(distribution of recharge and discharge areas)determine the direction of stratal water flow and location of mineralization resulted from the change in geochemical,thermodynamic,lithological,structural and other *** exfiltrational regime suggests a dependence of the epigenetic mineralization upon the distribution and degree of preservation of hydrocarbon ***,hydrocarbon matter serves as a reducing barrier and ore-concentrating factor during the formation of polymineral concentrations related to stratal oxidation *** supergene epigenetic ore-forming processes are induced by the interaction between the Earth’s sedimentary cover and *** rocks themselves commonly serve as a source of ore *** ore deposition zones on geochemical barriers and ore material source are often located significantly apart from each *** trend of these processes is determined by the position of ore-bearing depressions in large tectonic blocks.

关键词： Central Asia Kyzyl Kum Bukantau ore-forming systems epigenetic ore deposit geology

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Macroscopically-Zoned Grandite from the Garnetite Skarn of Meka Presedla(Kopaonik Mountain,Serbia)

引用

Acta Geologica Sinica(English Edition) 2012年第2期86卷 393-406页

作者： Pavle TANCIC Predrag VULIC Reinhard KAINDL Bernhard SARTORY Radovan DIMITRIJEVIC Geological institute of Serbia BelgradeSerbia Department of Crystallography Faculty of Mining and GeologyUniversity of BelgradeBelgradeSerbia 3 institute of mineralogy and petrography University of InnsbruckInnsbruckAustria

The macroscopically-zoned grandite from the garnetite skarn of Meka Presedla （Kopaonik Mountain, Serbia） was studied with optical microscopy, electron microprobe analysis （EMPA）, Fourier transform infra-red （FT-IR）, and Raman methods. The EMPA results indicate that the main core-rim compositional variations （Ca2.93-2.97Mn0.05-0.06Mg0.00-0.01AI1.14-L26 Fe0.72-0.83 Ti0.00-0.02Si2.97-3.02012） slightly differ along the zones, showing evidence for a quasi-cyclic alternation of the oscillatory zoning nature. Among this, considerable variation is observed only by the AI-Fe3＋ substitutions in the octahedral site. The EMPA also indicate that the grandite zones compositionally vary, mostly within ＋1 and ±2 mol% of the homogeneity level range, that is, Grs64±1Adra36±1SpS2 （A）, Grs62±1Adra38±1Sps2 （B）, Grs59±2Adr40±2Sps2 （C）, Grs58±2Adr41±2Sps2 （D）, and Grss±1Adr41±1Sps2 （E）. Therefore, the investigated garnet can be considered as relatively highly homogeneous. The majority of compositions lie within the narrow miscibility region of 0.58±2〈XGrs〈0.64±1, without gaps, and with only three outliers near the zone boundaries of approximately 0.38〈XGrs〈0.52. FT-IR and Raman bands are almost constant within the zones and adequate to the chemical compositions. All of the zones should be considered as anhydrous. From the results, formation temperatures between -600 and 720℃ and pressures 0f-2-3 kbars, are derived. Among five possible causes for the slightly optical anisotropy of grandite, three were reconsidered, and consequently rejected.

关键词： grandite anisotropy compositional variation zone homogeneities miscibility region

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Petrogenesis of siliceous high-Mg series:Evidence from Early Paleoproterozoic mafic volcanic rocks of the Vodlozero Domain,Fennoscandian Shield

引用

Geoscience Frontiers 2018年第1期9卷 207-221页

作者： M.Bogina V.Zlobin S.Svetov E.Sharkov A.Chistyakov institute of Geology of Ore Deposits Petrography Mineralogy and Geochemistry Russian Academy of Sciences Geological institute Russian Academy of Sciences institute of Geology Karelian Scientific Center Russian Academy of Sciences

Compositional peculiarities of the siliceous high-Mg series(SHMS)rocks formed at the Archean-Paleoproterozoic boundary as a function of plume activity are discussed using example of Early Paleoproterozoic mafic volcanic rocks of the Vodlozero Domain,Fennoscandian *** rocks are characterized by wide variations in Mg#(33-67)and Cr contents(25-1123 ppm),LREE enrichment,and weakly negative_(εNd)(from-0.7 to-2.9).The high Gd/Yb ratio in the primitive high-Mg rocks of the Vodlozero Domain suggests their generation from a garnet-bearing *** the same time,their negative _(εNd)in combination with LREE enrichment points to the crustal contamination.A new model was proposed to explain the remarkable global-scale similarity of *** rocks can be generated by the contamination of a high-degree(30%)partial melt derived from a depleted *** lower crustal sanukitoid-type rocks can be considered as a universal crustal *** showed that such mixing can provide the observed narrow_(εNd)variations in Early Paleoproterozoic *** Neoarchean sanukitoid suites,which are widespread on all cratons,presumably composed the lower crust at the beginning of the ***,this mechanism can be considered universal for the genesis of the SHMS *** high-to low-Cr rock series can be produced by the fractionation of the mafic melt coupled with an insignificant crustal assimilation of felsic end members of the sanukitoid suite of the Vodlozero Domain en route to the surface,as suggested by the positive correlation of_(εNd)with Cr and Mg#,negative correlation with Th,and slight decrease of_(εNd)in the more evolved varieties.

关键词： Early Palaeoproterozoic Siliceous high-magnesian series (SHMS) rocks Sanukitoids Mantle plume Depleted mantle Crustal contamination

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Alkali control of high-grade metamorphism and granitization

引用

Geoscience Frontiers 2014年第5期5卷 711-727页

作者： Oleg G.Safonov Leonid Y.Aranovich institute of Experimental mineralogy RAS ChernogolovkaMoscow RegionRussia Department of Petrology Moscow State UniversityMoscowRussia Department of Geology.University of Johannesburg Johannesburg.South Africa institute of Geology of Ore Deposits PetrographyMineralogy and Geochemistry

We review petrologic observations of reaction textures from high-grade rocks that suggest the passage of fluids with variable alkali activities. Development of these reaction textures is accompanied by regular compositional variations in plagioclase, pyroxenes, biotite, amphibole and garnet. The textures are interpreted in terms of exchange and net-transfer reactions controlled by the K and Na activities in the fluids. On the regional scale, these reactions operate in granitized, charnockitized, syenitized etc. shear zones within high-grade complexes. Thermodynamic calculations in simple chemical systems show that changes in mineral assemblages, including the transition from the hydrous to the anhydrous ones, may occur at constant pressure and temperature due only to variations in the H2O and the alkali activities. A simple procedure for estimating the activity of the two major alkali oxides, K2O and Na2O, is imple- mented in the TWQ software. Examples of calculations are presented for well-documented dehydration zones from South Africa, southern India, and Sri Lanka. The calculations have revealed two end-member regimes of alkalis during specific metamorphic processes： rock buffered, which is characteristic for the precursor rocks containing two feldspars, and fluid-buffered for the precursor rocks without K-feldspar. The observed reaction textures and the results of thermodynamic modeling are compared with the results of available experimental studies on the interaction of the alkali chloride and carbonate-bearing fluids with metamorphic rocks at mid-crustal conditions. The experiments show the complex effect of alkali activities in the fluid phase on the mineral assemblages. Both thermodynamic calculations and experiments closely reproduce paragenetic relations theoretically predicted by D.S. Korzhinskii in the 1940s.

关键词： High-grade metamorphismAlkali activityFluidsReaction texturesFluid-mineral reactionsThermodynamic modeling

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

FACTOR AND CLUSTER ANALYSES APPLIED TO THE QUANTITATIVE X-RAY SPECTRAL MICROANALYSIS OF THIN MINERAL INTERGROWTHS

引用

电子显微学报 1991年第2期 205-206页

作者： A.I.Tsepin institute of Geology of Ore Deposits PetrographyMineralogy and GeochemistryUSSR Academy of Sciences

One of the multivariate analysis methods-factor analysis isproposed in order to increase the information from x-raymicroprobe analysis. The factor analysis program uses both R andQ-models of the main factor method. The program algorithmincludes the latest data. The program language is "Quick Basic".Both R and Q-models of this method solve the following problems:

关键词： Th FACTOR AND CLUSTER ANALYSES APPLIED TO THE QUANTITATIVE X-RAY SPECTRAL MICROANALYSIS OF THIN MINERAL INTERGROWTHS

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：