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Late Cretaceous Adakitic Granites of the Southeastern Tibetan Plateau: Garnet Fractional Crystallization of Arc-Like Magmas at the Thickened Neo-Tethyan Continental Margin 被引量:1
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作者 XIANG Kun XUE Chuandong +4 位作者 YANG Tiannan XIE Zhipeng XIN Di JIANG Lili LAI Ruijuan 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2019年第4期857-873,共17页
The tectonic setting of Cretaceous granitoids in the southeastern Tibet Plateau,east of the Eastern Himalaya Syntax,is debated.Exploration and mining of the Laba Mo–Cu porphyry-type deposit in the area has revealed L... The tectonic setting of Cretaceous granitoids in the southeastern Tibet Plateau,east of the Eastern Himalaya Syntax,is debated.Exploration and mining of the Laba Mo–Cu porphyry-type deposit in the area has revealed Late Cretaceous granites.New and previously published zircon U–Pb dating indicate that the Laba granite crystallized at 89–85 Ma.Bulk-rock geochemistry,Sr–Nd isotopic data and in situ zircon Hf isotopic data indicate that the granite is adakitic and was formed by partial melting of thickened lower crust.The Ca,Fe,and Al contents decrease with increasing SiO2 content.These and other geochemical characteristics indicate that fractional crystallization of garnet under high-pressure conditions resulted in the adakitic nature of the Laba granite.Cretaceous granitoids are widespread throughout the Tibetan Plateau including its southeastern area,forming an intact curved belt along the southern margin of Eurasia.This belt is curved due to indenting by the Indian continent during Cenozoic,but strikes parallel to both the Indus–Yarlung suture zone and the Main Frontal Thrust belt.It is therefore likely that Cretaceous granitoids in both the Gangdese and southeastern Tibetan Plateau areas resulted from subduction of Neo-Tethyan lithosphere. 展开更多
关键词 adakitic granite geochemistry garnet fractional crystallization Cretaceous Neo-Tethyan subduction southeastern Tibetan Plateau
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Formation of anorthosite on the Moon through magma ocean fractional crystallization 被引量:2
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作者 Tatsuyuki Arai Shigenori Maruyama 《Geoscience Frontiers》 SCIE CAS CSCD 2017年第2期299-308,共10页
Lunar anorthosite is a major rock of the lunar highlands,which formed as a result of plagioclasefloatation in the lunar magma ocean(LMO).Constraints on the sufficient conditions that resulted in the formation of a t... Lunar anorthosite is a major rock of the lunar highlands,which formed as a result of plagioclasefloatation in the lunar magma ocean(LMO).Constraints on the sufficient conditions that resulted in the formation of a thick pure anorthosite(mode of plagioclase 〉95 vol.%) is a key to reveal the early magmatic evolution of the terrestrial planets.To form the pure lunar anorthosite,plagioclase should have separated from the magma ocean with low crystal fraction.Crystal networks of plagioclase and mafic minerals develop when the crystal fraction in the magma(φ) is higher than ca.40-60 vol.%,which inhibit the formation of pure anorthosite.In contrast,when φ is small,the magma ocean is highly turbulent,and plagioclase is likely to become entrained in the turbulent magma rather than separated from the melt.To determine the necessary conditions in which anorthosite forms from the LMO,this study adopted the energy criterion formulated by Solomatov.The composition of melt,temperature,and pressure when plagioclase crystallizes are constrained by using MELTS/pMELTS to calculate the density and viscosity of the melt.When plagioclase starts to crystallize,the Mg~# of melt becomes 0.59 at 1291 C.The density of the melt is smaller than that of plagioclase for P 〉 2.1 kbar(ca.50 km deep),and the critical diameter of plagioclase to separate from the melt becomes larger than the typical crystal diameter of plagioclase(1.8-3 cm).This suggests that plagioclase is likely entrained in the LMO just after the plagioclase starts to crystallize.When the Mg~# of melt becomes 0.54 at 1263 C,the density of melt becomes larger than that of plagioclase even for 0 kbar.When the Mg~# of melt decreases down to 0.46 at 1218 C,the critical diameter of plagioclase to separate from the melt becomes 1.5-2.5 cm,which is nearly equal to the typical plagioclase of the lunar anorthosite.This suggests that plagioclase could separate from the melt.One of the differences between the Earth and the Moon is the presence of water.If the terrestrial magma ocean was saturated with H_2O,plagioclase could not crystallize,and anorthosite could not form. 展开更多
关键词 Moon Anorthosite Magma ocean MELTS fractional crystallization
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Temperature of Prograde Metamorphism, Decompressional Partial Melting and Subsequent Melt Fractional Crystallization in the Weihai Migmatitic Gneisses,Sulu UHP Terrane:Constraints from Ti-in-Zircon Thermometer 被引量:5
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作者 续海金 叶凯 章军锋 《Journal of Earth Science》 SCIE CAS CSCD 2012年第6期813-827,共15页
In order to constrain temperature during subduction and subsequent exhumation of fel- sic continental crust, we carried out a Ti-in-zircon thermometer coupled with zircon internal structure and U-Pb age on migmatitic ... In order to constrain temperature during subduction and subsequent exhumation of fel- sic continental crust, we carried out a Ti-in-zircon thermometer coupled with zircon internal structure and U-Pb age on migmatitic gneisses from the Weihai region in the Sulu ultra-high pres- sure (UHP) metamorphic terrane, eastern China. The Weihai migmatitic gneisses are composed of in- tercalated compositional layers of melanosome and plagioclase (Pl)-rich lencosome and K-feldspar (Kfs)-rich pegmatite veins. Four stages of zircon growth were recognized in the Weihai migmatitic gneisses. They successively recorded informations of protolith, prograde metamorphism, decompres- sional partial melting during early stage exhumation and subsequent fractional crystallization of pri- mary melt during later stage cooling exhumation. The inherited cores in zircon from the melanosome and the Pl-rich leucosome suggest that the pro- tolith of the migmatitic gneiss is Mid- Neoproterozoic (-780 Ma) magmatic rock. Metamorphic zircons with concordant ages ranging from 243 to 256 Ma occur as over- growth mantles on the protolith magmatic zir- con cores. The estimated growth temperatures (625-717 "C) of the metamorphic zircons have a negative correlation with their ages, indicating a progressive metamorphism in HP eciogite-facies condition during subduction. Zircon recrystal- lized rims (228-2 Ma) in the PI-rich ieucosome layers provide the lower limit of the decompress-sional partial melting time during exhumation. The ages from 228^-2 to 219~2 Ma recorded in the Pl-rich leucosome and the Kfs-rich pegmatite vein, respectively, suggest the duration of the fractional crystallization of primary melt during exhumation. The calculated growth temperatures of the zircon rims from the Pl-rich leucosome range from 858 to 739 , and the temperatures of new growth zircon grains (219±2 Ma) in Kfs-rich vein are between 769 and 529 . The estimated temperatures have a positive correlation with ages from the Pl-rich leucosome to the Kfs-rich pegmatite vein, strongly indi- cating that a process of fractional crystallization of the partial melt during exhumation. 展开更多
关键词 Ti-in-zircon thermometer prograde metamorphism decompressional partial melting fractional crystallization migmatitic gneiss Sulu UHP metamorphic terrane.
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The Geochemical Effect of Lanthanides: Its Types and Application for Magmatic Rocks—A New Method to Semi-Quantitatively Determine Strength of Magmatic Fluid Complexation and Fractional Crystallization 被引量:2
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作者 Jianye Yang Lei Zhao Weiguo Zhang 《Journal of Earth Science》 SCIE CAS CSCD 2014年第2期252-262,共11页
In this paper, the relationship between rare earth elements (REEs) geochemical behavior and their ionic radii was studied. According to the basic law called the effect on geochemistry of lantha- nides, five types an... In this paper, the relationship between rare earth elements (REEs) geochemical behavior and their ionic radii was studied. According to the basic law called the effect on geochemistry of lantha- nides, five types and some of subtypes of REEs occurrence, both in magmatic rocks and their minerals, were found, which may correspond to the evolutionary way of magmatic rocks. Analysis of REEs data for an amazonite-topaz granite pluton in East Xinjiang, one of the administrative regions of West China, and Cenozoic alkaline volcanic-intrusive rocks in the Xialiaohe depression of Bohai Bay Basin, China show that types II1, III and IV of effect on geochemistry of lanthanides not only reflect fluid complexa- tion and fractional crystallization existed in magmatic evolution directly, but also can determine semi-quantitatively the strength of fluid complexation and fractional crystallization. Therefore, the ef- fect on geochemistry of lanthanides, a new way to study semi-quantitatively evolution of magmatic rocks, is probably practicable. Moreover, the mafic lavas of different sources from the margin of Gonghe Basin, Qinghai Province, China, can be effectively distinguished in the diagram which can be drawn with some parameters of linear equation of LREEs and its ion radius. 展开更多
关键词 effect of geochemistry of lanthanides magmatic evolution strength of fluid complexa- tion and fractional crystallization.
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Late Triassic Magma Mixing and Fractional Crystallization in the Qingchengzi Orefield,Eastern Liaoning Province:Regional Petrogenetic and Metallogenic Implications 被引量:1
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作者 Hongjing Xie Yuwang Wang +2 位作者 Dedong Li Guochao Zhou Zhichao Zhang 《Journal of Earth Science》 SCIE CAS CSCD 2021年第1期144-157,共14页
The Qingchengzi orefield is an important Pb-Zn-Au-Ag polymetallic orefield in NE Chi-na.The Indosinian magmatism has formed the Shuangdinggou batholith and the Xinling stock,as well as dikes of quartz monzonite porphy... The Qingchengzi orefield is an important Pb-Zn-Au-Ag polymetallic orefield in NE Chi-na.The Indosinian magmatism has formed the Shuangdinggou batholith and the Xinling stock,as well as dikes of quartz monzonite porphyry and lamprophyre.According to petrographic characteristics,the Shuangdinggou intrusion can be divided into the main suite and the central suite.Zircon U-Pb dat-ing yielded crystallization ages of 215.0-220.9 Ma for these various Qingchengzi magmatic units,which are within analytical error and represent coeval magmatism.The Shuangdinggou main suite contains abundant mafic microgranular enclaves(MMEs)and shows features of magma mixing.Geochemically,the major oxide contents of the MMEs and their quartz monzonite host show well-defined linear frac-tionation trends.The REE and trace element patterns of the MMEs and their host are similar,which demonstrates certain degree of geochemical homogenization between the two during magma mixing.The Shuangdinggou main suite shares similar geochemical characteristics with typical high Ba-Sr gra-nites(Ba=1082 ppm-2051 ppm,Sr=803 ppm-886 ppm),and was likely originated from the mixing between a melt derived from partial melting of the thickened lower crust and the enriched mantle.The central suite was likely formed by fractional crystallization of the main-suite magma.The Xinling in-trusion may represent a branch of the Shuangdinggou intrusion and has the same genesis as the central suite.The quartz monzonite porphyries geochemically mimic the Shuangdinggou main suite,and may also be an epioic facies of the Shuangdinggou intrusion.The MMEs and lamprophyres may have been derived from incomplete magma mixing.Formation of the Pb-Zn and Au-Ag deposits in the Qing-chengzi orefield may have been related to the granite/quartz monzonite porphyries near the Shuangdinggou intrusion,which were formed by magma mixing and fractional crystallization. 展开更多
关键词 Qingchengzi orefield Shuangdinggou intrusion magma mixing mafic microgranular enclave(MME) fractional crystallization
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Geology and mineralization of the Hongqiling large magmatic nickel-copper-cobalt deposit(22×10^(4)t)in Jilin Province,China:A review
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作者 Cong Chen Yu-chao Gu +14 位作者 Di Zhang Tao-tao Wu Ai Li Yun-sheng Ren Qing-qing Shang Jian Zhang Xiong-fei Bian Fei Su Jia-lin Yang Qiu-shi Sun Xiao-hai Li Wan-zhen Liu Zhen-ming Sun Sen Zhang Yu-hui Feng 《China Geology》 CAS CSCD 2024年第4期762-796,共35页
The Hongqiling large nickel-copper-cobalt deposit(hereafter referred to as the Hongqiling deposit),a typical mafic-ultramafic copper-nickel deposit in China,boasts proven Ni(Ni)resources of approximately 22×10^(4... The Hongqiling large nickel-copper-cobalt deposit(hereafter referred to as the Hongqiling deposit),a typical mafic-ultramafic copper-nickel deposit in China,boasts proven Ni(Ni)resources of approximately 22×10^(4)t,associated copper resources of 2×10^(4)t,and associated cobalt(Co)resources of 0.5×10^(4)t,with Ni reserves ranking 10th among China's magmatic nickel deposits.Geotectonically,the Hongqiling deposit is situated in the superimposed zone between the Xing'an-Mongolian orogenic belt and the circum-Western Pacific's active continental margin belt.Its ore-bearing plutons occur within the metamorphic rocks of the Ordovician Hulan Group,with the emplacement of plutons and the locations of orebodies governed by the deep-seated Huifahe fault and its secondary NW-trending Fujia-Hejiagou-Beixinglong-Changsheng fault zone.In the deposit,the rock assemblages of ore-bearing plutons predominantly encompass gabbro-pyroxenite-olivine pyroxenite-pyroxene peridotite(pluton No.1)and norite-orthopyroxenite-harzburgite(pluton No.7),with ore-bearing lithofacies consisting primarily of olivine pyroxenite and pyroxenite facies.The Hongqiling deposit hosts stratoid,overhanging lentoid,veined,and pure-sulfide veined orebodies.Its ores principally contain metallic minerals including pyrrhotite,pentlandite,chalcopyrite,violarite,and pyrite.Despite unidentified magma sources of ore-bearing mafic-ultramafic rocks,it is roughly accepted that the magmatic evolution in the Hongqiling deposit primarily involved fractional crystallization and crustal contamination.The ore-forming materials were primarily derived from the upper mantle,mixed with minor crustal materials.The ore-bearing mafic-ultramafic rocks in the deposit,primarily emplaced during the Indosinian(208-239 Ma),were formed in an intense extension setting followed by the collisional orogeny between the North China Plate and the Songnen-Zhangguangcai Range Block during the Middle-Late Triassic.From the perspective of the metallogenic geological setting,surrounding rocks,ore-controlling structures,and rock assemblages,this study identified one favorable condition and seven significant indicators for prospecting for Hongqiling-type nickel deposits and developed a prospecting model of the Hongqiling deposit.These serve as valuable references for exploring similar nickel deposits in the region,as well as the deep parts and margins of the Hongqiling deposit. 展开更多
关键词 Nickel-copper-cobalt deposit fractional crystallization Crustal contamination MAGMATIC MINERALIZATION Re-Os isotopic age Sulfur isotopic Metallogenic mode Prospecting model Western Pacific’s active continental margin Mineral exploration engineering Hongqiling Jilin
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Geochemistry of Micas from Issia Granite Complexe: A Marker of Geodynamic Evolution
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作者 Koffi Joseph Brou Alain Nicaise Kouamelan Koffi Raoul Teha 《Open Journal of Geology》 CAS 2024年第8期787-804,共18页
The granites and pegmatites located in the southern part of the Issia region, near the columbo-tantaliferous placers, are characterized by the presence of rare metals such as beryl, lithium and Nb-Ta oxides. They main... The granites and pegmatites located in the southern part of the Issia region, near the columbo-tantaliferous placers, are characterized by the presence of rare metals such as beryl, lithium and Nb-Ta oxides. They mainly consist of micas, quartz, plagioclase and potassium feldspar. The work carried out on the micas of these granites and pegmatites (EPMA analyses) has provided new geochemical data contributing to the understanding of the magmatic evolution of the Issia granite complex. Mineralogically, the most evolved G3 granites are characterized by their abundance of muscovite compared to biotite and the presence of pegmatite veins. Geochemically, the muscovites of the G1 and G2 granites are more ferriferous than those of the G3 granites, however, the latter display higher Na contents than the G2 and G3. The muscovites of the granites show an evolution from the pure muscovite series to the zinnwaldite series (micas of the pegmatites) which are lithium-bearing micas. The mineralogical and chemical data of the micas show that they are S-type peraluminous granites and demonstrate the formation of granites and pegmatites through fractional crystallization of the same parental magma. 展开更多
关键词 G3 Granites Peraluminous Granites Rare Metals fractional crystallization
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Source Enrichment Control on the Scale of Magmatic-Hydrothermal W-Sn Mineralization:Insights from Triassic and Jurassic Magma Reservoirs in the Continental Crust,Xitian,South China
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作者 GUO Chunli Simon AWILDE +2 位作者 Coralie SIEGEL CHEN Zhenyu WU Shichong 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2024年第1期132-149,共18页
There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit... There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic. 展开更多
关键词 W-Sn mineralization magma reservoir geometry crystal fractionation Xitian Triassic-Jurassic granitic batholith Nanling Range South China
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FRACTIONATED CRYSTALLIZATION OF HDPE IN PS/POE/HDPE/SBS BLENDS 被引量:1
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作者 傅强 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2008年第6期733-740,共8页
The fractionated crystallization behavior of the minor dispersed HDPE phase in PS/POE/HDPE/SBS quaternary blends was investigated by differential scanning calorimetry (DSC).Interestingly,we found that the fractionated... The fractionated crystallization behavior of the minor dispersed HDPE phase in PS/POE/HDPE/SBS quaternary blends was investigated by differential scanning calorimetry (DSC).Interestingly,we found that the fractionated crystallization behavior of HDPE was molecular weight dependent.At a fixed composition,HDPE with lower molecular weight showed more obvious fractionated crystallization behavior than HDPE with higher molecular weight.This was ascribed to a finer dispersion of HDPE with lower molecular weight,a... 展开更多
关键词 Fractionated crystallization HDPE Molecular weight dependent.
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Was the Panzhihua Large Fe-Ti Oxide Deposit,SW China,Formed by Silicate Immiscibility? 被引量:1
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作者 DING Xiangli CHEN Xuanhua SHAO Zhaogang 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2023年第5期1451-1461,共11页
The Panzhihua mafic intrusion,which hosts a world-class Fe-Ti-V ore deposit,is in the western Emeishan region,SW China.The formation age(~260 Ma),and Sr and Nd isotopes indicate that the Panzhihua intrusion is part of... The Panzhihua mafic intrusion,which hosts a world-class Fe-Ti-V ore deposit,is in the western Emeishan region,SW China.The formation age(~260 Ma),and Sr and Nd isotopes indicate that the Panzhihua intrusion is part of the Emeishan large igneous province and has little crustal contamination.To assess ore genesis of the Panzhihua Fe-Ti-V ore deposit,two different models have been provided to explain the formation,namely silicate immiscibility and normal fractional crystallization.Silicate immiscibility occurring around 1,000℃at the late stage of basaltic magma evolution argues against the silicate immiscibility model.Apatite-hosted melt inclusion research indicates that silicate immiscibility occurred at the late stage of Panzhihua magma evolution,which may not have offered potential to form such large ore deposits as Panzhihua.Alternatively,continuous compositional variations of the Panzhihua intrusion and calculations using thermodynamic modelling software support the hypothesis that the Panzhihua deposit was formed by normal fractional crystallization.Reciprocal trace element patterns of the Panzhihua intrusion and nearby felsic rocks also coincide with the fractional crystallization model.Normal fractional crystallization of high-Ti basaltic magma played a key role in the formation of the Panzhihua Fe-Ti-V ore deposit. 展开更多
关键词 liquid immiscibility fractional crystallization mafic intrusion Fe-Ti oxide deposit Panzhihua
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Petrogenesis of Oligocene volcanic rocks of the Lake Tana area,Ethiopian large Igneous Province
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作者 Ayenachew Alemayhou Desta Asfawossen Asrat Minyahl Teferi Desta 《Acta Geochimica》 EI CAS CSCD 2023年第6期1104-1123,共20页
The Lake Tana area is located within a complex volcano-tectonic basin on the northwestern Ethiopian plateau.The basin is underlain by a thick succession of Oligocene transitional basalts and sub-alkaline rhyolites ove... The Lake Tana area is located within a complex volcano-tectonic basin on the northwestern Ethiopian plateau.The basin is underlain by a thick succession of Oligocene transitional basalts and sub-alkaline rhyolites overlain in places,particularly south of the lake,by Quaternary alkaline to mildly transitional basalts,and dotted with Oligo-Miocene trachyte domes and plugs.This paper presents the results of integrated field,petrographic,and major and trace element geochemical studies of the Lake Tana area volcanic rocks,with particular emphasis on the Oligocene basalts and rhyolites.The studies reveal a clear petrogenetic link between the Oligocene basalts and rhyolites.The Oligocene basalts are:(1)plagioclase,olivine,and/or pyroxene phyric;(2)show an overall decreasing trend in MgO,Fe_(2)O_(3),and CaO with silica;(3)have relatively low Mg#,Ni and Cr contents and high Nb/La and Nb/Yb ratios;and(4)show LREE enriched and generally flat HREE patterns.All these imply the origin of the Oligocene basalts by shallow-level fractional crystallization of an enriched magma sourced at the asthenospheric mantle.The Oligocene rhyolites:(1)are enriched in incompatible while depleted in compatible trace elements,P and Ti;(2)show a strong negative Eu anomaly;(3)contain appreciable amounts of plagioclase,apatite,and Fe-Ti oxides;and(4)show clear geochemical similarity with well-constrained rhyolites from the Large Igneous Province(LIP)of the northwestern Ethiopian plateau.Low-pressure fractional crystallization of mantle-derived basaltic magma in crustal magma chambers explains the origin of these rhyolites.Our study further shows that the Oligocene basalts and rhyolites are co-genetic and the felsic rocks of the Lake Tana area are related differentiates of the flood basalt volcanism in the northwestern Ethiopian plateau. 展开更多
关键词 Large igneous province Oligocene basalt Oligocene rhyolite fractional crystallization Lake Tana
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Geochemical and Sr-Nd-Pb isotopic compositions of volcanic rocks from the Iheya Ridge,the middle Okinawa Trough:implications for petrogenesis and a mantle source 被引量:7
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作者 LI Xiaohui ZENG Zhigang +4 位作者 CHEN Shuai MA Yao YANG Huixin ZHANG Yuxiang CHEN Zuxing 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2018年第1期73-88,共16页
As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element ... As an active back-arc basin, the Okinawa Trough is located in the southeastern region of the East China Sea shelf and is strongly influenced by the subduction of the Philippine Sea Plate. Major element, trace element and Sr-NdPb isotopic composition data are presented for volcanic rocks from the Iheya Ridge(IR), the middle Okinawa Trough. The IR rocks record large variations in major elements and range from basalts to rhyolites. Similar trace element distribution characteristics together with small variations in ^87Sr/^86Sr(0.703 862–0.704 884), ^144Nd/^143Nd(0.512 763–0.512 880) and Pb isotopic ratios, demonstrate that the IR rocks are derived from a similar magma source. The fractional crystallization of olivine, clinopyroxene, plagioclase, and amphibole, as well as accessory minerals, can reasonably explain the compositional variations of these IR rocks. The simulations suggest that approximately 60% and 75% fractionation of an evolved basaltic magma can produce trace element compositions similar to those of the intermediate rocks and acid rocks, respectively. The analysis of their Sr-Nd-Pb isotopic content ratios suggest that the source of the rocks from the IR is close to the depleted mantle(DM) but extends to the enriched mantle(EMII), indicating that the mantle source of these rocks is a mixture between the DM and EMII end members. The simulations show that the source of the IR volcanic rocks can be best interpreted as the result of the mixing of approximately 0.8%–2.0% subduction sediment components and 98.0%–99.2% mantlederived melts. 展开更多
关键词 basic to intermediate-acid rocks fractional crystallization subduction sediment components Iheya Ridge Okinawa Trough
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The influence of fractionation of REE-enriched minerals on the zircon partition coefficients 被引量:3
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作者 Shihua Zhong Sanzhong Li +2 位作者 Reimar Seltmann Zhiqing Lai Jie Zhou 《Geoscience Frontiers》 SCIE CAS CSCD 2021年第3期249-258,共10页
Zircon is widely used to simulate melt generation,migration and evolution within the crust and mantle.The achievable performance of melt modelling generally depends on the availability of reliable trace element partit... Zircon is widely used to simulate melt generation,migration and evolution within the crust and mantle.The achievable performance of melt modelling generally depends on the availability of reliable trace element partition coefficients(D).However,a large range of D_(REE) values for zircon from natural samples and experimental studies has been reported,with values spanning up to 3 orders of magnitude.Unfortunately,a gap of knowledge on this variability is evident.In this study we model the crystallization processes of common REE-bearing minerals from granitic melts and show that the measured zircon D_(REE) would be elevated if there is crystallization of REE-enriched minerals subsequent to zircon.Nevertheless,compared to zircon D_(REE) values measured from experimental studies,this mechanism appears to have a less significant influence on those from natural granite samples since the quantity of crystallized REE-enriched minerals is very low in natural magmatic systems and/or most of them crystallize prior to zircon.Combined with recently published studies,this work supports that analysis of natural zircon/host groundmass pairs provides more robust D_(REE) values applicable to natural systems than those measured from experimental studies,which can be used to constrain the provenance of detrital zircons. 展开更多
关键词 Rayleigh fractionation Partition coefficient fractional crystallization REE ZIRCON
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Origin of the Volcanic Rocks Erupted in the Eastern Manus Basin:Basaltic Andesite-Andesite-Dacite Associations 被引量:3
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作者 MA Yao ZENG Zhigang +2 位作者 CHEN Shuai YIN Xuebo WANG Xiaoyuan 《Journal of Ocean University of China》 SCIE CAS CSCD 2017年第3期389-402,共14页
There has been much recent interest in the origin of intermediate lava and several hypotheses are: 1) direct melting of the mantle under water-saturated conditions, 2) partial melting of altered crust, 3) fractional c... There has been much recent interest in the origin of intermediate lava and several hypotheses are: 1) direct melting of the mantle under water-saturated conditions, 2) partial melting of altered crust, 3) fractional crystallization of parent magma, and 4) magma mixing of mafic magmas with dacitic/rhyolitic magmas. Volcanic rocks series ranging from basaltic andesite to dacite(SiO_2 ranges from 53.8 to 63.0 wt.%) from the eastern Manus Basin were detected for major and trace element compositions to understand their origin. Low H_2O contents, positive correlations of La-SiO_2 and Yb-SiO_2, oxygen isotope data and the indistinct change of trace element concentrations in oscillatory zoning of plagioclase phenocrysts rule out the models in which silicic lava results from direct melting of hydrous mantle, partial melting of altered oceanic crust or gabbros, and magma mixing, respectively. Besides, the geochemical data of whole rock and melt inclusions indicate that fractional crystallization plays a dominant role in generating the intermediate lava with subduction features. 展开更多
关键词 Eastern Manus Basin fractional crystallization volcanic rocks
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Glass and Mineral Chemistry of Northern Central Indian Ridge Basalts:Compositional Diversity and Petrogenetic Significance 被引量:2
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作者 Dwijesh RAY Ranadip BANERJEE +2 位作者 Sridhar D IYER Basavaraju BASAVALINGU Subir MUKHOPADHYAY4 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2009年第6期1122-1135,共14页
The glass and mineral chemistry of basaits examined from the northern central Indian ridge (NCIR) provides an insight into magma genesis around the vicinity of two transform faults: Vityaz (VT) and Vema (VM). T... The glass and mineral chemistry of basaits examined from the northern central Indian ridge (NCIR) provides an insight into magma genesis around the vicinity of two transform faults: Vityaz (VT) and Vema (VM). The studied mid-ocean ridge basalts (MORBs) from the outer ridge flank (VT area) and a near-ridge seamount (VM area) reveal that they are moderately phyric plagioclase basalts composed of plagioclase (phenocryst [An60-90] and groundmass [An35-79]), olivine (Fo81-88), diopside (Wo45-51, En25-37, Fs14-24), and titanomagnetite (FeOt -63.75 wt% and TiO2 -22.69 wt%). The wholerock composition of these basalts has similar Mg# [mole Mg/mole(Mg+Fe2+)] (VT basalt: -0.56-0.58; VM basalt: -0.57), but differ in their total alkali content (VT basalt: -2.65; VM basalt: -3.24). The bulk composition of the magma was gradually depleted in MgO and enriched in FeOt, TiO2, P2O5, and Na2O with progressive fractionation, the basalts were gradually enriched in Y and Zr and depleted in Ni and Cr. In addition, the ∑REE of magma also increased with fractionation, without any change in the (La/ Yb)N value. Glass from the VM seamount shows more fractionated characters (Mg#: 0.56-0.57) compared to the outer ridge flank lava of the VT area (Mg#: 0.63-0.65). This study concludes that present basalts experienced low-pressure crystallization at a relatively shallow depth. The geochemical changes in the NCIR magmas resulted from fractional crystallization at a shallow depth. As a consequence, spinel was the first mineral to crystallize at a pressure 〉10 kbar, followed by Fe-rich olivine at 〈10 kbar pressure. 展开更多
关键词 mineral chemistry fractional crystallization PETROGENESIS northern central Indian ridge
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Geochemical Characteristics of a Carbonatite Dyke Rich in Rare Earths from Bayan Obo, China 被引量:1
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作者 杨学明 杨晓勇 +2 位作者 陈天虎 张培善 陶克捷 《Journal of Rare Earths》 SCIE EI CAS CSCD 2000年第1期1-8,共8页
The whole-rock geochemistry of a rare earths rich carbonatite dykes that locates at Dulahala and lies 3 km north-east to the East Ore body of the giant Bayan Obo RE-Nb-Fe deposit was analysed. The dyke cuts cross H1 c... The whole-rock geochemistry of a rare earths rich carbonatite dykes that locates at Dulahala and lies 3 km north-east to the East Ore body of the giant Bayan Obo RE-Nb-Fe deposit was analysed. The dyke cuts cross H1 coarse quartz sandstone and H2 fine quartzite of the Proterozoic Bayan Obo group. RE content in the dyke varies greatly up to 20% (mass fraction), which comprises rich RE ores. Light RE in carbonatites are extremely enriched and strongly fractionated relative to heavy RE, but no Eu anomaly. The carbonatite may be produced by mechanisms as follows: the carbonatite mana is directly formed by very low degree (F <1%) partial melting of enriched lithospheric mantle, leaving residual minerals characterized by abundant garnet; then the magma arises into a chamber within the crust where they will undergo fractional crystallization, which makes RE further concentrated in carbonatite. The RE patterns and spider diagrams of the carbonatite are identical to those fine-grained dolomite marble that is the ore-host rock for the Bayan Obo deposit. However, the carbonatite is calcic, which is different from the fine-grained dolomite marble in major element geochemistry. The difference is suggested to be resulted from that the carbonatite dyke is not affected by a large scale dolomitization, while the fine-grained dolomite marble might be the product of dolomitized carbonatite intrusive body that might set up a hydrothermal system in the region, which transported Mg from the Bayan Obo sediments, especially form the shales to the carbonatite intrusion. 展开更多
关键词 rare earths CARBONATITE fractional crystallization hydrothermal fluid Bayan Obo
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Accretion Processes of Oceanic Crust in Slow-spreading Ridges:Plagiogranite Perspective of the Xigaze Ophiolite,South Tibet 被引量:1
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作者 LI Yuan LI Ruibao +2 位作者 YANG Shengbiao ZHANG Jian YANG Jingsui 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2022年第6期1945-1959,共15页
Structural and petrological data suggest that the Xigaze ophiolite from the Yarlung Zangbo Suture Zone(YZSZ)in south Tibet was a typical slow-spreading ridge.A new field,geochemical,mineral,and U-Pb zircon dataset of ... Structural and petrological data suggest that the Xigaze ophiolite from the Yarlung Zangbo Suture Zone(YZSZ)in south Tibet was a typical slow-spreading ridge.A new field,geochemical,mineral,and U-Pb zircon dataset of plagiogranite intrusions were used to constrain the dynamic processes of oceanic accretion in this slow-spreading ridge.Plagiogranites mainly occur as dykes or intrusions intruded into the whole sequence of the ophiolite and have a similar orientation to the dolerite dykes developed in the late stage of detachment faulting.U-Pb zircon ages of 122–123 Ma were obtained for two types of plagiogranites and associated dolerite dykes.Detailed geochemical and mineralogical examinations suggest that the plagiogranites are the product of low-pressure(2–3 kbar)fractional crystallization of midocean ridge basalt-like magma and unlikely to have been derived from the partial melting of hydrous gabbroic rocks.The complex cross-cut relationship between the plagiogranites and ophiolite sequence reflects that they are controlled by small discontinued melt lenses rather than a big magma chamber under the ridge axis and reveals multiple injections during the oceanic crust accretion.The formation of plagiogranites possibly reflects the complex characteristic of oceanic accretion at slow-spreading ridges,time-dependent on structural(external)and magmatic(internal)processes. 展开更多
关键词 Xigaze ophiolite PLAGIOGRANITE fractional crystallization multiple magma injection ocean-continent transition zone
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Discovery of Enclaves from Cenozoic PuluVolcanic Rocks in West Kunlun Mountains and ItsGeological Implications 被引量:1
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作者 Zhang Zhaochong Xiao Xuchang Wang Jun Wang YongInstitute of Geology , Chinese Academy of Geological Sciences, Beijing 100037 《Journal of China University of Geosciences》 SCIE CSCD 2002年第1期30-34,共5页
In this paper, we present the occurrence and mineral components of the enclaves firstly discovered in the Cenozoic Pulu volcanic rocks in west Kunlun Mountains, and propose that the enclave is accumulated by fractiona... In this paper, we present the occurrence and mineral components of the enclaves firstly discovered in the Cenozoic Pulu volcanic rocks in west Kunlun Mountains, and propose that the enclave is accumulated by fractional crystallization within high-level magma chamber. In addition, the chemical compositions of its primary magma are calculated. The calculated compositions are similar to those of the Kangxiwa volcanic rocks that belong to the same volcanic belt in the Pulu volcanic region, suggesting their origin from the same source region. However, the temperatures and oxygen fugacity of magmas at high-level magma chamber decreased along with fractional crystallization. 展开更多
关键词 ENCLAVE fractional crystallization volcanic rocks West Kunlun Mountains.
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Mineralogy and Magmatic Processes of Cenozoic Intraplate Alkaline Volcanic Rocks of Bafang and Its Environs (Cameroon Volcanic Line, West Africa) 被引量:1
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作者 Nicaise Blaise Tchuimegnie Ngongang Merlin Patrick Njombie Wagsong +6 位作者 François Mvondo Owono Innocent Badriyo Philippe Essomba Natalie Love Ngongang Tchikankou Dieudonné Youmen Pierre Kamgang Gilles Chazot 《Open Journal of Geology》 2021年第6期210-238,共29页
Alkaline basalts of Bafang and its environs are consisted of feldspars, olivines, pyroxenes and oxides which appear as phenocrysts, microphenocrysts and microcrysts. Feldspars are plagioclases (An<sub>67.97-15.8... Alkaline basalts of Bafang and its environs are consisted of feldspars, olivines, pyroxenes and oxides which appear as phenocrysts, microphenocrysts and microcrysts. Feldspars are plagioclases (An<sub>67.97-15.84</sub>Ab<sub>69.19-30.43</sub>Or<sub>20.59-1.51</sub>) and anorthoclases (Ab<sub>68.11-61.20</sub>Or<sub>33.87-20.91</sub>An<sub>10.98-4.93</sub>). Plagioclases are the most abundant amount these feldspars. Anorthoclases appear only in mugearite (BAF 3 and BAF 37) the most differentiated of the studied alkaline-basalts. In High Magnesian basalt, (HMg-B) plagioclases are labradorites (An<sub>67.97-59.3</sub><sub>0</sub>Ab<sub>38.74-30.43</sub>Or<sub>2.75-1.60</sub>) and sanidine (An<sub>45.44-31.82</sub>Ab<sub>62.66-51.79</sub>Or<sub>5.52-2.77</sub>), whereas in Low Magnesian basalt (LMg-B) there are labrador (An<sub>67.4.75-51.96</sub>Ab<sub>44.98-33.72</sub>Or<sub>3.06-1.51</sub>), andesine (An<sub>45.44-31.82</sub>Ab<sub>62.66-51.79</sub>Or<sub>5.52-2.77</sub>), oligoclase (An<sub>26.65-15.84</sub>Ab<sub>69.19-63.57</sub>Or<sub>20.59-8.55</sub>) and anarthoclase (Ab<sub>68.11-61.20</sub>Or<sub>33.87-20.91</sub>An<sub>10.98-4.93</sub>). Olivines are magnesian (Fo<sub>86.7-50.1</sub>) and ferriferous (Fo<sub>48.8-37.8</sub>). In HMg-B, olivine are only magnesian. These olivines are chrysolites and hyalositerite. In LMg-B, olivines are magnesian and ferriferous with the predominance of ferriferous. They are chrysolites, hyalositerite and hortonolite. Pyroxenes are Ca, Mg and Fe clinopyroxenes. There are diopsides (Wo<sub>51.94-45.02</sub>En<sub>44.41-33.16</sub>Fs<sub>16.42-10.70</sub>) and augites (Wo<sub>44.88-43.64</sub>En<sub>41.03-37.04</sub>Fs<sub>18.25-14.43</sub>). Oxides are magnetites represented by ulvospinel (Usp<sub>90-75</sub>Sp<sub>2-7</sub>Mt<sub>5-23</sub>). Fractionation of ferromagnesian minerals (opaque oxide, olivine and pyroxene) is the main differentiation process. Two stages of fractional crystallization can be distinguished: the first stage comes with basanites and the second with hawaiites to mugearites. Chemical compositions of phenocrystals in studied basaltics lavas record signatures of magma recharge by pulsatory intrusions of new magma into the existing magma reservoir before the eruptions. 展开更多
关键词 Cameroon Volcanic Line Bafang Alkaline Basaltic Lavas fractional crystallization Magma Recharge
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Geochemistry and petrogenesis of Rajahmundry trap basalts of Krishna-Godavari Basin,India 被引量:1
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作者 C.Manikyamba Sohini Ganguly +2 位作者 M.Santosh Abhishek Saha G.Lakshminarayana 《Geoscience Frontiers》 SCIE CAS CSCD 2015年第3期437-451,共15页
The Rajahmundry Trap Basalts (RTB) are erupted through fault-controlled fissures in the Krishna-Godavari Basin (K-G Basin) of Godavari Triple Junction, occurring as a unique outcrop sandwiched between Cretaceous a... The Rajahmundry Trap Basalts (RTB) are erupted through fault-controlled fissures in the Krishna-Godavari Basin (K-G Basin) of Godavari Triple Junction, occurring as a unique outcrop sandwiched between Cretaceous and Tertiary sediments along the east coast of India. Detailed geochemical studies have revealed that RTB are mid-Ti (1.74-1.92) to high-Ti (2.04-2.81) basalts with a distinct quartz tholeiitic parentage. MgO (6.2-13.12 wt.%), Mg# (29-50) and Zr (109-202 ppm) suggest that these basalts evolved by fractional crystallization during the ascent of the parent magma along deep-seated fractures. Mod- erate to high fractionation of HREE, as indicated by (Gd/Yb)N ratios (1.71-2.31) of RTB, suggest their generation through 3-5% melting of a Fe-rich mantle corresponding to the stability fields of spinel and garnet peridotite at depths of 60-100 km. Low K2O/P2O5 (0.26-1.26), high TiO2/P2O5 (6.74-16.79), La/Nb (0.89-1.45), Nb/Th 〉 8 (8.35-13), negative anomalies at Rb reflect minimum contamination by granitic continental crust. (Nb/La)PM ratios (0.66-1.1) of RTB are attributed to endogenic contamination resulted through recycling of subducted oceanic slab into the mantle. Pronounced Ba enrichment with relative depletion in Rb indicates assimilation of Infra- and Inter-trappean sediments of estuarine to shallow marine character. Geochemical compositions such as A1203/TiO2 (3.88-6.83), medium to high TiO2 (1.74 -2.81 wt.%), positive Nb anomalies and LREE enrichment of these RTB attest to their mantle plume origin and indicate the generation of parent magma from a plume-related enriched mantle source with EM 1 signature. Ba/Th (46-247), Ba/La (3.96-28.51) and Th/Nb (0.08-0.13) ratios suggest that the source enrichment process was marked by recycling of subduction-processed oceanic crust and lithospheric components into the mantle. Zr/Hf (37-41) and Zr/Ba (0.51-3.24) indicate involvement of an asthenospheric mantle source. The Rajahmundry basalts show affinity towards FOZO (focal zone mantle) and PSCL (post-Archaean subcontinental lithosphere) which reflect mixing between asthenospheric and lithospheric mantle components in their source. Origin of RTB magma is attributed to plume-lithosphere interaction and the upward movement of melt is facilitated by intrabasinal deep-seated faults in the K-G Basin. 展开更多
关键词 Rajahmundry Trap Basalts (RTB) Fault-controlled fissures fractional crystallization Enriched mantle source Plume-lithosphere interaction
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