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1.
R. A. Oktyabrsky A. A. Vrzhosek A. M. Lennikov T. A. Yasnygina S. V. Rasskazov E. Yu. Moskalenko T. A. Velivetskaya 《Russian Journal of Pacific Geology》2008,2(4):325-335
New geochemical data are presented on the magmatic rocks of the Late Jurassic Koksharovka alkaline-ultrabasic massif, which is associated with deposits of vermiculite, apatite, V-bearing titanomagnetite, and placer isoferroplatinum. The REE geochemistry and strontium, oxygen, and carbon isotopic composition of carbonatites and related ijolites and pyroxenites, together with geological observations, point to the magmatic origin of the Koksharovka carbonatites. The origin of associated magmatic rocks is discussed. Trace element modeling of partial melting of mantle sources was conducted to decipher the genesis of the melts of the Koksharovka carbonatites and host titanite-kaersutite pyroxenites. 相似文献
2.
碳酸岩Sr、Nd、Pb 同位素地球化学研究评述 总被引：3，自引：0，他引：3
碳酸岩是出露相对较少的幔源岩石，其中Sr与Nd是研究地幔物质组成的主要对象之一。本文统计了世界上主要碳酸岩的锶、钕、铅同位素组成特征；研究显示，碳酸岩源区主要是洋岛玄武岩高U／Pb的HIMU端员和富集端员(EM1或EM2)的混合作用；此外大部分碳酸岩的锶、钕同位素落在大洋玄武岩范围内；这些均表明其成因与地慢柱有密切联系。碳酸岩及与之共生的硅酸岩的同源或独立源区模式部很难充分解释两者同位素组成特征，逭反映碳酸岩的演化模式涉及更复杂的过程。可能是俯冲作用使碳酸岩源区经历不同时间和程度的富集、亏损过程导致地幔源区成分不均一。 相似文献
3.
鲁西地区中生代碳酸岩类的微量元素和锶、钕同位素组成特征 总被引：9，自引：0，他引：9
对鲁西地区早白垩纪的碳酸岩岩体的稀土、微量元素和同位素组成的研究表明 ,鲁西碳酸岩不同于任何沉积成因的灰岩和变质成因的大理岩 ,而与世界典型的幔源碳酸岩具有相似的稀土元素组成 ,说明其为幔源成因 ,碳酸岩极度富集轻稀土元素。鲁西碳酸岩的锶、钕同位素组成表明其地幔源区为具有EMI和EMII端元混合特征的富集地幔。 相似文献
4.
The In Ouzzal granulitic unit (IOGU) consists predominantly of felsic orthogneisses most of which correspond to granitoids emplaced during the Archaean, plus metasediments, including olivine-spinel marbles, of late Archaean age. All units were metamorphosed at granulite facies during the Eburnean (2 Ga). The stable isotope signature of the marbles (δ13C=–0.8 to –4.2‰/PDB; δ18O = 7.9 to 18.9‰/SMOW) does not record a massive streaming of C-bearing fluids during metamorphism. Most of the isotopic variation in the marbles is explained in terms of pregranulitic features. Metasomatic transformation of granulites into layered potassic syenitic rocks and emplacement of carbonate veins and breccias occurred during retrogressive granulite facies conditions. The chemistry of these rocks is comparable with that of fenites and carbonatites with high contents of (L)REEs, Th, U, F, C, Ba and Sr but, with respect to these elements, a relative depletion in Nb, Ta, Hf, Zr and Ti. The isotopic compositions of Nd (?Nd(T)=–6.3 to –9.9), of Sr (87Sr/86Sr(T)= 0.7093–0.7104), and the O isotopic composition of metasomatic clinopyroxene (δ18O = 6.9 to 8‰), all indicate that the fluid had a strong crustal imprint. On the basis of the C isotope ratios (δ13C =–3.5 to –9.7‰), the fluid responsible for the crystallization of carbonates and metasomatic alteration is thought to be derived from the mantle, presumably through degassing of mantle-derived magmas at depth. Intense interaction with the crust during the upward flow of the fluid may explain its chemical and isotopic signatures. The zones of metasomatic alteration in the In Ouzzal granulites may be the deep-seated equivalents of the zones of channelled circulation of carbonated fluids described at shallower levels in the crust. 相似文献
5.
碳酸岩与铂族元素地球化学 总被引：1，自引：1，他引：0
碳酸岩（carbonatite）被视为一种研究大陆地幔地球化学的“探针岩石”,通过对这类岩石的研究,在探讨地幔组成与演化、地幔交代作用与不均一性以及岩浆形成的动力学背景、岩浆来源及演化和有关矿产的成矿作用等方面,具有重要的理论意义和实际价值。铂族元素（Platinum—group elements,简称PGE）在研究核-幔分异、地幔组成与演化以及幔源岩石（主要为基性-超基性岩）形成的大地构造背景、岩浆起源及演化,以及探讨K／T界线与陨石撞击事件等方面具有重要意义。本文在概述国内外碳酸岩和PGE地球化学研究现状的基础上,结合地质事实和地球化学研究成果,认为碳酸岩熔体具有一定携带PGE的能力,可利用PGE地球化学来探讨碳酸岩的源区特征和岩浆形成与演化过程;同时指出,碳酸岩PGE地球化学研究过程中还存在许多悬而未决的科学问题。 相似文献
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7.
《International Geology Review》2012,54(12):1541-1552
The Mt Vulture carbonatites are the only carbonatite occurrence in the southern Apennines. We present new trace element data for these rocks in order to evaluate the factors influencing rare earth element (REE) and other trace element fractionations and their REE grade. This study focuses on massive hyalo-alvikites from two lava flows and one dike, which have different relative abundances of silicate and carbonate (i.e. Si/Ca). These differences are also evident from CaO/(CaO + MgO + FeO(T) + MnO) and Sr/Ba ratios. The REE grade of the Mt Vulture carbonatites is very similar to that of the global average for calcio-carbonatites. R-mode factor analysis shows that most of the trace element variance reflects the relative roles of carbonate and silicate minerals in influencing trace element distributions. Silicates largely control heavy rare earth element (HREE), transition metal, Zr, and Th abundances, whereas carbonate minerals control light rare earth element (LREE), Ba, and Pb abundances. In addition, apatite influences LREE concentrations. Increasing silica contents are accompanied by decreases in (La/Yb)N and (La/Sm)N ratios and less marked LREE enrichment. In contrast, higher carbonate contents are associated with increases in (La/Yb)N and (La/Sm)N. The Si/Ca ratio has little influence on Eu anomalies and middle rare earth element (MREE) to HREE fractionations. Apatite has a negligible effect on inter-REE fractionations amongst the carbonatites. 相似文献
8.
土库曼斯坦萨曼杰佩气田卡洛夫-牛津阶碳酸盐岩沉积-成岩系统 总被引：2，自引：0，他引：2
以土库曼斯坦阿姆河盆地萨曼杰佩气田主力油、气产层卡洛夫-牛津阶碳酸盐岩为例,根据沉积相、成岩作用方式、成岩演化序列和相对应的地质作用产物特征,综合研究Fe、Mn、Sr微量元素,C、O、Sr稳定同位素,流体包裹体和阴极发光等地球化学特征反映的成岩环境和成岩流体性质。按"水文体制"将卡洛夫-牛津阶划分为不同成岩阶段的海水-淡水、压实卤水和深循环温压水3个成岩系统,认为沉积-成岩系统与储层在时空上具有良好的耦合关系,可归结为:台地边缘生物礁和浅滩相控制了储层的区域分布;早成岩阶段淡水系统溶蚀作用和压实卤水成岩系统的浅埋藏白云岩化作用是形成储层的基础;中成岩阶段的温压水成岩系统埋藏溶蚀作用、中-深埋藏白云石化作用和构造破裂作用扩大了储层规模,提高了储层质量,对优质储层发育贡献最大。 相似文献
9.
V. K. Popov S. O. Maksimov A. A. Vrzhosek V. M. Chubarov 《Russian Journal of Pacific Geology》2007,1(4):371-389
Geological-petrological data were first obtained on the Early Miocene basaltoids and spinel-fassaite carbonatite tuffs of the Ambinsky volcanic structure in southwestern Primorye. The geological study of Ambinsky volcano allowed the reconstruction of stratigraphic sections across lava and pyroclastic basaltic rocks and stratified carbonatite tuffs. The chemical compositions of rocks and mineral phenocrysts from basalts and carbonatite tuffs are reported. The basaltoids are classed with undifferentiated moderately alkaline within-plate basalts. Evidence of carbonate-silicate immiscibility was found in the basaltoids and carbonatite tuffs. It was suggested that the formation of the carbonatite melt associated with simultaneous basification and abundant crystallization of spinel, fassaite, as well as oversaturation of the silicate system in Ca was caused by limestone assimilation, subsequent transformation of the melt, and liquid immiscibility. Thermal decomposition of carbonates with dissolution of released CaO in magma and accumulation of CO2 in a closed magmatic chamber gave rise to the autoclave gas effect and, correspondingly, heavy explosive eruptions atypical of such volcanic rocks. The genesis of carbonatite tuffs of Ambinsky volcano can serve as a model example of exsolution of carbonate melt in the moderately alkaline nonagpaitic basaltic system. 相似文献
10.
华北克拉通火成碳酸岩时空分布和锶钕同位素特征及其地质意义 总被引：2，自引：0，他引：2
已有的研究得出：华北克拉通火成碳酸岩在时间上主要形成于古元代末—中元古代初、早中生代和晚中生代3个时段,反映了华北克拉通演化历史上3个拉张阶段。在空间上,前两个拉张阶段形成的火成碳酸岩分布在华北克拉通的北缘和南缘;后一个拉张阶段形成的火成碳酸岩分布在克拉通的中部和东部。华北克拉通火成碳酸岩的钕同位素主要特征是εNd(t )全为负值,而且随时间由老到新负值趋于降低。在εNd(t )-I Sr图解上,其投影点都落到了第3和第4象限,除莱芜—淄博地区火成碳酸岩外,其它都在富集地幔演化线附近,而且从老到新富集程度越来越高。推测华北克拉通火成碳酸岩形成的深部动力学机制可能是：在热地幔柱活动或周边板块向华北板块俯冲之后华北克拉通构造环境转变为伸展拉张环境,因压力减小而引起地幔部分熔融形成的碱性基性—超基性岩浆或碱性中性岩浆沿区域深断裂上侵,又经分异作用冷凝结晶形成杂岩体,火成碳酸岩是这些碱性岩浆演化晚阶段的主要产物。部分火成碳酸岩可能是从上地幔低程度部分熔融形成的碳酸岩浆直接上侵冷凝结晶而成。 相似文献