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1.
Composite dykes consisting of leucominette and dacite as wellas discrete dykes and flows of minette and lamproite composition,occur in the Veliki Majdan area, western Serbia. This area ispart of the Serbian Tertiary magmatic province, which consistsof numerous small occurrences of ultrapotassic igneous rocks.The composite dykes have leucominette margins (up to 150 cmthick) enclosing a central part of dacite up to 100 m in width.Between these two lithologies, a decimetre-sized transitionzone may occur. Petrography, mineral chemistry and bulk-rockgeochemistry, including Sr, Nd and Pb isotopes, provide evidencethat the minettes and leucominettes formed by hybridizationbetween a felsic magma similar in composition to dacite anda mantle-derived lamproitic magma. The leucominettes and minettescontain all phenocryst types (biotite, plagioclase, quartz)present in the dacites, but in partly resorbed and reacted form.The mica displays a great diversity of resorption textures asa result of partial dissolution, incipient melting and phlogopitization,suggesting superheating of the felsic melt during hybridization;the mineral modes and mineral compositions of the leucominettesand minettes resemble those in the lamproites. A model for themodification of lamproite melt towards minette is presentedin which minette is formed by mixing of lamproite and <30%felsic magma. The lack of any significant correlation betweenPb isotopic ratios and some of the ‘mixing-indices’(SiO2, Zr, Zr/Nb, 143Nd/144Ndi) recognized in the hybridizationmodel for the Veliki Majdan dykes may be a result of similarityof the Pb-isotopic signature in the two end-members. Highlyphlogopitized biotite xenocrysts in the minettes are ascribedto the retention of volatile components after magma mixing andcrystallization of a new generation of phlogopite from the hybridizedmagma. The magma-mixing model explains the reverse zoning andresorption features of phlogopite macrocrysts commonly recognizedin calcalkaline lamprophyres elsewhere. Therefore, this mixingmechanism may be globally applicable for the origin of minettesassociated with calcalkaline granitic plutonism in post-orogenicsettings. KEY WORDS: Serbia; lamproites; micas; phlogopitization; calcalkaline lamprophyres; superheating; magma mixing 相似文献
2.
云南老王寨金矿煌斑岩地球化学研究中的某些问题──与宋新宇等同志商榷 总被引：2，自引：0，他引：2
本文对“云南老王寨金矿煌斑岩地球化学研究”一文中的部分结论及其解释，提出一些不同意见与原文作者宋新宇等先生商榷 相似文献
3.
幔源岩浆活动过程中的去气作用
——以云南老王寨金矿煌斑岩为例 总被引：7，自引：2，他引：7
黄智龙 《矿物岩石地球化学通报》2001,20(1):1-5
本文以云南老王寨金矿煌斑岩为例，从岩石产出的构造环境、源区地幔交代富集作用、岩浆演化中硅酸盐熔体-碳酸盐熔体液态不混熔作用、岩石中CO 相似文献
4.
云南老王寨金矿区煌斑岩的成因：稀土元素研究 总被引：6，自引：0，他引：6
云南老王寨金矿区煌斑岩与金矿化在时间上、空间上密切共生。主要元素分析表明，本区煌斑岩属钾质－富钾质钙碱性煌斑岩；与原始地幔和大洋中脊玄武岩相比，岩石相对富集稀土元素；模拟计算表明，岩石来源于稀土元素相对富集的交代富集地幔；地质发展史、不相容元素分配型式、Ｓｒ、Ｎｄ同位素组成及有关模拟计算表明，俯冲进入地幔楔的地壳物质脱水 流体是引起该区地幔交代作用的主要因素。 相似文献
5.
老王寨金矿煌斑岩稀土元素含量较高，平均约为１６０×１０￣（－６），稀土配分模式表现为轻稀土富集、重稀土亏损，且具有铕的负异常。地幔标准化的过渡元素分配型式呈“Ｗ”型，同中国东部碱性玄武岩相似。此外，煌斑岩中Ｃｒ，Ｎｉ含量高，以上都表明煌斑岩为地幔成因，是地幔部分熔融的产物。原生岩浆在演化分异的早期有铬尖晶石、橄榄石、黑云母及斜长石的结晶。煌斑岩中Ｂａ，Ｔｈ，Ｋ，Ｓｒ及稀土元素较高，而Ｎｂ，Ｐ呈明显亏损，表明岩浆上升过程中受到一定程度的壳层物质混染。 相似文献
6.
云南老王寨金矿区煌斑岩中碳酸盐的化学成分及其意义 总被引：3，自引：0，他引：3
本文报道了云南老王寨金矿区非矿化、矿化煌斑岩中不同产状碳酸盐的化学成分，结果表明本区煌斑岩中为次生碳酸盐，原生碳酸盐含量不超过１％；煌斑岩蚀变、矿化为不同阶段的产物；碳酸盐脉活动发生在成矿作用之后。 相似文献
7.
扬子地台西缘钾质煌斑岩类的岩石学研究 总被引：3，自引：0，他引：3
扬子地台西缘钾质煌麻岩的矿物组合中缺少钾碱镁门石、柱红石等富钾贫铝矿物，其辉石和白榴石富Ａｌ２Ｏ３，金云母贫ＴｉＯ２，透长石的Ｎａ２Ｏ含量高。全岩Ａｌ２Ｏ３高，Ｋ２Ｏ／Ａｌ２Ｏ３（＜０．７）低，（Ｇｄ／Ｙｂ）Ｎ低。岩体中含有二辉橄榄岩包体、镁铝榴石捕虏体晶。这些特点表明其岩浆源区的亏损程度低。此外，钾质煌斑岩明显亏损Ｎｂ、Ｔｉ，可能是与其源区经受过板块边缘活动影响有关。 相似文献
8.
《International Geology Review》2012,54(8):913-928
ABSTRACTLate Jurassic ultramafic lamprophyre (UML) sills and dikes occur as 3 km-long intrusions within the allochthonous Whara Formation of the Batain nappes, eastern Oman. The sills and dikes comprise macrocrystic phlogopite and spinel-bearing aillikite and damtjernite. Aillikite is a light grey, massive fine-grained tuffaceous rock with euhedral laths of mica, while damtjernite is a dark grey, medium- to coarse-grained rock with abundant pelletal lapilli and globular segregationary textures. Both lithologies are composed of calcite, phlogopite, apatite, magnetite, spinel, diopside, and richterite. Orthoclase occurs only within damtjernite. The rocks are strongly silica undersaturated (17.6–33.7 wt.% SiO2), with low MgO (4.7–10.2 wt. %) and high Al2O3 (3.5–8.6 wt.%). The aillikites are distinguished from the damtjernites by their lower SiO2, Al2O3, and Na2O abundances, and their higher MgO, CaO, and P2O5 contents. The rare earth element (REE) patterns of both rock types are similar and show strong light REE (LREE) enrichment. Both are enriched in Ba, Th, U, Nb, and Ta, with normalized concentrations of up to 1000 times those of primitive mantle. Relative depletions are apparent for high REE (HREE), K, Rb, Pb, Sr, P, Zr, and Hf. The rocks have initial 87Sr/86Sr ratios of 0.70435–0.70646, whereas initial 143Nd/144Nd ratios vary between 0 · 512603 and 0 · 512716 (εNdi 2.6–3.2). Pb isotopic ratios are more varied among the aillikites and damtjernites: 208Pb/204Pbi = 38.97–39.39 and 207Pb/204Pbi = 15.35–15.58, 206Pb/204Pbi = 18.08–18.96. The abundance of phlogopite, apatite, and rutile and enrichment in LREEs, Ba, Th, U, Nb, and Ta in the Sal UMLs suggest metasomatic enrichment of these rocks following a low degree of partial melting of a depleted source region. Ar–Ar age dating of phlogopite macrocrysts from the aillikites and damtjernites (154 and162 Ma, respectively) correlates with large-scale tectonic events recorded in the proto-Indian Ocean at 140–160 Ma. 相似文献
9.
Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation. 相似文献
10.
Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation. 相似文献