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辽西北票四合屯地区义县组高镁火山岩的稀土、微量元素特征及启示 总被引:7,自引:1,他引:7
辽西北票四合屯地区的义县组火山岩主要由高镁火山岩组成,其在稀土、微量元素特征方面有明显的特殊性。首先,具有高Mg^#,高相容元素含量的特点,反映了火山岩有明显的幔源岩浆的特征。同时该火山岩也具有明显的壳源物质的特征:稀土元素总量较高、稀土元素的分馏程度较高,高La/Nb,Ba/Nb比值;在蛛网图中击现为明显的Nb,Ta负异常和Pb正异常;在Sr-Nd-Ph同位素方而,(^87Sr/^86sr),的值较高,εNd(t)值区范围较大,显示出富集地幔的组分特征;结合该火山岩Sr,Ba,Y,Yb的古量,Sr/Y比值的分析,该高镁火山岩具有日本Setouchi岛弧的Sanukite火山岩的特征;说明了Sanukite不仅分布在板块边缘俯冲带附近的岛弧区,在板块内部也可同样存在。分析表明:该地区高镁火山岩是幔源岩浆和地壳物质共同作用的结果。说明辽西地区在早白垩世具有特殊的构造地球化学背景,在中国东部地区中生代火山岩的形成中具有特殊性,是进一步研究中国东部岩浆作用的特点,探讨壳-幔演化(物质交换)具体进程的理想研究地区。 相似文献
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浙东南山门地区早白垩世同源岩浆活动的稀土元素制约 总被引:1,自引:0,他引:1
对浙东南山门地区早白垩世中酸性火山-侵入杂岩进行了稀土元素含量的ICP-MS分析,对比研究了其稀土元素地球化学特征。不同类型岩浆岩的稀土元素除Eu外具有基本一致的轻稀土富集的右倾配分模式,以及稳定的Sm/Nd,La/Nd和La/Sm比值,表明它们具有一致的岩浆源区,只是分异演化程度不同。Eu/Sm比值(0.02~0.09和0.15~0.21)及一致的Nb/Ta比值(13.9~16.9),介于地壳和地幔值之间,表明其为壳幔岩浆混合作用的产物。稀土元素协变关系显示成岩过程可能以部分熔融作用为主。结合微量元素研究,山门地区早白垩世同源岩浆活动可能与古太平洋板块俯冲碰撞后岩石圈伸展引起的弧后引张构造有关。 相似文献
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本文依据攀枝花-西昌裂谷四十几个火成岩的主要元素、过渡金属元素、稀土元素和其他微量元素的分析结果,探讨了这些岩石的成因和岩浆过程。从主要元素成分来看,明显地显示出双众数岩套的特征。过渡金属元素显示了Cr和Ni的强烈亏损与Ti的明显富集,反映了复杂的结晶分离作用历史。所有岩石的稀土元素分配型式都是富集型的,暗示出原始岩浆可能来自原始地幔的低程度部分熔融,玄武岩的亲石岩浆元素丰度经原始地幔值标准化后的分配型式,显示出一种介于碱性玄武岩与大陆拉斑玄武岩之间的图形,这支持了它们的裂谷大地构造环境,也暗示了原始岩浆来自深处的原始地幔区,可能是石榴二辉橄榄岩部分熔融的产物。 相似文献
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辽宁宽甸黄椅山玄武岩REE及Sr,Nd,Pb同位素组成研究 总被引:4,自引:0,他引:4
通过主元素、矿物化学、REE及同位素体系的研究,根据郯庐断裂两侧新生代火山岩的同位素组成有差异的事实,指出由于太平洋板块的俯冲使源区产生壳、幔物质的混合作用和交代作用是导致这种变异的主要原因。交代型超镁铁岩捕虏体含有金云母和韭闪石,为地幔交代作用提供了实物证据。 相似文献
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新疆萨吾尔地区二叠纪火山岩成岩机制:来自稀土元素的约束 总被引:5,自引:1,他引:5
新疆萨吾尔地区发育大量二叠纪火山岩。通过研究该火山岩的稀土元素特征,并利用稀土元素与常量元素相关关系以及稀土元素协变关系判别图解,结合其区域地质背景和岩石学、岩石化学特征,判断该地区二叠纪基性、中性火山岩成岩过程以平衡部分熔融作用为主,分离结晶作用不明显,而中酸性火山岩成岩过程则受到部分熔融作用和分离结晶作用的共同影响。稀土元素地球化学研究为新疆准噶尔地区二叠纪后碰撞阶段的岩浆作用机理及地球动力学演化过程提供了重要证据。 相似文献
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苏丹哈佳吉金矿床成矿物质来源的微量元素地球化学特征 总被引:1,自引:0,他引:1
通过对主要微量元素数据的多元统计分析,探讨了该地区金矿的成矿物质来源.结果表明,成矿物质主要来源于洋壳向陆壳俯冲时产生的增生楔,地幔主要提供热源,并有少量物质参与;有效区分了不同类型的矿石和围岩,并分辨出了具过渡性质的蚀变围岩;对稀土元素的分析表明,除氧化矿石外,其它矿石的成矿物质来源应该是一致的. 相似文献
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西藏多不杂铜矿床稀土元素地球化学特征研究 总被引:1,自引:0,他引:1
探讨稀土元素地球化学对多不杂铜矿床成矿物质及流体来源的指示意义。选择相关岩矿石及金属矿物样品,测试其稀土元素组成。研究表明,岩矿石及金属矿物均具有轻稀土富集的特征,这是地幔流体作用成矿的标志。由磁铁矿→浸染状黄铁矿→脉状黄铁矿→黄铜矿演化,δEu值逐步从大于1过渡为小于1,即由正铕异常→负铕异常演化,这是含矿地幔流体作用导致熔浆→热液演化,引发交代蚀变,促使壳幔物质混染叠加成矿的依据。从花岗闪长斑岩→变质砂岩→玄武安山岩,总稀土元素呈现出逐步上升的趋势;花岗闪长斑岩和变质砂岩均为含矿地质体,构成了接触带成矿体系,它们的δEu值分别表现为大于1和小于1,即分别呈现出正铕异常和负铕异常;玄武安山岩不含矿,无明显的铕异常。 相似文献
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我国某些富碱侵入岩的稀土元素地球化学 总被引:24,自引:0,他引:24
根据对40个富碱侵入岩体的近300个样品的稀土元素分析,较系统地研究了我国富碱侵入岩的稀土元素组成特征,分析了控制稀土元素分布的主要因素。根据稀土元素、微量元素组合及Sr,Nd同位素组成特征,探讨了富碱侵入岩的源区物质和成岩过程,用部分熔融、多阶段分离结晶和分离结晶混染模型计算了紫金山、赛马、碾子山、山海关等富碱侵入岩的成岩模型。 相似文献
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富蕴县阿克塔斯铜金矿床火山岩地球化学 总被引:2,自引:0,他引:2
阿克塔斯铜金矿区位于新疆富蕴县内,矿区主体位于东准噶尔北部,靠近阿尔泰与北准噶尔两个具有不同构造特征和演化历史的构造单元。阿克塔斯金铜矿体主要赋存于石英脉、斜长花岗岩、蚀变安山岩及接触带内的千枚岩破碎带中。根据安山岩的微量元素分配模式的研究发现,岩浆在演化的过程中有大陆地壳的物质加入其中并进行混染。通过对含矿石英脉中黄铁矿和黄铜矿中的硫进行同位素分析,表明黄铁矿、黄铜矿中硫可能都来源于地幔。矿区区域地球化探异常发育,金、铜、砷元素含量高、相关性好,并与火山―岩浆岩有密切空间关系,是寻找评价与火山岩以及浅成岩有关铜金矿的有利地段。 相似文献
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A lot of granitoid rocks occur in Panxi area, SW China, which were formed during Jinningnian-Chengjiangnian, Hercynian-Indosinian and Yenshanian. According to their trace elements geochemical and petrochemical characteristics, they can be divided into calc-alkaline and alkaline granites. The petrogenesis and magma sources of these granitoid rocks are different. The Jinningnian-Chengjiangnian granitoid rocks include Mopanshan granite body, Moshaying granite body and Lugu granite body. The Mopanshan body might be formed by partial melting of the lower crust and due to refusion of basic volcanic rocks. The magma source of the Moshaying and the Lugu bodies might be formed by partial melting of the upper crust. The Hongge-Ailanghe granites belonging to the Hercynian-Indosinian may be products of complex melting from the crust-mantle materials caused by the increase of temperature during rifting stage in the area. The Cida and Taihe alkaline granites belonging to the Hercynian-Indosinian might be derived from 相似文献
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K. Gméling Sz. Harangi Zs. Kasztovszky 《Journal of Radioanalytical and Nuclear Chemistry》2005,265(2):201-212
Summary Boron and chlorine concentrations in geological standards and in representative volcanic rock samples were determined by prompt gamma activation analysis (PGAA). The results of the GSJ standard measurements proved the high precision of PGAA in measuring the boron, chlorine, other trace elements (Sc, Nd, Sm, and Gd) and the major element contents of the samples. The rock samples originate from the western part of the Northern-Pannonian Volcanic Field (NPVF), which includes the Central Slovakian Volcanic Field (CSVF), the Börzsöny and the Visegrád Mts. (VMt.). The oldest 16-13.5 Ma samples as the first products of the Miocene calc-alkaline volcanism are the most enriched in B (11-29 µg/g), whereas the primitive basaltic andesites (from CSVF), the latest products (9 Ma) of the volcanic activity have lower B content (8-9 µg/g). The measured B concentrations correlate positively with fluid-mobile elements, and the trace element pattern of the samples show subduction related signatures. The chlorine content of the investigated samples shows wide variation between 42.62 and 1148.45 µg/g. The 9 Ma samples from the CSVF show Cl contents between 150-160 µg/g. In agreement with the latest geodynamic models of the Neogene calc-alkaline volcanism1,2 in the NPVF during the shallow, prograding subduction, the fluid-mobile elements metasomatized the mantle wedge. Thus the oldest volcanic rocks have relatively higher B (>11 µg/g) and high but variable Cl contents. As the subduction waned and extension proceeded, the magma generation region changed to a not thoroughly metasomatized mantle by the former subduction event, resulting in lower B, low and stable Cl content of the younger (9 Ma) volcanic rocks. 相似文献
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S. Niese B. Gleisberg W. Kramer L. Pfeiffer C. -D. Werner 《Journal of Radioanalytical and Nuclear Chemistry》1988,122(2):253-259
With the help of NAA a number of trace elements were determined in ultrabasic rocks, xenolithes of alkali basalts, basalts, phonolites and pyroxene inclusions in phonolites from the South of the GDR. The formation of the investigated magmatites were explained by metasomatism, partial melting and fractionated crystallization in the earth mantle. 相似文献
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Hossain Md Anawar Maria do Carmo Freitas Nuno Canha Isabel Dionísio Ho Manh Dung Catarina Galinha A. M. G. Pacheco 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(3):377-381
Native plant species, lichens and tailings, sampled from a copper?Csulphide mining area located in southern?Ceastern Portugal, were analysed by neutron activation analysis (INAA) for determination of rare earth elements (REEs). Values of ??REEs and individual REEs concentration of tailing samples are higher than those of natural background concentrations. The higher values of REEs are found in modern slags and the mixture of oxidized gossan and sulphide disseminated country rocks when compared with the alluvial sediments contaminated by mine tailings. The total concentrations of light REEs are higher than those of heavy REEs in all tailing samples. Distribution patterns of PAAS-normalized REEs in mine tailings show slightly LREE enriched and flat HREE pattern with negative Eu anomaly. Lichens accumulated higher concentration of lanthanides than vascular plants. The elevated levels of REEs in lichen, native plant species and tailing samples reflect the contamination of REEs in S?o Domingos mining area. The Carlina corymbosa, Erica australis and Lavandula luisierra accumulated the higher amounts of La, Ce and other REEs than the other plant species grown in this mining area. 相似文献