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1.
陕西小花岔铀矿床位于北秦岭造山带的东北部,矿体产于黑云母花岗伟晶岩和黑云斜长片麻岩的接触带同化混染区。为了厘定研究区花岗质岩浆演化与铀矿化作用的关系,对矿区内出露的花岗岩、花岗伟晶岩开展了详细的年代学和岩石地球化学研究。LA-ICP-MS锆石U-Pb定年结果表明:灰池子花岗岩体的形成年龄为(444±4.0)Ma;高山沟花岗岩株的形成年龄为(422±0.82)Ma;产铀黑云母花岗伟晶岩的形成年龄为(417±2.6)Ma;非含矿黑云母花岗伟晶岩的形成年龄为(413±1.8)Ma。地球化学数据表明:矿区花岗质岩石富集大离子亲石元素Rb、Ba、K,亏损高场强元素Nb、Ta。含矿黑云母花岗伟晶岩由于同化混染作用及与围岩的元素交换等原因,其基性组分Fe、Mg和挥发分F-含量较高,同一条黑云母花岗伟晶岩脉元素组成的差异是由于伟晶岩浆的同化分离结晶所致,在伟晶岩-黑云斜长片麻岩的接触带发生化学组分的元素交换,使得伟晶岩浆中U-F络合物发生分解,并且在良好的成矿条件下(围岩的铀含量较高、较好的构造环境)使得铀饱和沉淀形成铀矿物,如晶质铀矿等。小花岔铀矿床的形成主要受到了伟晶岩浆、围岩成分、岩浆热液中挥发分共同的作用,最终导致了铀矿床的形成。  相似文献   

2.
为探讨广西岑溪地区糯垌岩体及其岩石包体的成因,对糯垌岩体的岩石包体进行详细的岩相学、LA—ICP—MS锆石U—Pb年代学和地球化学分析。岩相学研究表明糯垌岩体的岩石包体主要为斑状黑云母钾长花岗岩、黑云斜长片麻岩、黑云二长片麻岩、二长变粒岩、钾长变粒岩和花岗闪长岩,按成因分为捕掳体和残浆包体两类。斑状黑云母钾长花岗岩包体(样品F16—7—6)和黑云斜长片麻岩包体(样品F16—13—4)的LA—ICP—MS锆石U—Pb定年结果分别为(152. 3±2. 2) Ma和(252. 7±4. 4)Ma;斑状黑云母钾长花岗岩与寄主岩石形成时代一致,黑云斜长片麻岩与大冲花岗闪长岩的侵位时代一致。岩石包体和寄主岩石在hark图解、稀土元素配分曲线和微量元素蛛网图中具有相似的演化趋势,表明寄主岩石经历了一定程度的同化混染作用。  相似文献   

3.
陕西陈家庄铀矿床是我国北秦岭商州—丹凤伟晶岩型铀矿集区中一个重要的矿床,铀矿体均产于加里东期花岗岩体周边花岗伟晶岩脉与围岩(秦岭群变质杂岩)的接触部位。本文对矿区花岗岩体、花岗伟晶岩脉开展了详细的岩石学、岩石地球化学、锆石U-Pb年代学研究,进而对其成因、成岩构造环境和铀矿化机理进行了探讨。LA-ICP-MS锆石U-Pb年代学研究表明,黄龙庙黑云母花岗岩体,陈家庄二长花岗岩体和非矿、贫矿、富矿花岗伟晶岩脉的成岩年龄分别为(446±3) Ma、(419±2) Ma、(417±3) Ma、(414±4) Ma和(416±3) Ma。地球化学分析显示：黄龙庙黑云母花岗岩体具有Ⅰ型花岗岩、埃达克质岩特征,源自加厚下地壳的部分熔融,形成于块体碰撞构造环境;陈家庄二长花岗岩体也具有I型花岗岩特征,但源区深度略浅,形成于碰撞后的减压环境。花岗伟晶岩脉与陈家庄二长花岗岩体近于同时形成,且具有亲缘性。铀矿物及富铀黑云母均产于花岗伟晶岩脉中。对比研究揭示,非矿、贫矿、富矿花岗伟晶岩脉地球化学特征和铀赋存状况的差异由同化混染作用程度高低所致。在花岗伟晶岩脉与秦岭群变质杂岩的接触部位,同化混染作用较弱的部位形成的二云母花岗伟晶岩脉仅具有弱的铀富集,同化混染作用较强的部位所形成的富石英、黑云母花岗伟晶岩脉则高度富集铀且构成铀矿体。综合研究表明,花岗伟晶岩脉成岩期后的同化混染作用是铀富集成矿的主导因素。  相似文献   

4.
白土滩花岗质杂岩体主要由黑云二长花岗岩、正长花岗岩和花岗闪长岩构成。通过锆石LA-ICP-MS U-Pb法测得黑云二长花岗岩和正长花岗岩的年龄分别为(291±2)Ma和(277±3)Ma。岩石地球化学研究表明,与黑云二长花岗岩相比,花岗闪长岩中硅、碱较低,而铝较高;高∑REE和∑LREE,低铕负异常;富Cr,Zn,Sr,Zr,Ba和Hf,贫Rb,Ta和Th,Nb/Ta和Zr/Hf均升高,DI,Rb/Sr下降,从花岗闪长岩到黑云二长花岗岩表现出连续分异演化的趋势。结合区域地质特征认为,白土滩花岗质杂岩体为高钾钙碱性I型花岗岩,其源区物质是含水的、碱性和高钾钙碱性的安山岩和玄武质安山岩,形成于南天山东段碰撞造山的碰撞-后碰撞阶段。  相似文献   

5.
江西大湖塘地区发育多期次与钨、铜、钼多金属成矿关系密切的中生代花岗岩。本文对该地区出露的似斑状黑云母二长花岗岩和黑云母花岗斑岩进行矿物化学、岩石地球化学、锆石U-Pb年代学和Lu-Hf同位素研究。其中似斑状黑云母二长花岗岩样品的成岩年龄分别为145.6±1.4 Ma(昆山岩体)、148.4±2.4 Ma(燕子崖岩体中部)和145.7±2.9 Ma(燕子崖岩体边部);黑云母花岗斑岩成岩时代为143.7±2.4 Ma(狮尾洞岩体),四者的继承锆石均来自新元古代花岗岩源区。岩石地球化学特征显示主量元素特征相似,似斑状黑云母二长花岗岩和黑云母花岗斑岩普遍高硅(SiO_2分别为72.37%～73.33%和70.16%～73.8%);富铝,二者铝饱和指数A/CNK分别为1.23～1.47和1.30～3.02,均属过铝质高钾钙碱性系列,而稀土、微量元素特征存在明显差异,其中似斑状黑云母二长花岗岩轻重稀土分馏明显,(La/Yb)_N平均为26.18,Eu负异常明显,稀土元素配分曲线呈明显右倾型,富集大离子亲石元素(LILE)Cs、Rb、Th、U、K、Pb,亏损高场强元素(HFSE)Zr、Nb、Ti、Y,低Ba、Sr;而黑云母花岗斑岩轻重稀土分馏不显著,(La/Yb)_N平均为9.76,Eu负异常明显,稀土元素配分曲线呈"海鸥型",并显示"M"型四分组效应,微量元素富集LILE,亏损HFSE。似斑状黑云母二长花岗岩的锆石ε_(Hf)(t)值为-7.39～-5.19,两阶段模式年龄(T_(DM2))为1.53～1.67 Ga。综合分析表明,大湖塘晚侏罗世似斑状黑云母二长花岗岩应产于古太平洋板块向华南板块俯冲的构造背景之下,由中上地壳的新元古代黑云母花岗闪长岩部分熔融形成;而早白垩世黑云母花岗斑岩形成于古太平洋板块向华南板块俯冲—俯冲后伸展的构造转换背景之下,由于软流圈地幔上涌,诱发上地壳新元古代黑云母二长花岗岩部分熔融,且在结晶分异过程中还受到富Cl流体的交代。  相似文献   

6.
勐养侵入岩体位于滇西腾冲地块梁河县南勐养镇一带,主要由黑云母二长花岗岩和花岗闪长岩组成,其中发育闪长质包体。闪长岩包体与寄主岩石黑云母二长花岗岩和花岗闪长岩之间呈渐变过渡关系。锆石U-Pb LA-ICP-MS定年表明,黑云母二长花岗岩形成年龄为127.7Ma±0.7Ma,花岗闪长岩形成年龄为115.2Ma±1.1Ma。闪长岩包体形成年龄为122.6Ma±0.8 Ma。表明该花岗岩体的形成时代属于早白垩世。地球化学特征研究表明,闪长岩包体为准铝质、钙碱性系列,具有低SiO2、高MgO、高K20和Mg#的特征。Sm/Nd为0.18～0.20,ΣLREE/ΣHREE=2.91～4.64,Eu存在弱到中等程度的负异常。相对富集U,Th,Rb,Ba等大离子亲石元素(LILE),亏损Tb,Nb,Zr,Hf等高场强元素(HFSE);反映勐养闪长岩包体岩浆成分主要为幔源的特点。根据地球化学特征和微量元素构造判别图解判别结果表明,勐养早白垩世侵入岩形成于碰撞后岩浆弧环境。闪长岩包体的原生岩浆应是地幔橄榄岩部分熔融的产物。黑云二长花岗岩浆可能来源于本区中晚元古代高黎贡山群为代表的地壳物质的部分熔融。花岗闪长岩为幔源岩浆与高黎贡山群古老地壳部分熔融的岩浆混合的产物。腾冲地块早白垩世侵入岩与班公湖—怒江—泸水—瑞丽洋盆的闭合、洋壳向南西俯冲及板块间的碰撞造山作用密切相关。  相似文献   

7.
在花岗伟晶岩型铀矿床中,黑云母常见于与产铀相关的围岩地层、花岗岩体和花岗伟晶岩脉之中,并且常常与晶质铀矿紧密共生,在对岩石放射性元素的还原和吸附过程中起着重要作用。选取北秦岭柳树湾花岗伟晶岩型铀矿床中围岩地层、花岗岩体、含矿花岗伟晶岩和不含矿花岗伟晶岩中的黑云母作为研究对象,通过电子探针矿物化学特征研究表明:黑云斜长片岩和不含矿花岗伟晶岩中的黑云母分别为羟金云母和羟铁云母。灰池子二长花岗岩体和含矿花岗伟晶岩中的黑云母呈现出由富铁羟金云母向富镁羟铁云母演化的过渡关系,二者显示出较好的亲缘性。随着岩浆不断演化,灰池子二长花岗岩—含矿花岗伟晶岩—不含矿花岗伟晶岩形成的温度和氧逸度不断降低,母源岩浆显示出由壳幔混合来源向单一壳源成因演化的特点。黑云母成分示踪结合区域地质背景研究表明:与柳树湾铀矿有关的灰池子二长花岗岩体、含矿花岗伟晶岩和不含矿花岗伟晶岩分别形成于板块碰撞的挤压构造环境、挤压向伸展的构造体制转换阶段以及随后与拆沉减薄有关的伸展阶段,是晚古生代北秦岭三次构造活动的浅部岩浆反应。  相似文献   

8.
白云鄂博地区的克拉通基底岩石主要由糜棱岩化花岗片麻岩(2588±15Ma),正长岩、花岗闪长岩(2018±15Ma)和黑云母花岗片麻岩、含石榴石蓝晶石花岗片麻岩(～1890Ma)等组成,白云鄂博超大型稀土矿床就位于华北克拉通太古代基底之上。太古代克拉通基底在早元古代中晚期(2.0Ga)又经历了一次强烈的碰撞造山运动,造成了闪长质与花岗质岩浆侵位,以及1.9Ga片麻岩相变质事件。  相似文献   

9.
天山造山带是古生代多期碰撞增生作用的产物,其确切的造山时代是当前争议较多的热点问题。分布在西南天山的科克苏-穹库什太剖面经历了复杂的构造变形,最明显的两期变形事件分别为朝北的推覆作用和 NE-SW 韧性走滑作用。本剖面可分为伊犁岩浆岛弧、伊犁结晶基底、高压变质杂岩三个岩石-构造单元。野外可见黑云母花岗闪长岩侵入到绿片岩相变质岩中,岩脉切穿绿片岩中面理构造。通过锆石 U-Pb LA-ICPMS 测年,科克苏剖面钾长花岗岩的年龄为341±6Ma 和338±8Ma,穹库什太黑云母花岗闪长岩的年龄为313±4Ma。其中,花岗闪长岩发生了黑云母定向排列,通过对黑云母进行~(40)Ar/~(39)Ar 测年,获得坪年龄为263.4±0.6Ma,表明该花岗闪长岩受过后期热事件的干扰。地球化学分析表明,黑云母花岗闪长岩属于钙碱性系列,Nb 和 Ta 含量低而 Rb,Ba 和 Th 含量很高,与俯冲作用有关的岛弧岩浆岩地球化学组成非常相似。结合前人对该地区高压变质岩、花岗岩和火山岩的研究成果,本文提出,西南天山俯冲-碰撞造山作用发生在晚石炭世之前,研究区后碰撞区域走滑作用标志着西南天山碰撞造山作用在二叠纪之前全部结束。  相似文献   

10.
位于准噶尔西北缘萨吾尔地区的罕哲尕能Cu-Au矿床是新近发现的斑岩型矿床,具有很好的找矿前景。矿区岩浆活动早期以闪长岩为主,晚期以花岗闪长岩和二长花岗斑岩为主。钻孔中所见似斑状石英二长岩LA-ICP-MS锆石U-Pb年龄为343.6±5.7Ma~345.3±8.3Ma;二长花岗斑岩锆石U-Pb年龄为334.9±7.3Ma~336.4±7.5Ma,表明西准萨吾尔地区早石炭世存在一期重要的岩浆-热液Cu-Au成矿事件。花岗闪长岩、石英二长岩、闪长玢岩、闪长岩和二长花岗斑岩的主量元素具有一致的演化趋势,表明它们可能是同一岩浆演化的产物。富集大离子亲石元素(LILE:如Rb、Ba、K、Sr)和活泼的不相容元素(如:U、Th),相对亏损高场强元素(HFSE:如Nb、Ta、Ti),显示具有岛弧岩浆的地球化学特征。87Sr/86Sri比值在0.7033~0.7037之间,143Nd/144Nd比值在0.512538~0.512579之间,εNd(t)在+6.7~+7.5之间,显示源区具有类似亏损地幔的特征;而且具有年轻的Nd两阶段模式年龄为488~553Ma,这些特征表明罕哲尕能矿区岩石的岩浆源区可能来源于亏损地幔分异的新生玄武质下地壳。罕哲尕能Cu-Au矿床的形成时代明显早于该区域A型花岗岩的形成时代(290~300Ma左右),结合岩石微量元素特征反映其形成于岛弧构造背景,萨吾尔山具有寻找斑岩Cu-Au矿的成矿条件。  相似文献   

11.
Police, politics, and the right to the city   总被引：1，自引：0，他引：1  
Mustafa Dikeç 《GeoJournal》2002,58(2-3):91-98
Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete.  相似文献   

12.
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13.
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14.
Average concentrations of Pb, Zn, Cu, and other metals, as well as S and As, were calculated for the Aue granitic cupola, the contact aureole of which hosts the large vein-type uranium deposit of Schlema-Alberoda and the Schneeberg uranium-base metal deposit (Erzgebirge, Germany). The cupola was exposed by mine workings and boreholes, which provided an opportunity to evaluate variations in the abundances of metals in the granites over a vertical interval of more than 2.5 km and estimate their losses in the upper oxidized part of the investigated volume of the cupola (coefficient of iron oxidation, KO Fe, increases in the granites from bottom to top from 7 to 70%) compared with the lower unaltered and unoxidized part (with a KO Fe plateau at about 5%). The average concentrations of metals in the upper part of the cupola are lower than those in the lower part by a factor of 2.5 for Pb, 1.56 for Zn, 1.45 for Cu, 1.3 for Co, etc. A similar decrease in the abundances of ore elements along the vertical section associating with the relative epigenetic alteration and oxidation of the granite was previously described by us for U and Th and for the components of high-temperature ores, W, Sn, and Mo. The removal of ore elements from the granite was accompanied by a decrease in the bulk contents of sulfur and arsenic by a factor of 1.35 and 1.65, respectively. The leaching of trace metals from the granites of the upper part of the Aue cupola was followed by their partial redeposition above the cupola in the ore veins of the Schlema and Schneeberg deposits. Original Russian Text ? Vikt. L. Barsukov, N.T. Sokolova, O.M. Ivanitskii, 2006, published in Geokhimiya, 2006, No. 9, pp. 967–982.  相似文献   

15.
Mercury contamination in aquatic environments is of worldwide concern because of its high biomagnification factor in food chains and long-range transport. The rivers, estuary and the bay along the northwestern Bohai Sea coast, northeastern China have been heavily contaminated by Hg due to long-term Zn smelting and chlor-alkali production. This work investigated the distributions of total Hg (THg) and monomethylmercury (MMHg) in the water, sediment and hydrophytes from this area. Concentrations of THg in sediment (0.5–64 mg kg−1) and water (39–2700 ng L−1) were elevated by 1–3 orders of magnitude compared to background concentrations, which induced high concentrations of MMHg in these media. The highest concentration of MMHg in sediment reached 35 μg kg−1, which was comparable to that in the Hg mining area, Wanshan, China, and the highest MMHg concentration of 3.0 ng L−1 in the water sample exceeded the MMHg Chinese drinking water guideline of 1.0 ng L−1. Concentrations of THg in a sediment profile from Jinzhou Bay were found to be consistent with annual Hg emission flux from a local Zn smelter (r = 0.74, p < 0.01), indicating that Hg contamination was mainly caused by Zn smelting locally. For some freshwater hydrophytes, concentrations of THg and MMHg ranged from 5.2 to 100 μg kg−1 and 0.15 to 12 μg kg−1, respectively. Compared to sediment, concentrations of THg in hydrophytes were 2–3 orders of magnitude lower but MMHg was comparable or higher, indicating that the bioaccumulation in plants was distinct for the two Hg species studied. The data suggest that a significant load of Hg has been released into the northwestern coastal region of the Bohai Sea.  相似文献   

16.
The behavior of trace elements under conditions of partial melting of granitoid rocks has been studied. The element’s partition coefficients between minerals and the melt Dimin/melt depends, in the first place, on the composition of the primary melt. In biotite the HREE Di are a little below 1, while those of LREE, especially Di for Ce, are 1–3 orders of magnitude less. This leads to an efficient differentiation of REEs in anatexic melts especially when biotite is the main mineral phase of restite. On the contrary, there are feldspars, the Di of which cannot provide such a magnitude of differentiation. Unlike garnets and pyroxenes, whose stability in restite permits enrichment of anatexic melts produced in migmatization zones with Nb, Ti, and Cr, the presence of biotite in restite causes depletion of melts with those elements as well as with Rb. Feldspars, under conditions of their fractional crystallization or during differentiation of an anatexic melt, deplete the latter with Sr, Ba, and Rb, but enrich it with Nb, Ti, Cr, Y, Zr, and V.  相似文献   

17.
The dielectric constants and dielectric loss values of 4 Ca-containing minerals were determined at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: vesuvianitel κ′ a=9.93 tan δ=0.006 κ′ c=9.79 tan δ=0.005 vesuvianitel κ′ a=10.02 tan δ=0.002 κ′ c=9.85 tan δ=0.003 zoisite1 κ′ a =10.49 tan δ=0.0006 κ′ b =15.31 tan δ=0.0008 κ′ c=9.51 tan δ=0.0008 zoisite2 κ′ a =10.55 tan δ=0.0011 κ′ b =15.45 tan δ=0.0013 κ′ c=9.39 tan δ=0.0008 epidote κ′ 11= 9.52 tan δ=0.0008 κ′ 22=17.1 tan δ=0.0009 κ′ 33= 9.37 tan δ=0.0006 fluorapatite1 κ′ a =10.48 tan δ=0.0008 κ′ c = 8.72 tan δ=0.0114 fluorapatite2 κ′ a =10.40 tan δ=0.0010 κ′ c=8.26 tan δ=0.0178 The deviation (δ) between measured dielectric polarizabilities as determined from the Clausius-Mosotti equation and those calculated from the sum of oxide polarizabilities according to α D (mineral)=∑ α D (oxides) for vesuvianite is ～ 0.5%. The large deviations of epidote and zoisite from the additivity rule with Δ=+ 10.1 and + 11.7%, respectively, are attributed to “rattling” Ca ions. The combined effects of both a large F thermal parameter and possible F-ion conductivity in fluorapatite are believed to be responsible for Δ=+2–3%. Although variation of oxygen polarizability with oxygen molar volume (Vo) is believed to affect the total polarizabilities, the variation of Vo in these Ca minerals is too small to observe the effect.  相似文献   

18.
The 1988 good rainy season in the Sudan raised the hopes that desertification/land degradation and shortage of food so markedly observed in Western Sudan have been elevated. This was particularly so as large quantities of grains were produced in the mechanized rain-fed agricultural schemes in the clay plains of Eastern Sudan. But the field work carried by the author in the Umm Ruwaba district of Kordofan region in July/August 1989 shows that, although there has been some improvement in the crop production situation, desertification/land degradation and shortage of food produced locally are still prevailing in the district. The people are still living below the poverty line, but they are able to cope because of remittances from members of the families working abroad and because of donations of food by some world organizations.  相似文献   

19.
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.  相似文献   

20.
Humboldt, Arago, and the temperature of groundwater   总被引：1，自引：0，他引：1  
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