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1.
为解释冈底斯南缘新发现的中基性岩体构造环境及物质来源等信息,以西藏自治区贡嘎县昌果乡辉长闪长岩为研究对象,通过开展锆石U-Pb定年、Hf同位素组成、全岩地球化学分析,得到岩体锆石年龄为(165±1.1) Ma。样品富集大离子亲石元素,亏损高场强元素,具有富铝(Al2O3=18.84%~20.70%)、富钾的特征,在构造判别图解中样品多落在挤压岛弧区域,表明其形成构造环境应为俯冲岛弧环境。样品具较为平缓的稀土配分曲线,岩浆分异程度较低,无明显Eu异常,(La/Yb)N平均值为2.30(<4.3),与幔源岩浆的稀土配分型式相似。锆石Hf同位素显示εHf(t)值为很高的正值(12.97~18.74),二阶段模式年龄集中在150~218 Ma,略大于其侵位年龄,表明幔源岩浆在侵位过程中受到地壳物质的混染。结合区域构造演化史认为该岩体形成于新特提斯洋向冈底斯俯冲过程中的成熟岛弧期,从而也进一步证实了南冈底斯在中侏罗世处于俯冲岛弧构造环境。  相似文献   

2.
新疆巴尔鲁克地区石屋岩体主要由石英闪长玢岩、石英闪长岩组成。本文通过锆石U-Pb年代学、岩石地球化学和Sr-Nd-Pb-Hf同位素等研究,探讨其构造背景、岩石成因和成矿意义。LA-ICP-MS锆石U-Pb定年表明:石屋石英闪长玢岩的成岩年龄为322.1±1.5Ma,石英闪长岩的形成年龄为322.4±1.5Ma,二者形成时代为晚石炭世。石屋石英闪长玢岩和石英闪长岩地球化学特征相似,Mg~#为32.4~57.2,轻重稀土分馏较明显且富集轻稀土((La/Yb)N=2.36~6.04),Eu异常不明显,相对富集LILEs等,亏损Nb、Ta、P、Ti等高场强元素。Sr-Nd-Pb-Hf同位素显示:样品具有低的ISr值(0.7036~0.7045),正εNd(t)值(+4.61~+7.03),年轻的tDM1年龄(0.59~0.78Ga),初始铅同位素比值为(~(206)Pb/~(204)Pb)i=18.173~18.450,(~(207)Pb/~(204)Pb)i=15.542~15.562,(~(208)Pb/~(204)Pb)i=37.830~38.036,锆石εHf(t)值为+4.5~+15.3,t_(DM2)=0.36~0.62Ga。综合石屋岩体的地质、地球化学和年代学特征,认为石英闪长玢岩和石英闪长岩源区相同,它们均形成于晚石炭世早期俯冲背景下的岛弧环境,可能是在亏损玄武质岩浆(俯冲板片脱水交代地幔楔产生的上涌岩浆)底侵作用下,新生地壳发生部分熔融,并有部分玄武质岩浆加入,发生混合、侵位的产物。石屋岩体的形成环境及其岩浆演化过程可能有利于区内斑岩型铜矿化,其含矿性值得做进一步评价。  相似文献   

3.
于玉帅 《地质与勘探》2014,50(2):216-225
加多捕勒铁铜矿床位于冈底斯Pb-Zn-Ag-Cu-Fe成矿带西段。矿区出露的复式岩体由黑云二长花岗岩(50.9±1.8Ma)和石英二长闪长岩组成。本文以石英二长闪长岩为研究对象,分析了岩体地球化学特征、SHRIMP锆石U-Pb年龄以及原位锆石Hf同位素与稀土元素。分析结果显示石英二长闪长岩具岛弧岩浆活动特征,锆石U-Pb年龄84.3±1.4Ma,为晚白垩世岩浆活动产物,锆石Hf同位素与稀土元素指示岩浆源区具壳幔混源特征,且以古老地壳物质的部分熔融为主。综合分析已有研究成果及本文数据,笔者认为矿区晚白垩世岩浆活动可能与低缓角度俯冲的新特提斯洋壳有关。  相似文献   

4.
孙建东 《地质与勘探》2016,52(3):506-517
分析了船坑铜矿成矿岩体石英闪长玢岩主微量、稀土元素特征及锆石U-Pb测年数据,表明岩石具高钾偏铝质I型花岗岩特征,及岛弧成因岩浆特点;锆石稀土元素表明有地壳物质的加入,属壳幔混源。锆石U-Pb年龄162.9±3.6Ma,大致代表含矿岩体成岩年龄。该矿床形成于钦杭成矿带铜矿主成矿期,处于岩石圈拆沉或伸展-减薄的构造环境,受太平洋板块往欧亚大陆的俯冲的影响。  相似文献   

5.
在野外地质调查工作的基础上,对日土县—拉梅拉山口一带的日松花岗岩体开展了详细的岩相学、岩石地球化学、锆石U-Pb测年和Hf同位素分析。岩石地球化学数据表明,日松花岗岩体属钙碱性岩类型,绝大多数样品含透辉石标准分子。富集Rb、Pb、Th等而亏损K、Ba等大离子亲石元素,高场强元素Nb、Ta、Ti等明显亏损。稀土元素呈现出右倾缓倾斜型的特征,且存在较为明显的负Eu异常。与前人研究确定岩体的时代为晚白垩世—始新世不同,本文认为岩体的侵位时代主要为白垩纪,可分为早白垩世、晚白垩世两期。获得二长花岗岩样品(D1045-2)的LA-ICP MS锆石U-Pb年龄为108.4±2.1Ma(MSWD=2.4,n=18),结合锆石稀土元素特征、岩浆振荡环带特征(CL图像)及锆石Th/U比值,上述年龄可以代表岩体的形成年龄(早白垩世)。锆石Hf同位素特征显示,二长花岗岩样品(D1045-2)的εHf(t)为正值,介于1.49~3.86间(平均值为2.50);而石英闪长岩样品(D1045)的εHf(t)多数为负值,介于-2.09至0.15之间(平均值为-0.69)。Hf同位素地壳模式年龄分别在763.0~884.5Ma(D1045-2)、959.1~1073.5Ma(D1045)之间。两件样品的εHf(t)和Hf同位素地壳模式年龄均具有较小的变化范围,暗示岩体的岩浆物质来源应该具有较为均一的锆石Hf同位素组成。日松地区早白垩世花岗岩体的锆石U-Pb年龄和Hf同位素特征,基本反映了北冈底斯早白垩世的岩浆活动时间和源区等特征,其成因可能与班公湖-怒江特提斯洋岩石圈向南俯冲过程中幔源物质参与岩浆形成演化有关。本文研究成果,为研究班公湖-怒江结合带构造演化提供了新的资料证据。  相似文献   

6.
吐哈盆地南缘彩霞山东石英闪长岩岩株锆石SHRIMP U-Pb测年   总被引:4,自引:1,他引:4  
彩霞山东石英闪长岩岩株的锆石SHRIMP U-Pb年龄为267.8Ma±1.6Ma,结合克孜尔塔格岩体的同位素年龄综合分析,此年龄值介于王瑜等所研究剪切作用控制的克孜尔塔格岩体右行剪切年龄276~254Ma之间,表明该石英闪长岩岩株的侵位年龄比克孜尔塔格复式岩体晚,为中二叠世早期.  相似文献   

7.
以冈底斯中段曲水县西南方向卡热乡一带出露的辉长岩为研究对象,进行了LA-ICP-MS锆石UPb测年以及全岩地球化学的系统测定,据此讨论岩石的成因及其构造意义。该辉长岩主要由单斜辉石和斜长石组成,辉长岩具有低硅、贫碱、富铝,中等富集轻稀土,富集大离子亲石元素,亏损高场强元素的地球化学特征,与岛弧和大陆边缘地区产出的高铝玄武岩化学组成十分相似,表明辉长岩原生岩浆为被俯冲改造的岩石圈幔源岩浆,在演化过程中受到了上地壳物质的混染。锆石LA-ICP-MS U-Pb年龄为49.01±0.51Ma(MSWD=0.41),指示岩体形成时代为始新世。卡热辉长岩具有显著亏损的锆石Hf同位素组成,εHf(t)值均为正值,分布在+10.88~+13.71之间,综合分析表明卡热辉长质侵入体可能为近期遭受俯冲板片析出流体交代作用的亏损地幔部分熔融的产物。结合区域构造演化史认为该岩体在冈底斯南缘的始新世期间存在着强烈的岩浆底侵和壳幔岩浆混合作用。  相似文献   

8.
高腾  王立强  王勇  郑斯伦  胡宇 《地球学报》2019,40(6):884-894
西藏革吉县江玛—赛登地区是班公湖—怒江成矿带内近两年发现的成矿潜力较好的地区之一。本文对江玛南铜银矿点的石英闪长玢岩进行锆石U-Pb年代学、全岩地球化学和锆石Hf同位素组成研究。利用LA-ICP-MS测得206Pb/238U年龄为(118.6±2.8)Ma(N=13,MSWD=3.8),此年龄可解释为石英闪长玢岩成岩年龄。全岩主量和微量元素分析显示,石英闪长玢岩属于中钾钙碱性准铝质I型花岗岩。岩石轻、重稀土元素分馏明显(LREE/HREE=9.37~9.76),富集轻稀土元素;δEu值为0.94~0.9, Eu负异常不甚明显。岩石相对富集Rb、Th、U、K等大离子亲石元素(LILE),亏损Nb、Ta、Zr、Ti等高场强元素(HFSE),具有岛弧岩浆岩的岩石化学属性。锆石Hf同位素分析结果显示,锆石εHf(t)值为+7.9~+11.2,平均值为+9.5,两阶段模式年龄TDMC=456~675Ma,表现出明显的幔源成岩物质来源特征。通过年代学、岩石地球化学、Hf同位素及区域综合对比研究,认为江玛南石英闪长玢岩的形成与班公湖—怒江特提斯洋南向俯冲有关。  相似文献   

9.
本文系统报道了缅甸抹谷变质带中部Yinmabin花岗闪长岩体及其基性岩墙的主量元素、微量元素及锆石U-Pb年龄和Lu-Hf同位素组成,重点讨论了花岗闪长岩和基性岩墙的岩石成因、物质来源及其地质意义。抹谷Yinmabin花岗闪长岩体主量元素显示富钠(N2O/K2O=1.5~1.75)、准铝(ACNK=0.94~0.97)和钙碱性岩石系列的地球化学特征。样品富集轻稀土(LREE)元素、大离子亲石元素(LILE),相对亏损高场强元素(HFSE)。岩体的主、微量元素地球化学特征均显示其具有活动陆缘I型花岗岩的地球化学属性。抹谷Yinmabin花岗闪长岩的锆石U-Pb年龄为131~135 Ma,其εHf(t)值在-15.66~-2.99之间,平均值为-8.77,单阶段模式年龄(tDM)为795~1569 Ma;而后期侵位的辉绿岩的锆石U-Pb年龄为120~118 Ma,其εHf(t)值在-13.72~+5.82之间,平均值为-2.72,单阶段模式年龄(tDM)为570~1341 Ma,表明这些岩石可能主要来源于古老下地壳部分熔融但同时也受到地幔物质的加入混染。与滇西以及北拉萨岩浆带的Lu-Hf同位素特征十分相近,暗示抹谷-毛淡棉地块早白垩世岩浆岩带与波密-察隅-高黎贡-拉萨岩浆岩带形成环境相似,可能是腾冲岩浆岩带向南延伸的一部分。结合岩石成因、源区性质和区域构造演化,认为抹谷花岗闪长岩体及基性岩墙的形成与中特提斯洋板块的俯冲作用密切相关,同时俯冲-碰撞转换的时限应该在120 Ma左右。这对于研究抹谷地体在中生代期间中特提斯洋俯冲碰撞过程具有重要的地质意义。  相似文献   

10.
在野外地质调查工作的基础上,对日土县-拉梅拉山口一带的日松花岗岩体开展了详细的岩相学、岩石地球化学、锆石U-Pb测年和Hf同位素分析。岩石地球化学数据表明,日松花岗岩体属钙碱性岩类型,绝大多数样品含透辉石标准分子。富集Rb、Pb、Th等而亏损K、Ba等大离子亲石元素,高场强元素Nb、Ta、Ti等明显亏损。稀土元素呈现出右倾缓倾斜型的特征,且存在较为明显的负Eu异常。与前人研究确定岩体的时代为晚白垩世-始新世不同,本文认为岩体的侵位时代主要为白垩纪,可分为早白垩世、晚白垩世两期。获得二长花岗岩样品(D1045-2)的LA-ICP MS锆石U-Pb年龄为108.4±2.1Ma(MSWD=2.4,n=18),结合锆石稀土元素特征、岩浆振荡环带特征(CL图像)及锆石Th/U比值,上述年龄可以代表岩体的形成年龄(早白垩世)。锆石Hf同位素特征显示,二长花岗岩样品(D1045-2)的εHf(t)为正值,介于1.49-3.86间(平均值为2.50);而石英闪长岩样品(D1045)的εHf(t)多数为负值,介于-2.09至0.15之间(平均值为-0.69)。Hf同位素地壳模式年龄分别在763.0-884.5Ma(D1045-2)、959.1-1073.5Ma(D1045)之间。两件样品的εHf(t)和Hf同位素地壳模式年龄均具有较小的变化范围,暗示岩体的岩浆物质来源应该具有较为均一的锆石Hf同位素组成。日松地区早白垩世花岗岩体的锆石U-Pb年龄和Hf同位素特征,基本反映了北冈底斯早白垩世的岩浆活动时间和源区等特征,其成因可能与班公湖-怒江特提斯洋岩石圈向南俯冲过程中幔源物质参与岩浆形成演化有关。本文研究成果,为研究班公湖-怒江结合带构造演化提供了新的资料证据。  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.
13.
14.
Humboldt, Arago, and the temperature of groundwater   总被引:1,自引:0,他引:1  
  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.
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   

17.
Text, talk, things, and the subpolitics of performing place   总被引:1,自引:0,他引:1  
This article tells the story of how a group of Dutch and Belgian citizens organized themselves to promote an area that they valued, to put it on the map, to raise awareness about its qualities, and to protect it from urban and industrial development. Our theoretical perspective focuses on the performative and political aspects of this place-making process and the discursive and material practices involved. We connect this to Beck’s concept of subpolitics.Our findings show how the group performed this place not only through text and talk - giving the area a name, using their knowledge and expertise to raise awareness about its values, lobbying and cooperating with decision-makers -, but also through things - installing art objects and information signs that articulate certain characteristics and values of the area. Our findings demonstrate the struggles involved in these performances. The group involved multiple perspectives on what the important values and characteristics of the area are and on what strategies would work best in trying to influence decision-making and protect the area. However, the use of expertise as the main strategy to gain influence excluded the more critical and activist strategies and privileging archaeological and historical values and characteristics came at the expense of attention on agricultural and natural values.Our findings make clear that performing place cannot be taken to be homogeneous and that it inevitably involves multiple perspectives and demands. The struggles, power relations and dynamics of inclusion and exclusion that this multiplicity implicates reveal a form of sub-politics that involves both politicization and depoliticization. Also, it is a form of subpolitics that is more diverse and ambiguous than Beck’s conceptualization presupposes by its emphasis on the role of outsiders as a homogeneous group.  相似文献   

18.
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   

19.
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   

20.
The paper presents original authors' data on the O, H, C, S, and Sr isotopic composition of water and sediments from the basins into which the Aral Sea split after its catastrophic shoaling: Chernyshev Bay (CB), the basin of the Great Aral in the north, Lake Tshchebas (LT), and Minor Sea (MS). The data indicate that the δ18О, δD, δ13C, and δ34S of the water correlate with the mineralization (S) of the basins (as of 2014): for CB, S = 135.6‰, δ18О = 4.8 ± 0.1‰, δD = 5 ± 2‰, δ13C (dissolved inorganic carbon, DIC) = 3.5 ± 0.1‰, δ34S = 14.5‰; for LT, S = 83.8‰, δ18О = 2.0 ± 0.1‰, δD =–13.5 ± 1.5‰, δ13C = 2.0 ± 0.1‰, δ34S = 14.2‰; and for MS, S = 9.2‰, δ18О =–2.0 ± 0.1‰, δD =–29 ± 1‰, δ13C =–0.5 ± 0.5‰, δ34S = 13.1‰. The oxygen and hydrogen isotopic composition of the groundwaters are similar to those in MS and principally different from the artesian waters fed by atmospheric precipitation. The mineralization, δ13С, and δ34S of the groundwaters broadly vary, reflecting interaction with the host rocks. The average δ13С values of the shell and detrital carbonates sampled at the modern dried off zones of the basins are similar: 0.8 ± 0.8‰ for CB, 0.8 ± 1.4‰ for LT, and –0.4 ± 0.3‰ for MS. The oxygen isotopic composition of the carbonates varies much more broadly, and the average values are as follows: 34.2 ± 0.2‰ for CB, 32.0 ± 2.2‰ for LT, and 28.2 ± 0.9‰ for MS. These values correlate with the δ18O of the water of the corresponding basins. The carbonate cement of the Late Eocene sandstone of the Chengan Formation, which makes up the wave-cut terrace at CB, has anomalously low δ13С up to –38.5‰, suggesting origin near a submarine methane seep. The δ34S of the mirabilite and gypsum (11.0 to 16.6‰) from the bottom sediments and young dried off zone also decrease from CB to MS in response to increasing content of sulfates brought by the Syr-Darya River (δ34S = 9.1 to 9.9‰) and weakening sulfate reduction. The 87Sr/86Sr ratio in the water and carbonates of the Aral basins do not differ, within the analytical error, and is 0.70914 ± 0.00003 on average. This value indicate that the dominant Sr source of the Aral Sea is Mesozoic–Cenozoic carbonate rocks. The Rb–Sr systems of the silicate component of the bottom silt (which is likely dominated by eolian sediments) of MS and LT plot on the Т = 160 ± 5 Ma, I0 = 0.7091 ± 0.0001, pseudochron. The Rb–Sr systems of CB are less ordered, and the silt is likely a mixture of eolian and alluvial sediments.  相似文献   

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