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1.
新疆博格达东缘色皮口地区晚石炭世裂谷火山岩地球化学、锆石U-Pb年代学及Hf同位素研究 总被引：2，自引：1，他引：1
新疆色皮口地区位于博格达造山带东段北部,区域内的上石炭统柳树沟组火山岩为玄武岩-玄武安山岩、角斑岩-石英角斑岩和流纹岩,组成双峰式火山岩建造。岩石SiO 2含量为48.07%~77.62%,赖特碱度率(AR)为1.35~4.7,Na2O+K2O含量为3.74%~9.02%,K2O/Na2O值为0.04~1.04,为低钾高钠钙碱性-碱性岩石。玄武岩、玄武安山岩TiO 2=0.86%~1.7%,较高的Al、低Mg,以及低K2O/TiO 2和K2O/P2O5比值(分别为0.13~1.81、0.36~6.00),反映了在岩浆演化过程中发生了不明显的分离结晶作用。玄武岩、玄武安山岩、角斑岩不相容元素K、Rb、Th、Ba强富集,高场强元素Nb、Ta、Zr、Hf无富集,Ti亏损不明显,玄武岩(Th/Nb)N值为1.36~6.55,Nb/La值为0.29~0.44,具有较低的Nb/Zr比值(0.03~0.05)。由玄武岩到石英角斑岩,稀土元素组成略右倾平行曲线簇,倾斜度(轻重稀土分异度)略增大,铕负异常趋于明显(δEu=0.81~1.17)。流纹岩不相容元素K、Rb、Th、Ba富集,高场强元素Nb、Ta、Zr、Hf富集,流纹岩稀土总量增高,轻重稀土分异增大,明显铕负异常(δEu=0.27~0.50),显示后期较强的岩浆分异作用。石英角斑岩的锆石LA-ICP-MS U-Pb定年结果为314.9±1.2Ma(n=16,MSWD=0.4,Th/U比值在0.56~1.21之间),这表明石英角斑岩形成时代为晚石炭世。石英角斑岩中锆石的176Hf/177Hf比值均分布在0.282897~0.283097之间,并具有较高的正εHf值(11~18),平均值为14,Hf的模式年龄tDM2介于180~628Ma。所有锆石的176Hf/177Hf比值和εHf值位于亏损地幔演化线与下地壳之间,并靠近亏损地幔演化线。上述特点反映晚石炭世火山岩形成于板内裂谷环境,下部玄武岩与角斑岩-石英角斑岩具有同源特征,暗示岩浆源区来源于亏损地幔,并受地壳混染。 相似文献
2.
甘肃白银厂矿田早-中寒武世火山岩形成的构造环境 总被引：13，自引：0，他引：13
白银厂矿田早 -中寒武世火山岩主要由钙碱性玄武岩和流纹岩及少量的安山岩组成 ,被认为是大陆裂谷环境下的产物。本文的地球化学分析结果显示 :玄武岩具有低Ti,Nb和Ta负异常、富集LREE ,相对亏损HFSE ,Th/Ta比值高 (介于 9～ 15 ) ,La/Nb >1.4 ,低Ni,Th/La为0 .32～ 0 .5 6;低Zr/Nb(<16) ,(87Sr/ 86 Sr) i 为 0 .70 4～ 0 .70 7,εNd(t) =- 6.4 6,δEu≈ 1的地球化学特点 ;流纹岩同样具有低Ti,Nb和Ta负异常 ,Th/Ta为 6～ 12 ,低Ti/Zr比值 (介于 6.1～ 5 3)之间 ;稀土元素配分为MREE负异常 ,δEu为 0 .5～ 1.1,(87Sr/ 86 Sr) i 为 0 .70 2 6～ 0 .70 4 8,εNd(t)为+ 5 .60～ + 6.14。综合两类岩石的地球化学特征 ,可以推测它们是陆缘弧岩浆作用的产物 ,但并非同源岩浆演化的结果。玄武岩源于富集的岩石圈地幔 ,在岩浆上升过程中发生明显的陆壳混染作用 ,而流纹岩应为镁铁质下地壳部分熔融与地幔物质混合作用的产物 相似文献
3.
新疆阿尔泰南缘达拉乌兹双峰式火山岩年龄及岩石成因 总被引：4，自引：3，他引：1
阿尔泰南缘达拉乌兹一带出露了一套玄武岩和流纹岩频繁互层的双峰式火山岩组合。该套双峰式火山岩发生了绿片岩相变质作用,其基性端元——变质玄武岩和酸性端元——变质流纹岩具明显的变余斑状结构。利用LA-ICP-MS锆石U-Pb法获得流纹岩的喷发年龄365.6±1.6Ma和捕获的锆石年龄413.5±2.0Ma。变质玄武岩富TiO2、碱(富钠)(Na2O/K2O=4.43～19.33)和FeOT,贫MgO和CaO,轻微富集LILE和LREE,具弱的Nb、Ta和Ti的负异常,具有高于正常弧火山岩但低于OIB的HFSE元素(Nb、Ta、Zr、Hf)的含量,Eu负异常不明显。流纹岩具有高SiO2和全碱,具有低的TiO2、极低的MgO和FeOT,呈现明显的Ti、P、Sr、Ba负异常,Th、U、Pb的正异常,HFSE元素(Zr、Hf)和LREE略富集但Nb、Ta亏损的特征,并显示Eu的明显负异常(δEu=0.21～0.41)。它们均具有相似于N-MORB的较低的Pb同位素组成。玄武岩与流纹岩来自两个不同的岩浆房,玄武岩为受俯冲物质加入的亏损软流圈地幔部分熔融后并发生结晶分异作用的结果,流纹岩为新生的地壳物质受幔源岩浆加热熔融并与之混合后演化的产物。结合阿尔泰南缘地区的构造演化特征,推测该双峰式火山岩俯冲作用引起的局部拉张作用的产物。 相似文献
4.
东天山博格达造山带晚石炭世柳树沟组为一套由玄武岩和流纹岩组成的双峰式火山岩,形成于晚石炭世,其Si O_2含量介于46.18%～46.56%和76.06%～76.25%之间,具有明显的Daly成分间断。其中,玄武岩具富Na贫K特征,Ti O_2、Al_2O_3、Ca O和MgO含量均较高,∑REE为75.54×10~(-6)～80.22×10~(-6),LREE/HREE值为3.00～3.12,以富集Ba、Rb等大离子亲石元素(LILE)和不相容元素(P、K),相对亏损Ti、Ta、Nb等高场强元素(HFSE)和不相容元素(U、Th)为特征;流纹岩Na_2O/K_2O值为0.32～0.36,属低Ti、低Mg类流纹岩,∑REE为520.72×10~(-6)～595.26×10~(-6),LREE/HREE值为5.60～6.53,具有Rb、Th、K、La、Ce、Zr、Hf、Sm等元素的富集以及Ba、U、Ta、Nb、Sr、P和Ti元素的亏损特征。柳树沟组双峰式火山岩形成于大陆裂谷环境,具板内成因特征,玄武岩可能为亏损尖晶石相地幔橄榄岩向石榴石相地幔橄榄岩过渡相较高程度部分熔融的产物,受到地壳物质混染;流纹岩具典型的A型花岗岩的地球化学特征。 相似文献
5.
武当地块耀岭河群中两类不同性质的酸性火山岩研究 总被引：1，自引：0，他引：1
耀岭河群火山岩中可划分出两类不同性质的酸性火山岩:酸性岩A主要属碱流岩-白碱流岩类,酸性岩B主要属流纹英安岩/英安岩类。总体上看二者主量元素组成差异不大:SiO2含量为65.00%～79.85%,(Na2O+K2O)为5.26%～9.68%。强烈富集Th、Nb、Ta、La、Ce、Nd、Zr、Sm和Hf等微量元素,强烈亏损Ba、K、Sr、P、Ti等元素,稀土元素特征表现为∑REE很高(339.94～1152.85μg/g),具有强烈的铕负异常(δEu=0.18～0.32),与典型的大陆裂谷流纹岩的稀土曲线一致。酸性火山岩B显示K、Rb、Ba、Th和LREE的正异常和Sr、P、Ti和Nb的负异常,Eu具弱负异常(δEu=0.64～0.88),表现出与酸性火山岩A迥然不同的微量元素及稀土元素特征,而与耀岭河群基性火山岩相似,显示其成因可能与之有相同源区。 相似文献
6.
内蒙古敖汉旗晚侏罗世满克头鄂博组火山岩地球化学特征及构造背景分析 总被引：1，自引：0，他引：1
内蒙古敖汉旗满克头鄂博组火山岩是一套酸性火山熔岩及火山碎屑岩。主量元素分析显示Si O2为69.76%~76.04%,K2O为4.48%~6.78%,Na2O+K2O为7.63%~9.44%,表明满克头鄂博组流纹岩具有高钾钙碱性岩石的特征。LREE/HREEE为10.46~15.87,稀土配分曲线呈轻稀土富集的右倾模式,δEu值为0.10~0.51,负异常明显;富集大离子亲石元素Rb、Th、U、K、Pb,贫Ba、Sr;亏损高场强元素P、Nb、Ta、Ti。说明满克头鄂博组火山岩属低Ba—Sr酸性火山岩,是下地壳基性火山岩部分熔融,并发生了斜长石、角闪石源区残留或分异结晶而形成的。满克头鄂博组火山岩具有A型花岗岩特征,其形成的动力学机制为蒙古—鄂霍茨克洋闭合造山后的岩石圈伸展环境。 相似文献
7.
《新疆地质》2017,(2)
对西天山尼勒克一带大哈拉军山组流纹岩类研究表明,岩石具富硅(SiO_2=70.78%~76.85%)、富铝(Al_2O_3=11.05%~15.54%)、富碱(K_2O+Na_2O=7.87%~9.71%)、贫钙(CaO=0.16%~1.42%)、低钛(TiO_2=0.08%~0.41%)特征,属钙碱性低钛流纹岩类。稀土元素总量较低(∑REE=50.77×10~(-6)~88.77×10~(-6)),稀土分布模式为轻稀土富集右倾型,铕负异常明显(δEu=0.59~0.81),相对富集Rb,Th,K等大离子亲石元素,亏损Nb,Ta,Ti等高场强元素,具较高的Rb/Sr、Nb/Ta和Th/Ta比值和较低的Ti/Zr、Ti/Y及Ta/Yb比值,表明其可能为上地壳部分熔融产物,同时具大陆边缘弧亲缘性。结合区域构造演化,认为伊犁地块北缘早石炭世处于大陆边缘弧环境。 相似文献
8.
云南个旧碱性杂岩体由边缘相碱长正长岩和中心相霞石正长岩组成。全岩地球化学分析表明,该碱性杂岩体具有高碱、富钾、富铁、低镁、高分异的碱性-过碱性岩石特征,晚期更富集碱金属元素; LREE/HREE值为20～59,(La/Sm)N=8～50,(Sm/Yb)N=1.2～5.0,富集轻稀土元素,轻稀土元素较重稀土元素分馏程度高,具Eu负异常,亏损Ti、Nb、P、K、Sr等元素,富集Zr、Hf、Th、La、Ce、Nd、U、Rb等元素,岩浆来源与幔源物质有关;碱长正长岩和霞石正长岩具有相似的微量元素和稀土元素特征,具有同源岩浆分异演化的特点; Rb/Sr、Nb/Ta、Zr/Hf等比值均高于或接近于原始地幔的相应值; CIPW标准矿物计算结果表明边缘相碱长正长岩中出现紫苏辉石、锥辉石、橄榄石,中心相霞石正长岩中出现橄榄石。结合(Th/Nb)N和Nb/La值特征以及前人Sr-Nd同位素研究成果,认为个旧碱性杂岩体的岩浆来源于遭受交代作用的富集地幔部分熔融,同时受有限的地壳混染作用而成,形成于后碰撞的伸展环境。碱性岩浆演化晚期更加富碱、经历了更高程度的结晶分异作用是稀土元素、Nb、Ga和Zr元素超常富集的重要原因。 相似文献
9.
新疆博格达东缘色皮口一带辉绿岩地球化学、锆石U-Pb年龄及地质意义 总被引：1，自引：0，他引：1
博格达造山带内出露的晚石炭世辉绿岩,为研究博格达裂谷演化末期地球动力学背景提供了重要信息.色皮口地区辉绿岩主量元素以低TiO2、较高Al2O3、较低MgO、贫P2O5,较低的K2O/Na2O比值(0.12~0.53),ΣREE较高,LREE/HREE为2.45~3.56,铕负异常不明显(δEu=0.82~1.02)等为特征.与原始地幔相比,其不相容元素K,Rb, U,Ba富集,高场强元素Nb,Ta,Zr,Hf无富集,Ti亏损不明显,Nb,Ta,Th表现为明显负异常.U富集可能指示与地壳物质的加入有关,较低的Nb/Zr比值(0.02~0.06),暗示岩浆源区可能为受地壳混染的亏损地幔.辉绿岩LA-ICP-MS锆石U-Pb定年结果为(300.5±1.7) Ma(MSWD=2.3,Th/U比值为0.36~1.3),为晚石炭世晚期,代表了博格达裂谷闭合后地球动力学环境由挤压变为拉张的转折期. 相似文献
10.
塔里木板块西南缘克里阳山区的钾质煌斑岩呈脉状产于前寒武纪埃连卡特群变质沉积岩中,其主要岩石类型有:金云母透辉石煌斑岩、假白榴石透辉石煌斑岩和含球粒透辉石煌斑岩。所有岩石具有低的SiO2(41.31%～44.84%)、TiO2(0.75%～0.86%)和高的MgO(7.30%～11.33%)和K2O(4.01%～6.01%)含量,K2O/Na2O比值介于2.77～12.49之间。同时,它们具有富集大离子亲石元素(Rb、Sr、Ba、Th、U、K)和轻稀土元素(LREE),相对亏损高场强元素(Nb、Ta、Zr、Hf、Ti)的特征,并且具有高的Sr同位素比值、相似的高度分异的REE配分模式。这些岩石的母岩浆来自于金云母角闪石石榴子石二辉橄榄岩的富集地幔,是该富集地幔部分熔融约5%～10%的产物,岩浆在上升侵位过程中受到地壳物质的混染较弱。富集地幔是俯冲的板块释放的富含钾质流体交代的结果。 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.
E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
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
13.
Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA 总被引：1，自引：0，他引：1
Joseph L. Domagalski Steven P. Phillips E. Randall Bayless Celia Zamora Carol Kendall Richard A. WildmanJr Janet G. Hering 《Hydrogeology Journal》2008,16(4):675-690
Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N2 in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area. 相似文献
14.
扬子北缘马元铅锌矿床闪锌矿微量元素及S-Pb-He-Ar-C同位素地球化学研究 总被引：7，自引：3，他引：4
马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多1000,成矿温度以中-低温为主。金属硫化物ε~(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,~(206)Pb/~(204)Pb为17.858~17.918:~(207)Pb/~(204)Pb为15.603~15.694;~(208)Pb/~(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra~1.05Ra,~(40)Ar/~(36)Ar为326.1~765.1,~(38)Ar/~(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ~(13)C_(CH_4)值为-36.01‰~-28.80‰,δ~(13)C_(C_2H_6)值为-27.72‰~-22.44‰,δ~(13)C_(CO_2)值为-23.24‰~-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。 相似文献
15.
I. M. Gorokhov M. A. Semikhatov M. M. Arakelyants E. A. Fallick N. N. Mel’nikov T. L. Turchenko T. A. Ivanovskaya T. S. Zaitseva E. P. Kutyavin 《Stratigraphy and Geological Correlation》2006,14(3):260-274
Clay subfractions (SFs) of <0.1, 0.1–0.2, 0.2–0.3, 0.3–0.6, 0.6–2 and 2–5 μm separated from Middle Riphean shales of the Debengda Formation are studied using the TEM, XRD, K-Ar and Rb-Sr isotopic methods. The oxygen and hydrogen isotope compositions in the SFs are studied as well. The low-temperature illite-smectite is dominant mineral in all the SFs except for the coarsest ones. The XRD, chemical and isotopic data imply that two generations of authigenic illite-smectite different in age are mixed in the SFs. The illite crystallinity index decreases in parallel with size diminishing of clay particles. As compared to coarser SFs, illite of fine-grained subfractions is enriched in Al relative to Fe and Mg, contains more K, and reveals higher K/Rb and Rb/Sr ratios. The Rb-Sr age calculated by means of the leachochron (“inner isochron”) method declines gradually from 1254-1272 Ma in the coarsest SFs to 1038-1044 Ma in finest ones, while the K-Ar age decreases simultaneously from 1225–1240 to 1080 Ma. The established positive correlation of δ18O and δD values with dimensions of clay particles in the SFs seems to be also consistent with the mixing systematics. The isotopic systematics along with data on mineral composition and morphology lead to the conclusion that mixedlayer illite-smectite was formed in the Debengda shales during two periods 1211–1272 and 1038–1080 Ma ago. The first period is likely close to the deposition time of sediments and corresponds to events of burial catagenesis, whereas the second one is correlative with the regional uplift and changes in hydrological regime during the pre-Khaipakh break in sedimentation. 相似文献
16.
17.
Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean 总被引：2，自引：0，他引：2
The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston
situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine
fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and
at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological
(i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates)
controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution
sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were
<20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf
of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is
lost to sediments. 相似文献
18.
海南大坡岩体位于五指山褶皱带内,主要受昌江—琼海构造带、琼西构造带与潭爷断陷构造带控制.岩石地球化学及岩石学研究表明,大坡岩体形成于海西-印支晚期,岩性单一,主要为中细粒似斑状黑云母二长花岗岩.岩体显示为Ⅰ型花岗岩与S型花岗岩的混合,主体以地壳物质部分熔融为主,形成过程有少量地幔物质加入.元素对的比值及稀土元素配分特征说明岩体钨锡等多金属含矿性可能较差. 相似文献
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20.
Over the past decade researchers working on the rocks of the Beaufort Group in the main Karoo Basin of South Africa have vastly increased our understanding of this important Permo-Triassic sequence. Many new fossil forms have been discovered, allowing for breakthroughs into the biodiversity, biogeography and biostratigraphy of the group. Taxonomic and phylogenetic advances are many and varied, and cover most of the vertebrate taxa, but with emphasis placed on the temnospondyl amphibians, archosauriforms and non-mammalian synapsids, in particular the anomodontia. Biostratigraphic breakthroughs have centered on the Middle Permian Eodicynodon and Tapinocephalus assemblage zones, the Late Permian Dicynodon Assemblage Zone, and the Triassic Lystrosaurus and Cynognathus assemblage zones. Correlation of these biozones with better dated sequences in Europe, Russia and China has allowed for many chronostratigraphic refinements, which are in turn vital for sequence stratigraphical analysis of the basin fill. Based on fossil data, both the lower (Ecca–Beaufort) and upper (Beaufort–Molteno) contacts of the group have been proved to be highly diachronous. The refined chronostratigraphic framework has also allowed for a better analysis of the basin evolution through time, particularly in terms of the correlation of external stimuli that affect basin sedimentation patterns. 相似文献