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1.
班公湖-怒江缝合带及其两侧广泛分布白垩纪岩浆岩,这些岩浆活动记录了班公湖-怒江特提斯洋俯冲至闭合以及拉萨-羌塘板块碰撞过程。为了约束该缝合带在早-晚白垩世的演化过程,本文对缝合带中段尼玛地区花岗岩进行岩相学、地球化学、锆石年代学和Hf同位素研究。尼玛北部虾别错花岗岩侵入到中生代地层中,发育石英闪长质包体。锆石U-Pb定年结果表明寄主花岗岩和包体形成于早白垩世(122Ma和121Ma)。这些锆石均具有正的εHf(t)值,分别为+2.4~+7.0和+3.0~+5.1。寄主花岗岩具有高硅和高钾钙碱性特征,属于准铝质-弱过铝质系列。包体相对低硅,属于中钾钙碱性准铝质系列。寄主花岗岩和包体具有相似的微量元素分布,如均亏损Nb、Ta和Ti,富集Th、U和Pb。综合分析,虾别错寄主花岗岩和包体是壳幔熔体混合作用的产物。尼玛南部张乃错花岗岩侵入到古生代地层里。锆石U-Pb年龄为97Ma,形成于晚白垩世。锆石εHf(t)值在+2.2~+6.0之间。张乃错花岗岩具有高硅特征,属于高钾钙碱性弱过铝质系列。岩体显著亏损Ba、Sr、Ti和Eu,富集Rb、Th、U和Pb等元素。该花岗岩来源于新生地壳部分熔融,并在后期经历结晶分异。结合区域地质概况,虾别错早白垩世花岗岩(和包体)形成于班公湖-怒江特提斯洋闭合过程,而张乃错晚白垩世花岗岩形成于洋盆闭合之后拉萨-羌塘板块碰撞背景。尼玛地区早-晚白垩世岩浆活动记录了班公湖-怒江缝合带从洋盆闭合到拉萨-羌塘板块挤压碰撞的演变过程。 相似文献
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西藏班公湖-怒江结合带中段分布大量早白垩世岩浆岩,其岩浆源区和岩石成因与班公湖-怒江洋的演化密切相关。对班公湖-怒江结合带中段东卡错地体发现的花岗闪长斑岩进行了系统的岩相学、年代学和地球化学研究。锆石U-Pb年龄结果显示,花岗闪长斑岩成岩时代为早白垩世(109.4±1.9 Ma)。样品显示出较高的SiO 2(67.40%~69.48%)和Al2O 3(15.66%~15.81%)含量及较低的Mg#值(19.03~21.48),具有高钾钙碱性系列岩浆岩特征;稀土元素总量较低(ΣREE=196.45×10^-6~207.6×10^-6),轻稀土元素富集,重稀土元素亏损,轻、重稀土元素分异明显,且具有较明显的负Eu异常(δEu平均值为0.64);微量元素蛛网图总体呈右倾的锯齿状,富集大离子亲石元素,亏损高场强元素;锆石εHf(t)均为负值且变化范围不大(-4.21^-10.59),对应的Hf模式年龄t2DM在1438~1842 Ma之间,显示古老地壳的特征。综合以上特征并结合区域资料分析,认为东卡错地体发现的花岗闪长斑岩为I型花岗岩,来源于古老下地壳的部分熔融,可能是东卡错地体与北拉萨地体或聂荣地体/南羌塘碰撞过程中板片断离岩浆活动的产物。 相似文献
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江错蛇绿岩位于班公湖-怒江缝合带中段, 位于切里湖蛇绿岩亚带的最东端, 南邻蓬湖西蛇绿岩.江错蛇绿岩岩石组合相对较全, 主要由变质橄榄岩、辉长岩和辉绿岩等组成.江错蛇绿岩辉长岩-辉绿岩与N-MORB相比具有较高的Mg#、低Ti、K、Na和P的特征, 富集大离子亲石元素Sr、Rb、Ba和亏损高场强元素Th、Hf、Ta、Nb, REE配分图总体显示为平坦型分布模式.通过地球化学元素分析认为江错蛇绿岩是形成于SSZ之上的弧后盆地扩张脊环境.对其进行辉长岩锆石SHRIMP U-Pb定年, 得出加权平均年龄为189.8±3.3 Ma(MSWD=0.97), 该结果代表了班公湖怒江缝合带中段江错地区特提斯洋的扩张时代, 与中段东巧地区蛇绿岩年龄一致, 但晚于东段洋盆发育时代且早于西段洋盆发育时代, 表明整个班公湖-怒江洋盆发育时代存在东早西晚的特点. 相似文献
4.
西藏青草山Cu-Au矿床是班公湖-怒江缝合带北侧新发现的具有大型远景的斑岩型矿床,但该矿床含矿斑岩的年龄、成因及源区一直未得到有效的约束.对青草山花岗闪长岩以及含矿花岗岩闪长斑岩进行了锆石年代学、Hf同位素以及岩石地球化学研究.结果显示,花岗闪长岩与含矿花岗闪长斑岩的侵入时代分别为131.2±0.3 Ma与117.9±0.8 Ma,代表了班公湖-怒江缝合带早期的成岩作用以及斑岩Cu-Au成矿作用.二者具有相似的地球化学特征,表明二者可能具有相同的岩浆源区,是不同时期同源岩浆活动的产物.结合含矿花岗闪长斑岩锆石Hf同位素组成,认为青草山含矿斑岩形成于班公湖-怒江洋壳向北俯冲过程中,是下地壳部分熔融的产物,受到了少量地幔物质的混合. 相似文献
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西藏班公湖-怒江缝合带广泛分布中生代岩浆活动,对于认识特提斯洋的演化有重要的启示。班公湖-怒江缝合带中段东卡错微陆块去申拉组安山岩的锆石U-Pb测年和Hf同位素测试结果显示,其中21个测点给出的锆石~(206)Pb/~(238)U年龄加权平均值为110.3±0.7Ma;ε_(Hf)(t)值为-5.66～1.05,二阶段Hf模式年龄为1020～1448Ma,表现出壳幔混源的特征。综合区域构造沉积演化及前人研究成果,认为东卡错微陆块内发育的去申拉组火山岩很可能与早白垩世班公湖-怒江洋壳南向俯冲消减引起的板片断离有关,并形成于板内伸展环境,其岩浆来源于聂荣微陆块成熟地壳物质发生深熔或重熔作用形成的酸性熔体与古老岩石圈地幔部分熔融产生的基性熔体的混合。 相似文献
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班公湖中特提斯洋向南俯冲的时限:来自SSZ型辉长岩的制约 总被引：1，自引：0，他引：1
班公湖-怒江中特提斯洋的俯冲极性和俯冲时间一直存在争议。作者通过野外地质调查、岩相学、锆石U-Pb年代学及岩石地球化学研究,从西藏班公湖蛇绿混杂岩带中识别出一套早白垩世SSZ型蛇绿岩,岩石组合上主要由辉长岩和玄武岩组成,还有少量的硅质岩和超基性岩。本文对辉长岩进行了全岩主、微量元素地球化学及LA-ICP-MS锆石U-Pb年代学研究。地球化学组成特征显示,辉长岩富集轻稀土元素,重稀土元素平坦,相对富集大离子亲石元素,高场强元素存在一定亏损;Th/Ta比值与岛弧玄武岩相似(Th/Ta1.6),Ta/Hf比值较高(0.1),显示其既保留了俯冲环境的地球化学特征,也提供了伸展构造环境的信息。辉长岩中锆石U-Pb加权平均年龄为129.2±0.4 Ma(MSWD=0.36),该年龄是班公湖-怒江缝合带中迄今报道的最年轻蛇绿岩年龄。结合区域地质背景,认为这套蛇绿岩形成于班公湖-怒江古洋盆西段向南俯冲形成的弧前盆地,而班公湖-怒江古洋盆北向俯冲可能始于早侏罗世,晚侏罗世形成双向俯冲格局,直到早白垩世洋盆关闭,晚白垩世进入陆内构造环境。 相似文献
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班公湖-怒江缝合带及其两侧广泛分布早白垩世岩浆岩,它们是班公湖-怒江洋俯冲消减及拉萨地块与南羌塘地块碰撞过程的直接响应,为研究特提斯大洋演化、青藏高原早期陆块聚合提供了重要素材。本文报道了班公湖-怒江缝合带中段那曲地区黑云母二长花岗岩的锆石U-Pb定年、岩石地球化学和锆石Hf同位素分析结果。锆石LA-ICP-MS U-Pb定年结果表明,黑云母二长花岗岩形成于114～113 Ma(早白垩世晚期)。地球化学分析表明,岩石显示出高钾钙碱性—钾玄岩系列特征,同时具有高的Ga/Al×10000比值(介于2.02～3.15之间,平均为2.61)和Zr+Nb+Ce+Y含量(平均为524.87×10-6)。此外,锆饱和温度和锆石Ti温度计共同指示岩浆形成于高温的环境(>800℃),这些特征与典型的A型花岗岩相一致。黑云母二长花岗岩中锆石具有低的εHf(t)值(10.1～6.4),对应的Hf同位素二阶段模式年龄(tDM2)为1852～1547 Ma,指示其岩浆可能源自安多微陆块中下地壳古老结晶基底的部分熔融。结合区域研究成果,认为那... 相似文献
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《福建地质》2016,(4)
改则洞错蛇绿岩规模大,各组成单元齐全,其中斜长花岗岩广泛分布。地球化学分析结果表明,洞错斜长花岗岩SiO_2含量66.83%,Al_2O_3含量小于15%,K_2O含量大于2%,高强场元素(Zr、Hf)相对富集,CIPW标准矿物中含有少量的刚玉(C)与传统大洋斜长花岗岩相区别。稀土元素配分表现为LREE相对HREE富集、HREE近水平的型式,与传统的大洋斜长花岗岩相区别。所以洞错斜长花岗岩可能属于洋壳运移过程中剪切带岩石部分熔融作用形成。获得的锆石LA-ICP-MS锆石U-Pb年龄为(157.6±4.3)Ma,代表了班公湖—怒江特提斯洋壳俯冲-消减阶段的时间。 相似文献
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班公湖-怒江缝合带西段阿翁错地区中酸性侵入岩的成因及其对区域构造演化的指示 总被引：2，自引：0，他引：2
班公湖-怒江缝合带西段出露大量中酸性侵入岩,为特提斯洋俯冲、拉萨地块与羌塘地块碰撞造山过程中岩浆响应的重要组成部分。本文对该缝合带西段阿翁错地区的闪长岩、花岗闪长岩和花岗岩进行了详细的岩石地球化学和锆石U-Pb年代学研究。锆石LA-ICP-MS U-Pb定年结果表明闪长岩、花岗闪长岩、花岗岩成岩年龄分别为119.3±1.8 Ma、114.7±1.4 Ma和103.2±1.3 Ma。岩石地球化学特征显示中酸性侵入岩属高钾钙碱性系列,具准铝质-弱过铝质I型花岗岩特征;其LREE分馏程度较高,而HREE近于平坦,存在Eu负异常;富集Rb、La等大离子亲石元素和Th、Zr、Hf等高场强元素,亏损Nb、Ta、P、Ti等高场强元素,具有岛弧岩浆岩的特征。研究结果表明在早白垩世晚期(103.0±1.3 Ma)班公湖-怒江特提斯洋壳仍在向北俯冲于南羌塘地块之下,随着俯冲深度增加,大洋板片发生大规模脱水,释放的流体交代地幔楔并引发其部分熔融,产生的幔源岩浆向上运移,与下地壳物质不同比例混合形成了闪长岩和花岗闪长岩;而花岗岩主要由古老下地壳物质部分熔融形成,并有少量地幔物质的参与。 相似文献
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西藏多不杂斑岩铜矿床辉钼矿Re-Os和锆石U-Pb SHRIMP测年及地质意义 总被引：37，自引：10，他引：27
多不杂矿床是班公湖-怒江缝合带上发现的第一处大型斑岩铜矿床.该矿床位于班公湖-怒江缝合带的北侧,羌塘地块的南缘.含矿斑岩体属花岗闪长斑岩,其SiO2含量为61.3796-67.73%,平均为65.16%;稀土元素总量为(41.4-94)× 10~(-6),LREE>HREE,属轻稀土元素富集型;微量元素特征表现为富集大离子不相容元素Rb、K、Th、Ba、La、Ce、Sr,亏损高场强元素Nb、Ta、P、Ti.含矿斑岩的稀土元素和微量元素特点反映出岛弧带的岩浆作用特征.含矿斑岩中锆石的U-Pb SHRIMP测年获得(120.9±2.4)Ma(MSWD=4.3)谐和年龄,代表了含矿斑岩的形成时代.6个辉钼矿样品的Re-Os模式年龄范围非常一致,其变化范围为(117.6±1.3)～(118.5±1.4)Ma,等时线年龄为(118.0±1.5)Ma(MSwD=0.30),代表了该矿床的成矿年龄.该矿床的形成时代对应于班公湖.怒江早白垩世期间的多岛弧-盆系演化时期,其形成环境类似于东南亚的多岛弧-盆系统. 相似文献
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S. Viswanathan K. Surya Prakash Rao B. Mahabaleswar 《Journal of the Geological Society of India》2013,82(6):621-627
Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours. 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
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奥地利安东帕有限公司 《岩矿测试》2009,28(3):306-306
最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提 相似文献
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Mining induced subsidence can significantly affect mining costs where major surface facilities and natural environment need to be protected. Overburden grout injection is a technology used to control coal mine subsidence by injecting the mine waste material extracted from the coal back into the inter-burden rock during longwall mining. The flowing slurry is here categorised as a nonlinear viscous cohesive (Bingham plastic) fluid. During longwall mining the grout slurry is pumped into the separated beds of the rock mass through a central vertical borehole, which is drilled deep into the inter-burden rock strata above the coal seam. However, a blockage can occur in the injection system when the slurry velocity falls below a certain critical threshold velocity, indicating a material phase change from cohesive-viscous to cohesive-frictional. In situ field injection tests through boreholes have been simulated at a smaller scale at the CSIRO laboratory in Brisbane by pumping the slurry through a radial disk (gap = 4 mm) from its centre. Laboratory experiments indicate a general, nonlinear, cohesive, viscous, frictional model for shear behaviour of the slurry, in which the material shear parameters are functions of the disk radial distance. Complete dimensional and dimensionless analytical solutions have been developed based on an approach related to Bingham–Herschel–Bulkley fluid mechanics. The derived formulae include relations for minimum pump pressure, local pressure and pressure gradient, wall shear stress, volume rate, velocity and velocity gradient. The theoretical results match the experimental measurements. The experiments covered slurries with maximum particle sizes of 0.5 to 2 mm with about 50% being larger than 100 µm. The viscosities at the various solids concentrations were measured with a standard torsion viscometer. This study differs from the previous research in several distinct aspects, namely, consideration of the variable shear parameters rather than fixed values, inclusion of total nonlinear behaviour, and implementation of a friction function to mimic behaviour of the deposited and consolidating stiff slurry, which can cause a significant pressure rise as a result of the increased shear resistance. 相似文献
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Alexander E. C. Broberg J. S. Kehren A. R. Graziani M. M. Turri W. L. 《Environmental Geology》1993,22(4):353-361
Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×106 1 of partially treated effluent and about 600 m3 of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials between the lagoon and the bedrock surface, (3) the presence and construction of liners (seepage rate), and (4) the proximity to existing sinkholes. 相似文献
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岩石密度和超高压岩石折返速率 总被引：1，自引：3，他引：1
在常温常压条件下对中国大陆科学钻CCSD主孔100-3000米岩心样品进行了密度测量,建立了密度连续剖面,并界定了不同超高压岩石的密度值。通过对比高温高压物性实验资料,岩石密度随着退变程度增强而降低,榴辉岩密度变化序列为3.52g/cm3→3.49g/cm3→3.07g/cm3→2.93g/cm3。超高压长英质岩石密度变化序列为3.00g/cm→2.80g/cm3→2.65g/cm3。上述实验资料是讨论不同折返阶段岩石所受浮力的基础,为研究折返速率大小提供了基本参数。本文通过折返板块运动平衡时,上浮力与粘滞力平衡这一关系式,定量研究了大陆俯冲板块的折返速率,认为密度差产生上浮力从而引起折返,温度对板块折返速率的影响最为显著;密度差大小、折返角度、折返板块大小对折返速率也有直接的影响。定量模拟分析表明,在温度高于850℃时,板块的折返速率可以超过100mm/a;当温度降至700℃时,折返速率则低于1.5mm/a。作者认为在折返早期,温度较高,板块快速折返至60-70km榴辉岩相深度;随着传导散热,温度降低,板块以较慢的速率折返至中下地壳。折返速率的估算表明,浮力是板块折返第一阶段(从>100km深部折返至<40km的中下地壳)的主要驱动力。 相似文献
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滇东南锡、银、铅、锌多金属矿床主要分布在个旧、白牛厂、都龙3个矿区,而滇东南较大的3个花岗岩体又分别出露在3个矿区或附近.花岗岩体均形成于燕山晚期,岩石化学、矿物成分相似,富含锡、银、铅、锌、钨、铜等成矿元素.矿床主金属元素组合与岩体之间的距离由远而近出现由锡、钨、(铍、铌、钽)→锡、钨、(铁)、铜、铟→锡、铅、锌、银、铟、(锑)有规律的变化.花岗岩浆是成矿物质来源和成矿热源.岩浆侵入初期使上覆地层隆起产生背斜(凹陷部位成向斜);同时使地层产生一系列裂隙、压性断层或层间断裂;岩浆侵入晚期,这些断层再次活动,表现为张性,岩浆产生的含矿热液沿由其活动所造成的断裂迁移、充填、交代、沉淀而形成矿床. 相似文献