甘肃东南地区温泉流体地球化学特征     

吕超甲  刘雷  周晓成  杜建国  易丽 《地震》2017,37(1):52-60

根据氢、 氧、 氦同位素与水化学组分资料, 讨论了甘肃东南地区温泉水的来源、 地球化学变化及其与2008年汶川M_S8.0地震的关系。 测定结果表明: 样品的溶解性固体总量(TDS)范围为241.7~2 372.1 mg/L。 采集的7处温泉(通渭汤池河温泉、 清水地震台、 天水地震台、 武山地震台、 武山22号井、 成县地震台、 武都地震台)水样可归为四种化学类型: Na·Ca-SO₄、 Ca·Mg-SO₄、 Na-HCO₃·SO₄、 Ca·Mg-SO₄·HCO₃。 地下热水的化学类型与裂隙深度和围岩的岩性有关, 离子浓度和断裂深度基本成正相关。 通渭汤池河温泉和武都地震台的δ18O和δD值分别在-11.4‰ ~ -7.6‰和-85.7‰ ~ -57.1‰的范围内, 通渭汤池河温泉和武都地震台中³He/⁴He的值分别为0.4×10^-7和12.7×10^-7。 氢、 氧、 氦同位素组成特征表明温泉水源于大气降水, 在循环过程中经历了水岩反应, 且可能有地表水的混入。 2008年汶川M_S8.0地震发生后, 研究区域内温泉水中K⁺、 Ca²⁺含量总体上升, SO^2-₄、 Cl^-含量总体下降, Na⁺含量变化不明显; 热水循环深度受地震影响发生变化。 本文确定了甘肃东南地区温泉来源、 水化学类型成因及其与汶川M_S8.0地震的关系。  相似文献   

Early Devensian interstadial and glacigenic sediments in Gwynedd,North Wales     

K. Addison  M. J. Edge 《Geological Journal》1992,27(2):181-190

  相似文献   

Mineralogy, whole-rock and Sr-Nd isotope geochemistry of mafic microgranular enclaves in Cretaceous Dagbasi granitoids, Eastern Pontides, NE Turkey: Evidence of magma mixing, mingling and chemical equilibration   总被引：7，自引：0，他引：7  

Abdullah Kaygusuz  Emre Ayd?nçak?r 《Chemie der Erde / Geochemistry》2009,69(3):247-277

Rocks of the Late Cretaceous Dagbasi Pluton (88-83 Ma), located in the eastern Pontides, include mafic microgranular enclaves (MMEs) ranging from a few centimetres to metres in size, and from ellipsoidal to ovoid in shape. The MMEs are composed of gabbroic diorite, diorite and tonalite, whereas the felsic host rocks comprise mainly tonalite, granodiorite and monzogranite based on both mineralogical and chemical compositions. MMEs are characterized by a fine-grained, equigranular and hypidiomorphic texture. The common texture of felsic host rocks is equigranular and also reveals some special types of microscopic textures, e.g., oscillatory-zoned plagioclase, poikilitic K-feldspar, small lath-shaped plagioclase in large plagioclase, blade-shaped biotite, acicular apatite, spike zones in plagioclase and spongy-cellular plagioclase textures and rounded plagioclase megacrysts in MMEs. Compositions of plagioclases (An₃₃-An₆₀), hornblendes (Mg#=0.77-1.0) and biotites (Mg#=0.61-0.63) of MMEs are slightly distinct or similar to those of host rocks (An_12-57; hbl Mg#=0.63-1.0; Bi Mg#=0.50-0.69), which suggest partial to complete equilibration during mafic-felsic magma interactions.The felsic host rocks have SiO₂ between 60 and 76 wt% and display low to slightly medium-K tholeiitic to calc-alkaline and peraluminous to slightly metaluminous characteristics. Chondrite-normalized rare-earth element (REE) patterns are fractionated (La_cn/Lu_cn=1.5-7.3) with pronounced negative Eu anomalies (Eu/Eu*=0.46-1.1). Initial ε_Nd(i) values vary between −3.1 and 1.6, initial ⁸⁷Sr/⁸⁶Sr values between 0.7056 and 0.7067.Compared with the host rocks, the MMEs are characterized by relatively high Mg-number of 22-52, low contents of SiO₂ (53-63 wt%), low ASI (0.7-1.1) and low to medium-K tholeiitic to calc-alkaline, metaluminous to peraluminous composition. Chondrite-normalized REE patterns are relatively flat [(La/Yb)_cn=1.4-3.9; (Tb/Yb)_cn=0.9-1.5] and show small negative Eu anomalies (Eu/Eu*=0.63-1.01). Isotope signatures of these rocks (⁸⁷Sr/⁸⁶Sr_(i)=0.7054-0.7055; ε_Nd(i)=-1.0 to 1.9) are largely similar to the host rocks. Gabbroic diorite enclaves have relatively low contents of SiO₂, ASI; high Mg#, CaO, Al₂O₃, TiO₂, P₂O₅, Sr and Nb concentrations compared to dioritic and tonalitic enclaves.The geochemical and isotopic similarities between the MMEs and their host rocks indicate that the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust- and mantle-derived magmas. All the geochemical data suggest that a basic magma derived from an enriched subcontinental lithospheric mantle, interacted with a crustal melt that originated from dehydration melting of the mafic lower crust at deep crustal levels. The existence of compositional and textural disequilibrium and the nature of chemical and isotopic variation in these rock types indicate that magma mixing/mingling between an evolved mafic and a granitic magma was involved in their genesis. Microgranular enclaves are thus interpreted to be globules of a more mafic magma probably from an enriched lithospheric mantle source. Al-in-amphibole estimates the pluton emplacement at ca. 0.3-3.8 kbar, and therefore, magma mixing and mingling must have occurred at 3.8 kbar or below this level.  相似文献   

Satellite prediction of soil δC distributions in a southern African savanna     

Lixin Wang  Gregory S. Okin  Stephen A. Macko 《Journal of Geochemical Exploration》2009,102(3):137-141

Stable carbon isotopes have been frequently used to indicate carbon pools and processes in soils, plants, and the atmosphere. Carbon isotope compositions are particularly useful in partitioning soil carbon sources between C₃ and C₄ vegetation because of the distinct δ¹³C distributions for C₃ and C₄ vegetation. Remote sensing is a powerful tool used to identify ecosystem patterns and processes at larger scales. A union of these two approaches would hold promise for spatially continuous estimates of carbon isotope compositions. In the current study, a framework is presented for using high spatial resolution remote sensing to predict soil δ¹³C distributions across a southern Africa savanna ecosystem. The results suggest that if the vegetation–soil δ¹³C relationship can be established, soil δ¹³C distributions can be estimated by high-resolution satellite images (e.g., IKONOS, Quickbird). Despite limitations remote sensing is a promising tool to expand estimates of terrestrial δ¹³C spatial patterns and dynamics.  相似文献   

青藏高原及邻区晚更新世-全新世冰川活动的年代学及影响因素          下载免费PDF全文

姜英  陈建军 《地质科学》2009,44(1):159-182

山岳冰川发育是否同步于北半球冰期,西风与季风对山岳冰川发育的控制作用是青藏高原及周边山地的冰川年代学研究的关键.近年来就地宇宙成因核素和光释光测年技术的快速发展为山岳冰川发育规律研究提供了大量的数据支持.本文综合分析了近年来在青藏高原和周边山地获得的冰川年代学数据,发现该地区山岳冰川发育与北半球冰期不同步,冰川发育贯穿于整个MIS 3阶段.在MIS 2阶段冰川活动峰期明显滞后于北半球末次冰期冰盛期.但是,山岳冰川对Heinrich Event 1和Younger Dryas两次快速气候波动事件有显著响应.这可能说明了西风作为纽带可以将北大西洋气候变化与青藏高原联系起来,同时,来自南方的季风对高原冰川的发育也有着重要的控制作用.造山带地区的冰川进退与高原抬升、地貌及气候之间是一个复杂的耦合系统.  相似文献   

河南银洞沟造山型银矿床碳硫铅同位素地球化学   总被引：19，自引：8，他引：11  

张静  杨艳  胡海珠  王志光  李国平  李忠烈 《岩石学报》2009,25(11):2833-2842

河南内乡县银洞沟大型脉状银多金属矿床产于北秦岭造山带朱夏断裂北侧的二郎坪地体内,含矿围岩是二郎坪群火山岩-碎屑岩建造,矿体定位于断裂构造带内,产状受断裂构造控制,矿石组构、矿物组合、围岩蚀变类型和分带等地质特征均与典型造山型金矿一致,应属造山型银矿.矿床硫化物δ~(34)S介于+4.7～+8.1‰,高于有机物和岩浆岩.流体包裹体中CO_2的δ~(13)C介于-0.2～+0.9‰,与海相碳酸盐一致,高于其它所有地质体.矿石硫化(206)Pb/~(204)Pb=18.2026～18.4462,~(207)Pb/~(204)Pb=15.5835～15.7739,~(208)Pb/~(204)Pb=38.5478～39.0890,显示铀铅富集,钍铅微弱亏损.这些同位素地球化学特征均指示夹杂沉积硫酸盐的碳酸盐-碎屑岩沉积建造是最为理想的物源,对比研究东秦岭北坡相关地质单元,认为成矿物质和流体主要来自二郎坪群和秦岭群,尤其是雁岭沟组含碳酸盐岩地层对于成矿流体和物质的贡献不可替代.中生代华北与华南板块碰撞造山过程中,秦岭群沿朱夏断裂向北陆内俯冲到二郎坪地体之下,并通过俯冲变质脱水而为银洞沟矿床的形成提供了大量成矿物质和流体.朱夏断裂北侧依次出现银洞沟银矿、许瑶沟金矿、松垛隐伏花岗岩基、栾川斑岩钼矿带,构造-成岩-成矿空间格局与CMF模式(碰撞造山成岩成矿和流体作用模式)完全一致,证明了CMF模式的科学性和普适性和同位素示踪成矿物质和流体来源的有效性.银洞沟矿床的发现和研究结果证实了前人预测的朱夏断裂北侧"桑坪-米坪-许瑶沟铜金铅锌银等多金属矿化带"的客观存在,该带应作为银金多金属矿床勘查的重点区带.  相似文献   

Brief sea‐level fall event and centennial to millennial sea‐level variations during Marine Isotope Stage 19 in Osaka Bay,Japan          下载免费PDF全文

Kenta Maegakiuchi  Masayuki Hyodo  Ikuko Kitaba  Kotaro Hirose  Shigehiro Katoh  Hiroshi Sato 《第四纪科学杂志》2016,31(7):809-822

  相似文献   

同位素技术在河南省豫北平原地下水源地规划中的应用   总被引：1，自引：0，他引：1  

苗晋祥 《地下水》2011,(4):1-4

过去,在浅层地下水资源评价中,由于对地下水更新能力的认识不够,对地下水的可开采资源量估计的过高,因而许多地区的开采强度大大超过地下水的天然更新速率,产生了一系列与地下水开发利用有关的环境问题。在充分考虑了地下水的可恢复性,使用同位素T（3H）估算了浅层地下水更新速率与地下水年龄,开展地下水资源评价的基础上,制订地下水水...  相似文献   

干法灰化和湿法消解植物样品的铜锌铁同位素测定对比研究   总被引：2，自引：0，他引：2  

李世珍  朱祥坤  吴龙华  骆永明 《地球学报》2011,32(6):754-760

测定有机样品中元素含量和同位素时,处理样品常用的方法有干灰化法和湿法两种.目前,测定样品中Cu、Zn、Fe同位素时,多采用湿法处理样品.相对于湿法处理样品,干灰化法溶样迅速、耗酸量少,适合处理大量样品,但高温灼烧过程可能会导致样品中Cu、Zn、Fe同位素的分馏.本研究利用海州香薷植株,以湿法为基础,对干灰化法和湿法处理...  相似文献   

Origin and regional significance of late Precambrian and early Palaeozoic granitoids in the Pan-African belt of Somalia     

J. -L. Lenoir  J. -P. Liégeois  D. Küster  A. Utke  G. Matheis  A. Haider 《International Journal of Earth Sciences》1994,83(3):624-641

Granitoids within the Precambrian basement of north-eastern and southern Somalia are subdivided on the basis of geology, geochronology and petrology into three different assemblages. The post-kinematic assemblage in north-eastern Somalia ( 630 Ma) comprises granodiorites and granites which belong to a medium-K calc-alkaline suite. Average initial Sr, Nd and Pb isotopic ratios [Sr_i = 0.7048, _Nd = –1.8,²⁰⁶Pb/²⁰⁴Pb(i) = 17.704 and²⁰⁷Pb/²⁰⁴Pb(i) = 15.611] indicate that these melts were derived from a mantle or juvenile crustal source with only slight involvement of pre-existing crust as a contaminant. Two different assemblages are found in southern Somalia. The older assemblage is composed of crustal anatectic, synkinematic, parautochthonous granites ( 600 Ma) related to amphibolite facies retrogression of an intensively reworked pre-Pan-African crust [Sr_i = 0.7100, _Nd = –8.4,²⁰⁶Pb/²⁰⁴Pb(i) = 15.403 and²⁰⁷Pb/²⁰⁴Pb(i) = 15.259]. These monzo- and syenogranites are moderately potassic and peraluminous. The younger assemblage ( 470 Ma) consists of post-kinematic monzonites to syenogranites with A-type affinities. Initial Sr, Nd and Pb isotopic data for this metaluminous assemblage [Sr_i = 0.7114, _Nd = –13.1,²⁰⁷Pb/²⁰⁴Pb(i) = 16.913 and²⁰⁷Pb/²⁰⁴Pb(i) = 15.512] indicate a significant lower crustal component but, however, also a mantle signature. The late Proterozoic to early Palaeozoic granitoids in Somalia thus express contrasting regimes, characterized by strong juvenile input in the north, close to the Arabian-Nubian Shield, whereas intense crustal reworking with little addition of juvenile material prevailed in the south. Somalia was definitively not a cratonic area during the Pan-African, but a zone of high crustal mobility.  相似文献