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电感耦合等离子体质谱法(ICP-MS)测定大批量地质样品中的稀土和钴铪铟锰铌钽铊铬镉镓锗钒锡等金属元素,主要采用三酸或四酸溶解样品。由于地质样品组分复杂,稀土等金属元素含量低,各元素性质差异大,三酸或四酸溶样经常出现易挥发元素如钒铬镉镓锡的测定结果不稳定、镧铈镨钕等稀土元素溶解不完全的问题。本文在盐酸-硝酸-氢氟酸-高氯酸四酸基础上引入硫酸,形成盐酸-硝酸-氢氟酸-高氯酸-硫酸五酸溶样体系,用于水系沉积物、土壤和岩石等不同类型地质样品的一次敞口溶解,采用在线加入~(185)Re和~(103)Rh内标方式,建立了应用ICP-MS同时测定稀土等28种金属元素的方法。钒铬镉镓锡元素的准确度提高了1.4%～14.6%,镧和铈元素的准确度提高了0.2%～8.9%。该方法应用于分析水系沉积物、土壤、岩石标准物质(分别为GBW07301a、GBW07408、GBW07107),其测定值与认定值相一致,相对标准偏差(RSD)为1.14%～9.84%,准确度(△lgC)均≤0.1。该方法分析过程较简单,结果准确可靠,可满足测定大批量地质样品中稀土和钴铪铟锰铌钽等金属元素含量的要求。 相似文献
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南秦岭东河群碎屑锆石U-Pb年龄及其板块构造意义 总被引：2，自引：0，他引：2
南秦岭微陆块是秦岭造山带的重要构造单元,其早白垩世沉积物是研究物源区及南秦岭微陆块构造演化的理想对象.南秦岭微陆块南缘观音坝盆地早白垩世砂砾岩中的碎屑锆石LA-ICP-MS U-Pb年龄给出了5个年龄峰,范围分别是2600～2300Ma、2050～1800Ma、1200～750Ma、650～400Ma和350～200Ma,对应于Kenor、Columbia、Rodinia、Gondwana和Pangaea等5次超大陆事件.碎屑锆石源区复杂,但主要源自华北克拉通和北秦岭增生带,表明晚古生代南秦岭微陆块是秦岭-华北联合大陆板块的一部分,而非独立的微陆块.最年轻的锆石年龄峰给出了勉略洋向秦岭-华北大陆俯冲的时限,即350～ 200Ma;扬子与秦岭-华北联合大陆板块的碰撞造山作用始于三叠纪-侏罗纪之交,强烈的挤压造山作用发生在侏罗纪,而非三叠纪或更早. 相似文献
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The Qinling Orogen, central China, was constructed during the Mesozoic collision between the North China and Yangtze continental plates. The orogen includes four tectonic units, from north to south, the Huaxiong Block (reactivated southern margin of the North China Craton), North Qinling Accretion Belt, South Qinling Fold Belt (or block) and Songpan Fold Belt, evolved from the northernmost Paleo-Tethys Ocean separating the Gondwana and Laurentia supercontinents. Here we employ detrital zircons from the Early Cretaceous alluvial sediments within the Qinling Orogen to trace the tectonic evolution of the orogen. The U–Pb ages of the detrital zircon grains from the Early Cretaceous Donghe Group sediments in the South Qinling Fold Belt cluster around 2600–2300 Ma, 2050–1800 Ma, 1200–700 Ma, 650–400 Ma and 350–200 Ma, corresponding to the global Kenorland, Columbia, Rodinia, Gondwana and Pangaea supercontinent events, respectively. The distributions of ages and εHf(t) values of zircon grains show that the Donghe Group sediments have a complex source comprising components mainly recycled from the North Qinling Accretion Belt and the North China Craton, suggesting that the South Qinling Fold Belt was a part of the united Qinling–North China continental plate, rather than an isolated microcontinent, during the Devonian–Triassic. The youngest age peak of 350–200 Ma reflects the magmatic event related to subduction and termination of the Mian-Lue oceanic plate, followed by the collision between the Yangtze Craton and the united Qinling–North China continent that came into existence at the Triassic–Jurassic transition. The interval of 208–145 Ma between the sedimentation of the Early Cretaceous Donghe Group and the youngest age of detrital zircons was coeval with the post-subduction collision between the Yangtze and the North China continental plates in Jurassic. 相似文献
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藏南地区地热资源丰富,是喜马拉雅地热带的重要组成部分,有望成为新的地热资源开发靶区。本文以藏南桑日-错那活动构造带内模麓温泉群为研究对象,以水化学和氢氧氚同位素为研究方法,分析模麓温泉群的水岩作用、热储温度、补给来源及径流时间,揭示了地热水的成因机制。模麓地热水pH在6.6～7.2之间,TDS为1 908mg/L～2 326 mg/L,水化学类型以HCO3·Cl-Na型和HCO3·Cl-Na·Ca型为主。地热水中主要阴阳离子来源于硅酸盐矿物的溶解和少量地球深部物质。利用硅-焓方程法和硅-焓图解法计算的初始热储温度为198℃～256℃,冷水混入比例为68%～85%。此外,对地热水中的Li、B、F等微量元素分析得出,研究区温泉水中微量组分除来自水-岩作用外,应该还与深部流体的混入有关,且该地区的氢氧同位素特征表明地下水补给主要来源于大气降水,补给高程为5 652m～5 664m,模麓地热水中的氚含量<0.5TU,表明其地热水为老水,有更长的径流时间,为水-岩作用提供了充足的时间,而宿麦郎曲河水为新水,补给径流时间短。研究区地热水与围岩遮拉组砂板岩发生水-岩作用,进行离子交换作用,在地... 相似文献
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选取土壤、水系沉积物、岩石、超基性岩、黏土等标准物质,应用混合溶剂与样品质量比为14：1的高稀释比方法熔融制备测试样品,拟合校准曲线,建立X射线荧光光谱（XRF）同时测定硅酸盐岩石样品中18种组分（SiO2、Al2O3、TFe2O3、MgO、CaO、K2O、Na2O、TiO2、BaO、MnO、P2O5、Cr2O3、V2O5、Rb、Sr、Zr、Cu、Ni）的快速分析方法.应用帕纳科Eagon2全自动高频电感熔样机,称取7.0000 g（45Li2B4O7+10LiBO2+5LiF）混合溶剂与0.5000 g样品混合均匀,分别加入氧化剂饱和硝酸铵溶液2滴,脱模剂饱和溴化锂溶液4滴,于700℃先预氧化4 min,再1 120℃熔融9 min制备样片,自然冷却至室温.此熔样方法能保证样品中待测组分熔化完全,并制得表面光滑平整的样片.用国家标准物质验证,测试结果的准确度和精密度均符合《地质矿产实验室测试质量管理规范》（DZ/T 0130-2006）要求. 相似文献
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A weak form quadrature element formulation for consolidation analysis of non-homogeneous saturated soil is established based on Biot’s theory. Numerical examples are given, and the results are compared with the analytical solutions available or those from the commercial finite element software ABAQUS, demonstrating accuracy and rapid convergence of quadrature element solutions. The disparity between various treatments of non-homogenous soil is discussed, and the effectiveness and advantages of the quadrature element formulation in consolidation analysis of non-homogeneous soil are demonstrated. 相似文献
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《Ore Geology Reviews》2003,22(1-2):1-16
Numerous steel-gray microspherules were recently unexpectedly discovered in ore and rock samples from several disseminated gold deposits hosted in Middle–Upper Triassic turbidites in northwestern Sichuan Province, China. Both nature surfaces and part sections of 227 microspherules have been observed by reflected light microscope, scanning electron microscope (SEM), electron microprobe analyses, X-ray energy spectra, X-ray powder patterns, the results reveal them to be cosmic dust. It is the first discovery of cosmic dust in this kind of deposits in China.The size of the microspherules ranges from 25 to 185 μm and generally is less than 100 μm. According to their composition, they belong to chromium-rich iron cosmic dust. The microspherules have complex, diverse and diagnostic microscope structures and textures, and such as very distinct airprint structure that are compatible with extraterrestrial material. Variation of geochemical content of the microspherules in the gold deposits in generally positively correlates with both the Ir content of the enclosing strata and the intensity of mineralization and hydrothermal alteration. The abnormally high content of Ir is important evidence for an extraterrestrial source for the microspherules. The fact that a geological body with strong alteration and mineralization is rich in microspherules may raise a new concept: Under endogenic conditions, it is not only possible but also realistic for mineralized material to be transported mechanically, in addition to the generally accepted chemical transport of ore constituents in hydrothermal solution because it is obviously impossible for cosmic spherules to fall directly from space into cemented hydrothermal ore veins more than 1 km deep in the earth. 相似文献
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The enrichment of gold in arsenian pyrite is usually associated closely with the enrichment of arsenic in the mineral, generally known as As1−-pyrite [Fe(As, S)2]. Direct analyses of the valence state of Au in pyrite are, however, difficult due to generally low (∼ppm level) Au concentrations. By means of X-ray photoelectron spectroscopy (XPS), this study obtained reliable valence states of As in pyrite from the Yang-shan gold deposit, a giant “Carlin-type” Au deposit in the western Qinling orogen, central China. The arsenian pyrite specimens were sputtered with Ar+ beam in the vacuum chamber of an XPS to obtain pristine surfaces and to avoid As oxidation during sample preparation. Analyses before and after sputtering show that the As3+ peak are only present on surface that was once exposed to the air. In contrast, the peak of As−1 was essentially unchanged during continuous sputtering. The results indicated that As− is the predominant state on the pristine surface of arsenian pyrite; the peak of As3+ previously reported for Au-bearing arsenian pyrite was probably due to oxidation when exposed to air during sample preparation. It is unlikely that the coupled substitution of (Au+ + As3+) for 2Fe2+ takes place in the pyrite lattice. The so-called As3+-pyrite proposed by previous studies may occur in some special (oxidizing) geologic settings, but it is not observed in the Yang-shan gold deposit, and is unlikely to be important in typical orogenic or Carlin-type gold deposits, in which arsenian pyrite is a dominant Au carrier. Combining previous studies on Carlin-type Au deposits with our XPS experimental results, we suggest that the most likely state of Au in the Yang-shan Au deposit is lattice-bounded Au with or without nanoparticles (Au0). 相似文献
10.
《Gondwana Research》2013,24(4):1402-1428
The formation of collisional orogens is a prominent feature in convergent plate margins. It is generally a complex process involving multistage tectonism of compression and extension due to continental subduction and collision. The Paleozoic convergence between the South China Block (SCB) and the North China Block (NCB) is associated with a series of tectonic processes such as oceanic subduction, terrane accretion and continental collision, resulting in the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt. While the arc–continent collision orogeny is significant during the Paleozoic in the Qinling–Tongbai–Hong'an orogens of central China, the continent–continent collision orogeny is prominent during the early Mesozoic in the Dabie–Sulu orogens of east-central China. This article presents an overview of regional geology, geochronology and geochemistry for the composite orogenic belt. The Qinling–Tongbai–Hong'an orogens exhibit the early Paleozoic HP–UHP metamorphism, the Carboniferous HP metamorphism and the Paleozoic arc-type magmatism, but the three tectonothermal events are absent in the Dabie–Sulu orogens. The Triassic UHP metamorphism is prominent in the Dabie–Sulu orogens, but it is absent in the Qinling–Tongbai orogens. The Hong'an orogen records both the HP and UHP metamorphism of Triassic age, and collided continental margins contain both the juvenile and ancient crustal rocks. So do in the Qinling and Tongbai orogens. In contrast, only ancient crustal rocks were involved in the UHP metamorphism in the Dabie–Sulu orogenic belt, without involvement of the juvenile arc crust. On the other hand, the deformed and low-grade metamorphosed accretionary wedge was developed on the passive continental margin during subduction in the late Permian to early Triassic along the northern margin of the Dabie–Sulu orogenic belt, and it was developed on the passive oceanic margin during subduction in the early Paleozoic along the northern margin of the Qinling orogen.Three episodes of arc–continent collision are suggested to occur during the Paleozoic continental convergence between the SCB and NCB. The first episode of arc–continent collision is caused by northward subduction of the North Qinling unit beneath the Erlangping unit, resulting in UHP metamorphism at ca. 480–490 Ma and the accretion of the North Qinling unit to the NCB. The second episode of arc–continent collision is caused by northward subduction of the Prototethyan oceanic crust beneath an Andes-type continental arc, leading to granulite-facies metamorphism at ca. 420–430 Ma and the accretion of the Shangdan arc terrane to the NCB and reworking of the North Qinling, Erlangping and Kuanping units. The third episode of arc–continent collision is caused by northward subduction of the Paleotethyan oceanic crust, resulting in the HP eclogite-facies metamorphism at ca. 310 Ma in the Hong'an orogen and low-P metamorphism in the Qinling–Tongbai orogens as well as crustal accretion to the NCB. The closure of backarc basins is also associated with the arc–continent collision processes, with the possible cause for granulite-facies metamorphism. The massive continental subduction of the SCB beneath the NCB took place in the Triassic with the final continent–continent collision and UHP metamorphism at ca. 225–240 Ma. Therefore, the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt records the development of plate tectonics from oceanic subduction and arc-type magmatism to arc–continent and continent–continent collision. 相似文献