Synchronism in compression of the lithosphere in the central Atlantic and Western Tethys at the Tortonian-Messinian transition     

A. L. Knipper  Yu. N. Raznitsin 《Geotectonics》2008,42(1):21-30

The structure of anomalously uplifted areas in transverse ridges of the Vema, S o Paulo, and Romanche fracture zones is considered. It is concluded that their formation and eventual development in the present-day structure of the central Atlantic bottom proceeded during two stages. The first stage that corresponds to a short period at the Tortonian-Messinian transition (10 Ma ago) was marked by transportation of deep-seated rocks into the upper part of the lithosphere along thrust faults with mass motion in the meridional direction along the axis of the Mid-Atlantic Ridge. The second stage was characterized by contrasting highamplitude vertical movements from 10 to 3 Ma ago. It is suggested that near-meridional compression in the domains surrounding the Western Tethys in the Tortonian-Messinian resulted in deformation of the upper lithosphere within large transform fracture zones of the central Atlantic. The deformation that occurred 10 Ma ago was a manifestation of the global neotectonic epoch of the Earth.  相似文献   

Sorption of Ni on Na-rectorite studied by batch and spectroscopy methods     

Xiaoli Tan  Changlun Chen  Shaoming Yu  Xiangke Wang 《Applied Geochemistry》2008

Sorption of Ni²⁺ on Na-rectorite as a function of contact time, temperature, pH and fulvic acid (FA)/humic acid (HA) was studied under ambient conditions. A pseudo-second-order rate equation was used to simulate the kinetic sorption. The removal of Ni²⁺ increased with increasing pH. The presence of FA/HA enhanced the sorption of Ni²⁺ at low pH values, whereas no drastic effect of FA/HA on Ni²⁺ uptake to rectorite was found at high pH values. The diffuse layer model (DLM) fitted the experimental data of Ni²⁺ sorption in the absence and presence of FA/HA very well with the aid of FITEQL 3.2. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms of Ni²⁺ at different temperatures. The thermodynamic data (ΔH⁰, ΔS⁰, ΔG⁰) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Ni²⁺ on rectorite was spontaneous and endothermic. The sorption and species of Ni²⁺ on rectorite in the presence and absence of FA/HA was also investigated and characterized by XPS. The spectroscopic analysis indicated no drastic structural changes of Na-rectorite and the sorption of Ni²⁺ mainly occurred on the surface and at the edge position of Na-rectorite.  相似文献   

The Ruiga intrusion: A typical example of a shallow-facies paleoproterozoic peridotite-gabbro-komatiite-basaltic association of the Vetreny Belt,Southeastern Fennoscandia     

V. S. Kulikov  Ya. V. Bychkova  V. V. Kulikova  Yu. A. Kostitsyn  O. S. Pokrovsky  M. V. Vasil’ev 《Petrology》2008,16(6):531-551

The Ruiga differentiated mafic-ultramafic intrusion in the northwestern part of the Vetreny Belt paleorift was described for the first time based on geological, petrological, geochronological, and geochemical data. The massif (20 km² in exposed area) is a typical example of shallow-facies peridotite-gabbro-komatiite-basalt associations and consists of three zones up to 810 m in total thickness (from bottom to top): melanogab-bronorite, peridotite, and gabbro. In spite of pervasive greenschist metamorphism, the rocks contain locally preserved primary minerals: olivine (Fo _75–86), bronzite, augite of variable composition, labradorite, and Cr-spinels. A mineral Sm-Nd isochron on olivine melanogabbronorite from the Ruiga Massif defines an age of 2.39 ± 0.05 Ga, while komatiitic basalts of the Vetreny Belt Formation were dated at 2.40–2.41 Ga (Puchtel et al., 1997). The rocks of the Ruiga intrusion and lava flows of Mt. Golets have similar major, rare-earth, and trace element composition, which suggests their derivation from a single deep-seated source. Their parent magma was presumably a high-Mg komatiitic basalt. In transitional crustal chambers, its composition was modified by olivine-controlled fractionation and crustal contamination, with the most contaminated first portions of the ejected melt. In terms of geology and geochemistry, the considered magmatic rocks of the Vetreny Belt are comparable with the Raglan Ni-PGE komatiite gabbro-peridotite complex in Canada (Naldrett, 2003).  相似文献   

Zr/Hf ratio as an indicator of fractionation of rare-metal granites by the example of the Kukulbei complex,eastern Transbaikalia     

G. P. Zaraisky  A. M. Aksyuk  V. N. Devyatova  O. V. Udoratina  V. Yu. Chevychelov 《Petrology》2008,16(7):710-736

The concept of granitic melt fractionation as the main process in the concentration of rare elements in granites calls for the development of a reliable method to determine the evolutionary sequences of granite series. We propose to use for this purpose a zirconium-hafnium indicator, the Zr/Hf weight ratio in granitic rocks (Zaraisky et al., 1999, 2000). By the example of three classic regions of rare-metal deposits, eastern Transbaikalia, central Kazakhstan, and Erzgebirge (Czech Republic and Germany), it was empirically shown that the Zr/Hf ratio of granites decreases during the fractional crystallization of granite magmas in the sequence granodiorite → biotite granite → leucogranite → lithium-fluorine granite. The reason is the higher affinity of Hf compared with Zr to a granite melt. This implies that the crystallization and settling of accessory zircon will cause the progressive enrichment of Hf relative to Zr in the residual melt. As a result, the Zr/Hf ratio decreases regularly in the series of sequential phases of granite intrusion related to a single magma chamber from granodiorite to biotite granite, leucogranite, and Li-F granite (from 45-30 to 10-2). Our experimental investigations supported the preferential enrichment of haplogranite melt in Hf and zircon crystals in equilibrium with melt in Zr (T= 800°C and P = 1 kbar). The Zr/Hf indicator was tested by the example of the wellknown Kukulbei rare-metal granite complex of eastern Transbaikalia (J3), which is unique in the degree of fractionation of initial granite melt with the formation of three phases of granite emplacement and vein derivatives. An important feature of the complex is its “short” differentiation trend. It was supposed that the granite magma of the first phase is parental, and the later phases forming small intrusive bodies in large massifs of biotite granites of the first phase are sequential products of its crystallization differentiation in a magma chamber. The biotite granites of the first phase are barren. The leucocratic granites of the second phase are accompanied by tin-tungsten greisen deposits (e.g., Spokoininskoe), and the upper part of cupola-like stocks of Li-F amazonite granites of the third phase host apogranite-type tantalum deposits (Orlovka, Etyka, and Achikan). In addition to three granite phases, the Kukulbei complex includes dikes of ongonites, elvans, amazonite granites, and chamber miarolitic pegmatites. All of the granitic rocks of the complex have similar isotopic ages of 142± 0.6 Ma. The Zr/Hf ratio decreases systematically from phase 1 (40–25), to phase 2 (20–10), and phase 3 (10–2). The ongonites, elvans, and pegmatites have similar Zr/Hf ratios (15-5), falling between the ranges of leucocratic muscovite granites and Li-F granites. Compared with other granite series, the granitic rocks of the Kukulbei complex show specific petrographic and geochemical features: they are strongly enriched in Rb, Li, Cs, Be, Sn, W, Mo, Ta, Nb, Bi, and F but depleted in Mg, Ca, Fe, Ti, P, Sr, Ba, V, Co, Ni, Cr, Zr, REE, and Y. From the early to late intrusion phases, the degree of enrichment and depletion in these element groups increases regularly. This is accompanied by a significant decrease (from 40 to 2) in Zr/Hf, which can be used as a reliable indicator of genetic relations, degree of fractionation, and rare-metal potential of granites. Granites with Zr/Hf values lower than 25 are promising for prospecting for Sn, W, Mo, and Be greisen deposits, whereas the formation of Ta deposits requires Zr/Hf values lower than 10.  相似文献   

Opacitization conditions of hornblende in Bezymyannyi volcano andesites (March 30, 1956 eruption)     

P. Yu. Plechov  A. E. Tsai  V. D. Shcherbakov  O. V. Dirksen 《Petrology》2008,16(1):19-35

The paper is devoted to the conditions under which opacite rims developed around hornblende grains in andesite of the catastrophic eruption (March 30, 1956) of Bezymyannyi volcano, Kamchatka. The opacite rims were produced by a bimetasomatic reaction between hornblende and melt with the development of the following zoning: hornblende → Px + Pl + Ti-Mag → Px + Pl → Px → melt. Biometasomatic reaction was accompanied by the active removal of CaO from the rim, addition of SiO₂, and more complicated behavior of other components. The hornblende also shows reactions of its volumetric decomposition under near-isochemical conditions. The opacite rims developed under isobaric conditions, at a pressure of approximately 6 kbar. The main reason for the instability of the hornblende was the heating of the magma chamber from 890 to 1005°C due to new hot magma portion injection. The time interval between the injection and the start of eruption was estimated from the thickness of the opacite rims and did not exceed 37 days. Hence, the March 30, 1956, eruption was not related to the volcanic activity in November of 1955 but to the injection of a fresh magma portion in February–March of 1956.  相似文献   

运用3DEEMs及荧光偏振方法研究pH、离子强度及浓度效应对腐殖酸荧光光谱特性的影响   总被引：6，自引：0，他引：6  

梅毅  吴丰昌  王立英  白英臣 《地球化学》2008,37(2):165-173

利用三维荧光激发.发射光谱(3DEEMs)及荧光偏振法研究了3例腐殖酸和1例湖泊溶解有机物(DOM)在不同腐殖酸浓度、离子强度和pH条件下的荧光光谱特性.实验结果表明,随着浓度增大,各腐殖酸样的荧光强度增大,其中垃圾渗滤液腐殖酸和Pahokee泥炭腐殖酸的荧光峰出现红移.随着浓度进一步增大,腐殖酸的荧光偏振值增大,由此推断在此浓度范围内腐殖酸由于分子间的排斥作用使其构型出现伸展.离子强度增大导致腐殖酸及阿哈湖DOM的荧光强度降低.随着氯化钾(KCI)浓度增大,Fluka腐殖酸的荧光峰A蓝移,荧光峰B的荧光偏振值出现减小,推测是由于静电中和作用使其荧光基团发生卷曲造成的.离子强度对其余腐殖酸样和阿哈湖DOM的其他荧光特性没有明显的影响.总的来说,pH值的变化对腐殖酸和湖泊DOM的荧光特征的影响是很明显的.随着pH值增大,腐殖酸和湖泊DOM的荧光强度增强.而pH值减小时,Fluka腐殖酸和Pahokee泥炭腐殖酸的荧光峰(A峰)蓝移,当pH值降到5时,Fhka腐殖酸的荧光峰突然红移到最大,随后又继续蓝移;垃圾渗滤液腐殖酸和阿哈湖DOM的荧光峰位无明显的漂移.所有样品的荧光偏振值都减小(但阿哈湖DOM的A峰变化不大),但在pHi≤5时又增大,这种现象表明随着pH值降低,腐殖酸和湖泊DOM中有机大分子发生卷曲,但在pH≤5时由于羧基的质子化又以平面伸展构型出现在溶液中.  相似文献   

Composition and sources of biomarkers from surface sediment in Qiyi glacier,Qilian Mountains     

LI Quan-lian  WANG Ning-lian  WU Xiao-bo  PU Jian-chen  HE Jian-qiao  JIANG Xi 《地球化学》2008,37(6)

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储量计算与勘探线剖面计算机辅助成图一体化   总被引：1，自引：0，他引：1  

马小刚  李伟忠  吴冲龙  张夏林 《地质与勘探》2008,44(2):73-76

引入关系教据库和GIS自动编图技术,改进传统的垂直断面法储量计算过程,可实现矿山储量计算和勘探线剖面计算机辅助成图的同步和一体化.在共用的矿山地矿信息点源数据库平台基础上.通过设置本地数据库,形成GIS操作时的外挂属性库,用来保存储量计算和机助成图过程中的动态数据.储量计算中的每一步骤中,用户以GIS为操作界面来同步实现对空间图元和外挂属性的操作,这其中对工程样段组合、矿体边界圈连和剖面制图综合等开发了大量自动化辅助功能.储量计算的各步完成后,勘探线剖面图和储量报表即同步生成.这种改进的工作方式实现了垂直断面法全过程的计算机辅助化,将提高这一传统方法的应用效率.  相似文献   

Enrichment and geochemical origin of some trace elements in high-sulfur coal from Kaili,eastern Guizhou Province     

WU Yan-yan  QIN Yong  YI Tong-sheng  XIA Xiao-hong 《地球化学》2008,37(6)

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Biogeochemical characteristics of the Hetai goldfield, Guangdong Province, China     

Li Miao  Ruisong Xu  Yueliang Ma  Jinhong Xu  Jie Wang  Rui Cai  Yu Chen   《Journal of Geochemical Exploration》2008,96(1):43-52

In the Hetai goldfield, Guangdong Province, China, samples including rocks, soils and leaves of four plants (Pinus massoniana, Rhodomyrms tomenlosa, D. linearis var. dichotoma and Embelia laeta) collected from the gold mineralization zone and the background area were analyzed for Au, Ag, Cu, Pb, Zn, Hg, As and physiological parameters. The objective of this investigation is to study the geochemical and biogeochemical characteristics of studied plants, aiming at biogeochemical methods in Au exploration. The goldfield region shows geochemical and biogeochemical anomalies. Abundances of Au in rocks, soils, plants and the leaf pigments in the mineralized area are much higher than those in the surrounding region. The plants display unhealthy physiological and ecological characteristics in the Hetai goldfield area. The cell structures of the goldfield plants were anomalous and aberrant, and there were many nano-metal particles diffused in mitochondria and chloroplasts. Macro- and microscopic evidences of the vegetation in the goldfield areas are distinctly different from the background regions. The strongly anomalies in responses to Au are profound in further geochemical and botanic exploration studies.  相似文献