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981.
V. E. Strikha 《Geochemistry International》2006,44(8):791-807
Geochemical and isotopic data were used for a comparative analysis of Late Mesozoic (150–120 Ma) granitoids in various geological
structures of the upper Amur area. The granitoids are metaluminous high-potassic I-type rocks of the magnetite series. They
have variable alkalinity and consist of the monzonite-granite and granosyenite-granite associations. The monzonite-granite
association consists of calc-alkaline granitoids of normal alkalinity belonging to the Umlekan-Ogodzhinskaya volcanic-plutonic
zone and the Tynda-Bakaran Complex of the Stanovoy terrane. The rocks are characterized by negative anomalies of U, Ta, Nd,
Hf, and Ti (in patterns normalized to the primitive mantle), with Eu anomalies pronounced weakly in the granodiorites and
quartz and monzodiorites and more clearly in the granites: Eu/Eu* = 0.37–0.95, and (La/Yb)n = 7–24, Tbn/Ybn = 1.4–3.2. The granosyenite-granite association comprises of moderately alkaline rocks, which are subdivided into three groups
according to their geochemistry. The first group consists of phase-I granosyenites of the Uskalinskii Massif of the Umlekan-Ogodzhinskaya
zone with the highest concentrations of Sc, V, Cr, Co, Ni, Cu, Cs, Rb, Sr, Y, Zr, Yb, and Th; negative anomalies at Ba, Ta,
Sr, and Hf; Eu/Eu* = 0.50–0.58, (La/Yb)n = 15–16, and Tbn/Ybn = 1.8. The second group comprises of moderately alkaline granitoids of the Umlekan-Ogodzhinskaya zone and the Khaiktinskii
Complex of the Baikal-Vitim superterrane. Geochemically, the granitoids of this group are generally similar to the monzodiorite-granite
association and differ from it in having lower concentrations of REE and Y, Eu/Eu* = 6.2–1.0, (La/Yb)n = 28–63, and Tbn/Ybn = 2.1–4.5. The third group consists of granitoids of the Chubachinskii Complex of the Stanovoi terrane, which typically show
negative Cs, Rb, Th, U, Ta, Hf, and Ti anomalies; the lowest concentrations of V, Cr, Co, and Ni; and the highest contents
of Sr. The granosyenites of the first phase display clearly pronounced negative Eu anomalies (Eu/Eu* = 0.53–0.68), (La/Yb)n = 7–24, and Tbn/Ybn = 0.8–2.0. The granitoids of the second phase have (La/Yb)n = 51–84, no Eu anomalies, or very weak Eu anomalies (Eu/Eu* = 0.97–1.23). The silica-oversaturated leucogranites of the third
phase are characterized by elevated concentrations of REE, clearly pronounced Eu anomalies (Eu/Eu* = 0.48), and flat REE patterns
(Tbn/Ybn = 1.3). The diversity of the granitoids is demonstrated to have been caused largely by the composition of the Precambrian
source, which was isotopically heterogeneous. The rocks of the monzodiorite-granite association and first-group granosyenites
of the granosyenite-granite association of the Tynda-Bakaran Complex were supposedly derived from garnet-bearing biotite amphibolites.
In contrast to these rocks, the source of the second-group granites of the granosyenite-granite association was of mixed amphibolite-metagraywacke
composition. The third-group of granitoids were melted out of Early Proterozoic crustal feldspar-rich granulites of variable
basicity, with minor amounts of Archean crustal material. The granitoids were emplaced in a collisional environment, perhaps,
during the collision of the Amur superterrane and Siberian craton. This makes it possible to consider these rocks as components
of a single continental volcanic-plutonic belt.
Original Russian Text ? V.E. Strikha, 2006, published in Geokhimiya, 2006, No. 8, pp. 855–872. 相似文献
982.
An 11-month observation of dissolved and particulate organic matter, chlorophyll a(Chl a), C18 Sep-Pak extractable hydrophobic dissolved organic matter (hDOM) fraction and associated dissolved trace metals (Cd,
Cu, V, Co, Ni, Mo, U) was performed in the Lot–Garonne River system. This system includes the Riou Mort, the Lot River and
the downstream reaches of the Garonne River and represents the fluvial transport path of trace metals between the major point
source of polymetallic pollution, located in the Riou Mort watershed and the Gironde estuary. Spatial and temporal variations
of dissolved and particulate organic carbon and Chl areflect the presence of different types of organic matter and their relation with the hDOM fraction. Maximum Chl a/POC ratios (up to 0.03), indicate intense phytoplankton production from March to May. In the Lot River (Temple), DOC and
POC concentrations were clearly higher and mean Chl a concentration (2.8 mg g−1) was about three times higher than those of the other sites. High Chl a/POC ratios suggest high phytoplankton activity with maxima in spring and late summer. In the Riou Mort River, very high POC
concentrations of up to 40 (mean: 20) occurred, whereas Chl a concentrations were relatively low indicating low phytoplankton activity. High, strongly variable DOC and POC concentrations
suggest important natural (Carboniferous soils, forests) or anthropogenic (e.g., former coal mines, waste areas, agriculture,
sewage) carbon sources within the small Riou Mort watershed. Despite high DOC concentrations in the Riou Mort River, hDOM
metal fractions were generally lower than those at the other sites. The general order of decreasing binding strength between
metals and the organic hydrophobic phase (Cu, U > Co, Ni > V, Mo > Cd) at all four sites was in good agreement with the Irving–William
series of transition element affinity towards organic ligands. Accordingly, the role of the hydrophobic phase in dissolved
Cd transport appeared to be negligible, whereas the hDOM–Cu fraction strongly contributed to dissolved Cu transport. 相似文献
983.
The aim of this work is the joint application and integration of non-invasive geoelectrical methods for studying the landfill of Savoia di Lucania (Southern Italy). This landfill for its engineering features and small dimensions (70 m × 30 m × 6 m) represents an optimal test site to assess a geophysical survey protocol for municipal solid waste landfills investigation and monitoring. The landfill of Savoia di Lucania has been built with a reinforced concrete material and coated with a high-density polyethylene (HDPE) liner. Three electrical resistivity tomographies (ERT), two self-potential (SP) map surveys and one induced polarization (IP) section have been performed, both in the surrounding area and inside the waste landfill. The geophysical investigations have well defined some buried boundaries of the landfill basin and localized the leachate accumulation zones inside the dumpsite. Comparison of our results with other engineering and geological investigations could be the key for evaluating the integrity of the HDPE liner. Finally, the joint use of the ERT, IP and SP methods seems to be a promising tool for studying and designing new monitoring systems able to perform a time-lapse analysis of waste landfill geometry and integrity. 相似文献
984.
M. V. Charykova E. L. Fokina V. G. Krivovichev O. S. Yakovenko E. V. Klimova V. V. Semenova 《Geology of Ore Deposits》2015,57(7):570-578
The aim of this study is the experimental investigation of the synthetic analogs of cobaltomenite, CoSeO3 ? 2H2O, ahlfeldite, NiSeO3 ? 2H2O, members of the cobaltomenite–ahlfeldite solid solution series (Ni x Co1–x )SeO3 ? 2H2O, and singularities of their dehydration and dissociation. The intermediate members of the cobaltomenite (CoSeO3 ? 2H2O)–ahlfeldite (NiSeO3 ? 2H2O) series have been synthesized and studied with a combination of X-ray diffraction, scanning electron microscopy, and the simultaneous application of thermogravimetry (TG) and differential scanning calorimetry (DSC) within the temperature range from 25 to 640°C. The complete solid solution series corresponds to the monoclinic space group P21/n. Unit-cell dimensions decrease in all crystallographic directions as the amount of Ni increases. The angle β increases from 98.82(1) (cobaltomenite) to 99.05(1)° (ahlfeldite). It has been established that CoSeO3 ? 2H2O and NiSeO3 ? 2H2O dehydrate at 120–340°C through two stages apparently corresponding, to the formation of intermediate hydrated species CoSeO3 ? H2O and NiSeO3 ? 1/3H2O. The reaction enthalpies for each dehydration stage of CoSeO3 ? 2H2O and NiSeO3 ? 2H2O have been determined. Changes of the unit-cell dimensions and dehydration temperatures are rationalized in terms of the Co and Ni site occupancy in the structure of the cobaltomenite–ahlfeldite solid-solution series members. 相似文献
985.
Quaternary minettes and associated volcanic rocks of Mascota,western Mexico: a consequence of plate extension above a subduction modified mantle wedge 总被引:12,自引:0,他引:12
I. S. E. Carmichael R. A. Lange James F. Luhr 《Contributions to Mineralogy and Petrology》1996,124(3-4):302-333
Pleistocene-Holocene volcanism in the Jalisco block of western Mexico is confined to two conspicuous grabens, where potassic
eruptives range from absarokites (48–52% SiO2) and minettes (49–54% SiO2) through basaltic andesites (53–57% SiO2), the most voluminous type, to andesites and their lamprophyric equivalent spessartite (58–62% SiO2); there are no contemporary rhyolitic rocks. This suite has high concentrations of Mg, Cr (<550 ppm) and Ni (<450 ppm) accompanied
by large concentrations of K, P, Ba (<4000 ppm) and Sr (<5000 ppm) and elements such as LREE and Zr (<600 ppm). No combination
of crystal fractionation and/or crustal contamination can reproduce the compositional range of these magmas, which nevertheless
are believed to be genetically related because of their proximity in time and space. Hydrous minerals in the lamprophyres
and the typical absence of plagioclase phenocrysts in both basaltic andesites and andesites reflect the relatively high concentrations
of water in the magmas, which suppressed the crystallisation of feldspar. Experimental verification of the minimal amounts
of water required to reproduce the phenocryst assemblages in selected rocks range from 3.5 to 6%. During ascent in a volcanic
conduit, andesitic magma may lose water and consequently precipitate plagioclase, or it may ascend more rapidly, retaining
more of its initial water, which stabilises phenocrysts of hornblende at the expense of plagioclase. Our estimates of water
concentrations, which are consistent with the various low pressure phenocryst assemblages, will be minimal for the magmas
in their source regions, and the process of magmatic dewatering on ascent may be typical in well established volcanic conduits.
In accord with the compositions of phenocrystic olivine in the basaltic andesites and the minettes, the values of FeO and
Fe2O3 of the bulk lavas and scoriae are demonstrably pristine. As a consequence, there are two characteristic features of the Mascota
suite: the high range of relative oxygen fugacities (ΔNNO=1–5) and the high Mg# (MgO/MgO+FeO) that ranges from 0.70 to 0.91
(with only one andesite as low as 0.66). From the evidence of phlogopite phenocrysts, a partial melt involving phlogopite
would have a higher Mg# than one from olivine (Fo90) and pyroxene alone. As the Mascota series shows a correlation between K2O and Mg#, we conclude that it was generated by partial fusion of the mantle wedge, with a variable contribution of phlogopite
and apatite from veins throughout the lherzolitic assemblage. In conformity with an origin by varying increments of partial
fusion of a phlogopite-bearing mantle, all incompatible elements vary linearly with Ti (or K) as if phlogopite (+apatite)
in the source dominated their contribution to the partial melts. Fluids from dehydration of the subducting slab presumably
deposit hydrous and other minerals in veins in the mantle wedge and also increase its redox state. As the Mascota volcanism
occurs in grabens closer to the trench than the main andesite arc, it is concluded that the eruption of these small volumes
of hydrous magmas require the tectonically favored ascent paths offered by the extensional grabens to reach the surface from
their mantle sources.
Received: 24 January 1995 / Accepted: 21 February 1996 相似文献
986.
The age and thermal history of Cerro Rico de Potosi, Bolivia 总被引:1,自引:0,他引:1
C. G. Cunningham R. E. Zartman E. H. McKee R. O. Rye C. W. Naeser O. Sanjinés V G. E. Ericksen F. Tavera V 《Mineralium Deposita》1996,31(5):374-385
Cerro Rico de Potosi, Bolivia, is the world’s largest silver deposit and has been mined since the sixteenth century for silver,
and for tin and zinc during the twentieth century, together with by-product copper and lead. The deposit consists primarily
of veins that cut an altered igneous body that we interpret to be a dacitic volcanic dome and its underlying tuff ring and
explosion breccia. The deposit is compositionally and thermally zoned, having a core of cassiterite, wolframite, bismuthinite,
and arsenopyrite surrounded by a peripheral, lower-temperature mineral assemblage consisting principally of sphalerite, galena,
lead sulfosalt, and silver minerals. The low-temperature assemblage also was superimposed on the high-temperature assemblage
in response to cooling of the main hydrothermal system. Both the dacite dome and the ore fluids were derived from a larger
magmatic/hydrothermal source at depth. The dome was repeatedly fractured by recurrent movement on the fault system that guided
its initial emplacement. The dome was extruded at 13.8±0.2 Ma (2σ), based on U-Th-Pb dating of zircon. Mineralization and
alteration occurred within about 0.3 my of dome emplacement, as indicated by a 40Ar/39Ar date of 13.76±0.10 Ma (1σ) for sericite from the pervasive quartz-sericite-pyrite alteration associated with the main-stage,
high-temperature, mineralization. The last thermal event able to reset zircon fission tracks occurred no later than 12.5±1.1 Ma
(1σ), as indicated by fission-tract dating. Minor sericite, and magmatic-steam alunite veins, were episodically formed around
11 Ma and between 8.3 and 5.7 Ma; the younger episodes occurring at the time of extensional fracturing at Cerro Rico and widespread
volcanism in the adjacent Los Frailes volcanic field. None of these younger events appear to be significant thermal/mineralizing
events; the exceptionally flat thermal release pattern of 39Ar from sericite and the results of the fission-tract dating of zircon show that none of the younger events was hot enough,
and lasted long enough, to cause significant loss of Ar or annealing of zircon fission tracks. U-Th-Pb dating of zircon cores
indicates a Precambrian progenitor for some zircons, and REE analyses of dated samples of hydrothermally altered dacite show
the presence of a prominent positive Eu anomaly, which constrains interpretations of the origin and evolution of the magmatic/hydrothermal
system.
Received: 14 October 1995/Accepted: 29 January 1996 相似文献
987.
Summary In-situ microprobe LREE analyses of perovskite and titanite (La, Ce, Nd), and apatite (La, Ce), from SW Ugandan clinopyroxenite xenoliths and kamafugite lavas indicate that LREE distribution in these minerals is determined by a number of factors related to their different parageneses: In particular LREE content is affected by whether the LREE-bearing minerals have crystallised from metasomatic carbonate or from silicate (i.e. metasomatic or magmatic) melts in the mantle. In this situation LREE partition favours carbonate over silicate melts. Distribution of LREE in perovskite and apatite crystallised from magmatic mantle melts or mantle-derived lavas is chiefly determined by preference of LREE for perovskite > apatite > titanite. LREE zoning in perovskite is influenced by changes in melt structure: increasing melt polymerisation enhancing mineralLREE/meltLREE partition into perovskite rims in magmatic xenoliths; decreasing melt polymerisation depleting LREE in lava perovskite rims. This zoning is reinforced by perovskite competition with apatite for LREE: perovskite (cores/rims) co-crystallising with apatite is reduced in LREE. There are 37 instances of perovskitewith Ce below detection while La and Nd levels are normal. These occur in both xenoliths and lavas; in grain zones or whole grains. Likewise Ce alone of the LREE is below detection in six out of ten titanite analyses. These observations are interpreted as evidence for increased fO
2, Ce4 + being excluded from these mineral structures. Recognition of these various processes can elucidate the interpretation of bulk rock and bulk mineral LREE signatures in kamafugite volcanism.
With 3 Figures 相似文献
LREE Verteilung in Perovskit, Apatit und Titanit aus Xenolithen und kamafugitischen Laven Südwest-Ugandas
Zusammenfassung In-situ LREE Analysen von Perovskit und Titanit (La, Ce, Nd) und Apatit (La, Ce) aus Klinopyroxenit-Xenolithen und kamafugitischen Laven Südwest-Ugandas zeigen, daß die LREE Verteilung in diesen Mineralen durch eine Vielzahl von Faktoren, die mit Unterschieden in den Paragenesen zusammenhängen, bestimmt wird: Der LREE-Gehalt wird im besonderen davon bestimmt, ob die LREE-führenden Minerale aus metasomatischen Karbonat- oder aus (metasomatischen oder magmatischen) Silikatschmelzen im Mantel auskristallisierten. Dabei erfolgt die LREE Fraktionierung zu Gunsten der Karbonatschmelzen. Die LREE-Verteilung von Perovskit und Apatit, die aus magmatischen Mantelschmelzen oder -laven kristallisierten, wird vorrangig durch den bevorzugten Einbau der LREE in Perovskit > Apatit > Titanit kontrolliert. Der LREE Zonarbau von Perovskit wird durch die Änderungen der Schmelzstruktur beinflußt: Verstärkte Schmelzpolymerisation führt zu verstärkter MineralLFEE/SchmelzeLREE Fraktionierung in den Perovskiträndern magmatischer Xenolithe, eine Abnahme der Schmelzpolymerisation hingegen resultiert in einer Abreicherung der LREE in den Perovskiträndern. Diese Art der Zonierung wird durch den Wettbewerb von Perovskit mit Apatit um die LREE verstärkt. Perovskit (Kerne/Ränder), der mit Apatit gemeinsam auskristallisierte, ist ärmer an LREE. 37 Fälle, in denenCe nicht nachweisbar war, La und Nd aber in normaler Konzentration auftreten, wurden sowohl in den Xenolithen als auch in den Laven gefunden; und zwar entweder in Kornbereichen oder in ganzen Körnern. Vergleichsweise liegt Ce nur in sechs von zehn Titanitproben unterhalb der Nachweisgrenze. Diese Beobachtungen werden als Hinweise auf erhöhte SauerstoffFugazitäten, bei denen Ce4– aus der Mineralstruktur ausgeschlossen wird, angesehen.Ein Verständnis dieser verschiedenen Prozesse kann zur besseren Interpretation von LREE Gesamtgesteins- und Gesamtmineral-Signaturen in Kamafugiten beitragen.
With 3 Figures 相似文献
988.
Porewater pressure increases in soil and rock from underground chemical and nuclear explosions 总被引:3,自引:0,他引:3
Wayne A. Charlie George E. Veyera Deanna S. Durnford Donald O. Doehring 《Engineering Geology》1996,43(4):225-236
A review and analysis of chemical and nuclear explosive-induced porewater pressure increases and induced rise in groundwater table elevations (groundwater mounding) is presented. Our analysis indicates that residual pore pressure increases and groundwater mounding can be induced by underground chemical and nuclear explosions to scaled distances of 879 m/(kt)1/3. This relationship is linear over seven orders of magnitude of explosive energy ranging from a 0.01 kg chemical explosion to a 100 kt nuclear explosion and is valid for a wide variety of saturated geological profiles. Underground chemical explosions, and probably underground nuclear explosions have the potential to induce liquefaction of water-saturated soils to scaled distances of about 260 m/(kt)1/3. 相似文献
989.
E. Tavarnelli 《International Journal of Earth Sciences》1996,85(2):363-371
The Umbria-Marche foreland fold-and-thrust belt in the northern Apennines of Italy provides excellent evidence to test the
hypothesis of synsedimentary-structural control on thrust ramp development. This orogenic belt consists of platform and pelagic
carbonates, Late Triassic to Miocene in age, whose deposition was controlled by significant synsedimentary extension. Normal
faulting, mainly active from Jurassic through Late Cretaceous-Paleogene time, resulted in significant lateral thickness variability
within the related stratigraphic sequences. By Late Miocene time the sedimentary cover was detached from the underlying basement
and was deformed by east-verging folds and west-dipping thrusts. Two restored balanced cross sections through the southernmost
part of the belt show a coincidence between the early synsedimentary normal faults and the late thrust fault ramps. These
evidences suggest that synsedimentary tectonic structures, such as faults and the related lithological lateral changes, can
be regarded as mechanically important controlling factors in the process of thrust ramp development during positive tectonic
inversion processes. 相似文献
990.
Kusuma G. Rao V. N. Lykossov A. Prabhu S. Sridhar E. Tonkacheyev 《Journal of Earth System Science》1996,105(3):227-260
An attempt has been made here to study the sensitivity of the mean and the turbulence structure of the monsoon trough boundary
layer to the choice of the constants in the dissipation equation for two stations Delhi and Calcutta, using one-dimensional
atmospheric boundary layer model withe-ε turbulence closure. An analytical discussion of the problems associated with the constants of the dissipation equation is
presented. It is shown here that the choice of the constants in the dissipation equation is quite crucial and the turbulence
structure is very sensitive to these constants. The modification of the dissipation equation adopted by earlier studies, that
is, approximating the Tke generation (due to shear and buoyancy production) in theε-equation by max (shear production, shear + buoyancy production), can be avoided by a suitable choice of the constants suggested
here. The observed turbulence structure is better simulated with these constants. The turbulence structure simulation with
the constants recommended by Aupoixet al (1989) (which are interactive in time) for the monsoon region is shown to be qualitatively similar to the simulation obtained
with the constants suggested here, thus implying that no universal constants exist to regulate dissipation rate.
Simulations of the mean structure show little sensitivity to the type of the closure parameterization betweene-l ande-ε closures. However the turbulence structure simulation withe-ε. closure is far better compared to thee-l model simulations. The model simulations of temperature profiles compare quite well with the observations whenever the boundary
layer is well mixed (neutral) or unstable. However the models are not able to simulate the nocturnal boundary layer (stable)
temperature profiles. Moisture profiles are simulated reasonably better. With one-dimensional models, capturing observed wind
variations is not up to the mark. 相似文献