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1.
Sharkov E. V. Chistyakov A. V. Bogina M. M. Bogatikov O. A. Shchiptsov V. V. Belyatsky B. V. Frolov P. V. 《Doklady Earth Sciences》2019,486(2):638-643
Doklady Earth Sciences - The Tiksheozero ultramafic–alkaline–carbonatite intrusive complex, like numerous carbonatite-bearing complexes of similar composition, is a part of a large... 相似文献
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3.
Jonathon Dale Tim Holland Roger Powell 《Contributions to Mineralogy and Petrology》2000,140(3):353-362
Calibrations are presented for an independent set of four equilibria between end-members of garnet, hornblende, plagioclase
and quartz. Thermodynamic data from a large internally-consistent thermodynamic dataset are used to determine the ΔG° of the equilibria. Then, with the known mixing properties of garnet and plagioclase, the non-ideal mixing in amphibole is
derived from a set of 74 natural garnet–amphibole–plagioclase–quartz assemblages crystallised in the range 4–13 kbar and 500–800 °C.
The advantage of using known thermodynamic data to calculate ΔG° is that correlated variations of composition with temperature and pressure are not manifested in fictive derived entropies
and volumes, but are accounted for with non-ideal mixing terms. The amphibole is modelled using a set of ten independent end-members
whose mixing parameters are in good agreement with the small amount of data available in the literature. The equilibria used
to calibrate the amphibole non-ideal mixing reproduce pressures and temperatures with average absolute deviations of 1.1 kbar
and 35 °C using an average pressure–temperature approach, and 0.8 kbar with an average pressure approach. The mixing data
provide not only a basis for thermobarometry involving additional phases, but also for calculation of phase diagrams in complex
amphibole-bearing systems.
Received: 8 November 1999 / Accepted: 7 July 2000 相似文献
4.
To test a recently developed oxybarometer for silicic magmas based on partitioning of vanadium between magnetite and silicate melt, a comprehensive oxybarometry and thermometry study on 22 natural rhyolites to dacites was conducted. Investigated samples were either vitrophyres or holocrystalline rocks in which part of the mineral and melt assemblage was preserved only as inclusions within phenocrysts. Utilized methods include vanadium magnetite–melt oxybarometry, Fe–Ti oxide thermometry and -oxybarometry, zircon saturation thermometry, and two-feldspar thermometry, with all analyses conducted by laser-ablation ICP–MS. Based on the number of analyses, the reproducibility of the results and the certainty of contemporaneity of the analyzed minerals and silicate melts the samples were grouped into three classes of reliability. In the most reliable (n = 5) and medium reliable (n = 10) samples, all fO2 values determined via vanadium magnetite–melt oxybarometry agree within 0.5 log units with the fO2 values determined via Fe–Ti oxide oxybarometry, except for two samples of the medium reliable group. In the least reliable samples (n = 7), most of which show evidence for magma mixing, calculated fO2 values agree within 0.75 log units. Comparison of three different thermometers reveals that temperatures obtained via zircon saturation thermometry agree within the limits of uncertainty with those obtained via two-feldspar thermometry in most cases, whereas temperatures obtained via Fe–Ti oxide thermometry commonly deviate by ≥50 °C due to large uncertainties associated with the Fe–Ti oxide model at T-fO2 conditions typical of most silicic magmas. Another outcome of this study is that magma mixing is a common but easily overlooked phenomenon in silicic volcanic rocks, which means that great care has to be taken in the application and interpretation of thermometers and oxybarometers. 相似文献
5.
Prakash Abhishek Piazolo Sandra Saha Lopamudra Bhattacharya Abhijit Pal Durgesh Kumar Sarkar Saheli 《International Journal of Earth Sciences》2018,107(6):2265-2292
International Journal of Earth Sciences - In the present study we investigate the microstructural development in mullite, quartz and garnet in an anatectic migmatite hosted within a Grenvillian-age... 相似文献
6.
Martina Bertelli Timothy Baker James S. Cleverley Thomas Ulrich 《Journal of Geochemical Exploration》2009
The Bismark deposit (northern Chihuahua, Mexico) is one of several base metal-rich high-temperature, carbonate-replacement deposits hosted in northern Mexico. Previous fluid inclusion studies based on microthermometry and PIXE have shown that the Zn-rich, Pb-poor Bismark deposit formed from a moderate salinity magmatic fluid [Baker, T. and Lang, J.R., 2003. Reconciling fluid inclusion types, fluid processes, and fluid sources in skarns: an example from the Bismark Deposit, Mexico. Mineralium Deposita 38(4), 474–495; Baker, T., van Achterberg, E., Ryan, C.G. and Lang, J.R., 2004. Composition and evolution of ore fluids in a magmatic-hydrothermal skarn deposit. Geology 32(2), 117–120]. The exact precipitation mechanisms are unclear and may have due to cooling, salinity decrease and wall rock reaction. Furthermore, PIXE data suggested that Pb and Zn concentrations were comparable and inconsistent with the Zn-rich nature of the ore. However, Pb was commonly below the limit of detection for PIXE and the data presented by Baker et al. [Baker, T., van Achterberg, E., Ryan, C.G. and Lang, J.R., 2004. Composition and evolution of ore fluids in a magmatic-hydrothermal skarn deposit. Geology 32(2), 117–120] are regarded as the maximum concentrations of Pb in the fluid. In this study new LA ICP MS analysis was carried out on the same fluid inclusion population to compare with the PIXE data in order to constrain the uncertainty related to the Pb data and the new results are used to model possible ore deposition mechanisms. The new laser ablation data reveal overall lower concentrations of Pb in the ore fluid (average value ~ 285 ppm) than previously indicated by PIXE analysis (average value ~ 713 ppm). Chemical modelling using the new laser ablation data tested the following ore deposition processes: 1) cooling; 2) fluid–rock reaction at constant temperature; 3) cooling and simultaneous fluid–rock interaction. Modelling results show that the gangue and ore minerals observed at Bismark are best reproduced by fluid–rock interaction and simultaneous cooling. Results from the simulations strongly indicate that ore deposition was mainly driven by a pH increase due to the neutralization of the acidic ore fluid (pH = 3.9) as the result of the reaction with the limestone. Modelling results also suggest that the deposit likely formed under cooling conditions, but do not support the hypothesis of a temperature decrease as the principal ore-forming process. 相似文献
7.
The Olyutorsky–Kamchatka foldbelt formed as a result of two successive collisions of the Achaivayam–Valaginsky and Kronotsky–Commander island arcs with the Eurasian margin where the two terranes docked after a long NW transport. We model their motion history from the Middle Campanian to Present and illustrate the respective plate margin evolution with ten reconstructions. In this modeling the arcs are assumed to travel on the periphery of the large plates of Eurasia, North America, Pacific, and Kula, for which the velocities and directions of motion are known from published data. The model predicts that the Achaivayam–Valaginsky arc was the leading edge of the Kula plate from the Middle Campanian to the Middle Paleocene and then moved slowly with the Pacific plate as long as the Middle Eocene when it accreted to Eurasia. The Kronotsky arc initiated in the Middle Campanian on the margin of North America and was its part till the latest Paleocene when the terrane changed polarity to move northwestward with the Pacific plate and eventually to collide with Eurasia in the Late Miocene. The predicted paleolatitudes of the Achaivayam–Valaginsky and Kronotsky–Commander island arcs for the latest Cretaceous and Paleogene are consistent with nine (out of eleven) reliable paleomagnetic determinations for samples from the two arcs. Additional changes imposed on the initial model parameters (kinematics of the large plates, relative position of the Kula–Pacific Ridge and the Emperor seamount chain, or time of active volcanism within the arcs) worsen the fit of the final reconstructions to available geological and paleomagnetic data. Therefore, the suggested model appears to be the most consistent one at this stage of knowledge. 相似文献
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Despite a recent increase in the number of vulnerability analyses there has been relatively little discussion of vulnerability
assessment of social–environment system, especially when they face multiple hazards. In this study, we developed an applicable
and convenient method to assess vulnerability of social–environment system at a regional scale. Vulnerability is quantified
by measuring three critical elements (i.e. hazards, sensitivity, and resilience) through some key variables. The results showed
that vulnerability is high in Miaofeng Mountain in Mengtougou District, the hills of Pinggu County and the riparian zones
of the lower courses of the Beiyun and Yongding Rivers; but low in the city of Beijing and the southwestern part of the Fangshan
District. Areas of very high, high, medium, and low-vulnerability account for 6.19, 25.48, 33.06, and 35.27% of the total
area, respectively. The degree of vulnerability decreases in a northwest direction in mountainous areas and declines from
watercourses to riparian zones along a lateral direction in the plain. Some adaptive strategies are also proposed. 相似文献
10.
The Aitik Cu–Au–Ag deposit in the Gällivare area in northern Sweden is Sweden's largest sulphide mine with an annual production of 35 Mt of ore, and the biggest open pit operation in northern Europe. It is proposed in the present study that the Aitik deposit represents a Palaeoproterozoic, strongly metamorphosed porphyry copper deposit that was affected ca. 100 Ma later by a regional IOCG-type hydrothermal event. Consequently, the Aitik deposit might represent a mixed ore system where an early copper mineralisation of porphyry type has been overprinted by later regional IOCG mineralisation.Several attempts have previously been made to genetically classify the Aitik Cu–Au–Ag deposit as a distinct ore type. New geochemical, petrographic, structural, and fluid inclusion results combined with published data have provided the opportunity to present new ideas on the genesis and evolution of the Aitik Cu–Au–Ag deposit. The emplacement of a ca. 1.9 Ga quartz monzodiorite that host the ore at Aitik was related to subduction processes and volcanic arc formation, and synchronous with quartz vein stockwork formation and porphyry copper mineralisation. Highly saline aqueous (38 wt.% NaCl) fluid inclusions in the stockwork veins suggest entrapment at 300 °C and a pressure of nearly 3 kbar, a high pressure for a typical porphyry copper ore, but consistent with conditions at associated deep root zones of intrusion-related magmatic–hydrothermal systems. The highly saline fluid formed disseminated and vein-type ore of mainly chalcopyrite and pyrite within comagmatic volcaniclastic rocks, and caused potassic alteration (biotite, microcline) of the host rocks. The early porphyry copper mineralising event was followed, and largely overprinted, by CO2 and aqueous medium- to high-salinity (16–57 wt.% salts) fluids related to a ca. 1.8 Ga tectonic and metamorphic event (peak conditions 500–600 °C and 4–5 kbar). Extensive deformation of rocks and redistribution of metals occurred. Magnetite enrichment locally found within late veins, and late amphibole–scapolite and K feldspar alterations within the deposit, are some of the features at Aitik implying that aqueous fluids responsible for IOCG-mineralisation (200–500 °C and ~ 1 kbar) and extensive Na–Ca alteration in the region during the 1.8 Ga tectonic event also affected the Aitik rocks, possibly leading to addition of copper ± gold. 相似文献
11.
Rohana Chandrajith Dinusha Chaturangani Sumith Abeykoon Johannes A. C. Barth Robert van Geldern E. A. N. V. Edirisinghe C. B. Dissanayake 《Environmental Earth Sciences》2014,72(3):867-877
The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (18O/16O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl? > HCO 3 ? > SO 4 2? > N-NO3 ? while cations showed a decreasing order of abundance with Na+ > Ca2+ > Mg2+ > K+. Dominant groundwater hydrogeochemical types were Na–Cl and mixed Ca–Mg–Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region. 相似文献
12.
Paul Duuring Wouter Bleeker Steve W. Beresford Nicholas Hayward 《Mineralium Deposita》2010,45(3):281-311
Perseverance is a world-class, komatiite-hosted nickel sulphide deposit situated in the well-endowed Leinster nickel camp
of the Agnew–Wiluna greenstone belt, Western Australia. The mine stratigraphy at Perseverance trends north-northwest (NNW),
dips steeply to the west, and is overturned. Stratigraphic footwall units lie along the western margin of the Perseverance
Ultramafic Complex (PUC). The PUC comprises a basal nickel sulphide-bearing orthocumulate- to mesocumulate-textured komatiite
that is overlain by a thicker, nickel sulphide-poor, dunite lens. Hanging wall rocks include rhyodacite that is texturally
and compositionally similar to footwall volcanic rocks. These rocks separate the PUC from a second sequence of nickeliferous,
E-facing, spinifex-textured komatiite units (i.e. the East Perseverance komatiite). Past workers argue for a conformable stratigraphic
contact between the PUC and the East Perseverance komatiite and conclude that the PUC is extrusive. This study, however, clearly
demonstrates that these komatiite sequences are discordant, implying that the PUC may have intruded rhyodacite country rock
as a sill with subsequent structural juxtaposition against the East Perseverance komatiite. Early N–S shortening associated
with the regional DI deformation event (corresponding to the local DP1 to DP3 events at Perseverance) resulted in the heterogeneous partitioning of strain along the margins of the competent dunite. A
mylonite developed in the more ductile footwall rocks along the footwall margin of the PUC, while isoclinal F3 folds, such as the Hanging wall limb and Felsic Nose folds, formed in low-mean stress domains along the fringes of the elongated
dunite lens. Strata-bound massive and disseminated nickel sulphides were passively fold thickened in hinge areas of isoclinal
folds, whereas basal massive sulphides lubricated fold limbs and promoted thrust movement along shallowly dipping lithological
contacts. Massive sulphides were physically remobilised up to 20 m from their primary footwall position into deposit-scale
fold hinges to form the 1A and Felsic Nose orebodies. First-order controls on the geometry of the Perseverance deposit include
the thermomechanical erosion of footwall rocks and the channelling of the mineralised komatiitic magma. Second- or third-order
controls are several postvolcanic deformation events, which resulted in the progressive folding and shearing of the footwall
contact, as well as the passive fold thickening of massive and disseminated sulphide orebodies. Massive sulphides were physically
remobilised into multiple generations of fold hinges and shear zones. Important implications for near-mine exploration in
the Leinster camp include identifying nickeliferous komatiite units, defining their three-dimensional geometry, and targeting
fold hinge areas. Fold plunge directions and stretching lineations are indicators of potential plunge directions of massive
sulphide orebodies. 相似文献
13.
正1 Introduction In the present paper,MgCl2·6H2O,FeCl3·6H2O,and CeCl3·6H2O were used as raw materials in the precipitationhydrothermal method to synthesize MgF eC e hydrotalcite.The effects of the Fe:Ce molar ratio on the composition,crystal structure,and thermal stability of hydrotalcite are examined.Energy-dispersive X-ray spectroscopy(EDS),X- 相似文献
14.
《International Journal of Mineral Processing》2003,68(1-4):17-36
A simple theoretical model of magnetic–hydrophobic coagulation considering the total interaction potential energy between two spheres exposed to an external magnetic field as a sum of the van der Waals, electrostatic, magnetic, and hydrophobic components is proposed. The model was used to interpret experiments on coagulation of fine siderite particles in distilled water and 10−2 M KCl, hydrophobized by sodium oleate. In the experiments, a relative extent of the coagulation/stability equilibrium of the siderite suspension was evaluated photoelectrically. To estimate the model parameters, the ζ-potential and hydrophobicity of siderite particles were measured.A qualitative agreement was obtained between the model predictions (energy maximum and secondary minimum) and the experimental results (voltage changes after a selected interval of sedimentation) of the siderite suspensions. Moreover, a statistically significant correlation was found between the experimental voltages and the calculated energy maximum (a crucial factor of theories on the fine particle coagulation kinetics), which can be represented by a linear regression equation with the correlation coefficient of 0.979. 相似文献
15.
The main objective of this study was to assess the spatial and temporal variability of groundwater level fluctuations in the
Amman–Zarqa basin, during the period 2001–2005. In the year 2003, as a consequence of war, there was a sudden increase in
the population in this basin. Knowing that the basin is already heavily populated and witnesses most of the human and industrial
activities in Jordan, this study was prompted to help make wise water resources management decisions to cope with the new
situation. Data from 31 fairly distributed wells in the upper aquifer of the basin were subjected to geostatistical treatment.
Kriging interpolation techniques have indicated that the groundwater flow directions remained almost constant over the years.
The two main directions are SW–NE and E–W. Kriging mapped fluctuations have also showed that drop and rise events are localized
in the basin. Forecasting possibilities for management purposes were tackled using autocorrelation analysis. The constructed
autocorrelograms indicated, in general, the temporal dependence of seasonal water level fluctuations, and that forecasting
can be carried out within a period of 3–21 months. Several suggestions were made to mitigate the drop and rise hazards in
the detected sites. 相似文献
16.
A new high sulfidation epithermal Cu–Au occurrence (Nadun) has been discovered adjacent to the Cretaceous Duolong porphyry Cu–Au deposit within the Bangong–Nujiang metallogenic belt, central Tibet. The Nadun Cu–Au mineralization is hosted in a tectonic–hydrothermal breccia with advanced argillic alteration, which occurs above sandstone, associated with quartz–pyrite veins. The granodiorite porphyry with strong argillic alteration yields a zircon U–Pb age of 119.1 ± 1.3 Ma, whereas the weakly argillic granodiorite porphyry intruded into the breccia has a younger age of 116.1 ± 1.3 Ma. This indicates that Cu–Au epithermal mineralization likely occurred between ~ 116 Ma and ~ 119 Ma, consistent with the duration of magmatic–hydrothermal activity at Duolong (~ 115–118 Ma), and providing evidence that Nadun and Duolong were formed during the same event. Moreover, the Nadun and Duolong porphyries have similar Hf isotopic compositions (εHf(t) values ranging from − 8.8 to 8.1; mean = 5.0 ± 1.1, n = 32), likely indicating that the deposits are comagmatic. In addition, boiling assemblages in vapor-rich inclusions coexisting with brines occur in early stage quartz–pyrite veins, and likely record phase separation at a temperature of > 550–300 °C and pressure of 700–110 bars. Most liquid-rich fluid inclusions formed at the breccia stage show similar salinity (1.7–19.3 wt.% NaCl equiv) to vapor-rich inclusions from the underlying quartz–pyrite veins, likely indicating vapor contraction during cooling at elevated presssure. This suggests that quartz–pyrite veins may act as conduits for ore-forming fluid traveling from the porphyry to the epithermal hydrothermal system. O and H isotopic compositions (δ18Ofluid = 0.42–9.71‰ and δD = − 102 to − 66‰) suggest that ore-forming fluids are dominantly from a magmatic source with a minor addition of meteoric water at a later stage. The S and Fe isotope compositions of sulfides (δ34S = − 5.9 to 0.5‰ and δ57Fe = − 2.15 to 0.17‰) decrease from the quartz–pyrite vein to breccia ore, indicating that ore-forming fluids gradually become SO42-enriched and relatively oxidized. This body of evidence suggests that the Nadun Cu–Au mineralization may represent the root of a high sulfidation epithermal deposit. 相似文献
17.
Hang Lei Gao YuFeng He Jia Li Chi Zhou YunDong van Paassen Leon A. 《Acta Geotechnica》2022,17(12):5429-5439
Acta Geotechnica - In the biocement–geosynthetic system, biocement is combined with geosynthetic to increase the pullout resistance of the geosynthetic and thereby the stability of reinforced... 相似文献
18.
Sara Abedi Mirna Slim Ronny Hofmann Taras Bryndzia Franz-Josef Ulm 《Acta Geotechnica》2016,11(3):559-572
The organic–inorganic nature of organic-rich source rocks poses several challenges for the development of functional relations that link mechanical properties with geochemical composition. With this focus in mind, we herein propose a method that enables chemo-mechanical characterization of this highly heterogeneous source rock at the micron and submicron length scale through a statistical analysis of a large array of energy-dispersive X-ray spectroscopy (EDX) data coupled with nanoindentation data. The ability to include elemental composition to the indentation probe via EDX is shown to provide a means to identify pure material phases, mixture phases, and interfaces between different phases. Employed over a large array, the statistical clustering of this set of chemo-mechanical data provides access to the properties of the fundamental building blocks of clay-dominated organic-rich source rocks. The versatility of the approach is illustrated through the application to a large number of source rocks of different origin, chemical composition, and organic content. We find that the identified properties exhibit a unique scaling relation between stiffness and hardness. This suggests that organic-rich shale properties can be reduced to their elementary constituents, with several implications for the development of predictive functional relations between chemical composition and mechanical properties of organic-rich source rocks such as the intimate interplay between clay-packing, organic maturity, and mechanical properties of porous clay/organic phase. 相似文献
19.
The enrichment of lead isotopic composition of nonuranium minerals, in the first place galena in 206Pb and 207Pb, as compared to common lead is a remarkable feature of uranium deposits. The study of such lead isotopic composition anomalous in 206Pb and 207Pb in uranium minerals provides an opportunity for not only identification of superimposed processes resulting in transformation of uranium ores during deposit history but also calculation of age of these processes under certain model assumptions. Galena from the Chauli deposit in the Chatkal–Qurama district, Uzbekistan, a typical representative of hydrothermal uranium deposits associated with domains of Phanerozoic continental volcanism, has been examined with the highprecision (±0.02%) MC-ICP-MS method. Twenty microsamples of galena were taken from polished sections. Six of them are galena hosted in carbonate adjacent to pitchblende spherulites or filling thin veinlets (approximately 60 μm) cutting pitchblende. Isotopically anomalous lead with 206Pb/204Pb and 207Pb/204Pb values reaching 20.462 and 15.743, respectively, has been found in these six microsamples in contrast to another fourteen in which the Pb–Pb characteristics are consistent with common lead. On the basis of these data and with account for the 292 ± 2 Ma age for the Chauli deposit, the age of epigenetic transformation of uranium ores of this deposit has been estimated. During this process, radiogenic lead partly lost from pitchblende was captured into galena. The obtained date is 170 Ma. In the Chatkal–Qurama district, these epigenetic processes are apparently caused by the interaction of uranium minerals with activated underground water under tectonic activity and relief transformation, which took place from the post-Permian (i.e., after the Chauli formation) to the Jurassic period. 相似文献