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1.
Symmetrical folding of a single layer and folding process of an overfold are analyzed by using the finite element method. In the analysis, the constituent substances are assumed to be isotropic and incompressible and to behave as Newtonian fluids. The penalty function method is used to deal with incompressibility, The results of the analysis are compared with the data measured in the field and with those obtained by the elastopla(?)e finite element analysis, It shows that the overfold geometry may be well simulated by using the viscous fluid model. Thus, a possible mechanism of the formation of overfold is proposed.  相似文献   

2.
Mesozoic ophiolites crop out discontinuously in the Indo‐Myanmar Ranges in NE India and Myanmar, and represent the remnants of the Neotethyan oceanic lithosphere. These ophiolites in the Indo‐Myanmar Ranges are the southern continuation of the Neotethyan ophiolites occurring along the Yarlung Zangbo Suture Zone in southern Tibet farther northwes, as indicated by their coeval crystallization ages and geochemical compositions. The Kalaymyo ophiolite is located in the central part of the Indo‐Myanmar Ranges (Myanmar). The Kalaymyo ophiolite are composed of olivine (Fo = 89.8–90.5), orthopyroxene (En86‐91Wo1‐4Fs8‐10; Mg#=89.6–91.9), clinopyroxene (En46‐49Wo47‐50Fs3‐5; Mg# = 90.9–93.6) and spinel (Mg# = 67.1–78.9; Cr# = 13.5–31.5), and have relatively homogeneous whole‐rock compositions with Mg# of 90.1–90.8 and SiO2 (41.5–43.65 wt.%), Al2O3 (1.66–2.66 wt.%) and CaO (1.45–2.67 wt.%) contents. They display Light Rare Earth Element (LREE)‐depleted chondrite‐normalized REE patterns and show a slight enrichment from Pr to La. The Kalaymyo peridotites are characterized by Pd‐enriched chondrite‐normalized PGE patterns with superchondritic (Pd/Ir)CN ratios (1.15–2.36). Their calculated oxygen fugacities range between QFM–0.57 and QFM+0.90. These features collectively suggest that the Kalaymyo peridotites represent residual upper mantle rocks after low to moderate degrees (5–15%) of partial melting at a mid‐ocean‐ridge environment. The observed enrichment in LREE and Pd was a result of their reactions with enriched MORB‐like melts, percolating through these already depleted, residual peridotites. The Kalaymyo and other ophiolites in the Indo‐Myanmar Ranges hence represent mid‐ocean ridge–type Tethyan oceanic lithosphere derived from a downgoing plate and accreted into a westward migrating subduction–accretion system along the eastern margin of India.  相似文献   

3.
Results of RbSr, PbPb and SmNd whole rock, Rbr biotite and PbPb zircon evaporation analyses are presented for certain granitoid rocks from the Johannesburg Dome. These data indicate that the granodiorite, granite and leucosome from migmatite were emplaced ∼ 3090 Ma ago, were genetically related and were derived primarily from a source between ∼ 3300 and ∼ 3500 Ma old. A portion of the granodiorite and granite might have been derived from a source between ∼ 4000 and ∼ 4300 Ma old. The tonalite was emplaced ∼ 3170 Ma ago and was derived from a source between 3.3 and 3.5 Ga old. RbSr biotite-whole rock ages, ranging between about ∼ 2614 and ∼ 2080 Ma, probably reflect complete resetting during differential uplift, erosion and cooling of the granitoid rocks in the Neoarchæan and Palæoproterozoic. If so, they apparently were not influenced by the emplacement of the ∼ 2060 Ma Bushveld Igneous Complex or the ∼ 2000 Ma Vredefort event. The granodiorite, granite and leucosome were emplaced coeval with and may be genetically related to compositionally similar plutonic and volcanic rocks in the Barberton area, Vredefort structure and Dominion Group.  相似文献   

4.
This paper examines the influence of sorbed gas type and pressure on the strength of coal. Particular attention is focused on the influence of gas type and pressures on drillability characteristics of coal and particle size distribution of drill cuttings. Drillability of coal has a strong bearing on the strength properties of coal. Based on fracture mechanics and mechanical rock cutting, weaker rocks are easier to drill and the drill cuttings produced are generally coarse in size. Accordingly a specially designed precision drill was used to drill coal samples under both normal atmospheric and confined gas pressure conditions. Indications of changes to coal strength as a result of increased sorbed gas pressure were examined by analysing the particle size distribution of the drill flushing. A laser controlled Malvern Mastersizer S particle size analyser with measuring range between 0.05 m and 900 m was used to study the particle size distribution. This paper demonstrates that there is a definite variation in the range of particle size distribution with particles obtained from drilling coal samples not subjected to gas pressures in comparison with those obtained from samples drilled under confined gas pressure. Gas types also have an influence. Higher proportions of coarse particles were produced when the confined gas was changed from CH4 to CO2. A change in the rate of drilling under varying confining pressure and gas type was also evident. The rate of drilling in air (at normal atmospheric conditions) was slower than at higher confining pressures. The highest drill rates were obtained with CO2 confinement.  相似文献   

5.
On the basis of analysing and studyingthe mineralizing conditions and content ratinglaws, the authors infer the geology and oresnear old placers by applying the remote sens-ing technology and analogous method, and  相似文献   

6.
Travin  A. V.  Buslov  M. M.  Bishaev  Yu. A.  Tsygankov  A. A. 《Doklady Earth Sciences》2023,507(3):S396-S399
Doklady Earth Sciences - The thermal history of the Late Paleozoic granitoids of the Angara–Vitim batholith (AVB) was reconstructed using a comprehensive approach including U/Pb, 40Ar/39Ar,...  相似文献   

7.
In the strdy of the source material of granites ,it is found that cosmic dust can be used as one of the indicators for identifying the genetic types of granites.It is suggested that granites can be grouped into two genetic types, dust-barren granite and dust-containing granite, corresponding to I-type and S-type respectively as defined by Chappell et al.  相似文献   

8.
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9.
<正>The Tengchong geothermal area,an active tectonic region with frequent earthquakes,is located in Yunnan Province of southwestern China.This area contains abundant active hot springs, which often display high metal concentrations and obvious mineralization phenomena.At 19:19 on 9 July 2009,an earthquake occurred in Yao'an,Chuxiong,Yunnan Province,which is 300 km to the northeast of the Tengchong geothermal area.We sampled water in the hot springs in the Tengchong area from 4 July to 9 July 2009 and from 10 July to 15 July 2009 to study the changes of elemental concentrations before and after the earthquake and discuss the influence of the earthquake on the mineralization of the hot springs.The concentrations of most trace elements increased slightly,but the concentration of REE(rare earth elements) decreased by 50%after the earthquake in the hot springs around a NS-trending fault.The elemental concentrations remained unchanged in Longtan and Suanshuigou,which are related to an inactive crater.The elemental concentrations in other springs controlled by superficial and small-scale faults decreased after the earthquake.The earthquake can stimulate the activity of deep faults and magma chambers,as is responsible for the increase of metal concentrations in the hot springs along the NS-trending deep fault;whereas it can decrease the porosity of permeable rocks,resulting in the decline of the flux of ore-bearing fluids and the corresponding mineralization in the hot springs related to superficial faults.  相似文献   

10.
Households vary in their ability to deal with disasters, and this may lead to different recovery results. Aiming to examine this differentiation, this paper studied the 2009 Yao??an earthquake in China. Surveys of 200 destroyed rural households were conducted in field investigations and follow-ups at 1?month, 1?year, and 1.5?years after the earthquake. The results showed a clear difference in recovery, the households observably being classified into five groups. These are the O group, which has different recovery time and economic cost from the other four; and the special group, comprising E L T O and E O T L (vulnerable during recovery); E H T O (strong during recovery); and E L T S (neither vulnerable nor strong). Logistic regression analysis revealed that differentiation in recovery patterns arose from the combined effect of demographic factors and external assistance provided to households. Lower income is the root cause of vulnerability in some households during the recovery process. However, other factors cause recovery differences between the two vulnerable groups, causing the economic recovery cost of the E L T O group to be lower, and the recovery time of the E O T L group to be longer. There was consensus that external assistance had an impact on all households. The more provided and the earlier it arrived, the lower the cost for recovery and the shorter the recovery time. This study shows that research on group differentiation of recovery is useful in understanding post-earthquake recovery processes and calls for taking group differentiation considerations into account in post-disaster recovery resource allocation practices.  相似文献   

11.
This paper reports an oxygen isotopic study of corundums and associated minerals from the Yogo lamprophyres (Montana, US), plagioclase-corundum inclusions in alkali basalt (Tunkin depression, Russia), and from modern alluvium of Podgelbanochnyi alkaline basaltic volcano (Primorye, Russia). It is shown that all sapphires genetically related to mafic magmatic rocks have a similar oxygen isotopic composition (the variations of δ18O are within 2.5‰) with most values plotting between +4.5 and +7.0‰ SMOW. The oxygen isotopic ratios in the associated minerals (olivines, pyroxenes, mica, and others) and host rocks are plotted in the same interval. This indicates that the sapphire crystallized during evolution of the parental mafic magma. However, there are xenogenic corundums, which were only transported by basaltic magma to the Earth’s surface. They have a sharply distinct oxygen isotopic composition, which suggests their disequilibrium with the host lavas, and, correspondingly, a different genetic nature.  相似文献   

12.
Rethinking space: an outsider’s view of the spatial turn   总被引：1，自引：0，他引：1  
Santa Arias 《GeoJournal》2010,75(1):29-41
Geographical concerns with space and place have escaped the confines of the discipline of geography. Many humanities scholars now invoke such conceptions as a means to integrate diverse sources of information and to understand how broad social processes play out unevenly in different locations. The social production of spatiality thus offers a rich opportunity to facilitate interdisciplinary dialogues between different schools of critical theory. Following a brief assessment of the spatial turn in history, history of science, and political philosophy, this paper explores its implications for literary and cultural studies. It invokes a detailed case study of late 18th century Lima, Peru to explicate the dynamics of colonialism, the construction of racial identities, and different power/knowledge configurations within a particular locale. Space in this example appears as both matter and meaning, i.e., as simultaneously tangible and intangible, as a set of social circumstances and physical landscapes and as a constellation of discourses that simultaneously reflected, constituted, and at times undermined, the hegemonic social order. The intent is to demonstrate how multidisciplinary and interdisciplinary scholarship can be facilitated by paying attention to the unique of circumstances that define places within given historical moments. As seen in this example from literary colonial studies, other disciplines, therefore, can both draw from and contribute to poststructuralist interpretations of space as a negotiated set of situated practices.  相似文献   

13.
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14.
《Applied Geochemistry》2002,17(12):1543-1550
A recent discovery of Pliocene tree trunks (Taxodium, Glyptostrobus or Sequoia) perfectly preserved in the fluvial lacustrine sediments deposited in the old Tiberin Lake (near the town of Dunarobba, Central Italy) has led to the study of the conditions responsible for the trunks preservation. The present work has applied Sr isotope techniques to examine and confirm fluid migration in the different sediment types which cross the entire fluvial-lacustrine sequence. Based on the 87Sr/86Sr ratios measured in carbonate and in silicate fractions of samples collected from a bore hole (from 0 to 120 m) it is concluded that each sedimentary level has limited communication between zones and is characterised by different isotope values. This suggests that the intrinsic properties of these clays make them a good material for isolating waste, both for direct use and for a better buffer in other formations, possibly less secure, such as salt or granite. The results obtained in the present work have demonstrated some of the potential uses of the 87Sr/86Sr isotopic ratio as an environmental tracer for confirming results from some of the geotechnical (such as permeability) and geochemical parameters of these host sediments.  相似文献   

15.
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16.
A contact zone sandwiched between an arc and an oceanic crust was discovered in the Laohushan area in the present study. It consists of a series of north-dipping imbricated thrust sheets and is exposed on the surface as a narrow arcuate belt, which extends for about 30 km in an E-W direction and measures about 1-3 km wide. Lithologically, it can be divided into four subzones. Subzone 1 consists of meta-andesite and metasandstone; subzone 2, psammitic schists; subzone 3, psammitic and pelitic schists, quartz diorite and hornfelses; and subzone 4, metagabbro, epidote amphibolite and pelitic schists. The metamorphism has the following grading sequence: low greenschist facies in subzone 1 → high greenschist facies in subzone 2 →low amphibolite facies in subzone 3→ epidote amphibolite facies in subzone 4. Petrographic and geochemical evidence shows that rocks in subzones 1, 2 and 3 are arc rocks, whereas those of subzone 4 are oceanic crustal rocks. The metamorphic mineral assemblages and especially miner  相似文献   

17.
According to isotopic analysis of rocks of the Reft gabbro–diorite–tonalite complex (Middle Urals), gabbro and related diorite and dikes and vein-shaped bodies of plagiogranitoids, crosscutting gabbro, are similar to the depleted mantle substance in εNd(T) = 8.6–9.7 and εHf(T) = 15.9–17.9. Their model Hf ages are correlated with the time of crystallization. Here, the tonalites and quartz diorites constituting most of the Reft massif are characterized by lower values: εNd(T) = 3.7–6.0, εHf(T) = 11.1–12.7, and T DM values significantly exceeding the age datings. This is evidence that Neoproterozoic crustal rocks were a source of parental magma for these rocks. The primary 87Sr/86Sr ratio in rocks of both groups is highly variable (0.70348–0.70495). The data obtained allow us to reach the conclusion that the Reft gabbro–diorite–tonalite complex was formed as a result of nearly synchronous processes occurring in the crust and the mantle within a limited area.  相似文献   

18.
Mineralogy and Petrology - The present work deals with some Pan-African serpentinites of Neoproterozoic age from five localities in the Eastern Desert of Egypt namely, Abu Fannani, Fawakhir,...  相似文献   

19.
《China Geology》2018,1(3):453-454
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20.
The development of immunodetection method of 2, 2-Bis （4-chlorophenyl） acetic acid （DDA）, the decomposition product of organochlorine insecticide DDT, was performed in this study. DDA was conjugated with bovine serum albumin （BSA） and ovualbumin （OVA） for the use of immunogen to produce antibodies and coating ligands to measure the titration level of antibody and the displacement of free analytes. Evaluation of the antisera by antibody capture assay showed that the antibody titer of antisera raised against DDA-OVA was higher than 1 ： 80000. Using 5#PAb, an indirect competitive enzyme immunoassay was developed for measurement of DDA. The working range for quantitative measurement of DDA and the quantitative limit for DDA were estimated to be 2.5-2000 ng/mL and 2.5 ng/mL for seawater, 12.5 ng/g for shellfish, respectively.  相似文献   

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