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1.
The earthquake catalogue of the European area, 1901–1985, with unified magnitudes, has been used for the preparation of epicentre maps of the Mediterranean area. Epicentres have been plotted on three sheets for different magnitude ranges,M
B
(orm
B
) 5, 0,M
S
(orm
B
) = 4.4–4.9,M
S
(orm
B
) 4.3, according to the estimated levels of homogeneity. The first map (M 5) enables an objective comparison of seismicity over the whole Mediterranean area. The other two maps are complementary without the guarantee of completeness. Epicentres define the position of principal earthquake zones and levels of earthquake activity. The maps also serve as the starting point for further data processing. Graphs illustrating the time variation of earthquake activity in the whole area and the mean magnitude-frequency relationships are included. 相似文献
2.
The results of a geoelectrical survey of the Mshentsy area located in Tver oblast near the Moscow–St. Petersburg express road, which is under construction, are presented. In order to obtain information about the geological composition of the area and the processes that occur in it (karst and water flow zones ), we performed our measurements using the electrical resistivity imaging, self potential survey, water electrical conductivity and temperature measurements. Using petrophysical resistivity modeling of the rocks, taking the geoelectric data into account, we completed a lithology differentiation of the section and calculated the hydraulic conductivity values of the rocks. By interpreting this data, we found a wide distribution of fractured carbonates that compose the lower part of the section of the studied territory. The conclusion was drawn that the Mshentsy area belongs to the intense local karst zone. 相似文献
3.
Khadija Semhi Osman A. E. Abdalla Salah Al Khirbash Tabisam Khan Salim Asaidi Sardar Farooq 《Arabian Journal of Geosciences》2009,2(2):143-150
Groundwater samples from six wells and various species of plants from soils developed on ophiolites were collected from an arid area (AlKhod area, Oman) and analyzed for trace elements including rare earth elements (REEs). The distribution patterns of REEs in plants indicated an enrichment in middle REEs (MREEs?=?Sm to Dy) and heavy REEs (HREEs?=?Ho to Lu), when they are normalized to the REE composition of the Post Archean Australian Shale (PAAS), with a significant negative anomaly in Ce and a positive anomaly in Eu. Compared to Oman ophiolites, the REEs in different species of plants are depleted in Ce and enriched in MREEs and slightly enriched in light REE (LREE?=?from La to Nd). Relative to PAAS, the distribution of REEs in groundwaters revealed similar patterns to the REE distribution in plants. The distribution patterns of REEs in plants relative to those in waters are nearly flat. These patterns suggest that the transfer of REEs from soil solutions to the groundwaters in Oman occurs without any significant fractionation. 相似文献
4.
Katja Ruschel Lutz Nasdala Andreas Kronz John M. Hanchar Daniel M. T?bbens Radek ?koda Friedrich Finger Andreas M?ller 《Mineralogy and Petrology》2012,105(1-2):41-55
This study addresses whether Raman spectra can be used to estimate the degree of accumulated radiation damage in monazite-(Ce) samples whose chemical composition was previously determined. Our results indicate that the degree of disorder in monazite–(Ce), as observed from increasing Raman band broadening, generally depends on both the structural state (i.e., radiation damage) and the chemical composition (i.e., incorporation of non-formula elements). The chemical effects were studied on synthetic orthophosphates grown using the Li-Mo flux method, and non radiation-damaged analogues of the naturally radiation-damaged monazite–(Ce) samples, produced by dry annealing. We found that the “chemical” Raman-band broadening of natural monazite–(Ce) can be predicted by the empirical formula, $$ {\hbox{FWHM}} {\hbox{[c}}{{\hbox{m}}^{ - {1}}}{]} = {3}{.95} + {26}{.66} \times {\hbox{(Th}} + {\hbox{U}} + {\hbox{Ca}} + {\hbox{Pb)}} {\hbox{[apfu]}} $$ where, FWHM = full width at half maximum of the main Raman band of monazite–(Ce) (i.e., the symmetric PO4 stretching near 970?cm?1), and (Th+U+Ca+Pb) = sum of the four elements in apfu (atoms per formula unit). Provided the chemical composition of a natural monazite–(Ce) is known, this “chemical band broadening” can be used to estimate the degree of structural radiation damage from the observed FWHM of the ν1(PO4) band of that particular sample using Raman spectroscopy. Our annealing studies on a wide range of monazite–(Ce) reference materials and other monazite–(Ce) samples confirmed that this mineral virtually never becomes highly radiation damaged. Potential advantages and the practical use of the proposed method in the Earth sciences are discussed. 相似文献
5.
A Long-Lived Center of Gas–Fluid Emanations on the Western Slope of the Kuril Basin (Sea of Okhotsk)
Derkachev A. N. Nikolaeva N. A. Tsoy I. B. Baranov B. V. Barinov N. N. Mozherovskiy A. V. Krylov A. A. Kuznetsov A. B. Minami H. Hachikubo A. 《Lithology and Mineral Resources》2021,56(4):309-332
Lithology and Mineral Resources - The paper presents the results of multidisciplinary studies in the carbonate–barite mineralization area revealed on the western slope of the Kuril deep-water... 相似文献
6.
Yu. L. Gulbin 《Geology of Ore Deposits》2015,57(8):699-711
Phase equilibria in medium-grade metapelites of the Northern Ladoga area are calculated with the pseudosection method and Theriak/Domono software on the basis of zoning in garnets. It is shown that garnet in the staurolite-bearing parageneses crystallized at 520–600°C against the background of a pressure release from 7.0 to 3.5–4.0 kbar. The evolution of the mineral composition of rocks in the course of porphyroblast formation is discussed, placing special emphasis on the comparative analysis of P–T paths of garnet growth under decompression conditions. 相似文献
7.
8.
C. Bernhard R. Carbiener A. R. Cloots R. Froehlicher Ch. Schenck L. Zilliox 《Environmental Geology》1992,20(2):125-137
The area studied is part of the Ried Central of the Ill river (Middle Alsatian plain in northeastern France). This area is located mainly in the present floodplain of the Ill. The closeness of the water table to the surface results in quasi general soil hydromorphism.The economic constraints of the last two decades led to deep changes in agricultural activities in the study area. These have essentially involved a marked extension of intensive cultivation of grain corn at the expense of grasslands. The study of the influence of this change on the parallel increase in the concentration of nitrate in groundwater is only feasible when a multidisciplinary approach is adopted.The analyses carried out in the field and in the laboratory show that nitrate reduction occurs in gleyed or peaty horizons of hydromorphic soils. The aptitude and efficiency of the permanent ambient vegetation (alluvial forests and grasslands) in retaining nitrate must be emphasized. The amount of nitrate eliminated from the aquifer by rivers fed by this aquifer is considerable. This evacuation of nitrate into the Ill is a fine example of waste and illustrates the absurdity of the economic situation responsible for excessive nitrogen fertilization of farmlands.In determining hazard zones, this study also proposes practical solutions to the problem of nitrate pollution: diminution of land area under cultivation, reintroduction of grasslands, and a more judicious use of nitrogen manure. 相似文献
9.
10.
The reflectance of sediments (gray level) were measured on 11 sediment cores from the Norwegian–Greenland–Iceland Sea (Nordic
seas). The analyzed time interval covers the past five glacial–interglacial cycles. Although the results demonstrate that
the gray-level method has a potential for stratigraphic purposes, it is indicated that gray-level changes in the Nordic seas
are not necessarily driven by variations in the content of biogenic calcite. A detailed comparison of gray-level values with
contents of total CaCO3 (carbonate) and total organic carbon (TOC) reveals no overall causal link between these proxies. However, specific glacial
core sections with layers containing organic-rich sediment clasts as a consequence of iceberg-rafting seem to correlate well
with law gray-level values. Of those cores which show relatively high and comparable carbonate values in the last three main
interglacial intervals (stages 11, 5.5, and 1), stage 11 is always marked by the highest gray-level values. A close inspection
of the surface structure of the foraminiferal tests as well as the conduction of reflectance measurements on these tests leads
to the conclusion that enhanced carbonate corrosion occurred during stage 11. The test corrosion not only affected the reflectance
of the tests by making them appear whiter, it also seems responsible for the comparatively high gray-level values of the total
sediment in stage 11. In contrast, the relatively low gray-level values found in stages 5.5, and 1 are not associated with
enhanced test corrosion. This observation implies that variable degrees of carbonate corrosion can have a profound effect
on total sediment reflectance.
Received: 6 September 1998 / Accepted: 4 April 1999 相似文献
11.
The El Kef area, Tunisia, is host of the official stratotype of the K/P boundary and of a complex metallic and non-metallic
mineralization at Djebel Sekarna, encompassing syn(dia)genetic shale- and carbonate-hosted Zn–P and epigenetic Pb–Zn–Ba ore
mineralizations. Micropaleontological, geological, mineralogical, and chemical studies (major and minor elements, C- and O-isotopes)
of Upper Santonian to Lower Eocene calcareous-siliciclastic sediments resulted in a subdivision of this mineralization into
eight mineralizing stages. Stages 1 and 2 (late Cretaceous–early Paleogene) are representative of syn(diagenetic) shale- and
carbonate-hosted sulfidic and siliceous (Fe)–Zn–P mineralization deposited in shallow marine to slightly brackish sediments.
Stages 3–5 (early Eocene respectively—pre- and post-Nummulites involutus-exilis zones) are representatives of epigenetic sulfidic and sulfatic (Fe)–Zn–Pb–Ba mineralizations at temperatures as high as 170/200°C
and stages 6 and 7 (early Eocene respectively—post-Alveolina oblonga zone) cover the non-sulfidic Zn–(Pb) mineralization at temperatures as high as 60°C which is transitional from hypogene into
supergene mineralization (“epithermal calamine deposits”). Stage 8 represents alteration of the pre-existing mineral assemblages
in course of the Holocene weathering. The Cretaceous through Paleogene aquatic system is characterized by a poisoning of the
sea with base metals, mainly Zn, and the atmosphere was chocked with clouds of fine-grained volcanic ejecta. Both processes
contributed to the build-up of Zn–(Pb) deposits and vast, but uneconomic bentonitic clay deposits around the K/P boundary.
Ore mineralization in the El Kef area is a multiple-phase process which reached its climax during the early Eocene as indicated
by the large foram zones. These inorganic concentration processes resulting in the formation of mineral deposits had obviously
also a negative effect on the long-term course of regional Earth’s biological history during the late Cretaceous–early Eocene
period with lethal consequences for some species. The joint studies of inorganic and organic data reveal that such extraordinary
metallogenetic processes close to the K/P boundary in its stratotype area in Tunisia were “strictly terrestrial”. 相似文献
12.
Comparative analysis of the composition and formation conditions of the dunite–pyroxenite association of the Guli Pluton and ultramafic vulcanite (meimechite) showed the similarity of their initial melts and the same type of crystallization, demonstrating the cumulative origin of dunite. 相似文献
13.
Chen D. 《大地构造与成矿学》2015,(1):110-127
After years of prospecting and mining of the basaltic copper deposits in the border area of Yunnan-Guizhou provinces, many people think the potential of metallogenic prospect is dismay and the deposits are of small sized. However, some researchers proposed in 2002 that these deposits have characteristics similar to those of the Keweenaw copper deposits, and thus their significance is worthy of further consideration. To investigate the resource potential in the region, we carried out a comparative study of the deposits in the two regions. The results show that the existence of redbed may be an important facor controlling the potential of copper mineralization. Therefore, we suggest that the native copper mineralization in the mid-low Triassic sandrocks demands further investigation and it is promising for metallogenic prospecting. ©, 2015, Science Press. All right reserved. 相似文献
14.
L. G. Bragina 《Stratigraphy and Geological Correlation》2016,24(2):141-166
A scheme of radiolarian zonal subdivision is proposed for the upper Albian–Santonian of the Tethyan regions of Eurasia. The upper Albian contains one zone: Crolanium triangulare; the Cenomanian contains three zones: Patellula spica (lower Cenomanian), Pseudoaulophacus lenticulatus (middle Cenomanian), and Triactoma parva (upper Cenomanian); the Turonian contains four zones: Acanthocircus tympanum (lower Turonian (with no upper part)), Patellula selbukhraensis (upper part of the lower Turonian), Phaseliforma turovi (middle Turonian (with no upper part)), and Actinomma (?) belbekense (upper part of the middle Turonian–upper Turonian); the Coniacian contains two zones: Alievium praegallowayi (lower part of the Coniacian) and Cyprodictyomitra longa (upper part of the Coniacian); the Santonian contains three zones: Theocampe urna (lower Santonian), Crucella robusta (middle Santonian–lower part of the upper(?) Santonian), and Afens perapediensis (upper part of the upper Santonian). The biostratigraphic subdivisions are correlated with biostrata in the schemes proposed previously for the Tethys and Pacific. A new species Patellula selbukhraensis Bragina sp. nov. is described. 相似文献
15.
The revision of the stratigraphy of the Cerro Bayo in the Bajo Grande area (Argentinean Patagonia) and the new 206Pb/238U age of 116.85 ± 0.26 Ma constrain the dating of the Baqueró flora, one of the most abundant Aptian floras of southern Gondwana. This flora, preserved in the Baqueró Group, represents an extinct biome that flourished ca. 118 Ma ago and was affected by increasing regional volcanism during the subsequent four millions years. The outcrops of the Cerro Bayo are characterized by fluvio-lacustrine deposits divided into three facies associations that include nine lithofacies. The first palynological record for the locality confirms the correlation of the lower part of the outcrops with the Anfiteatro de Ticó Formation (the oldest unit of the Baqueró Group). The new radiometric age and stratigraphy support recognition of the Bajo Tigre Formation (the middle unit of the Baqueró Group) in the area and date the earliest stage in angiosperm diversification in southern South America. Stratigraphic relationships among the Baqueró, Chubut and Divisadero groups are briefly discussed. 相似文献
16.
Doklady Earth Sciences - In this work we considered the origin of the Verkhoyansk–Kolyma, Chukotka, and Southern Anyui belts, which are part of the Verkhoyansk–Chukotka folded area. It... 相似文献
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18.
David W. E. HONE 《《地质学报》英文版》2020,94(5):1676-1692
The anurognathids are an enigmatic and distinctive clade of small, non-pterodactyloid pterosaurs with an unusual combination of anatomical traits in the head, neck, wings and tail. They are known from very limited remains and few have been described in detail, and as a result, much of their biology remains uncertain. This is despite their importance as potentially one of the earliest branches of pterosaur evolution or even lying close to the origins of pterodactyloids. This review covers the taxonomy and palaeoecology of the anurognathids, which remain an interesting branch of pterosaurian evolution. 相似文献
19.
V.N. Smirnov 《Russian Geology and Geophysics》2012,53(5):467-474
The Verkhoyansk–Chukchi orogenic area formed on the vast land mass that had appeared as a result of collision in the Early Cretaceous and that had consolidated the Mesozoic protoorogenic structures in northeastern Asia. This heterostructural land mass was the basis on which spatially and structurally coupled orogens developed in the late Mesozoic and Cenozoic. The protoorogenic stages in the evolution of the Verkhoyansk–Chukchi area were followed by several large orogenic stages: Albian–Cenomanian, Eocene, and Pliocene–Quaternary. The Okhotsk–Chukchi volcanic-block and the Yana–Kolyma fold-block orogenic systems formed at stage 1. The Taui–Anadyr continental-margin rift system formed at stage 2. This shaped the structure of the Verkhoyansk–Chukchi area. The internal structure of the orogenic systems formed through the Pliocene–Quaternary (neotectonic) stage, which was dominated by uplifting throughout the Verkhoyansk–Chukchi area. The neotectonic structure was mostly inherited from the previous orogenic stages. 相似文献
20.
Dobretsov N. L. Zhmodik S. M. Lazareva E. V. Bryanskaya A. V. Ponomarchuk V. A. Saryg-ool B. Yu. Kirichenko I. S. Tolstov A. V. Karmanov N. S. 《Doklady Earth Sciences》2021,496(2):135-138
Doklady Earth Sciences - Data indicating the important role of microorganisms in the redistribution of REEs in the weathering crust and the decisive role in the concentration of REEs during the... 相似文献