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1.
正Introduction The rectangular block of Proterozoic formation lying between north of the Singhbhum Mobile Belt(SMB,2.3-2.4 Ga,Saha 1994),Neogene sediments of the Bengal basin and the Quaternary-Recent alluvium of the Ganga  相似文献   

2.
正In addition to an extrusive volcanic component and associated sills,the Neoproterozoic Franklin Large Igneous Province(LIP)comprises a giant radiating dyke swarm spanning an arc of ca.110?,as well as a less-  相似文献   

3.
正The 1780-1760 Ma Taihang dyke swarm and the coeval Xiong'er volcanic province are the most widespread magmatic events occurring post the amalgamation of the two North China cratons.It has been debated whether  相似文献   

4.
Geologic, petrographic and petrochemical studies of the late Mesozoic K-rich melanocratic dykes, including lamprophyres, andesite porphyrites and dacite-porphyry in the gold field system in the Jiaodong Peninsula, China, have shown that these dykes are characterized by rich potassium and alkali but poor titanium. They belong to an ultra-high potassic, shoshonitic and high potassic calc-alkaline rock series. The parental magma has relatively high initial strontium ratios ((87Sr/86Sr)i=0.70895-0.71140) and low (143Nd/144Nd)i ratios (varying from 0.51135 to 0.51231); and its δ18OSMow. whole rock values vary from +5.8‰ to +10.6‰ with a mean of+7.1‰. These features suggest that the source region of the magma is an enriched mantle wedge transformed from a continental lithosphere mantle which has experienced metasomatism by mantle-derived fluids with H2O-dominated fluids that were provided during the underthrusting of an ocean crust. The initial magma was generated by low-degree partial melting of the enri  相似文献   

5.
正The mafic dykes from the Paleoproterozoic Bomdila Group of metasedimentary rocks,Arunachal Pradesh,NE Lesser Himalaya,India have been analyzed for major and trace elements geochemistry essentially to understand their  相似文献   

6.
正Several generations of mafic dyke swarms(2.7 to 0.8Ga),highlighted by aeromagnetic data,petrography,geochemistry,isotope geology and mostly U-Pb baddeleyite ages,crosscut the Archean and  相似文献   

7.
正About 200 mafic dykes intruded Mesoproterozoic gneisses and granites of Bornholm,a Danish island situated in the southern Baltic Sea between Sweden,Germany and Poland.Field studies along the northern coast document  相似文献   

8.
Geotectonics - We present paleomagnetic data acquired on 276 samples from 24 Mesoproterozoic (ca 1132 Ma) postkinematic gabbro–dolerite dykes in the Bunger Hills (Queen Mary Land, East...  相似文献   

9.
正Virtual absence of igneous complexes with ages between1.8 Ga and 0.8 Ga in southern part of the Siberian Craton allowed to Galdkochub et al.(2010)to formulate a hypothesis of long magmatic quiescence.Most reliable  相似文献   

10.
正It is yet unclear whether large-scale segregation of immiscibile liquids and eruption of high-Si lavas exist in nature(Charlier et al.,2013).We present a possible case of segregation of immscible liquids in the 1780 Ma Taihang  相似文献   

11.
Geochemistry of Basic Dykes in Wudang Block and Its Tectonic Significance   总被引:1,自引:0,他引:1  
Geochemical characteristics of the Neoproterozoic basic dykes widely exposed in the Wudang block of South Qinling show that the dykes possess the characteristics of continental tholeiitic basalts and were formed in a setting of continental rifting.Therefore,there was an ancient continental block in the areas of southern Qinling and Yangtze block during the Jinning period,and an important firting event of this ancient block occurred in the Early Neoproterozoic.  相似文献   

12.
正An intrusive dyke is linear in regional scale,tectonic stresses play an important role in controlling the orientation of fractures that form for the dyke when magma rises buoyantly into the lithosphere  相似文献   

13.
正The Nagar Parkar complex consists of Neoproterozoic igneous and metamorphic rocks dissected by episodic mafic and felsic dykes.The latter can be classified broadly into porphyritic felsic dykes and aplitic felsic dykes(minor)  相似文献   

14.
In the present paper, we propose a new method for the estimation of the variogram, which combines robustness with efficiency under intrinsic stationary geostatistical processes. The method starts by using a robust estimator to obtain discrete estimates of the variogram and control atypical observations that may exist. When the number of points used in the fit of a model is the same as the number of parameters, ordinary least squares and generalized least squares are asymptotically equivalent. Therefore, the next step is to fit the variogram by ordinary least squares, using just a few discrete estimates. The procedure is then repeated several times with different subsets of points and this produces a sequence of variogram estimates. The final estimate is the median of the multiple estimates of the variogram parameters. The suggested estimator will be called multiple variograms estimator. This procedure assures a global robust estimator, which is more efficient than other robust proposals. Under the assumed dependence structure, we prove that the multiple variograms estimator is consistent and asymptotically normally distributed. A simulation study confirms that the new method has several advantages when compared with other current methods.  相似文献   

15.
正1 Introduction Lithium and its compounds as national strategic resources are extensively used in national defense,industrial and agricultural production.As we know,the salt lakes in the western of China are famous for its high  相似文献   

16.
Crisis? What crisis? Displacing the spatial imaginary of the fiscal state   总被引:1,自引:0,他引:1  
Angus Cameron   《Geoforum》2008,39(3):1145-1154
This paper argues that there is an immanent and evolving relationship between the prevailing form of taxation and the economic geographies of the state. Despite this, the geographic significance of taxation has been obscured by the language in which its historic transformation tends to be couched. Prevailing fiscal systems tend to be presented as essentially static – institutionally and spatially fixed and routinely inscribed within the fixed boundaries and territories of the ‘sovereign’ fiscal state. Any threat to, or change in the nature or geography of the fiscal state tends to be couched in terms of ‘crisis’ – of negative and discontinuous change. This paper contends that these related and essentially conservative discourses of fiscal geography mask the degree to which fiscal spaces are both multiple and continuously evolving. More importantly, it argues, this fluidity and multiplicity does not threaten the stability and viability of state form, but it is an essential process in its maintenance and reproduction. Running counter to the prevailing discourse of the ‘national economy’, the practice of fiscal geography is an under-analysed but key aspect of the historical evolution and transformation of the imagined geographies of economies.  相似文献   

17.
Since a 1921 law the harnessing of the Rhône River from Lyon to the Mediterranean has been directed by a national company composed of the public sector (fromthe valley) as well as of various consumers or distributors of current such as the SNCF or the EDF. This company, the National Company of the Rhône (CNR), was a precursor to the establishment of the TVA in the United States, although it did not begin operations until aftetr the TVA due to prolonged technical negotiations and to the difficulties involved in locating financial support in a period of economic crisis. Even though the utilization of hydraulic power constitutes the prime aim of the CNR, it has also focused on navigation, irration and other agricultural uses from the outset.This article will not further discuss the hydro-electric stations on the Rhône which usually supply more than 22% of French hydro-electric output from thirteen stations now in operation (total power is 2,350 MW and annual average output is 13,000 GWh). This paper will treat the question of the nature and importance of the side effects of the harnessing of the Rhône apart from its essential energy function.  相似文献   

18.
正Paleomagnetism of the Neoproterozoic Xiaofeng dykes exposed in the Three Gorges region of Hubei Province bear important implications for the paleogeography of the South China block(SCB).New high-precision U-Pb  相似文献   

19.
The Triassic?Jurassic (Tr?J) boundary marks a major extinction event, which (~200 Ma) resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr?J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected: the Late Triassic (Rhaetian) Aratrisporites?Alisporites Assemblage, the Early Jurassic (Hettangian) Perinopollenites?Pinuspollenites Assemblage, and the Sinemurian Perinopollenites?Cycadopites Assemblage. The Tr?J boundary is placed between bed 44 and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha (?), Unio?Ferganoconcha and Waagenoperna?Yananoconcha bivalve assemblages are recognized. The Ferganoconcha (?) bed is limited to the upper Haojiagou Formation, Unio?Ferganoconcha and Waagenoperna?Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites and the marine?littoral facies bivalve Waagenoperna from the Badaowan Formation indicate that the Junggar Basin was influenced by sea water caused by transgressions from the northern Tethys, during the Sinemurian.  相似文献   

20.
Endo  Shintaro  Shimada  Ryo  Ishikawa  Toshinori  Komine  Tsutomu 《Natural Hazards》2022,110(3):2017-2033

Drowning accidents at beach in Japan are caused by rip currents. To reduce these accidents, a new technology that can detect rip currents and notify beachgoers by using the Internet of Things (IoT) and Artificial Intelligence (AI) was proposed. However, studies on the effect of visualizing rip currents or considering the effect of optimism bias have not been conducted. This study investigates if visualization of rip currents might help in preventing drowning accidents, while considering the effect of optimism bias. The participants were 90 Japanese beachgoers. They were asked to answer questions based on their knowledge of the beach and rip currents, their optimism bias regarding rip currents, and awareness with or without visualization. The results of the analyses suggest that despite optimism bias, the visualization of rip currents increases the tendency of beachgoers to perceive and avoid rip currents. As described above, it was found that by visualizing the rip current, beachgoers were able to perceive and avoid rip currents. In addition, an understanding of rip currents is positively related to the intent to avoid rip currents even when rip currents are visualized. Therefore, it is necessary not only to enhance the avoidance tendency by visualizing rip currents, but also to further enhance knowledge of beachgoers to deepen the understanding of rip currents including the danger associated and methods to avoid them.

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