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排序方式: 共有67条查询结果,搜索用时 218 毫秒
21.
A three-dimensional finite-difference multilevel hydrodynamic model is developed using an explicit scheme on a staggered grid. The model has been tested against four cases, namely (i) wind-induced circulation (ii) density-driven circulation (iii) seiche oscillation in a closed basin and (iv) tide-induced circulation in a open channel. The results obtained in the present study compare well with those obtained from the corresponding analytical solutions under idealised conditions for the above four cases. The model was also tested against the case of circulation induced by wind and Coriolis force and the results obtained are compared with the results of Davies and Owen (1979). 相似文献
22.
Sr, Nd and Pb isotopic compositions of the Cenozoic basalts were analyzed from Baengnyeongdo Island, Jeongok, Ganseong, and Jejudo Island of Korea. They reveal relatively enriched Sr and Nd isotopic compositions (87Sr/86Sr = 0.703300.70555, 143Nd/144Nd = 0.512980.51256) compared with MORB.207Pb/204Pb and 208Pb/204Pb values of all the analyzed Korean basalts lie above the Northern Hemisphere Reference Line (NHRL) defined by Hart (1984). Pb isotopic compositions of basalts from Jejudo Islands (206Pb/204Pb = 18.6119.12, 207Pb/204Pb = 15.5415.69, 208Pb/204Pb = 38.9839.72) are significantly more radiogenic than the rest (206Pb/204Pb = 17.7218.03, 207Pb/204Pb = 15.4415.58, 208Pb/204Pb = 37.7738.64). The Cenozoic Korean basalts thus can be divided into two groups based on their Sr, Nd and Pb isotopic compositions. The north group reveals mixing between DMM and EM1 while the south group displays DMM-EM2 mixing. Such a distribution is the same as Chinese Cenozoic basalts and it can be interpreted that the subcontinental lithospheric mantle under Korea represents simple lateral continuation of the South and North China Blocks. We suggest that Korean continental collision zone cross the Korean Peninsula through the region between the north and south basalt groups of Korea. 相似文献
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24.
Sang Woo Ji Young Wook Cheong Gil Jae Yim Jayanta Bhattacharya 《Environmental Geology》2007,52(6):1033-1043
Acid rock drainage (ARD) is a longstanding problem often associated with the resulting corrosion due to the acidity generated
from sulfidic oxidation. To evaluate characteristics of ARD and corrosion, samples from the road side rock mass of Boeun and
Mujoo were analysed using X-ray diffraction, acid/base accounting and Leaching tests. The results indicated that many samples
had a pyritic origin and can be regarded as acid-generating rocks. The Leaching test showed that the average pH of the leachates
of samples from both Boeun and Mujoo were moderately acidic, ranging from 3 to 4. Interestingly, as acidity increases from
pH 4, the SO4−, Fe, Al and Mg concentrations increase abnormally. Samples from roadside slope of Mujoo showed high corrosive potential.
Maximum sulfide oxidation rate of a sample taken from Mujoo was as high as 5,166 mg/kg/week. 相似文献
25.
Abstract We present chemical and Sr–Nd–Pb isotopic compositions of three Triassic (226–241 Ma) calc‐alkaline granitoids (the Yeongdeok granite, Yeonghae diorite and Cheongsong granodiorite) and basement rocks in the northern Gyeongsang basin, south‐eastern Korea. These plutons exhibit typical geochemical characteristics of I‐type granitoids generated in a continental magmatic arc. The Yeongdeok and Yeonghae plutons have similar initial Sr, Nd and Pb isotope ratios (87Sr/86Srinitial = 0.7041 ~ 0.7050, ?Nd(t) = 2.3 ~ 4.0, 206Pb/204Pbfeldspar = 18.22 ~ 18.34), but distinct rare earth element patterns, suggesting that the two plutons formed from partial melting of a similar source material at different depths. The Cheongsong pluton has slightly more enriched Sr–Nd–Pb isotopic compositions (87Sr/86Srinitial = 0.7047 ~ 0.7065, ?Nd(t) = 3.9 ~ 2.8, 206Pb/204Pbfeldspar = 18.24 ~ 18.37) than the other two plutons. The Nd model ages of the basement rocks (1.1 ~ 1.4 Ga) are slightly older than those of the plutons (0.6 ~ 1.0 Ga). The initial Sr and Nd isotopic ratios of the plutons can be modeled by the mixing between the mid‐oceanic ridge basalt‐like depleted mantle component and the crustal component represented by basement rocks, which is also supported by Pb isotope data. The Sr and Nd isotope data from granitoids and basement rocks suggest that the Gyeongsang basin, the Hida belt and the inner zone of south‐western Japan share relatively young basement histories (middle Proterozoic), compared with those (early Proterozoic to Archean) of the Gyeonggi and Yeongnam massifs and the Okcheon belt. The Nd isotope data of basement rocks suggest that the Hida belt might be better correlated with the basement of the Gyeongsang basin than the Gyeonggi massif, the Okcheon belt or the Yeongnam massif, although it may represent an older continental margin of East Asia than the Gyeongsang basin considering its slightly older Nd model ages. 相似文献
26.
27.
Lithospheric mantle signatures as revealed by zircon Hf isotopes of Late Triassic post‐collisional plutons from the central Korean peninsula,and their tectonic implications 下载免费PDF全文
Chang‐Sik Cheong Namhoon Kim Hui Je Jo Moonsup Cho Sung Hi Choi Hongying Zhou Jian‐zhen Geng 《地学学报》2015,27(2):97-105
The Mesozoic tectonic architecture of the Korean peninsula is largely governed by the continental collision between the North and South China blocks. Zircon Hf isotopic compositions presented in this study and whole‐rock geochemical and Sr‐Nd isotope data in the literature collectively suggest that the lithophile‐elements‐enriched signature of the Late Triassic post‐collisional plutons from the Gyeonggi massif in central Korea is a primary feature inherited from the metasomatized mantle lithosphere. Highly negative zircon εHf (t) values (?23 to ?19) of plutons from the middle and eastern parts of the massif indicate an ancient metasomatism of their mantle source. Distinctly higher zircon εHf (t) values (?15 to ?12) from the southwestern plutons are ascribed to a contribution from an accreted component of the South China‐like block. The involvement of asthenospheric mantle is not recognized in zircons from either group. The implications of these isotopic features are discussed in the context of Mesozoic collisional tectonics. 相似文献
28.
A new direction in coastal management 总被引:2,自引:0,他引:2
This paper argues for a stronger integration of marine sciences and coastal management studies that generates better formulated marine policies and viable policy implementation strategies. Integration of natural and social sciences in environmental management has surfaced as a key issue recently in the fields of sustainability science, ecosystem-based management, and social–ecological resilience. This paper promotes such trend in marine studies, and examines the rationale, progress, and examples of the integration. 相似文献
29.
地震属性可以由多种地震子波的特征来定义。并且根据不同的标准分类。选择叠前地震数据特征可提供丰富的诸如偏移和方向的资料,此次研究中,我们将限制叠后地震数据以提取地震属性,叠后地震数据可以通过子波特征和瞬时特征来分类。 相似文献
30.
This paper presents a laboratory technique for measurement of reflected waves by a submerged horizontal plate. A simple method is proposed to decompose the composite wave record obtained from the wave reflection experiments in the wave flume. The data collected were used to compute the reflected wave height by means of two and three probe methods proposed by other investigators and compared with the directly computed reflected wave using the measured incident wave. The experiment was carried out for a horizontal plate of 1 m length spanning the full width of the flume with wave periods ranging from 0.8 to 1.8 sec with 0.1 sec increments and wave heights of 5, 10 and 15 cm. The methods using two and three probes with phase measurement yield better results than the three probe method without phase measurement, and in general they have a wider range of application. The method using three probes without the phase measurement generally fails due to numerical instability of the scheme. The results obtained by the proposed method are compared with the two and three probe methods and a comparative analysis of the four methods is presented and discussed. 相似文献