检索结果-南通市图书馆

Differential rotation of geomagnetic field

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2003年第24期48卷 2739-2742页

作者： WEI Zigang & xu wenyao institute of geology and geophysics, chinese academy of sciences, Beijing 100029,{3. Correspondence should be addressed to Wei Zigang (e-mail: magstorm @***) institute of geology and geophysics Chinese Academy of Sciences China

The latitudinal dependence of the westward drift in the main geomagnetic field is examined by using the correlation analysis of moving random pattern. The study reveals the characteristics in the differential rotation of the main field. The results show that the global geomagnetic field drifts westward with an average speed of 0.18/a during 1900—2000. The westward drift rate is not symmetrical with re-spect to the equator. The maximum westward drift rate, 0.3./a, occurs at the latitude j = -15? forming a Rapid Westward Drift Belt (RDB) around this latitude. Going northward and southward from this belt, the drift rate de-creases and reaches the minimum (0.12/a) at j = 50?and the minimum (0.14/a) at j = -56? forming a Northern Hemi-sphere Slow Westward Drift Belt (N-SDB) and a Southern Hemisphere Slow Westward Drift Belt (S-SDB). Three phases can be detected in the evolution of the westward drift. In the first phase (1900—1940), the RDB dominates the global drift pattern. The westward drifts in this belt are much faster than those in other areas. In the second phase (1940—1960), the drift rates in the RDB are less than those in the first phase, while the drifts in the N-SDB and S-SDB are relatively large. In this phase, the differential rotation becomes less obvious. In the third phase (1960—2000), the westward drift in the RDB increases again and the differen-tial rotation gradually becomes apparent.

关键词：地磁场赤道快速西移带 RDB

Patterns of platinum-group elements in mantle peridotite, granulite xenoliths and basalt in Hannuoba

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 1999年第18期44卷 1676-1681页

作者： CHU xuelei, LI Xiaolin, xu Jiuhua and LIU Jianming1. The Research Center of Mineral Resources Exploration , chinese academy of sciences , Beijing 100101,{3. 2. institute of geology , chinese academy of sciences , Beijing 100029,{3. 3. institute of High Energy Physics , chinese academy of sciences , Beijing 100817 ,{3. 4. Beijing University of Science and Engineering , Beijing 100083.{3. Corresponding author The Research Center of Mineral Resources Exploration Chinese Academy of Sciences Beijing China institute of geology Chinese Academy of Sciences Beijing China institute of High Energy Physics Chinese Academy of Sciences Beijing China Beijing University of Science and Engineering Beijing China

Neutron activation analysis after preconcentration of nickel sulfide fire assay was used in measurement of Ru, Ph, Pd, Os, Ir, Pt (i.e. PGE elements) and Au concentrations for basalt, mantle and granulite xenoliths in Hannuoba. The chondrite- and primitive mantle-normalized PGE patterns generally exhibit flat (for Iherzolite), negative slope (for harzburgite),

关键词： mantle xenolith granulite xenolith basalt platinum-group element Hannuoba.

Si-and alkali-rich melt inclusions in minerals of mantle peridotites from eastern china:Implication for lithospheric evolution

在线全文

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第1期49卷 43-49页

作者： FAN Qicheng1, SUI Jianli2, xu Ping2, LI Ni1, SUN Qian1 & WANG Tuanhua1 1. institute of geology,{3. Seismological Bureau, Beijing 100029,{3. 2. institute of geology and geophysics, chinese academy of sciences, Beijing 100029,{3. 1. institute of geology China Seismological Bureau Beijing 100029 China 2. institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China

Minerals of spinel- and garnet-facies mantle xenoliths entrained in Cenozoicbasalts from eastern china (North china, Northeastern china and Southeastern china coastal area)contains lots of melt inclusions. Studies on these melt inclusions show that the glass inclusionsare rich in SiO_2 (60%—68%) and alkalis (K_2O+Na_2O = 5%—11%, especially for K_2O) as well asvolatiles such as H_2O and CO_2 (2%—7%), which belong to dacites and andesites of the high-K calcicalkali series rocks with few shoshonites. High Al and Ca diopside in melt inclusion is the productof melt crystallization at high temperature and pressure, rather than the product ofdevitrification. Results show that these K-rich (in general K_2O > 3.) intermediate-acidic silicatemelt inclusions have characteristics of continent without a genetical link to host basalts and theirphenocrystic minerals. Thus, these trapped melt inclusions represent melts of Mesozoic lithosphericmantle-crust interaction and imply that the continental lithospheric mantle beneath eastern chinahad undergone fragmentation and recreation processes during the Mesozoic and Cenozoic periods. Thisresult undoubtly provides important implication for the evolution of sub-continental lithospherebeneath eastern china. We propose that these Si- and alkalis-rich melts should be responsible forthe mantle chemical heterogeneity underneath eastern china.

关键词： Si- and alkali-rich melt inclusion, mantle peridotite, lithospheric evolution, eastern china.

Fluid differentiation and gold mineralization

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 1999年第S2期44卷 13-15页

作者： QIN Dajun, CAI Xinping and xu Xingwang institute of geology,{3., Beijing 100029, china institute of geology Chinese Academy of Sciences Beijing 100029 China

GOLD mineralization is closely related to ore-forming fluids. During the evolution of fluids, their naturescontinuously change, and the differentiation of the fluids dominates these changes. Fluid differentiationincludes fluid from melt, fluid immiscibility, gasseparating from fluids and so on. We can understand fluids through inclusions, stable isotope andore-forming experiments. Under the poststage reformation, the composition and phases of inclusionsmight be changed, hence, the initial forming conditions of fluids are difficult to be defined onlythrough the observation of these inclusions. Theexistence of solution phase, gas phase and solidphase (fig. 1) indicate that differentiation

关键词： fluid differentiation gold mineralization.

Uncertainty in magnetic activity indices

在线全文

学校读者我要写书评

暂无评论

Uncertainty in magnetic activity indices

Geological analysis and physical modeling of structural pumping in high effective formation of Kela 2 gas field

中国科学院地质与地球物理研究所2008学术年会

作者： xu wenyao institute of geology and geophysics,chinese academy of {3.,Beijing 100029,china

Magnetic activity indices are widely used in theoretical studies of solar-terrestrial coupling and space weather ***,the indices suffer from various uncertainties,which limit their application and even mislead to incorrect conclusion. In this paper we analyze three most popular indices,Kp,AE and *** categories of uncertainties in magnetic indices are discussed:"data uncertainty" originating from inadequate data processing,"station uncertainty" caused by incomplete station covering,and "physical uncertainty" stemming from unclear physical mechanism.A comparison between magnetic disturbances and related indices indicate that the residual Sq will cause an uncertainty of 1—2 in K measurement, the uncertainty in saturated AE is as much as 50%,and the uncertainty in Dst index caused by the partial ring currents is about a half of the partial ring current.

关键词： magnetic activity indices Kp AE Dst solar-terrestrial coupling space weather

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science china Earth sciences 2006年第10期49卷 1070-1078页

作者： ZHAO Wenzhi1, WANG Hongjun1, SHAN Jiazeng2, WANG Zecheng1 & xu Dafeng1 1. Research institute of Petroleum Exploration and Development, Petrochina, Beijing 100083.{3. 2. institute of geology and geophysics, chinese academy of sciences, Beijing 100029,{3. 1. Research institute of Petroleum Exploration and Development Petrochina Beijing 100083 China 2. institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China

In a 3.D closed geological body, in case “structural expanding” inside is induced by stress, it can produce the pressure difference between the expanding cell and surrounding rock, then generate a pumping force directed toward the cell and accelerate the directional flow of fluid in the strata. The structural style and conditions of gas reservoir-formation in the Kuqa depression are favorable to the structural pumping. According to similarity principle, a physical modeling of structure formation and gas filling process of the Kela 2 gas field has justified the occurrence of structural pumping and its important role in gas-reservoir formation with high efficiency under the compressive and well-sealed circumstance. Therefore, authors propose that structural pumping is an important mechanism of gas reservoir-formation with high efficiency in the Kuqa depression.

关键词： Kela 2 gas field, structural pumping, gas-reservoir formation mechanism, high efficiency,physical modeling.

Climate as the dominant control on C_3.and C_4 plant abundance in the Loess Plateau: Organic carbon isotope evidence from the last glacial-interglacial loess-soil sequences

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2003年第2期48卷 1271-1276页

作者： GU Zhaoyan, LIU Qiang, xu Bing, HAN Jiamao, YANG Shiling, DING Zhongli & LIU Tungsheng institute of geology and {3., chinese academy of sciences, Beijing 100029, china Correspondence should be addressed to Gu Zhaoyan (e-mail: zgu@ ***) institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China

Abundance of C3.and C4 photosynthesis plants can be inferred relatively from stable carbon isotopic composi-tion of organic matter in soils. The samples from five sequences of the last glacial-interglacial loess-soil in the chinese Loess Plateau have been measured for organic carbon isotopic ratios (d 13.org). The organic carbon isotope data show that relative abundance (or biomass) of C4 plants was increased ca. 40% for each sampling site from the last glacial maximum (LGM) to Holocene optimum, and increased southeastward on the Loess Plateau during both periods of LGM and Holocene. Statistic analyses on the steady maximum d 13.org values of Holocene soils and modern climatic data from the Loess Plateau and Inner Mongolia indicate that the C4 plant abundance increases with increasing temperature and decreasing precipitation. The C4 plant abundance is related much closer with mean April tem-perature and precipitation than annual. These results lead us to deduce following conclusions. First, temperature is the major factor for control on variations in C4 plant abundance in the Loess Plateau from the last glacial to interglacial. In the absence of favorable temperature condition, both of low moisture and low atmospheric CO2 concentration are insufficient to drive an expansion of the C4 plants in the plateau. Second, d 13.org in the loess-paleosol sequences, as a proxy of the relative abundance of C4 plants in the Loess Plateau, could not be used as an indicator of changes in the summer monsoon intensity unless the tem-perature had changed without great amplitude. Since all C4 plants are grasses, finally, the increase of the C4 plants supports that forest has not been dominant in the ecosystem on the Loess Plateau during Holocene although precipitation and atmospheric CO2 were largely increased relative to those during LGM.

关键词： C3.C4 plants d 13.org Loess Plateau LGM Holocene.

Sporopollen analysis of Core B10 in the southern Yellow Sea and the reflected characteristics of climate changes

在线全文

学校读者我要写书评

暂无评论

chinese Science Bulletin 2003年第B06期48卷 42-48页

作者： FU Mingzuo~(1,2,3., LI Zhen~1, xu Xiaowei~1 & SHl xuefa~1 1. Key Laboratory of Marine Sedimentology and Environmental geology, First {3. of Oceanography. State Oceanic Administration, Qingdao 266061. china 2. {3. of Oceanology, chinese academy of sciences, Qingdao 266071. china 3. Graduate School, chinese academy of sciences, Beijing 10003.. china 1. Key Laboratory of Marine Sedimentology and Environmental geology First institute of Oceanography State Oceanic Administration 266061 Qingdao China 2. institute of Oceanology Chinese Academy of Sciences 266071 Qingdao China 3. Graduate School Chinese Academy of Sciences 100039 Beijing China

Eight sporopollen zones have been divided based on the results of high-resolution sporopollen analysis of Core B10 in the southern Yellow Sea. Based on the results along with ^14C datings and the subbottom profiling data,climatic and environmental changes since the last stage of late Pleistocene are discussed. The main conclusions are drawn as follows: (1) the vegetation evolved in the process of coniferous forest-grassland containing broad-leaved trees→coniferous and broad-leaved mixed forest→coniferons and broad-leaved mixed forest-grassland prevailed by coniferous trees→coniferous and broad-leaved mixed forest-grassland containing evergreen broad-leaved trees→coniferons and broad-leaved mixed forest-grassland prevailed by broadleaved trees→deciduous broad-leaved forest-meadow containing evergreen broad-leaved trees→coniferous and broadleaved mixed forest-grassland prevailed by broad-leaved trees→coniferous and broad-leaved mixed forest containing evergreen broad-leaved trees; (2) eight stages of climate changes are identified as the cold and dry stage, the temperate and wet stage, the cold and dry stage, the warm and dry stage, the temperate and wet stage, the hot and dry stage, the temperate and dry stage, then the warm and dry stage in turn; (3. the sedimentary environment developed from land,to littoral zone, to land again, then to shore-neritic zone; and (4) the Yellow Sea Warm Current formed during early-Holocene rather than Atlantic stage.

关键词：中国黄海气候变化碳14年代测定底基压型数据更新世沉积环境大西洋

Dating of the Karakorum Strike-slip Fault

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2001年第1期75卷 10-18页

作者： ZHOU Yong, xu Ronghua, YAN Yuehua, PAN Yusheng,Tsanyao Frank YANG, Wei LO and WU Chunming Laboratory of Lithosphere Tectonic Evolution, institute of geology and {3., chinese academy of sciences, Beijing 100029Department of geology, National Taiwan University, 245 Choushan Road, Taipei 106-17, TaiwanDepartment of geology, chinese Culture University, Hwa-kang, Yang-Ming-Shan, Taipei, Taiwan institute of geology, chinese academy of Geological {13., Beijing 10003. Laboratory of Lithosphere Tectonic Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 Department of geology National Taiwan University 245 Choushan Road Taipei 106–17 Taiwan Department of geology Chinese Culture University Hwa-kang Yang-Ming-Shan Taipei Taiwan institute of geology Chinese Academy of Geological Sciences Beijing 100037 [?]5Zhou Yong Male born in 1968 graduated from Chengdu College of geology with a master's degree in 1991. From 1991 to 1995 he focused on ore deposit investigation. Since 1995 he has studied structural geology associated with the Qinghai-Tibet plateau. Tel: (010) 62008438.

This paper mainly discusses the timing of the Karakorum strike-slip fault, and gives a brief introduction of its structures, offset, and deformational style. This fault strikes NNW-SSE. Asymmetrical folds, stretching lineation, S-C fabrics, feldspar and quartz s?-porphyroclasts, domino structure, shear cleavages and faults in the fault zone are products of tectonic movements. They all indicate a dextral slip sense of faulting. Mylonitic bands are widely developed along this fault. Phengite appears, indicating rather high deformational pressure. Geochronological data indicate that the Karakorum strike-slip faulting occurred from 6.88±0.3. to 8.75±0.25 Ma. The cumulative displacement from Muztag Ata to Muji is about 13. km.

关键词： Karakorum fault kinematics timing displacement