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911.
五台山区金矿床的多金源多期次多成因多类型叠加成矿特征 总被引:1,自引:0,他引:1
五台山区的金矿床都是叠加成因的矿床。金源层的微量分散金,被构造热事件所活化,迁移到容矿构造中重新,同一容矿构造多次活动和成矿,致使金品位逐次升高,形成矿床。这些金矿床具多源性、多期性、多成因和多类型叠加之特征。 相似文献
912.
红磷锰铍石是一种很罕见的铍磷酸盐矿物,在国外,目前仅知发现于芬兰等几个国家,其量也极少。我国是1984年首次发现于福建南平花岗伟晶岩田中的白云母—钠长石—锂辉石型伟晶岩中,沿粗粒原生绿柱石中的微裂隙分布,是伟晶岩形成晚期热液蚀变作用的产物。本文较系统地研究了南平伟晶岩中红磷锰铍石的矿物学特征,包括产状及共生组合、物性及光性、化学成分、X射线衍射特征和红外吸收光谱分析等,最后概述了该矿物的鉴定特征。 相似文献
913.
A PRELIMINARY STUDY OF SNOW MASS VARIATIONS IN CHINA OVER THE PAST 30 YEARS 总被引:1,自引:0,他引:1
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李培基 《Acta Meteorologica Sinica》1992,(2)
Daily snow data for 2300 climate stations covering the period from 1951 through 1980 have been used to monitorand diagnose secular variations,year-to-year fluctuations,and the spatial characteristics of snow variation trends inChina.An examination of time series reveals that there is a strong teleconnction to ENSO,to major volcanic eruptions,as well as to the CO_2-induced warming.The country-wide snow mass variations are positively correlated with globalmean temperature,increasing during the current warming period and decreasing during the recent cooling period priorto the mid 1960s.A synchronous relationship exists between El Nino/Southern Oscillation and snowy winter in China.The year-to-year snow fluctuations seem to be generally out of phase with volcanic activity.The anomaly map showsthat snow mass increased in high altitudes and moist regions,while it decreased in arid lowland and the southern bounda-ry zone during the warming period.The potential CO_2-induced changes in snow mass will further aggravate the regionaldifferentiation between high mountains and lowlands,between moist and arid regions.The number of snow cover dayswill decrease in the northern lowlands,and snowfall will increase in the Qinghai-Xizang Plateau,high mountains,andthe lower reaches of the Changjiang(Yangtze)River. 相似文献
914.
浙西南中元古界龙泉群的地质年代学 总被引:13,自引:0,他引:13
龙泉群区域变质岩系的时代一直被归属于震旦纪—早古生代(闽北的相当层位被置于震旦系)。笔者首次获得该群的全岩等时线年龄为1376.5±82.1Ma(Sm-Nd)和988.6±40.2Ma、951.7±11.4Ma(Rb—Sr),由此确定龙泉群的时代为中元古晚期(1000—1400Ma),其主期区域变质年龄约为950±50Ma。龙泉群副变质的Nd模式年龄t_(DM)=1.8—2.0Ga,其主要蚀源区为早前寒武纪陆壳。变质基性火山岩的ε_(Nd)(t)=1.63±0.63,反映其岩浆源自壳下亏损地幔并经古老硅铝壳的污染。结合基础地质研究成果分析,龙泉群系早元古代浙闽克拉通内地槽(裂陷糟)火山—沉积产物,属内硅铝壳造山带而非洋壳残块。 相似文献
915.
鄂西震旦纪陡山沱组磷块岩稀土元素地球化学 总被引:1,自引:0,他引:1
鄂西陡山沱组磷块岩的稀土元素总量较低,变化较小,具有轻稀土相对富集,重稀土贫乏的特点。稀土元素含量与磷块岩的结构类型、成因和粘土矿物含量有关。震旦纪生物成因的磷块岩以低稀土元素含量为特征,这与寒武纪以来生物成因的磷块岩截然不同。鄂西陡山沱组含有三个工业磷矿层,各矿层稀土元素配分模式、参数等有明显差异,依据这些特征可准确地进行矿区和区域矿层的划分与对比,也可用于对物质来源和沉积环境的解释。 相似文献
916.
917.
Guo Shiqin Sun Wenhong China Ocean Mineral Resources Research Developmetn Association Institute of Mineral Deposits Chinese Academy of Geological Sciences Liu Linqun 《《地质学报》英文版》1992,66(4):371-383
Manganese nodules in areas CP and CC of the central Pacific are rich in REE. Comparatively speaking,the REE contents of nodules in area CP are hihger than those in area CC; and the REE contents of nodulesfrom seamounts are higher than those of nodules from sea-floor plains and hills. Within the nodules, the REEshow a zonal distribution. The REE distribution patterns of the nodules are similar to those of the sedimentsand have a mirror image relationship with those of the sea water. Trivalent REE were not obviously differenti-ated when they entered into the nodules from the sea water.A major factor causing the difference of REE abundances between nodules and sediments is the redoxconditions. The redox intensity of the ocean floor of the Pacific is controlled mainly by Antarctic Bottom Wat-er(AABW), The iron-bearing facies in the nodules is the main carrier of REE. 相似文献
918.
During ancient times the natural deposition fluxes of lead which can be leached with dilute acid from sediments in Santa Barbara, Santa Monica and San Pedro basins offshore from the Los Angeles Urban complex, were about 0.7, 0.1 and 0.2 μg Pb/cm2 yr respectively. Since there was little difference in biological productivity in surface waters of these basins, it is proposed that clay is a major transport vehicle for sequestered soluble lead, which then explains why the lead deposition flux within the Santa Barbara basin was so much larger compared to the other basins. The fluxes of silicate mud in the basins in ancient times were about 92, 19 and 30 mg/cm2 yr in Santa Barbara, Santa Monica and San Pedro basins respectively. Today deposition fluxes of acid soluble lead within these three basins are 3- to 9-fold greater, being about 2.1, 1.1 and 1.8 μg Pb/cm2 yr respectively, partly in the form of directly deposited large sewage particles, which account for none, and of the total industrial lead deposition fluxes in the respective basins. Concentrations of leachable lead in varve dated sediment layers increase with time and isotopic compositions of these leads change in accordance with corresponding known changes of isotopic compositions of industrial lead in the Los Angeles atmosphere. Lead remaining in acid leached sediment residues originates from igneous and clay minerals, exhibiting no change in concentration or isotopic composition since pre-industrial times.Deposition fluxes of total barium in sediments among the three basins were proportional to mass deposition fluxes before 1950 in the same manner as for lead. Afterwards, there are barium concentration maxima with time in both Santa Monica and San Pedro Basin sediments which are attributable to industrial sewage rather than to episodic erosion from barium-rich sedimentary evaporite strata exposed locally along the shore. An increase of barium concentrations in present day Santa Barbara basin sediments may reflect dispersal of barium-rich drilling mud from local drilling operations. 相似文献
919.
ZHOU Jiyuan CUI Bingfang CHEN Shizhong Nanjing Institute of Geology Mineral Resources Chineese Academy of Geological Sciences Zhongshan East R Nanjing. Jiangsu Fei Zhenbi 《《地质学报》英文版》1999,73(1):19-29
The Hongshan porphyry-cryptoexplosive breccia type copper deposit occurs in a metamorphic rockseries of the Mesoproterozoic Zhongcun Group. Orebodies are distributed inside and outside porphyry-cryptoexplosive breccia pipes. The deposit involves five ore-forming types, Le the porphyry type, crytoexplosivebreccia type. contact-zone veinlet-disseminated type, in-pipe fracture-zone filling-replacement type and out-of-pipetracture-zone filling-replacement type, forming an ore-forming system of "five ore-forming types within a singlerock body" Fluid inclusion and isotope geochemical studies indicate the following: S, Pb, O and Sr were derivedfrom the lower crust, Nd was derived from the continental crust or depleted mantle and rare earth elements (REE)and trace elements have the crustal source characters; fluids consist dominantly of formation water, metamorphic wa-ter and meteoric water with a part of magmatic mater; heat came from porphyry while the latter originated from par-tial melting caused by shear heating in the lower crust and upper mantle. According to its origin the deposit is classi-fied as the hypabyssal and near-surface, meso-and hypothermal copper deposit ussociated with the late Yanshanianporphyry-cryptoexplosive breccia. 相似文献
920.
Center-to-limb variations indicate that a type III burst is likely to be emitted in a radial direction while a type IIIb emission is more perpendicular to the stream. 相似文献