Based on well-replicated tree-ring width indices of Picea crassifolia,A tree-ring chronology up to 248-years was used to reconstruct runoff of Huangshui river from June to July in the paper.Most of the annual results were verified by historical documents.The relatively low runoff periods were 1753-1766、1785-1802、1815-1832、1861-1887、1918-1941、1963-1978、1993-1998;the relatively high runoff periods were 1767-1784、1803-1814、1834-1860、1891-1916、1944-1961、1979-1992.Power spectrum analysis displayed the cycles of 2.00a,2.29a,2.31a,2.33a,2.35a,34.29a,40a and 48 a.
A set of Late Triassic acid-intermediate-basic volcanic rocks in Songsainong area is composed of basalt,andesite,dacite,rhyolite and a small amount of pyroclastic rocks as well as some other components.In the volcanic rocks,SiO_2 values are in the range of 48.89-88.15%(67.44%on average),TiO_2 vary between 0.22 and 1.85%(0.63%on average),and MgO range from 0.23 to 7.81%,similar to things of island arc calc-alkaline volcanic rocks.High field intensity elements such as Nb,Ta,Zr,Hf and Ti are depleted,large-ion lithophile elements like Rb,Sr and Ba are relatively concentrated,(La/Sm)n are 1.79-5.19,and LREE/HREE ratios vary mostly in the range of 4.08-6.63,suggesting a light REE enrichment type.δEu values are 0.47-0.99,Eu assumes negative anomalies,La/Nb ratios are mostly higher than 2.00,Nb/Zr0.04,Th/Ta4.41,and Th×Ta/Hf~20.042,implying a margin of the volcanic arc.The above characteristics show that Late Triassic volcanic rocks in Songsainong of Zhidoi area were mostly produced in an environment where mainland collision and epicontinental arc are coexistent.
The potash-resource status of our country is described in this paper. The distribution and forming disciplines of large potash deposits in the world are concluded: foundation of substance, geological constructions, facies and paleo-geography conditions and special climate. The general situations and the history of the geological evolution of Tarim basin between the late Cretaceous Period and the early Tertiary are analyzed. Then it analyzes the characters of the facies of the late Cretaceous Period and the early Tertiary. And two concentration centers——Kuche sag and Tarim south-west sag are achieved. This paper also reviews the status of seeking potash deposits in Tarim basin. A favorable geological foundation is set up for seeking potash deposits.
Through analyzing the data of K,Li and B in the mining area of Lake Xitaijinair,the study results re- vealed the dynamic changes of K,Li and B and their seasons during early mining(from 2003 to 2004).The results show that the changes of contents of K,Li and B in lake brine mainly are controlled by the seasonal changes of sur- ficial runoff.Three elements' contents in underground brine during recovering are higher than those during mining. But their contents in pore brine are higher than those in intercrystalline brine and three elements'spatial differentia- tion are obviously different.Studies on the phase diagram suggest that the brine during recovering has arrived the step when the sylvite is precipitating.The brine in mining area is basically in stagnation and there was no signifi- cant correlation between water levels and three elements'contents in underground brine.The changes of K,Li and B in underground brine probably are due to the physical and chemical changes of brine itself.And in short time, mining action and surficial runoff can not evidently influence the elements'changes in hydrochemistry.
Clay mineral recording plentiful environmental information of source areas during the course of its formation is one of the deposits distributed extensively on the surface of the earth.According to the contents and assembiling changes of clay minerals,the rules of paleoclimate evolution can be inferred,and the paleoenvironment can be reconstructed.So,clay mineral is one of the important proxy indexes for studying the paleoenvironment evolution,the same as loess,ice core and tree ring,In arid region where there are no other proxy indexes such as loess,ice core,tree ring and so on,clay minerals may be the most important proxy to be used to reconstruct paleoclimate.Thus,it can be seen that clay minerals will have a vast application prospect in the future study on paleoenvironment evolution.
Methods of monitoring and determining sulfate such as gravimetric method,titration,atomic absorption,spectrophotometric,fluorescence method,ion chromatography,ion selective electrode method and ICP-AES are reviewed.It can provide the basis for medicine,food,chemical production and environmental monitoring,etc.
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