Experimental Study of Partial Melting of Mantle Peridotite -A Discussion about the Genesis of Sih'ca-rich Fluids (Melts)

Experiments on partial melting of mantle lherzolite have been realized at 0.6 and 1.0 GPa and the chemical compositional variations of melts during different melting stages have been first discussed. The results show that the trends of variations in SiO2, CaO, Al2O3, Na2O and TiO2 are different at different melting stages. The melts produced at lower pressure are richer in SiO2 than those at higher pressure. The mantle-derived silica-rich fluids (silicate melts) are polygenetic, but the basic and intermediate-acid silicate melts in mantle peridotite xenoliths from the same host rocks, which have equivalent contents of volatile and alkali components and different contents of other components, should result from in-situ (low-degree) partial melting of mantle peridotite under different conditions (e.g. at different depths, with introduction of C-O-H fluids or in the presence of metasomatic minerals). The intermediate-acid melts may be the result of partial melting (at lower pressure) Opx + Sp + K-Na-rich f     

EFFECTS OF VARIATION OF WINTER SEA-ICE AREA IN KARA AND BARENTS SEAS ON EAST ASIA WINTER MONSOON

By analyzing the observation data and performing the numerical simulation tests,it is shownthat the Kara and the Barents Sea area is a key region to influence climate variation over theNorthern Hemisphere.The variation of winter sea-ice area in the key region is closely associatedwith that of the EU teleconnection pattern at 500 hPa and East Asia winter monsoon(EAWM)intensity.When a heavy sea-ice prevails in the key region,the EU teleconnection pattern at 500hPa is excited easily(there are positive 500 hPa height anomalies over around Japan and WestEurope),and winter Siberia high is weakened,meanwhile,sea level pressure(SLP)has positiveanomalies over the Northern Pacific.Therefore,EAWM will be weakened,winter temperatureover East Asia is above normal and the frequency of cold-air activity in February in China will bedecreased.When the light sea-ice occurs in the key region,the results will be opposite.     

WAVELET CHARACTERISTICS OF RAINFALL VARIATION IN THE THREE GORGE REGION OF CHANGJIANG RIVER

Making the climatic diagnosis of Changjiang Three Gorge Region by the maximum entropyspectrum analysis and wavelet analysis,we discovered that the main periods of the annual andwintertime precipitation variation in the east subregion differ from that in the west subregion.Theformer is a period of about 2 years,and the latter is about 5—6 years.Their wavelet patterns arealso apparently different between two subregions:the alternate positive and negative waveletpatterns for the west,but not so regular for the east.These provide a climatic background for theimplementation of Three Gorge Project.We also found that the historical reason of the mainperiods by combing synthetically spectrum analysis and wavelet analysis could be realized.Inaddition we suggest a gist of the climate forecast by analogy analysis based on the 2-dimensionalwavelet figures.     

Micro-area Chemical Composition and Preserved P-T Evolution Trace of Phengite in Albite Gneiss from the Donghai Ultrahigh-Pressure Metamorphic Area, East China

Study of micro-area chemical compositions indicates that phengite in albite gneiss from hole ZK2304 of the Donghai region has evident compositional zoning. SiO2 and tetrahedrally coordinated Si contents decrease, and Al2O3, AlIV and AlVI contents increase gradually from core to rim. However, K2O, MgO and FeO contents basically remain unchanged from core to rim. According to P-T estimates obtained from geothermometers and barometers, combined with previous experimental data, the core belt (micro-area I) of phengite was formed at T=637-672℃ and P=1.55-1.73 GPa, and the transitional belt (micro-area II) of the phengite were formed at r=594-654℃ and P=1.35-1.45 GPa. Towards the rim belt (micro-area III), the temperature decreased slightly, but the pressure decreased rapidly with r=542-630℃ and P=1.12-1.19 GPa. The P-T evolution path recorded by the compositional zoning of phengite is characterized by significant near-isothermal decompression, revealing that the gneiss has. undergone high-pressure-ultrahi     

Evidence of the Pan-Lake Stage in the Period of 40-28 ka B.P. on the Qinghai-Tibet Plateau

The Qinghai-Tibet plateau is one of major saline lake regions in China, where saline lakes are widespread and constitute an important object of researches on the palaeoclimatic change in the region. On the basis of comprehensive investigations of the evolution of the lake's surface and sediments on the plateau, the authors have further demonstrated the existence of a pan-lake stage (river and lake flooding stage) on the Qinghai-Tibet plateau during the period of about 40+-28 ka B.P. and analyzed the palaeoclimatic characteristics of the pan-lake period and relationships between the ancient monsoons and the uplift of the plateau since the beginning of the Quaternary.     

Control of Melt Structures on Cu-Au Mineralization in Basic-Ultrabasic Complexes of Northern China

Based on systematic analyses of 72 samples of different basic-ultrabasic rocks, the present paper discusses the relationship between melt structure and Cu and Au mineralization. It is found that if the NBO/T, NBO, M2+, FeO and MgO values are relatively high and the T, M3+, Fe2O3 and CaO values are low the basic-ultrabasic melt will be favourable to Cu (Ni) mineralization, but if the former are low and the latter are high it is favourable to Au metallization. Cu ions occupy dominantly octahedra in basic-ultrabasic melt and the higher the NBO/T, NBO and M2+ values, the more the octahedra in the melt. Au element mainly takes the form of Au+ ions in basic-ultrabasic melt and the Au+ ions constitute tetrahedral sites together with Fe3+ ions. Therefore, low M2+ and high Fe3+, i.e. high oxygen fu-gacity, can promote the enrichment of Au+ ions and Au mineralization. Components NT (other than Au+), Al2O3 and SiO2 in basic-ultrabasic melt have no effect on metallogenetic species. As mentioned above, in relevant d     

Changes of Atmospheric Circulation since the LastInterstadial as Indicated by the Lake-statusRecord in China

The effective precipitation and the frame of atmospheric circulation in the past three key periods, i.e. 30 ka BP, 18 ka BP and 6 ka BP, have been analyzed on the basis of the palaeolake status record produced by the Chinese Lake Status Data Base. The results show that the west-central part of China was characterized by high lake-levels at 30 ka BP, resulting from strengthened southwest monsoons; whereas the high lake stand, occurring in the west-central part of China at 18 ka BP, was caused by the southward shift and the strengthening of westerlies although the high-stand distribution was reduced. Meanwhile, the east-central part of China was under the control of strong winter monsoons at 18 ka BP. The high lake-levels, which occurred in the east-central part of China at 6 ka BP, are related to the enhanced East-Asian summer monsoons; while the lowering of the lake-level in the west-central part of China at 6 ka BP was due to the northward shift and corresponding shrink of the westerlies.A comparison b     

Tetrahedrite-Group Minerals in the Jinjitai Gold Deposit,Western Sichuan

There are quite a few tetrahedrite-group minerals in the Jinjitai gold deposit, western Sichuan, which occur in an interstratified fractured zone of Middle Devonian carbonate rock series. The gold ore consists of pyrite, chalcopyrite, tetrahedrite-group minerals, galena, sphalerite and gold-silver series minerals, with an element association of Au-Cu-Ag-Pb-As-Sb-Bi. Electron microprobe analyses of the tetrahedrite-group minerals gave the following results: copper 40.04 to 42.27% (average 40.04%), iron 1.24 to 7.78% (average 4.13%), zinc 0.39 to 7.06% (average 3.58%), arsenic 5.41 to 17.40% (average 8.84%), antimony 2.70 to 20.46% (average 15.87%), and silver 0.02 to 0.73% (average 0.28%). The mineral varieties include zinc-antimony-tetrahedrite, iron-antimony-tetrahedrite, iron-tennatite and zincotennatite. These data show that there is a complete isomorphous series between Sb and As. From above downwards tetrahedrite varies from zinc- and antimony-rich to iron- and arsenic-rich compositions. Their occu     

Mineral Surface after Reaction with Aqueous Solution at High Temperatures and Pressures

This work presents new experimental results on surface chemistry of reacting minerals and interface kinetics between mineral and aqueous solutions. These experiments were carried out using a flow reactor (packed bed reactor) of an open system as well as a continuous stirred tank reactor, CSTR. The authors measured reaction rates of such minerals as zeolite, albite and carbonate (rhodochrosite, dolomite) in various solutions, and tested corresponding mineral surface by using SEM, XPS, SIMS, etc. This paper mainly presents the experimental results of zeolite dissolution in water and in low pH solutions at room temperature, and dolomite dissolution at elevated temperatures. The results show that the release rates of Si, Al and Na of zeolite are different in most cases. The incongruent dissolution of zeolite is related to surface chemical modifications. The Na, Al and Si release rates for dissolution of albite and zeolite in water and various solutions were measured as a function of temperature, flow veloci     

新疆罗布泊K1孔磁性地层及古纬度初析

Ｋ１孔位于罗布泊“耳轮”构造的北缘。磁性地层初步研究得知,在孔深６１～６２ｍ处为界,以上为布容正向极性时（Ｂｒ）,以下为松山反向极性时（Ｍａ）。在孔底９７～１００ｍ处的正向极性偏移应属Ｃｏｂｂ Ｍｏｕｎｔａｉｎｓ事件,对照Ｓ．Ｃ．Ｃａｎｄｅ和Ｄ．Ｖ．Ｋｅｎｋ修定的古地磁极性年表,氏地层的年代为１．２Ｍａ,归属早更新世中期。中更新世地层厚５０余米,晚更新世地层厚１０ｍ左右,全新世地层厚度小于５ｍ。根