Abstract:A series of post_orogenic granite plutons occur on the southern margin of Altay orogenic belt. A gneissic deformed granitic pluton occurs in the Ertix faulted zone to the south of Fuyun, intruded by an underformed granitic pluton. The former pluton is datedby U-Pb TIMS method at 281±5 Ma and the latter at 275±2 Ma. These data indicate that shearing deformation still took place to some extent along Ertix zone during ca. 280～275 Ma in the post-orogenic period. The deformation probably ended or became much weaker after 275±2 Ma.

Abstract:The Dashishan intrusive in Beishan area of Gansu Province mainly consists of biotite potassium-feldspar granites. The granites of Dashishan are metaluminous (Al2O3=12.18%～13.37%) and are characterized by high SiO2（74.22%～78.38%），Na2O+K2O（7.60% ～8.50%)，FeO T/MgO ratio，REE（102.3×10-6 ～120.02×10-6），Y，Nb and F，and low CaO（0.01%～0.99%），MgO（0.05％～1.15％），Sr and Ba．These characteristics are very different from characteristics of I_type and S-type granites in Beishan area，but quite similar to A2 type granites．The Dashishan intrusive has a Rb-Sr isochron age of 273 Ma. Itis therefore suggested that crustal rifting might have started in late Hercynian in that area．

Abstract:The Yanshanian Huashan-Guposhan granites in Guangxi are characterized by high silicon,high potas- sium,high alkaline,low phosphor and metaluminous nature,with relatively high FeO~T/MgO ratios and enrich- ment of LILE,HFSE and REE.In addition,they commonly contain allanites.They can thus be assigned to the high-potassium calc-alkaline granite(or KCG in the classification system of Barbarin,1999).They were formed during the conversion of the tectonic setting from compression to extension.The extension-thinning of litho- sphere,the upwelling of the depleted mantle,and the partial melting of the lithospheric mantle rich in phlogo- pite and K-richterite might have served as the principal factors in producing this kind of granitic rocks.

Abstract:Based on studies of petrology, petrochemistry and REE geochemistry of the Muluozhai REE ore deposit in Sichuan and the granite related to REE mineralization, it is known that the granite is nordmarkite instead of previously-considered biotite granite. From the study of Pb-Sr-Nd isotopic geochemistry, it is shown that the nordmarkite and ores in this area are characterized by deep source or even mantle source rocks. Obviously, the granite is different from the biotite granite which is generally regarded as a rock with crust source. Igneous rock related to mineralization of the Muluozhai ore deposit in Mianning County is similar to that of the Maoniuping ore deposit, a large-size REE ore deposit in the same county. They are both nordmarkite and have similar metallogenic features. The confirmation of the Muluozhai nordmarkite is of great significance in understanding regional magmatism and searching for REE mineral resources of the same kind.

Abstract:Mengyin komatiites are characterized by typical spinifex texture,high MgO,low TiO_2,and unde- pleted Al.They show positive Rb,Ba,Sr and U anomalies,depleted LREE,flat HREE and low total REE content.There occurs fractionation of HFSE from REE,and Nb/Nb~* is positive.These data indicate that the source of komatiites is depleted in LREE and enriched in HFSE.Fractionation of HFSE from REE also shows that the plume could not have come from the mantle source area where olivine,pyroxene and garnet or majoritite were dominant.The latest Sm-Nd isotopic data of Mengyin komatiites not only prove that komatiites were de- rived from a prolonged depleted mantle but also indicate that the plume only underwent very insignificant assimi- lation of old continental crust.It is inferred that such a magmatic event might have constituted a component part of the continental growth in late Archean.

Abstract:On the basis of petrology, mineral composition and peak p-T conditions of the eclogites from Taihu area in southern Dabie terrain, the authors hold that southern Dabie Terrain is composed of three metamorphic zones, namely, the ultrahigh pressure zone, the high/ultrahigh pressure ‘mixed' zone, and the high pressure zone, with a regional p-T gradient trend. Five Grt-Cpx thermometers and Grt-Cpx-Phe barometers were used to evaluate the peak p-T conditions of these eclogites. Four p-T regions have been identified, and their metamorphic temperature and pressure decrease gradually from north to south, being 760～950℃, 3.5～4.1 GPa; 660～750℃, 2.7～3.1 GPa; 640～780℃, 2.0～2.7 GPa; and 550～680℃, 1.5～2.3 GPa respectively. These features imply that southern Dabie Terrain was a coherent terrain during the subduction. However, the existence of the pressure gaps between the UHP zone and the HP zone or among adjacent eclogites in different metamorphic zones, the chaotic spatial distribution of eclogites and their relationship with country rocks all demonstrate that southern Dabie terrain was shortened or juxtaposed during the exhumation, and that the present distribution of eclogites represent the status of exhumed eclogites. 

Abstract:The author have studied the sedimentary environment and formation mechanism of nodular limestones in the Middle Ordovician rhythms of Keping Area,Xinjiang.In these limestones,thin layers of limestone are interbedded with mudstones.According to detailed field work as well as cathode fluorescence and dyeing under microscope,these nodular stones can be classified into three types on the basis of their structures,namely,mas- sive limestone,wavy limestone and lentoid limestone.Based on a synthetic analysis of elements with XRD,C and O isotopes with MS,and a study of mineralogy,petrology and paleontology,it is believed that they were formed in a sedimentary environment of shelf to deep basin.The carbonate-argillite rhythms were formed under the cyclic influence of surface currents,ocean bottom currents and source of sedimentary substance.Nodular limestones were formed in the early period of sedimentation-diagenesis and their formation mechanism is as fol- lows:under the periodic influence of the surface currents and the deep currents,the massive limestone was formed around the nucleus through coagulation,multiplication and cementation during the quiet period.The wavy limestone resulted from periodic washing of the carbonate marl by the salt-nonsaturated deep water during the period of syngenesis.The lentoid limestone was formed by the differential pressures between the water body and the overlying sediments.Every kind of nodular limestones had its main influential factor.

Abstract:Taxkorgan complex, mainly composed of alkaline syenites and subalkaline granitoids, is the largest Cenozoic alkaline complex in Pamirs region. Based on geography and geochemistry of the rock-forming minerals in Kuzigan intrusion, this paper discusses the classification, intergrowth, and crystalline sequence of minerals. The mineralogical characteristics suggest that different rock types of Kuzigan intrusion are products of the same magma, and that the magma, instead of being affected much by fractional crystallization, has dominantly experienced equilibrating crystallization. According to temperature, pressure, and chemical evolution of mineral crystallization in the magma chamber, it is held that the magma of intrusive rocks ascended rather fast and was emplaced at the relatively shallow place.

Abstract:In order to study mineral composition and morphology of atmospheric dust fall and to estimate the source of the particles, the authors employed XRD and SEM/EDX to perform investigations in such aspects in Changsha City. The results reveal that the main minerals are illite, plagioclase, chlorite, quartz, calcite, dolomite and amorphous matter, with the illite and chlorite derived from the surface raised dust, and the amorphous from the industrial ash. There are four morphological types, namely grained and flaky individual mineral, chain-like aggregates, spherical flying beads and irregular aggregates, with the chain-like and spherical aggregates being indicators of industrial ash, and other particles derived from other sorts of raised dust. The mineral composition and morphology of atmospheric dust fall serve as important criteria in identifying pollution sources.