Abstract:The quartz-dioritic intrusions in Tongguanshan of Tongling district, Anhui Province, are spatially and temporally associated with copper mineralization. Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb zircon dating of quartz diorites from Xiaotongguanshan in the Tongling ore district indicates felsic intrusive activity at 139～133 Ma, which also represents the copper mineralization epoch. Some of the zircon grains yield 207Pb/206Pb ages of (2 670～2 025) Ma, implying the involvement of the Precambrian metamorphic basement in the formation of quartz diorites. The presence of such zircon grains in these quartz diorites suggests that either the parental magmas were assimilated by basement rocks during the ascent of magma or the lower/middle crustal rocks served as one of the important components during the melting process.

Abstract:A number of different lahars were recognized during the systematic survey of a mapping project. The high setting temperature feature of the deposits indicates a relationship between the lahar and the Millennium eruption event of Tianchi volcano. The lahars caused serious disasters. Recognition of the huge avalanche scars and deposits around Tianchi volcano implies another highly destructive hazard. Three different structural types of the avalanche deposits have been recognized. There frequently existed magmatic mixing processes during the Millennium eruption of Tianchi volcano, indicating a mixing and co-eruption regime of the eruption. This paper has also discussed some features of the historically accounted eruptions.

Abstract:Melt structure plays an important role in governing physical and thermodynamic characteristics of magmas. Exemplified by Jingpohu Holocene volcanic rocks, this paper has discussed the relationship between melt structure and volcanic eruptive mechanism. The NBO/T values (the non-bridge oxygen numbers per unit of cations) are calculated on the basis of the concentrations of major elements and volatiles. The results show that the proportion of lava in the total eruptive volume and its flowing capacity increase with increasing NBO/T values. The lava with high NBO/T values is liable to generate the lava channel. Volatiles such as H2O and F are likely to concentrate in magma with high NBO/T values.

Abstract:In the foreland basin researches of China, the deep and accurate understanding of the concept and meaning of the foreland basins and the comprehension of the features of the typical foreland basins abroad are absolutely necessary so as to prevent the excessive broadening of the concept of the foreland basin. In addition, the research on “Sino-type basin" in central western China should be strengthened. The main part of the Helan Mountain is composed of Triassic-Jurassic strata, which comprise from west Alxa massif to east Ordos BasinZhifang-Yanchang Group, Yan'an Formation, Zhiluo Formation and Anding Formation. The Helanshan Mountain lifting might have taken place at the end of Mesozoic-Cenozoic period. The stratigraphic sequence is characterized by the increasing depth of water. The lithic fragment components and the rose diagram of paleocurrent show that the sediments must have come from Helanshan Group in the north. The stratigraphic isopaches which describe the shape of the basin and the depth of water extend into Alxa massif instead of being ended on the eastern side of the Helan Mountain. The thrusting direction of the main thrust faults is westward on the eastern side of the mountain and eastward on the western side. The above_mentioned features are not consistent with the characteristics and criteria of the foreland basin. The western edge of Ordos Basin, at least the central northern part of the western edge, is not a foreland basin.

Abstract:The Wulashan gold deposit, Inner Mongolia, China, which is characterized by intensive alkali feldspar metasomatism, is hosted by the late Archean gneiss, amphibolite, migmatite, and marble of the Wulashan Group and surrounded by several intrusions. The general mineral assemblage of mineralized lodes is alkali feldspar + quartz + plagioclase + carbonate (calcite and Fe-dolomite etc). Alkali feldspar is also present as a major component within country rocks. On the basis of the microprobe analyses for coexisting alkali feldspar and plagioclase, the equilibrium temperatures of the alkali feldspars are calculated using several ternary two-feldspar geothermometers. The obtained temperatures at 5 kbar are 353℃ for alkali feldspars from gold-bearing veins I (K-feldspar-quartz veins), and 281℃ for alkali feldspars from gold-bearing veins Ⅱ (quartz veins), in good agreement with the estimated temperatures for coexisting carbonates, mica minerals and gold, and with the homogeneous temperatures of fluid inclusions in quartz and alkali feldspars. Therefore, the gold mineralization in The Wulashan gold deposit, Inner Mongolia, China, which is characterized by intensive alkali feldspar metasomatism, is hosted by the late Archean gneiss, amphibolite, migmatite, and marble of the Wulashan Group and surrounded by several intrusions. The general mineral assemblage of mineralized lodes is alkali feldspar + quartz + plagioclase + carbonate (calcite and Fe_dolomiteetc). Alkali feldspar is also present as a major component within country rocks. On the basis of the microprobe analyses for coexisting alkali feldspar and plagioclase, the equilibrium temperatures of the alkali feldspars are calculated using several ternary two_feldspar geothermometers. The obtained temperaturesat 5 kbar are 353℃ for alkali feldspars from gold_bearing veins I (K-feldspar-quartz veins), and 281℃ for alkali feldspars from gold_bearing veins Ⅱ (quartzveins), in good agreement with the estimated temperatures for coexisting carbonates, mica minerals and gold, and with the homogeneous temperatures of fluid inclusions in quartz and alkali feldspars. Therefore, the gold mineralization in the Wulashan gold deposit formed at the temperatures ranging from 280～360℃ and the pressure of 5 kbar. On the other hand, the temperatures of alkali feldspars from regional metamorphic gneiss and granite are lower than the equilibration temperatures of coexisting almandine and biotite, indicating that the temperatures of almandine and biotite may represent the peak temperature of metamorphism and alkali feldspars in metamorphic rocks and granite may re-equilibrate after experiencing numerous overprinting thermal / magmatic events.

Abstract:The microarea compositional variations of garnet, plagioclase and biotite in Zhoutan Group show obvious regularity. Garnet displays typical growth zoning, which reflects the crystallization and growing process of garnet. The contact edge compositions of the coexisting Grt, Bi and Pl should reflect the temperature and pressure of the peak metamorphic stage. On the basis of garnet zoning and Grt-Bi geothermometry as well as GASP barometry, it is known that the pattern of the metamorphic pT paths is of the clockwise type, and that metamorphism must have taken place in the tectonic environment of continental collision zone.

Abstract:This paper deals with standardization of length measurement in fission-track thermochronology and describes the main factors affecting the length measurement, etching procedure and measurement error. The (application) of the same etching procedure and etching standard and the establishment of a reference for length measurement are proposed in this paper. As for zircon, because of different contents of uranium, the etching standard is the main research contents for the standardization of length measurement.

Abstract:Chromium-bearing sericite and chlorite occur in the Jinchang gold deposit of Mojiang County, Yunnan Province. Sericite is distributed extensively in pyritic chrome-phyllic rocks, pyritic siliceous rocks, pyritic chrome-mica and quartz veins, whereas chlorite is spread in quartz veins, siliceous rocks and pyritic chrome-phyllic rocks. Montmorillonite occurs in etched surrounding rocks, while kaolinite in gold-rich quartz veins. Based on 72 electron microprobe analytical data of the above minerals, the authors set up a series of compositional types related to the rock types. Studies show that all of the above layered chromium-high silicate minerals occur at the northernmost ends of different orts within Jinchang rock body. The SiO_2-Cr_2O_3 diagram of the chromium-aluminum mica reveals that different plot areas reflect specific genetic type features of source rocks. It is thus considered that the high-content spots of Si and Cr in chromium sericite series typical of the Jinchang gold deposit are basically attributed to the post-metamorphism hydrothermal fluid of the ultrabasic rock body.

Abstract:Concentrations of As, B, Ba, Cd, Cu, Hg, Pb, Se, Sr and other microelements were determined for channel samples collected from main active mines in southern Jilin Province. Microelements in coals of Taiyuan Formation are different from those of Shanxi Formation, which is attributed to different coal-forming environments. As, B, Hg, Pb, Se and Zn concentrations in Taiyuan Formation are obviously higher than those in Shanxi Formation, while the concentrations of Ba, Cr, Cu, Mn and V are lower in Taiyuan Formation. Analy-(tical) results show that As, B, Hg, Pb and Se concentrations of coals in southern Jilin Province are markedly higher than their average values of the earth crust, Co and Cd concentrations of coals are close to their earth crust average values, and other microelements are rare. Compared with their average values in other areas, the concentrations of As, Ba, Co, Cr, Cu, Hg, Ni, Pb, Se, V and Zn are higher in southern Jilin Province, and B, Mn and Sr concentrations are lower. The analyses and modes of occurrence of microelements show that such harmful elements as As, Cu, Hg, Pb and Se are correlated with Fe, suggesting that pyrite and sulfide in coals are carriers of many harmful microelements.

Abstract:This paper reports the discovery of cinnabar during Hg-anomaly inspection in cities and outskirts of eastern China plain areas and describes its mineralogical characteristics. Such problems as the spatial correspondence of Hg anomaly with cinnabar distribution and the correlation between cinnabar amounts and Hg anomaly are also discussed. The research indicates that cinnabar is an important existing form of Hg in Hg-anomaly soil. This discovery has important academic and application significance in the study and evaluation of environmental effects of Hg-anomaly soil.

Abstract:Using AFM and traditional SEM, the authors studied the super-microscopic structure of pearls from micron-size to nanometer-size by observing the surfaces of pearls with different qualities, and discussed the correlation between the nanometer-size surface structure invisible with SEM and the physical properties (luster, roughness and concomitant color) of pearl. The research shows that the grade of pearl has a positive correlation with ordering and compactness of layers, microlayers, blocks and aggregates of aragonite. It is also suggested that quantified standard should be added to the classification for cultivation and trade of pearls by using such data as the mean roughness (Ra).