Abstract:Petrology and genetic mechanism of volcanic magma can be studied thro-ugh low pressure experiments.The Ol-Di-Ne tertiary phase diagram shows that the Ol-CPx-Pl saturated cotectic lines of alkaline basalts formed in different geotectonic environments do not coincide with each otber,and Ol-CPx-Pl saturated cotectic lines of alkaline basalts formed in the same tectonic environment simply move toward the Ol vertex with the increasing oxygen fugacity.The silica-alkali evolution trend of low pressure crystallization fractionation of volcanic magma exhibits positive slope and is approximately parallel to the boundary of volcanic series in the TAS diagram(Le Bas,1986).The 1-atom experimental liquid lines of descent are different from the evolution trend of the natural rocks,implying that low-pressure crystallization fractionation could not be the major mechanism for the magmatic evolution of the Datong volcanic cluster.It seems that high pressure crystallization fractionation was the major factor controlling the evolution of the volcanic magma from the early stage to the late stage of Middle Pleistocene.

Abstract:On the basis of the hydrogeological characteristics of hot mineral springs in Xiaotangshan area,Beijing,authors engaged in the experiments of water-rock reaction using dolomite (90%)and granite (10%)as starting materials and quadratic distilled water as reactive solution, which were put into Ti-high pressure vessels under 50-200℃and (200一500)×lO5Pa. The results of experiment showed that the quantites of ions and oxides for K+, Na+, Ca2+, Mg2+,Al3+，HCO3-,N03-，F-，C1-，SO42-,∑Fe and Si02 extracted from the rocks into the solution cange with the variations of rock compositions, temperatures,pressures, pH values of water, grain sizes of rock, redox state, and numbers of time for water cycle etc. These laws brought to light the mechanism of the main elemental change in the formation of hot mineral springs in Xiaotangshan area. Authors provided the oretical evidences for opening up hot fields and man-made hot springs.

Abstract:The Huashan granitic batholith in Xiongershan area, western Henan, is composed of three granitic bodies, i.e. Wancun biotite moyite-adamellite，Haoping amphibole-biotite adamellite and Jinshanmiao moyite. Being a product of Yanshanian intracontinental compression-subduction on the southern margin of the North China platform, the batholith was formed by remelting of the crystalline basement of this area (metamorphic rocks of Arcbean Taihua Group) under appropriate P-T conditions. The early stage Wancun granitic body represents the average composition of the remelted magma, whereas the late stage Jinshanmiao body might have been formed by crystallization differentiation of the middle stage Haoping granite body. Various stages of rock bodies making up the Huashan granitic batholith are comparable with I-type granites proposed by Chappell(1974) or South China syntectic granites in mineralogy, petrology, geochemistry and stable isotope composition, but are obviously different from the South China transformation type granites proposed by Xu Keqin et al.(1984) in spite of their similarity in petrogenic style. This is because the source rocks of the Huashan batholith are metamorphosed intermediate-basic volcanic rocks, suggesting that characteristics of granites formed by crustal anatexis depend to considerable extent on properties of source rocks. It is therefove concluded that in genetic classification of granites, their geological settings, properties of their source rocks and their petrogenic styles should be considered synthetically.

Abstract:Using trace element concentrations of consanguineous primary magmas formed by different degrees of equilibrium partial melting, the author has put forward an inverse method for quantitatively calculating trace element abundances of source rocks. In the inverse calculation, there is no need to assume parameters such as C0, D and F, so it provides an effective means for studying geochemical composition of the provenance.In addition, the paper has dealt with the genesis of the Cenozoic olivine tholeiites and alkali basalts and the characteristics of the upper mantle in Hannuoba area. The inverse results show that the upper mantle had obviously undergone enrichment of REE relative to chondrite before the melting process, with different rare earth elements experiencing obviously different degrees of enrichment.

Abstract:The Caledonian orogenic belt in Gjersvik area of Central Norway is composed of a series of terranes,and the volcanic rocks in the Gjersvik terrane consisting mainly of dark and light-colored tholeiitic greenstone and quartz keratophyric pyroclastic rocks exhibit an obvious bimodal pattern.Volcanic activities can be divided into three stages which were closely asso-ciated with the evolution of rift structure. Undifferentiated tholeiite derived from the depleted mantle was formed at the early stage of rift evolution,felsic volcanic rocks from partial melting of basalt or gabbro were produced at the middle stage,and differential tholeiite derived from the deeper enriched mantle came into being at the late stage.A series of massive sulfide deposits have been found within the Gjersvik terrane,which were related to volcanic activities and are spatially in close association with felsic pyroclastic rocks.Studies show that the formation of these deposits was related to the submarine hydrothermal system accompanying the volcanic activity.

Abstract:on the basis of geochemical data, dolomites in the offshore facies of the Cambrian Bonneterre Formation were classified and identified by the artificial neural network,with the rate of discrimination reaching 100%.The results show that the neural network approach is fairly satisfactory and might be expected to become an effective technique for the classification and identification of rocks.

Abstract:The present paper deals mainly with chemical composition of pyroxenes which constitute the major rock-forming minerals in the Huangshandong mafic-ultramafic complex.Orthopyroxenes in the Huangshandong complex are exclusively bronzitc, which seems related to host rocks in chemical composition, being rich in "En" in the ultramafic facies and enriched in "Fs" in the hornblende-gabbro facies. Clinopyroxenes vary considerably in chemical composition, covering augite, diopside and enstatite-diopside. In the same host rock, clinopyroxenes contain more TiO2, A1203, Cr203, Ca0 and Na2O but less MgO, FeO, Mn0 and SiO2 than orthopyroxenes.Statistical analysis indicates that from the ultramafic facies to the hornblende-gabbro facies, chemical composition of orthopyroxenes varies from the enrichment of MgO, SiO2 and Al2Os to the enrichment of FeO, TiO2, Ca0 and MnO, whereas that of clinopyroxenes from the richness of A1203, Cr203, Na2O and MgO to the richness of FeO, Mn0 and CoO. There exists linear positive correlation between Fe2+/Mg values of coexisting two pyroxeness; KD values vary in the range of 0.92-3.42, equivalent to KD values of pyroxenes of magmatic origin. Their equilibrium t and P are 947-1157℃ and 0.58-10.58 (0.1 GPa) respectively. Chemical composition of the pyroxenes indicates evidently that their parental magma was tholeiitic magma formed by partial melting of garnet-lherzolite in a plate-tectonic setting of island arc.

Abstract:Four samples of aeschynites have been studied, including one Ce-aeschysite, two Nd-aeschynite, and one Y-aeschynite, of which the first three were collected from the Bayan Obo iron and REE deposit in Inner Mongolia and the last from Xihuashan granite in Jiangxi.The present paper deals with characteristics of differential thermal curves of four metamict aeschynite samples and X-ray powder diffraction data of these samples at different temperatures, together with a discussion on linear relations between ThO2 and TiO2, ThO2 and Nb2O5, Ce203 and Nd203, and TiO2 and Nb2O5. From the study it is known that the four metamict aeschynite samples have the following characteristics:(1)so far as differential thermal curves are concerned, there is no exothermal peak at 700-800℃ for aeschynites which suffered no metamictization, but metamict aeschynites do have such a peak, and the higher the metamictization degree, the steeper the peak;(2)the deeper the metamictization, the higher the temperature of heating treatment required for restoring crystal form of the mineral] however, the temperature should not exceed 1200℃，(3)the higher the contents of radioactive elements thorium and uranium in aeschynites, the deeper the metamictization, e.g., No.1 sample (ThO2 5.79%)has suffered higher degree of metamictization than No.2 sample ( ThO2 1.28%)，(4)the metamictization degree of aeschynites is related to the variety of thorium and uranium; the Main No.1 (Th02 5.79%)sample, for example, has suffered higher degree of metamictization than Y-aeschynite which contains 10.08% U203.

Abstract:The Zhangjiakou gold deposit in the northwest of Hebei is a large-size quartz vein type deposit on the northern margin of the North China platform. The present paper deals in detail with characteristics of two major types of ore-bearing quartz (milky quartz and ashy quartz) from this deposit in such aspects as gas-liquid inclusions and their compositional characteristics,micro-deformation, and pomorphic characteristics of the composition and of the cell parameters.In addition, a discussion is made on the relationship between gold content and different typomorphic characteristics of quartz,together with a comparison of typomoiphic characteristics of quartz between this deposit and some other typical gold deposits of the world. The above study shows that ashy quartz is different from milky quartz in such characteristics as gas-liquid inclusions, micro-deformation and trace elements, and that the ore-forming solution of the Zhangjiakou gold deposit must have been a kind of Na+-Ca2+-Cl- type and Na+-Ca2+ -S042- type mesothermal-hypothermal solution with moderate salinity and weak alkalinity.These results combined with the geological setting of the deposit have led the authors to conclude that the Zhangjiakou gold deposit is of metamorphic mesothermal-hypothermal type.

Abstract:The Danxia Group in Jinjiling area of north Guangdong is mainly composed of fluvial facies calciferous sandstone.On the basis of grain size analysis and artificial placer mineral analysis, four detrital minerals, i.e, quartz,feldspar,tourmaline and zircon were studied under a scanning electron microscope, and it is thus discovered that their surface textures are much more comlilex than the surface textures of similar minerals from any modern coastal and fluvial arenaceous sediments the authors have ever studied. The reason is that the surface of detrital minerals in ancient sandstone not only underwent transformation in the process of weathering, trapsportation and sedimentation like what detrital minerals are experiencing in modern rivers or coastal areas, but also suffered superimposition of further transformation during diagenesis. The composition of intergranular liquid and the change in temperature and in pH value under the diagenetic conditibns played an important role in the formation of surface textures of minerals. It is therefore obvious that the various characteristics of surface textures of minerals are related not only to mineral behaviors but also to the action and influence of the media in the diagenetic environment. A comparison of surface textures of various minerals shows that, in addition to the physical and chemical properties of minerals, the temperatures and pH values of the media in the diagenetic environment are also important factors affecting the formation of surface textures of minerals, with the main reaction being dissolution.The degree of transformation of the four minerals is in decreasing order of tourmaline-feldspar-quartz-zircon, which is not qcite consistent with the sequence of stability of these minerals.