Abstract:Taking the volcanic-intrusive complex in the Yanbei porphyry tin ore district as an example and based on the covariance plots of Ce, Nd, Sm, Eu, Yb in six different element-element,ratio-ratio coordinates, the authors have reestablished the petrogenic mechanism of the volcanic-intrusive complex in this district. The results suggest that the melt of the first acidic magmatic cycle was formed as a result of accumulative melting of basement rocks in South China(F=0.3). A part of acidic magma of the first cycle which was not extruded onto the surface might be crystallized in fractional crystallization state at depth,leading to the formation of residual granitic melts(F=0.2).

Abstract:There are lots of granitoids exposed in Mudanjiang-Jixi area, represented by such rock bodies as Chaihe, Shichang，Guangfutun and Gangzigou，which were formerly regarded as Proterozoic granite bodies. With the single zircon stepwise evaporation-deposition method proposed by Kober, zircon samples collected from granite, granite porphyry migmatite and granitic veins in this area were dated isotopically, and the results indicate that the emplacement and migmatization of granitoids in this area mainly took place during the Variscan orogcny of 290-250 Ma，that some granite bodies were probably formed in Caledonian period of 488-409 Ma instead of in Proterozoic, and that the Precambrian metebasement might exist on both sides of the Bamiantong complex，as is evidenced by the age data of inherited zircon (2871士8 Ma and 1134士14 Ma) obtained in granite and migmatite.

Abstract:A comparison of the Lushan granulite facies rocks and related amphibolite facies rocks with the granulite facies rocks in other parts of the world shows that the former rocks are not apparently depleted in LIL elements. The slight Rb and U depletion accompanied by no Th depletion suggests that granulite facies rocks have not been transformed by special fluids or melts,and that the slight Rb and U depletion might be attributed to the devolatilization that occurred during or bofore amphibolite facies metamorphism. The geochemical features, combined with the fact that there exist no CO2-rich fluid inclusions in the rocks and no positive Eu anomaly in the chondrite-normalized REE patterns of the rocks, have ruled out the possibility that the permeation of CO2 fluids and partial melting might have acted as the metamorphic mechanism of the granulite facies rocks. The trace element dlstribution patterns of the Lushan granulite facies rocks are equivalent to the patterns of the average crustal compositions on the southern margin of the North China platform, and this implies that there has been no obvious crust growth in this area since Proterozoic and that the material cycling1 has been mainly intracrustal recycling.The high heat-producing element contents of the Lushan granulite and amphibolite facies rocks might be one of the factors thathave caused the long heat nonequilibrium in the crust of the area and a series of tectonic activities since Proterozoic.

Abstract:Basic and ultrabasic rocks were dated by the Sm-Nd mineral isochron technique. The results show that these rocks were formed at 320 Ma B.P.after the Early Carboniferous volcanism, being products in an extonsion tectonic setting at the late stage of collision between the Tarim plate and the Gongnaisi microplate.

Abstract:The corrosion holes on the crystal faces of zircon from the Mesozoic intermediate-acid intrusive rocks of Tongling area resulted from the rising temperature caused by heat or latent heat of crystallization arising from upward intrusion of deep magma after the crystallization of zircon. Statistics of zircon crystal faces show asymmetric normal and asymmetric lognormal distribution patterns noted for unimodal, bimodal and hyperbolic forms, and there exists the association of different crystal forms of zircon which belong to different end-member zircon groups in the same intrusive body, suggesting the hybridization of different genetic types of magma. The crystallization temperatures of different types of rocks as shown by statistics of zircon crystal faces are in the range of 900-700℃; for pyroxene monzodiorite, 850-650℃ for quartz monzodiorite, 800-650℃ for granodiorite,and 650-600℃ for granodiorite porphyry respectively. Studies of magma physics have shown that the composition，crystalline state and temperature of magma decided the viscosity of magma, which，in turn, conditioned the development of different zircon crystal faces in intermediate-acid intrusive rocks. For example, the high viscosity of granodiorite was favorable for the development of(311) face while the low viscosity of pyroxene monzodiorite for that of(111)face. The correlogram between the average alkalinity index and the average temperature index of zircon demonstrates that magmatic materials responsible for the intermediate- acid intrusive rocks in the area were derived from the mantle-crust mixtures.

Abstract:The studied platinum-gold placer occurs in Quaternary alluvial-diluvial sediments within a piedmont valley of ultrabasic rocks, Northwest China. Several platinum group element(PGE)minerals from the placer were studied under microscope and by electron microprobe and X-ray diffraction analysis, The Os-Ir-Ru minerals include iridosmine, rutheniridosmine, osmium and osmiridium. The Pt-Fe mineral is identified as isoferroplatinum.The studied mineral assemblage is Os-Ir-Ru minerals+ isoferroplatinum+native gold+native silver+chrome-ceylonite+chromite+magnetite+ ilmenite+cinnabar,suggesting that the placer is probably derived from the chrome-bearing ultra-basic rocks.The result of the study provides useful mineralogical data for evaluation of the placer,and also serves as a valuable indicator in the prospeacting for primary PGE deposits related to chrome-bearing ultrabasic rocks in the area.

Abstract:Hosted in the Archean greenstone belt，the Nuanquanzi gold deposit is of ductile shear metamorphic hydrothermal origin, with the mineralization controlled by the NW-trending shear belts. Native ruthenium and hedleyite were identified in the pyrite quartz lodes. Ruthenium occurs as tabular or irregular grains or aggregates，mostly less than 10 um in grain size. It usually occurs at the contacts between pyrite and quartz，or less commonly, in cracks of quartz.Structures and textures suggest that the native ruthenium is coeval with the pyrite and quartz. Compared with the native ruthenium from the oxidation zones of ultramafic rocks，the native ruthenium from the Nuanquanzi deposit is more enriched in W, Co and Fe and relatively lower in Ru, with the chemical formula being Ru0.675W0.l25Fe0.095Co0.064. Pt is extremely inhomogeneous in ruthenium. Hedleyite contains considerable amounts of Pt. The coexistence between Ru, Pt and Au throws light on the sources of ore-forming materials.The mafic and ultramafic rocks in the Anshan Group may be the major "gold rcs}rvoir". During the tectono-magmatic remobilization, PGE and gold were transported upwards, resulting in gold mineralization in the upper part of the greenstone belt. Such an inference is consistent with the sulfur isotope data， suggesting that S, Au and PGE are derived from the mantle. The first discovery of platinum group minerals in the deposit supports the suggestion that mafic and ultramafic rocks in greenstone belts seem most likely to be the source bed of gold.

Abstract:The rocks in Taipingzhai area are mainly composed of charnockite and metabasic intrusive bodies. Granulite, amphibolitc, pyroxenite, garnet biotite plagioclase gneiss and BIF are scattered as inclusions in the charnockite.Clinopyroxene occurs widely in various metamorphic rocks of this area. According to the grain size and the mode of occurrence of clinopyroxene as well as its relationship with the other minerals, the three generations of the mineral have been recognized.The large and oriented clinopyroxene grains associated with hypersthene and plagioclase constitute the first generation, whose stable temperature is about 880±60℃.The fine-grained clinopyroxenc surrounding hornblende and the first generation pyroxene make up the second generation, with the formation temperature being 820±60℃.The stable condition of tliese two generations is equivalent to pyroxene granulite subfacies. The third generation clinopyroxene associated with garnet and quartz was formed by the metamorphic reaction of early pyroxene and plagioclase，with the formation temperature being 775℃±.Besides the three generations of clinopyroxene，there is another kind of clinopyroxene which occurs in metagabbro and metabasic dikes. In these rocks，clinopyroxene and plagioclase large in size make up blastophitic texture, suggesting that the clinopyroxene is of magmatic origin and belongs to relict clinopyroxene. The relict clinopyroxene is mainly augite in the metabasic intrusive bodies, whereas most blastic clinopyroxene belongs to sahlite. The composition of the protolith is also one of the main factors controlling the composition of clinopyroxene.

Abstract:In this paper a new method of X-ray quantitative phase analysis is proposed for analysing samples with or without pure phase standards. It isn't necessary to add intternal standard to samples when measuring the intensities of the analyzed phases. The effects of apparatus attenuation can be excluded by using outer standard, a pure reference phase. For this method, there are two sets of parameters, Kjs and usj(j=1，…，n);n is the number of analyzed phases; s represents reference phase, which can he obtained by means of measuring m typical samples(m>=n)and computing the least square solutions of two-paired system of linear equations shown as (6)and(7). After determination of the parameters, each sample can be analyzed independently and simply. The discriminant cf residual phase defined by equation(15) plays an important rule in guiding quantitative analysis and simplifying the operation. In addition,a detailed discussion is given concerning the calculation of samples containing amorphous or unknown phases, the measurement of the absorption coefficient of a sample, and the intensity correction for superposed peaks. The author points out in this paper that this method has overcome various defects existing in other procedures and that, being convenient, practical, adaptable and stable, it has many distinctive features. It has been successfully used in the analysis of thousands of samples, such as scpiulitc clay and magnesium chloride hydroxide cement.

Abstract:The ore deposit occurs at the exocontact zone of Yanshanian granite,controlled by a NW-trending interlayer-gliding structural shatter zone.Ore-bearing hydrothermal solutions filled along the structural shatter zone,forming large-scale and well-continued composite orebodies,with silver,tin,lead and zine all reaching the reserves of large deposits. The ore-forming process exhibits polygenetic,multiphase and polystage features.Silver mainly occurs as silver minerals which are sulfosalt minerals of silver-antimony, silver-copper-antimony, and silver-lead-antimony. Silver minerals are extremely fine-grained and exist mostly in the mosaic form, associated especially closely with galena. Through ore microscopic and systematic energy spectral srudies with the help of individual mineral analysis, the authors have preliminarily found out the distribution, enrichment, interrelationship and physical properties of these silver minerals.