Abstract:Nd-Sr isotopic compositions for 20 granitoid bodies of syntexis series in South China have been studied in this paper. Based on the isotopic com positions of samples and their distribution characteristics on the €Nd-T,(87Sr/86Sr)-T, €Nd-Єsr,diagra ms, these granitoids of syntexis serves are considered as mixing products of upper crust end-member and depleted mantle end-member in certain proportion. Crust-mantle mixing proportions of these granitoids are calculated by using the two-component mixing equations. According to tectonic environments and material sources, granitoids of syntexis series in South China can be divided into three types: the continental margin type,the continental interior type, and the fault depression zone type.

Abstract:In Nanling Mountain area, a very important metallogenic province of China, the various granitic rocks with different ages are widely distributed. During the evolution of these granitoids which resulted from rejuvenation and anatexis of the old basement (1200-2000Ma), the main ways for REE differentiations were: (1) partial melting; (2) fractional crystalization; (3) thermogravitational diffusion; (4) differentiations of metamorphism and migmatism, and (5) hydrothermalism. Among them the (2) and (3) processes are the most important ones for HREE concentration in magma. Based on the data of tectonic setting, lead and strontium isotopic compositions and zircon population types, it is concluded that local physicochemical environment of magma is the key constraints to REE fractionations.

Abstract:The mineral assemblage of impure carbonate rocks is closely connected with the total pressure and partial pressure of CO_2. The production temperature of tremolite, diopside and olivine is raised with the rising of total pressure. There are two extreme types of fluid behavior during metamorphism, i.e. infiltration and buffering. During infiltration metamorphic reaction takes place at certain determined temperature and all reactions will occur discontinuosly. All mineral assemblages in closely spaced outcrops are stable at same partial pressure of CO_2. The point of infiltration metamorphism on TX_(co_2) diagram is rarely on the reaction curve. In the field there is no abrupt boundary between different mineral assemblages. Minerals controlled by infiltration metamorphism are enriched or deprived in some elements with uneven grain size and without inclusions. Based on above mentioned characteristics metamorphism controlled by buffering could be distinguished from metamorphism controlled by infiltration. The impure carbonate rocks of Susong Group, Hebei and Hongqiyingzi Group, Hebei are metamorphosed under infiltration. The impure dolostone of Banyukou Formation, Wutai Group, Shanxi is metamorphosed by combination of infiltration and buffering.

Abstract:Having study of the petrography of the welded tuffs, the author divided the crystalline textures in the welded turfs into two types, i. e., the crystalline texture in the plastical fragments, such as pumice and plastically deformed glass shard, and the texture in rigid glass shard and volcanic dust. Using the theory and the experimental achivement of supercooling crystallization, this paper puts the stress on discussing the genesis of the first type and suggests that it may be formed not by devitrification, but by supercooling crystallization.

Abstract:The tremolitite deposit has been found recently in Xiaomeiling area of Liyang County, Jiangsu Province. By studying, the author suggests that the tremolitite body mainly consists of tremolite, and part of the tremolitites are possessed of the limpid feature, which are similar to the rough nephrite. In this paper,the occurence and uses of the tremo]itite are introduced simply, and including the study of mineralogy and petrology for the deposit and the ini- tial discussion of its origin. We suggest that the origin of the deposit is the result of a typical contact metasomatic metamorphism.

Abstract:The ophiolites of east Qinling are mainly distributed within a narrow zone lying along the southern fringe of east Qinling and to the north of Shangnan-Danfeng fault zone, winding nearly latitudinally as a discontinuous belt. The ophiolites in Shangnan一anfeng area make up an important and typical component part of this belt. This paper deals emphatically with the genetic mineralogical characteristics of amphibole, an important rock-forming mineral extensively-distributed in ophio- lites of Shangnan-Danfeng area, including its main characteristic components,trace elements, lattice cell parameters and cationic occupancy. On such a basis,it is demonstrated that (1) the amphibole in the ophiolites is a product of regional orthometamorphism, (2) the material sources thus formed show consanguinity,and the original rocks are ultramafic-mafic magmatic rocks and volcanic lava, and (3) being under basically identical thermodynamic condition, the metamorphism belongs to epidote-amphibolite facies or amphibolite facies, with the metamorphic temperature being 610℃ or so and pressure higher than .5× 108 Pa. In addition, the similarity in genetic mineralogical characteristics between various amphiboles from ophiolites of Shangnan-Danfeng area suggests that the ophiolite zone of east Qinling is the metamorphic belt of a tectonic margin resuping from the subduction and collision of North China plate and Yangtze plate.

Abstract:Anshan Archaean metamorphic complex occurs in Anshan-Benxi area that can be subdivided into three districts, i.e., Anshan, Liaoyang and Benxi. The metamorphic grade of all the rocks belongs to amphiholite facies. In general, the grade of metamorphism increases from the west to the east. The typical metamorphic minerals which firstly occur in the metamorphic rocks are respectively almandine, staurolite and sillimanite in Anshan, Liaoyang and Benxi. Nevertheless, the grade of retrogressive metamorphism with strong deformation increases from the east to the west, and the metamorphic rocks in Anshan district have become greenschist facies ones. The previous metamorphic minerals of amphibolite facies occur only as metasomatic residual minerals in chlorite and sericite. Hypersthene, andalusite and spinel have been found in metamorphic rocks at Xiaolingzi in Anshan district. The metamorphic grade of these rocks discords with other rocks in the same district. It is evident that these rocks suffered contact metamorphism after regional metamorphism of amphibolite facies.

Abstract:The authors selected zircon, tourmaline, quartz and feldspar from 67 samples of different facies on the coast of Guangdong for ultrastructural observation with a magnification from 300 to 10, 000 under an electron scanning microscope. It has been found that the mineral grains vary ultra-morphologically from place to place, suggesting the influence of different environmental factors. The grains from rivers mostly show simple but irregular collision pits, some being disc-shaped or desqua- mated, which probably resulted from physical erosion. The exposed areas have yielded rounded grains covered with mini-pores, fissures and funnel-shaped corrosion pits, suggesting a physical erosion together occasionally with chemical corrosion. The morphology of the rounded grains from some periodically exposed facies zones, e. g. intertidal zone, is varied, assuming shell-or honeycomb-shaped raini-pits, small directional striae, curved fissures, V-shaped corroded pits and some Si02 precipitates, which are considered to have been formed by physical erosion in combination with chemical corrosion. An equally complicated texture was also found at the surface of the mineral grains from the underwater zones. It is characterized by honeycomb, corroded pits, irregular or parallel fissures, curved stepIike and funnel-shaped corroded pits as well as Si02 precipitates. This texture is probably a product of chemical corrosion associated with a joint physicalchem ical corrosion. All these characters seem to indicate the origins of different facies zones in this particular coastsl area.

Abstract:Megaphenocrysts of ferrifayalite occur in biotite monzonitic granite in Jixi county, Anhui province. The rock shows finegrained granitic texture and consists of perthite, oligoclase. quartz and. biotite. The megaphenocrysts can reach 5cm in grain size, and contain small euhedral magnetite crystals in the form of dissemination or discontinuous veins. Under hypergene conditions, ferrifayalite has been partly converted into limonite through oxidation, and the megaphenocryst is quite similar to wolframite in shape, color and luster. The megaphenocrysts were formed in upper mantle under the condition of high temperature and pressure. The high-pressure metacrysts of fayalite were first separated out from the granitic magma through crystallization; during the upward migration of magma along the deep fault, these metacrysts were oxidized into ferrifayalite with the increasing oxygen partial pressure.

Abstract:Searlesite was discovered in Miyang depression of Henan Province in 1987. It occurs in oil shale of Tertiary alkali-bearing rocks, and its discovery fills a gap in mineralogy of China. Its molecular formula is NaBSi2O5(OH)2, and its crystals show the following features: assuming spherical and bunchy aggregates; colorless; biaxial negative; Ng=1.5345, Nm=1.532 and Np=1.512. Searlesite is of some significance in explaining the depositional environment and material sources of the alkaline deposit in which it occurs.

Abstract:The phosphoric acid method established by J. M. MeCrea in 1950 is generally used to determine the carbon and oxygen isotopic ratios in carbonate minerals. Nevertheless, that method requires the experimenter to select highly pure individual minerals. The method suggested by the authors is based on J. M. McCrea}s technique. Using the different activities of calcite and dolomite at different temperatures and under different reaction conditions, one can collect COz gas step by step from the same sample containing both of the two minerals and then determine carbon and oxygen isotopic ratios separately. Through the experim ent on method conditions and the determining of natural carbonate sa m pies, it is thought that the determination is highly precise and can be used to judge the origin of dolomite. The method is of practical significance. Furthermore, the method has the advantage of determining carbon and oxygen isotopic ratios of the two minerals simultaneously and separately, and rendering it unnecessary to choose and separate individual minerals. The method is easy to use with low production cost and can spare a lot of time and energy.

Abstract:The Archean granulite rocks in Inner Mongolia occur mainly in Dining and Wulashan Groups which extend from $adamengou near $aotou in the west to Jining- Xinghe area in the east, roughly in E-W direction. The main rock-forming mineral is pyoxene widely distributed in the granulitc rocks. Integrated studies indicate that the orthopyroxene there is commonly rich in iTOn; that the variation in iron content of the mineral is in direct correlation with that of the rock, That the FeO,Mgt and Ca0 contents of elinopyroxene vary in a rather small range and that the Mg0 content of clinopyroxene is similar to that of orthopyroxene, both controlled by the components of the rocks. The two pyroxene in this paper belongs to the equilibriumassociated relation. The metamorphic temperatures obtained for the’two-pyroxene pair are 800-900 C. In the light of rock types and paragenetic association of the minerals it is inferred by calculation that the pressure is between(7-10)× lO8Pa, suggesting that the granulite belongs to the medium pressure phase.