Abstract:Abundant strontium isotopic data have been accumulated in the studies of the Circum-Pacific belt of continental volcanic rocks in eastern China; inclu- ding the work done by the author of this paper. Among the data. there are 15 initial ratios determined by ftb-Sr isochron method. The Jurassic volcanic rocks of western Liaoning and eastern Jilin Province and the Mfiddle Jurassic granite of Fujian Province have similar initial 87Sr/86Sr ratios in the range of 0.7050-0.7060. The initial 87Sr/86Sr ratios obtained from andesites and rhyo- lites. of 145-137Ma (referred to Late Jurassic in current stratigraphical time- table) in Yen-Liao region fall in the range of 0.706-0.709. The seven intitate ratios of the volcanic rocks of the Jiande Group in Fujian-Zhejiang region are 0.7067一0.7089, most of the samples for dating being collected from rhyo- lites. Based on the available data, the initial 87Sr/gsSr ratios of the igneous rocks older than 140Ma (i. e., Jurassic volcanic rocks and granites) are less than 0.706 whereas the initial ratios of the Cretaceous volcanic rocks are greater .than 0:706. The Early Cretaceous acidic volcanic rocks have initiate 87Sr/86Sr ratios of 0.707-0.709. This is obviously higher than that of basic rocks. The difference、of these two values are between 0.002-0.003. The contamina- tion of magma can be recognized merely from the comparison of the two values. The present data show that the initial 87Sr/86Sr ratios of the volcanic belt are in the range of 0.705-0.709. Howevea, all the high values are obta- fined from the acidic rocks which are prone to contamination. So, the value of 0.705士0.001 may be taken as the possible range of the iinitial ratios of the parent magma. Based on the fact that both the present ratios of 0.705- 0.709 and the inferred ratio of the parent magma (0.704-0.706) fall in a narrow range, the volcanic roclcs studied may be regarded as a type of rock between island-arc andesites and continental-volcanics. The are quite similar to rocks of the typical rift type (such as those in Oslo amd western Africa). This suggests tliat a mechanism similar to rif ting possibly existed at the eastern margin of China mainlapd during 240-95Ma B.P.as a result of the interaction between the Pacific plate and the Eurasian plate.

Abstract:This paper is a comprehensive diseussion based on field observations and laboratory studies of metamorphic rocks and minerals in the Miyun Group. The mineral assemblages of the major rock groups (ultramafic, mafic and felsic metamorphic rock gsoups)and their evolution have been studied and the equilibrium among coexisting minerals in each metamorphic episode has been determined. On this basis, ACF and A'KF diagrams for two progxade zones of the first metamorphic episode and a µNaZO-µK2O diagram of the second me- tamorphic and inigmatitic, episode are produced. According to the results obtained, the metamorphism and the evolution of the mineral assemblages in the Miyun Group can be divided into three episo- des. The progressive metamorphism of the first episode belongs to granulite fades under intermediate pressure; the metamorphism and migmatization of the second,episode proceeded in an open system, with a general tendency of rising in µNa20 and dropping in temperature; and the third .regressive meta- morphic episode took place more later and superimposed heterogeneously on the previously , metamorphosed rocks. In the first two episodes,both mica and amphibole were stable. Orthopy- roxene was stable mainly in the Opx-Cpx none in the first episode, but in a few cases, it also occurs in some rocks with special composition in other zones. Glinopyroxene was stable in the first episode and the first stage of the second episode. Garnet appears only in the rocks with specific composition in the first episode, whereas in the second episode, but distributed widely in various rock types in the second episode.

Abstract:The late Archean I}iuoqiu Group metamorphic rock series is distributed on the southern margin of North China platform. The lower part of tms group consists cnieriy or mtc:zoeaaea plagioclase gneiss, leptite, and amphibolite. The upper part is composed mainly of interbe- dded and plagioclase schists and-Ieptite intercalated with amphibolite and magnetite-quaa-tzite, and uppormost containing lenticular marble at its top. These rocks had undergone metamorphism of the amphibolite facies. The upper strata show rhythmic stratification and relicts of volcanic tex- ture were found in the amphibolile and leptite. Based on petrological, petrochemical and trace element studies the original rocks of this group are considered to belong to intermediate-basic volcano- sedimentary rocks.

Abstract:For investigation of the crystal chemistry, oxygenation and facies changes of calcium amphibole, two specimens from Guangdong ands Beijing (named G- and B-specimen, respectively) were studied with Mossbauer spectroscopy. Each specimen was divided into five groups, four of them were heat treated under 600，800℃，1000℃，1200℃，respectively, and left one untreated. The results of Mossbauer measurements indicated that the occupancy ratio of Fe2+ and Fe3+ and oxygenation of Fe2+ change slowly with temperature below 600ºC，the oxygenation of Fe2+ increases-sharply between 600t to 801Jt，and the temper- atures of perfect oxygenation of Fe2+ to Fe3+ for these specimens are near 1000℃.During 1000℃ to 1200℃，the facies changes take place in the speci- mens. The new facies are magnetite and pyroxene mineral etc. For calcium amphiboles formed in different . geological occurrence, the ranges of perfect oxygenation temperature are somewhat different. For the B-specimen formed in lower temperature, perfect oxygenation and facies change take place at <1000℃，for G-specimen, at >1000℃. These results are coincident with X- ray powder diffraction analyses.

Abstract:In studying the characteristics of magnetite and other accessory minerals 'in various granitic rocks of Central-South Xizang, the author found that magi betites from different types of granites formed under different geological con- dlitions and of different ages have distinctly different characteristic features. The content and chemical composition of magnetite as well as the mineral assemblage and rare-earth pattern in the granite all reflect either the man- tle or crustal origin of the rock. It is concluded that the granodiorite in the Gangdise belt is characterized by mantle origin and the muscovite-biotite granite and tourmaline granite in Nielamu district are of crustal origin.

Abstract:Nolanite was found for the first time in China from a sandstone-type uranium deposit in Sichuan province. It occurs in the dark gray medium-fine -grained lithic sandstone of a terrestrial red elastic rock formation in the basal part of the Lower Cretaceous. The associated mineravls are pitchblende, coffinite, pyrite and ferroselite. The nolanite` is black and brittle, with pris- snatic and sheetlike single crystals and aggregates appearing in vugs. Cross- section hexagonal. Microhardness: 460-765kg/mm on longitudinal section, 275- 382kg/mm2 on cross-section. Under reflected light, it appears creamy in color, parallel to C axis, but colorless along vertical C axis. It is strongly anisotro- pi, brown to dull blue along。axis, and approximately isotropic in the base section. Reflectance values; Rs-15.6-16.65 (440-66Onm)，Rω-14.43- 14.86 (440-660nm).Color indices; Rvis-16.56, 15.08, X-O.337, 0.334，Y- 0.337, 0.337, λd-582nm, 563 nm, Pe-0.021, 0.013.Chemical analysis gave V2O5-44.75, V204-26.11, Fe203-28.79, and trace minor amounts of Ti02, A12O3 SiO2 totalling 1o1.74. Approximate formula; V5.90Fe2.64O18.

Abstract:In 1983 found a mixture of ultramicro native lead and native tin in volcanic tuff in the west of Liaoning province.The mineral looks black-grey with many blue and purple points on it. In general, the mixture minerals pre- sent tabula and strip mode. It shows metallic luster. Moss scale of hardness is 1.5. Under the microscope, it appears weak heteropic. The reflective power is about 65%. Under a double-axle Camera, the single-grain minerals; are considered mic- rolitic aggregate by analyzing with X-ray diffraction. The obtainted debye patterns are the fold of native lead and native tin. Studing the minerals with energy spectrum and rapid electron probe scan proves that: the minerals are composed of Pb and Sn. Pb Sn elements do not well-distributed. The determi- nation results of different grains and same grains in different point region by electron probe show that the content ratios are quite different. The analysis with a transmission lens (probe) proves that when some -points are determi- ned on one scale, the content of Sn is 100%，the content Of Pb is approxi- mately 100%. Based on all above, the researched minerals still do pot form a new pha- se. They are only ultramicro mixtures of native lead and native tin. The for- mation of the mixture is due to the exsolution of lead-tin solid solution. The exsolution proceeds when the high temperature of lead-tin solid solution drops to 183℃.

Abstract:Through the study of some rock-forming minerals in intermediate-basic ig- neous rocks by means of UJniversal Stage, the author found that some mineral pairs occurred widely in regular intergrowth with each othea，e. g., olivine with orthopyroxene or clinopyoxene; or thopyroxene with clinopyroxene or hornb- lender; clinopyroxene with hornblende, and plagioclase with orthoclase etc. The cora-esponding crystal axes and planes of the pair of minerals in re- gular intergrowth are close to each other, and their opticaa elements appear to be orientated and symmetrical. The regular intergrowth of different minerals depends on their crystal structure, with the density of plane nets and the unit-cells playing the decisive role. The orientation in optical elements is due to their close relationship with their crystallographic elements, while biaxial their symmetry is due to their having the same symmetry type of indicatrix.