Abstract:The Mesozoic volcanic suite located in the Tianmushan Mount., northwestern Zhejiang Province, China, is, in ascending order, composed of rhyolite, dacite and andesite. A model of physically and chemically zoned magmatic chamber has been used for explaining this reversed compositional sequence. Gradients of temperature, density and viscosity in the chamber have been established according to some thermodynamic methods. Modeling for major and trace elements supports the idea that fractional crystallization is a main mechanism responsible for the chemical variation. The settling velocities of observed minerals in different magmas, which are estimated from Stocks' law, indicate that gravitative settle is impossible, especially in the acid magma. Thus, convective fractionation (Huppert et al., 1988) is considered most probably to be the process accounting for the fractional crystallization in the zoned chamber.

Abstract:The authors have made simulation experiments on the interactions of valcanic gas-hydrothermal solutions with subvolcanic-volcanic rocks (diaba- se, andesitic-tdff, a.ndesite and tuffaceous sandstone) based on field observa- tions of three iron ore deposits in volcanic rock areas of Cihai and Yamansu, Xinjiang and Huanggangliang, Inner Mongolia. The results of experiments has proved that paragenetic associations of the minerals of metasomatic rocks formed at 380-7000℃ temperatures and (250-800) × O.1MPa pressures are similar to those in the aforementioned three iron ore deposits, are TFe= 11.89-3881.89mg/1 is extracted from sdbvolcanic-volcanic rocks. It follows that metasomatism of the wall rocks of previo}xsly formed subvolcanic- volcanic rocks by late volcanic gas-hydrothermal solutions continuously rising along structural zones, led to the extraction of a great quantity of iron from these rocks and to the formation of the Cihai, Yamanstt and Huanggangliang(western part) iron deposits under the favorable tempera- ture, pressure, and other physico-chemical conditions.

Abstract:This paper briefly discusses the mineralogic and petrologic characterist- tics of potassic lamprophyre in western Sichuan-Yunnan, and its tectonic setting of occurrence as well as the comparison with that in western Austra- lia and Guizhou, China, in order to determine the favorable areas and the prospects of searching for diamond-bearing lamproite on the Yangtze Plate. The diamond-bearing lamproite in western Australia is the product of infra-plate magmatic activity, rich in Ba, K, Rb, Sr, volatile components and light REE, with K20/Na20>10, K20/A1203=1.2, and high content in Ti02. It belongs to the ultrapotassic rock series enriched in K，Ti and Mg, and poor in Al, with high speed of explosion and thus is undifferentiated. The mineral assemblages are of high-pressure facies and low-pressure facies, and no me- drum-pressure facies is found. The diamond-free lamproite in western 'Sichuan-Yunnan is formed as a result of magmatic activity at the plate margin. K20/Na2O=1-5, and K2O/Al203 = 0.22-0.58. Obvioulsly these ratios are low. It belongs to potassic rock series with moderate K and Ti contents and slight A1 and Na satua- tion. Its explosion speed is slow and the mineral facies have the characteris- tics of the evolution from high-pressure through medium-pressure to low- pressure facies. Comprehensive comparison of the lamproite in this area with that in western Australia and Guizhotu, China seggests that the increasing in K，Ti and volatile components is related to both the stability of the plate and the depth of the magma generation. Therefore the diamond-bearing lamproite within the Ya.ngtze plate should be of common occurrence in the southeas- tern peripheral areas of the central Sichuan oldland core.

Abstract:The Ningzhen granitic body is situated between Nanjing and Zhenjiang, formed in the Late Yanshanian period and belongs genetically to syntectic granitoids. Its major rock types are granodiorite porphyry, granodiorite, quartz diorite-porphyry and so on. This paper deals with the magmatic inclu- sions developed in two dark dikes-olivine gabbro dike and monchiquite dike intruding into the granitic body. These inclusions are enclosed in clino-pyro- xene and olivine phenocrysts. Most of them are well-developed primary mag- matic inclusions of evolution type, consisting of daughter minerals such as pyroxene, ilmenite, biotite and potassium feldspar. Some CO2 fluid inclusions are also observed. The homogenized temperatures of the magmatic inclusions are between 1220-1270℃. The results of electron microprobe analyses of homo- genized inclusions indicate that magmas trapped in the early crystallized pyroxene phenocrysts are evidently more acidic than host rocks. Combined with other evidences it suggests liquid immiscibility took place during the formation of the dikes, thus providing an evidence for the hypothesis of la- yered magma chamber to explain reversed magmatic activity.

Abstract:The ancient Passive continental margin of the northern Yangtze plate was developed through Late Proterozoic-Middle Ordovician rifting and Middle Ordovician-Late Silurian drifting. This paper deals with the geochemical characteristics of the ancient passive continental margin of the northern Yangtze plate.a. The volcanic rocks developed at the early stage of rifting are alkalic and bimodal, while the volcanic rocks, dikes and swarms formed during the late stage of rifting to the early stage of drifting are not bimodal, although alkalic.b. Sandstones and shales formed during the evolution of this continental margin show two different geochemical characteristics. The sandstones and shales produced in the rifting stage are geochemically similar to those of active continental margins. Only do those rocks produced in the drifting stage possess the geochemical characteristics of sandstones and shales of a passive continental margin.

Abstract:Magnesiohulsite is a new mineral species found in China in 1985. It oc- curs in the magnesian skarn zone between biotitic granite (γ5(2))and Carbonife- rous dolomitic limestone in Dayi Mountain, Hunan Province. Quite a lot of its crystals have microtwins. The electron diffraction spots split regularly. Using the selected area electron diffraction method (SAED)，We have obta- ined the splitting electron diffraction spots patterns of [010], [141] acnd [121] zone axes. Through matrix analysis of the microtwins, it is determined that the two sets of splitting spots are of twin structure relationship, belong- ing to face-law twin with (101) twinning pla.ne.Its microshapes are demon- strated by bright field image. Different kinds of electron diffraction pat- terns show that the mineral belongs to monoclinic system with a0 10.7A，bo 3.01A，co 5.39A and β 94.5º.Charactezistic} of this twin structure and its crystallographic data are quite comparable with the result of X-ray single- crystal analysis. This paper provides a quite good mineralogical method for studying twins, especially microtwins of the mineral.

Abstract:Ge-, Sn-bearing sulvanite, a variety of sulvanite, occurs in the Gacun Agbearing polymetallic ore deposit, Sichuan Province. It is normally square, rectangular or irregular in form and light lemon yellow in color; its grain sizes are commonly 0.01-0.1 mm with the greatest being 0.3 mm. Microhardness 137.8kg/mm2, equivalent to 3.49 on Mohs hardness scale; reflectance 31.54% (589 nm). The main chemical components are Cu 52.29-54.71%, S 30.59-32.49%, V 5.70-6.50%, Ge 4.3-6% and Sn 2.43-3.65%, with trace amounts of Zn, Fe, As, Sb and Bi, giving a simplified formula of Cu3 (V,Ge, Sn) S4. The mineral is of cubic system, a0=10.66A, V=1211.36A3, with space group P3m.

Abstract:Olivine in kimherlites of Shandong Province is known to have six main modes of occwrrence:(1)megacry}ts一(>l Omm )，(2)coarse-grained olivine ( 5-l Omm)，(3)medium-grained olivine (2-5 mm)，(4) microgranular or groundmass olivine(<0.2mm)，(5)olivine as inclusions in diamond; and (6)olivine in deep-seated xenoliths of kimberlite. Megacrystalline and macrocrystalline olivine occurs as rounded crystals, whereas groundmass olivine as subhedral and euhedral erystals. Olivine in Shandong kimberlites ranges from colorless through light green to green in color, and the relationship between the color and the size is like this, large crystals (macrocrysts) are colorless and light green, while small crystals (groundrnass olivine) are green, stfggesting that the former contain higher Fo than the latter. Three compositional variation trends have been observed from core to rim of the olivine:(1)iron-increasing trend;(2)magnesium -increasing trend;(3)coexistence of the above two trends in the same oli- vine. However; the zonal variation is very limited, e.g., Fo varies in the ran- ge of 0.2-1.6% from core to rim. Usually with Fo decreasing Ni0 contents decrease and Ca0 contents increase. With the increase in diamondcontent of kimberlites, Fo values of olivine increase, e. g.，olivine of diamond-rich kimberlite from Shengli-1 of Shan- dong contains higher Fo (90.2-92.5%) than that of diamond-poor kimber- liter from Tiongqi-6 of of Sha.ndong(88-89.5%). There are 10 strong absorption bands(982, 948, 880, 837, 606, 510, 465, 420, 380 and 363cm-1) within the range of 350-1200 cna-1` in infrared spectra of olivine from Shengli-1 kimberlite pipe. The presence of 420 cm-1and 606 cm-1 shows that the olivine in question belongs to forsterite.

Abstract:Synantectic phenomenon refers to the growth of a new mineral along the boundary of two neighboring minerals throrugh their reaction. Synantectic reaction is well developed in a Ni-bearing basic rock body in the Changbai mountain area. The author holds synantectic minerals to be of multiple geneses. Based upon the study of mineralogy, mineralogical chemistry and thermodyna- mics, he has classified the synantectic zone into two types-primary and secondary. The primary synantectic mineral was formed as a resaIt of mag- matic reaction and is called corona structure whereas the secondary ones. were formed through regional metamorphic process of thermal metamor- phism, hydrothermal metasomatism and contamination, respectively named contact corona texture, metasomatic kelyphitic structure and contamination reaction rim texture. The research of syna.ntectic minerals will协eld a lot of information for the stuidy of diagenesis and metallogenesis.

Abstract:The quartz in Echassieres area is genetically related to the La Bosse granite, and the later Beauvoir granite penetrating the stockwork has di- vided it into two parts; the upper part and the lower part. Wolframite has the composition of ferberite which contains Mn0 1 .2- 10.4% and is rich in Nb (Nb2O5=0.1-5.1%)but poor in Ta