Abstract:In view of the discovery of Early Paleozoic microfossil group, the Dengshan Group Complex in Guangfeng-Shangrao district of northeastern Jiangxi is considered to be of Early Paleozoic. In this paper, the geology of oceanic volcanic rocks in Dengshan Group Complex is described, and the petrochemistry, geochemistry and genesis of Bazhukeng and Yejia volcanic rocks are studied. It is suggested that all volcanic rocks belong to island arc tholeiitic series, and are somewhat transitiona to oceanic tholeiitic series, being products of the expansion of the back-arc small oceanic basin. There are some differences between volcanic rocks of two formations in volcanic activites and magmatic evolution forms and degrees, which are consistent with the thinning of the oceanic crust from early to late stage.

Abstract:Using the single zircon U-Pb technique, the authors have geochronologically investigated two glaucophane eclogites sampled from Gaoqiao and Chenjiadian in western dabie Mountain, which provide the age information ofHP/LT(high pressure/low temperature) metamorphism and their Archean protolith. Seven analyses of zircons from the Gaoqiao eclogite and five analyses of zircons from the Chenjiadian eclogite have yielded the lower intercept ages of 1138± 39 and 1127±234 Ma and the upper intercept ages of 2872±40 and 2674±249Ma. Considering the petrological evidence and tectonic evolution of the Dabie orogenic belt, the ages of 1138 and 1127 Ma are regarded as the time of HP/LTmetamorphism, and the protolith of the eclogite is dated at 2647-2872 Ma. The present work confirms the existence of an Early Jinning HP/LTmetamorphism in the Dabie orogenic belt, which represented the closure of the ancient Dabie ocean. Moreover, the primary opening of the Dabie ocean occurred at Neoarchean. All this suggests that the tectonic evolution during the Jinning period took place under the plate-related mechanism.

Abstract:The Liuyuan granitoid, associated with eclogite, serves as a key to understand the regional tectonic evolution. U-Pb single zircon gives an upper intercept age of 880±31Ma. The REE pattern shows LREE-enriched and Eu negative anomaly, and the whole-rock sample givesεNd value of -0.9 at 880 Ma and Nd model age of 1530 Ma related to a depleted mantle. The authors conclude that the Liuyuan granitoid crystallized at Neoproterozoic of 880 Ma and was derived from a source composed of the mixture of a deep-seated Paleoproterozoic crust-derived (probably 1800~2200Ma) and a mantle-derived magma. It is inferred that the granitoid was formed against the setting of continental-continental collision.

Abstract:In the Ordos area of North China, the Ordovician consists of dolostones and limestones deposited on a broad shallow carbonate platform. In the southeast part to the study area, a special type of dolostone characterized by wheat dolomite crystals (WDC for short) is developed in the Middle Ordovician Majiagou 4th Formation. Restricted within the southeast part of the study area and covering an area of about 20000 km2, these dolostones are closely associated with gypsum/anhydrite rocks. The wheat dolomite crystals are elongated rhombohedra different from normal rhombohedral dolomite crystals. The optic axis c of the wheat dolomite crystals is at right angles to their elongation. In this respect, such crystals are similar to anhydrite crystals. The degree of order of wheat dolomite crystals is from 0.52 to 0.60, averaging 0.56; the molar concentration of CaCO3is from 51.22 to 52.05%, averaging 51. 64%; theδ13C is from -0.12‰to -0.20‰(PDB), averaging 0.16‰; theδ18O is from -5.75‰to -6.28‰(PDB), averaging -6.02‰; Fe2+is from 2980 to 3140×10-6,averaging 3063×10-6; Mn2+is from 83 to 105×10-6, averaging 94×10-6; K+is from 1200 to 1410×10-6, averaging 1305×10-6; and Na+is from 840 to 850×10-6, averaging 845×10-6. In the study area, the dolostones consisting mainly of wheat dolomite crystals were formed by SO2-4_rich brine through deep burial dolomitization of open marine limestones of the Ordovician Majiagou 4th Formation. It was the presence of SO2-4that made dolomite crystals grow like anhydrite crystals. The sulphate ions were derived from dissolution of gypsum/anhydrite deposits in adjacent strata.

Abstract:This paper deals with the formation conditions of black shales based on such analytical techniques as ICP_MS, GC_MS, isotope, organic carbon, element facies and micropetrology. Studies show that the Upper Sinian_Lower Cambrian black shales were formed in an anoxic environment, and the organic sources were algae and fungi (Thallophyta). The paper points out five geochemical indicators of anoxic environment. The organic matter, especially lipids, can be well preserved in an anoxic environment. Black shale is also an indicator of the oceanic anoxic event. During the slow degradation of organism, the organic matter absorbed and combined many elements. At the early diagenetic stage, the organic matter was decomposed, and some elements were remobilized. Hence the elements exhibit multi_stage enrichment and varied forms. The key factor is the adsorption of organism and the combination with the organic matter. The strata of Ni_Mo, coal stone, barite and phosphorite deposits are controlled by the change of sea level, and the ore_bearing sets are developed in the transgressive series and condensed sections. The black shales are characterized by high content of Ni, Mo and Mn, lower total REE, comparative enrichment of HREE, and negative Ce anomaly. Geochemical and REE features indicate that black shales were deposited in an epeiric sea environment.

Abstract:It is shown in this paper that intermediate bodies synthetized by sol-gel technique can lower the melting points of melts. The authors synthetized 9 quenching silicate melts in SiO2Al2O3-Na2O(K2O) series at 1750~1850℃and 2.0~4.0GPa. The Laser Raman Microprobe (LRM) study of these quenching melts has obviously shown that within the high frequency region (900~1200cm-1), the higher the pressure, the smaller the frequency of T-Onb symmetry and antisymmetry stretching vibration. The silicate melts of Na(K)/Al<1 may have six-coordination aluminum, and the aluminum tends to transform its coordination number from four-coordination to six-coordination when the pressure of silicate melts become higher.

Abstract:Situated in the eastern edge of the North China craton, Banshigou is one of the most typical terrains for the Precambrian study in China. Metamorphic complex around Banshigou iscomposed of TTG (80%) and metasupercrustal rocks (20%), with the latter being the inclusion of the former. Six samples from the metasupercrustal rocks of Banshigou were dated by the Sm-Nd method and, among them, four samples had a very good linear isochron, which gives an age of 2605±98(2σ) Ma, withINd0.50933±7(2σ), andεNd(t)+1.5±1.1. It represents the age of amphibolite facies metamorphism. The model agestDMfrom the four smples are within the range of 2790~2845 Ma, and the averge value is 2818 Ma, suggesting that the original rock of the metasupercrustal rocks in Banshigou area was derived from the depleted upper mantle about 2818 Ma and was formed in 1818~2605 Ma.

Abstract:The Chinese and English names, chemical formulae and other data of thirty six new minerals wich were approved by IMA CNMMN from January 1994 to Decembr 1994 and published by mineralogical journals of various countries are listed in this paper. These data of new minerals include their crystallographic systems, space groups, unit cell parameters, main powder diffraction data (I, hkl), physical properites (crystal form, color, streak, luster, cleavage, luminescence, hardness, density etc.), optical properites (uniaxial or bioxial crystal, positive or negative character, refractive index, reflectance, bireflectance, 2V, dispersion, absorbability, polychroism etc.), modes of occurrence, paragenetic minerals and references.

Abstract:Water-bearing cuspidine, a very rare mineral, was discovered by the authors in calcic skarn of the exocontact zone between Late Yanshanian granite and Triassic limestone in the Gejiu tin deposit, Yunnan Province. Its mineralogical characteristics, paragenesis, chemical composition, optical features, X-ray powder diffraction data, infrared absorption spectroscopy and thermal analysis were studied systematically. Associated with andradite, B_vesuvianite, diopside, datolite, fluorite, wollastonite and nordenskioldine, the mineral is characterized by clear polysynthetic twin, strong dispersion of refractive index and optic axial angle. Its optical properties areNg=1.604,Nm=1.595,Np=1.592,Ng-Np=0.012, (+)2V=62°, c∧Ng=6.5°. Electron microprobe and chemical analyses of the mineral give SiO230. 64%, TiO2 0.04%, Al2O30.01%, Cr2O30.06%, FeO 0.02%, CaO 55.61%, MgO 0.09%, MnO 0.14%, Na2O 0.02%, H2O+4.55%, F 8.63%, B2O30.59%, and CO21.43%, with the calculated empirical formula being (Ca3.979Mg0.009Mn0.008Na0.003Fe2+0.001)4(Si2.046B0.068 Cr0.003Ti0.002Al0.001)2.120O7(F1.823OH0.322)2.145(CO3)0.130·0.854 H2O. The unit cell parameters area0=10.94°A,b0=10.50°A,c0=7.623°A,β=110.42°. Infrared absorption spectral analysis suggests that there exists stretch_back vibration of OH at3560cm-1. Thermogravimetric analysis shows that the loss for H2O is about 2.8% and about1.6% for OH-. The authors consider that water-bearing cuspidine was formed in the hypabyssal exoskarn zone, being a product of contact metasomatism under the active role of F(B)-rich fluids. It was for the first time that water_bearing cuspidine was discovered in China.

Abstract:With natural minerals as raw materials, silicone rubber reinforcement fillers, namely the modified ultrafine powders with excellent properties, are prepared through ultrafine crashing, surface chemical modification and mechanical chemical modification. The reinforcement properties of the products are close to those of fumed silica, and can be used in silicone rubber to replace part of fumed silica. 1. Preparation of ultrafine powders Four kinds of natural minerals, viz. talc, quartz, needle wollastonite and grained wollastonite, are crashed into powder and, if necessary, purification, fractionation and demoisturing should be carried out to obtain powders finer than 43μm(325 mesh) with moisture content lower than 5%. Then, these powders are processed in a QS-50 micronizer, where they become ultrafine powders with the average particle size smaller than 2μm. Theparticle size distribution and specific area are presented in Table 1. It is obvious that under the same processing condition, the change of particle size and specific area of a mineral powder differs from that of other kinds of mineral powder. 2. Preparation of surface chemical modifying filler The mixture of mineral powder and coupling agent is treated in the GH_10 high speed mixer to prepare surface modified powder, with the temperature controlled at 120℃. The mechanism of surface chemical modification is studied by means of IR spectra of quartz powders and the determination of reinforcement effect of modified quartz powder in silicone rubber. It is pointed out that OHgroup concentration on the surface of sintered quartz becomes so small that the surface modification can not take place effectively. The surface energy of mineral powders before and after chemical modification is also determined and approached. 3. Mechanical chemical modification Mechanical force makes mineral particles crashed, with the new surface having larger surface activity. This makes mineral powder easy to react with the coupling agent and to be modified. In the experiment, the coupling agent (B_5) is mixed with mineral powders and thneral products are determined and presented in Table 4. It is pointed out that under the same processing condition, different kinds of minerals obtain different effects of modification. The larger the quanity of coupling agent used, the greater the decrease of surface energy and the increase of specific area.

Abstract:Based on analyzing the character of infrared specrum of water in the sepiolite structure, this paper assigned every infrared band of structure hydroxyl (OH), water of crystallization (OH2) and zeolite water (H2O). In high frequency area (3700~300 cm-1),the Mg-OH stretchingabsorption bandνMg_OHis around 3 6 8 0 cm-1, the Al - OHstretching adsorpti bandνAl-OHis around 3625 cm-1, the stretching absorption bandνOH2 of crystal water OH2is around 3560 cm-1, the bandνH2Oof zeolite water and adsorption water H2O is around 3400~ 3500 cm-1, and the band around 3260 cm-1is the bandνH_boundof hydrogen bond among water. In middle frequency area (1700~1600 cm-1), the band around 1640~1600 cm-1is the bending vibration bandδH2Oof zeolite water and adsorption water, and band around 1615~1630 cm-1is the bending vibration bandδOH2of crystal water. In low frequency are (700~ 600 cm-1), the band around 690 cm-1is the librating bandρAl-OHof Al-OH, and the band around 642 cm-1is the librating bandρMg-OHof Mg-OH. Moreover, the authors have studied the difference in infrared spectra between hydrothermal sepiolite and sedimentary sepiolite, and found thatνMg-OHof hydrothermal sepiolite is stronger than that of sedimentary sepiolite, whileνAl-OHof hydrothermal sepiolite is weaker than that of sedimentary sepiolite. By analyzing infrared spectrum of heated sepiolite, it is found that the variation character of infrared specrum of heated sepiolite is consistent with the phase change. Finally, the authors point out that infrared spectrum of water in the sepiolite plays the role of indicating structural stability.

Abstract:The authors studied 439 zircon grains collected from Cishan biotite monzonite granite and found that most zircon grains keep perfect crystal forms, and that there exist corroded zircon crystals. Based on such evidence, the authors believe that Cishan granite is of magmatic origin.93 By comparing characteristics of zircon groups from three main types of gold_hosting granite, namely Linglong granite, Guojialing granodiorite, Kunyushan granite, the authors have also drawn the conclusion that, Cishan and Linglong granites are similar to each other in evolution. It is considered that, as Linglong granite was formed in Late Jurassic, Cishan granite must have also intruded in Late Jurassic. The TET curve of zircon from Cishan granite starts from metamorphic rock and migmatite region, and the low_temperature part is located in the crust origin region, suggesting that partial remelting of Jiaodong group led to the formation of Cishan granite. The crystallization temperature of zircon spanned a wide range from 800℃to 600℃, which implies the richness of water and the favorable condition for mineralization of Cishan granite. Nevertheless, due to its high emplacement position and weak oxidizing capacity, its mineralizing capability is lower than that of Linglong granite.