Abstract:A suite of low-grade metamorphic sedimentary rocks, exposed in Huashikoujing area of eastern Longshoushan, was originally regarded as the Paleoproterozoic "Longshoushan Group". Detrital zircons from two low-grade metamorphic sedimentary rocks yielded ages ranging from 0.52 Ga to 3.56 Ga, similar to the age spectrum of the rock from neighboring Cambrian Dahuangshan Group. Thus, the metamorphic sedimentary rocks were probably deposited in the middle-late Cambrian period. A total of 129 concordant data were obtained from two sandstone samples from Huashikoujing area and a sandstone sample from Dahuangshan Group, whose ages predominately range between 0.7 Ga and 1.2 Ga (47%, peaks at around 0.8 Ga, 0.94 Ga, 1.0 Ga) and between 2.5 Ga and 2.8 Ga (31%, peaks at around 2.5 Ga, 2.7 Ga). Two smaller age groups range from 0.5 Ga to 0.6 Ga (7%, peaks at around 0.56 Ga) and from 1.4 Ga to 1.8 Ga (10%, peaks at around 1.5 Ga). The other zircons have sporadic ages ranging from 1.8 Ga to 2.4 Ga, with a few zircons older than 3.0 Ga. Provenance analysis shows that detrital matters of Dahuangshan Group were mainly derived from Qilian Block. Late-Neoproterozoic to early-Paleozoic grains were probably derived from related igneous rock in north Qilian orogen, Neoproterozoic grains were derived from magmatic rock distributed widely in Qilian Block, and Mesoproterozoic to Archean grains were probably derived from recycled meta-basement rocks in Qilian Block. Based on regional geological information, the authors consider that the low-grade metamorphic sedimentary rocks and Cambrian Dahuangshan Group, which were probably deposited in continental margin of Qilian Block, belong to the Qilian orogen rather than the Alxa Terrane.

Abstract:The large Tiantang Cu-Pb-Zn polymetallic skarn deposit in Yuexi area is hosted in limestone of Devonian Tianziling Formation, and the ore bodies occur in the skarn and skarnized marble in stratoid, lamellar, lenticular and irregular forms. Metallic minerals consist mainly of chalcopyrite, galena, sphalerite and pyrite, whereas gangue minerals are composed of garnet, diopside, epidote, wollastonite, chlorite etc. With skarn minerals as the study object and by using electron microprobe technology, the authors investigated the mineralogical characteristics. Electron microprobe analyses show that the skarns in the Tiantang Cu-Pb-Zn polymetallic deposit belong to typical calcic skarns. Garnets in the ore deposit are mainly andradite-grossularite and varied with time from grossular to andradite, suggesting that the ore-forming fluid had a evolutionary trend from acidic to basic. Augites are mainly diopside. Components of garnet and proxene are Adr_4.60～96.47Grs_2.10～94.28(Prp+Sps)_0.41～3.88 and Di_{88.51～95.09} Hd_3.31～9.76 Jo_0.28～3.98, respectively, and their wide compositional variation range suggests that skarns were not formed under a totally enclosed equilibrium condition. The end member of the epidote group is dominated by epidote, and contains a little zoisite. The Mn/Fe ratio of pyroxene may be related to mineral metals. Characteristics of skarn in the Tiantang Cu-Pb-Zn polymetallic deposit shows that it is a typical skarn deposit resulting from the replacement of the marble by granitoid magma.

Abstract:LA-ICP-MS U-Pb zircon ages and whole rock geochemical data are reported for tonalites from the Ashele Cu-Zn deposit on the southern margin of Altay. The zircons from tonalite samples yielded mean ²⁰⁶Pb/²³⁸U ages of 375.3±2.1 Ma and 386.2±3.8 Ma, suggesting that the intrusion took placed between Early Devonian and Middle Devonian. These tonalites have high SiO₂(74.72% to 77.72%), moderate Al₂O₃ (12.06% to 13.5%) and total alkali (Na₂O+K₂O) (5.84% to 6.59%), and low P₂O₅ (<0.04%) and CaO (0.34% to 1.65%). In addition, they are enriched in Na (Na₂O/K₂O=3.3 to 10.9) with high A/CNK values (1.10 to 1.18), implying low-K peraluminious granites. They display negative anomalies of Nb, Ta, Ti, Sr, Ba and P and obvious enrichment of LREE and LILEs (Th, U and Pb) with significant Eu (0.47～0.81) negative anomalies. Combined with the tectonic evolution of the southern margin of the Altay, the authors hold that these tonalities were generated from the melting of continental crust in an island arc tectonic setting.

Abstract:The inconsistent opinions concerning the tectonic setting, the surrounding rock environment and, especially, the age of the wall rocks, have caused much controversy about the metallogenic type of the Kendekeke Fe-Co polymetallic deposit in Qimantag area, East Kunlun Mountains. According to Fusulinida and brachiopod fossils, the authors re-assigned the southern part of the country rock to Lower Permian. LA-ICP-MS zircon U-Pb dating of the dacitic ignimbrite from the north of the deposit yielded the age of 227.1±1.2 Ma, which provides direct evidence for the assigning of this strata to Upper Triassic Elashan Formation. Field investigation and petrographic study have led the authors to believe that the "skarn" on the northern side of the Kendekeke Fe-Co polymetallic deposit should belong to the volcanic middle-high temperature mineralization-alteration zone rather than being a typical skarn. Based on a comprehensive analysis, the authors hold that the mineralization age of the Kendekeke Fe-Co polymetallic deposit should not be earlier than Early Permian, and the main mineralization likely took place in Late Triassic. The metallogenic type may belong to volcanic-hydrothermal polymetallic type. The middle-high temperature mineralization-alteration zone in the lower part of the Upper Triassic Elashan Formation should be one of the important prospecting criteria in search for this kind of Fe-Co polymetallic deposits in this region.

Abstract:The Dayinhe intrusion, located in the northwest of the Xiao Hinggan Mountains, is mainly composed of alkali-feldspar granite and syenogranite. Zircon U-Pb age obtained by LA-ICP-MS analysis of the alkali-feldspar granite is 304.4±1.3 Ma, suggesting that it intruded in the Late Carboniferous period rather than the Late Jurassic period as proposed before. Petrochemically, the Dayinhe intrusion is characterized by high Si, Na, K and low Ca. It is enriched in Rb, La, Th and depleted in Ba, Sr. Nb, Ta, Zr, implying the effect of plagioclase as the stable residual phase in the magma source. Regionally, the Dayinhe intrusion, together with the Shierzhan, Xinkailin, Longzhen and Zhalantun granites that share the same petrologic and geochemical characteristics, forms the Late Carboniferous post-orogenic I-type and A-type granite belt in the Da Hinggan Mountains, implying the end of the collision and orogen between the Hinggan block and the Songnen block and the beginning of post-orogeic extension in this region.

Abstract:The Jiulong Emeishan basalt is distributed on the western margin of Yangtze block, and the Gangdagai Formation baslat is distributed in Zhongza massif in the neighborhood of Yangtze block. They both have rich alkali, high titanium characteristics, thus mostly belonging to the alkaline basalt series. On the whole, Gangdagai Formation basalt exhibits richer Ti, higher FeO^*, lower MgO, lower SiO₂ and lower Mg^#(0.34～0.43). Jiulong Emeishan basalt exhibits higher Mg^#(0.31～0.70), thus belonging to the moderate evolution magma. The two groups of basalt are both characterized by strong enrichment of light rare earth elements, and enrichment of LILE and HFSE (Th, Ta, Nb, Hf), partly with Sr, Zr negative anomalies, hence belonging to the plate basalts derived from the enriched mantle under the influence of mantle plume. Rb, Ba in Jiulong Emeishan basalt show obvious fluctuation, probably influenced by source area contamination; the trace element ratios show features of EM1-OIB and EM2-OIB mixture, suggesting the origination from garnet lherzolite, with molten degree being 4%～7%. The element ratios of lower Gangdagai Formation basalt are stable, and EM1-OIB shows great similarities, suggesting that its formation depth was deeper than that of Jiulong Emeishan basalt, that its origination was from an garnet stable region with low molten degree (2%～5%), and that it was produced at the mantle plume edge. The source area materials of basalt distributed in Zhongza massif and the western margin of Yangzi landmass were influenced by Emeishan mantle plume, with obvious familiarity, and the activities of Emeishan mantle plume provided power for plate splitting.

Abstract:Located in the East Qinling molybdenum belt of Shaanxi Province, the Shijiawan ore deposit is a large porphyry deposit. Mineralization of the deposit consists of quartz-molybdenite veinlets and stockworks which occur in altered granite porphyry and wall rocks. Hydrothermal alteration is composed of potash feldspathization, silicification and sericitization. Direct Re-Os dating of molybdenites collected from different ores in the Shijiawan deposit was carried out to better understand the age of mineralization. The results show that molybdenite samples yield ¹⁸⁷Re-¹⁸⁷Os model ages ranging from 143.1±2.1 Ma to 145.1±2.2 Ma, with the average of 144.0±1.1 Ma (MSWD=0.91), and give an isochron age of 145.4±2.1 Ma (MSWD=0.83). These ages are close to the zircon U-Pb ages of Shijiawan feldspar-granite porphyry (141.4±0.6 Ma), indicating that mineralization occurred in Late Jurassic-Early Cretaceous period. In combination with the evidence from S isotope, Re content and chemical characteristics of the related pluton, the authors hold that the ore-forming materials were mainly derived from the crust, with the addition of a little mantle material.

Abstract:The research on the relationship of mineral associations constitutes the basis of revealing metallogenic geochemical conditions and is also an important aspect in the study of the formation environment, thus having great significance for the development of the metallogenic theory. With the Haigou gold deposit as an example, the authors initially determined its physical and chemical conditions. Its metallogenic process can be divided into four stages: the stage of quartz-K-feldspar, characterized by alkaline nature (pH=7.1～9.2) and weak oxidation environment to weak reducing environment (Eh=-0.3～+0.5 V); the gold-quartz-pyrite stage, belonging to intermediate-acid weak redox environment; the gold-polymetallic sulfide-quartz stage, characterized by acid (about 4) and weak reducing environment (lower than -0.2 V); the gold-quartz-carbonate stage, characterized by the gradual transition from pH=4.5 to pH=5.3 with the decreasing temperature, accompanied by the transition of the metallogenic Eh value from weak reduction (-0.3 V) to weak oxidation (+0.5 V).

Abstract:15 coal samples were collected from No. 5 and No. 4 Permian coal seams in the Huaibei coalfield, Anhui Province. Inductively coupled-plasma atomic-emission spectrometry (ICP-AES, VISTA-PRO, America Varian) was used to determine the major element composition of coal ash after the ashing of samples at 815℃, and the minerals in raw coal and coal ash samples were investigated by X-ray diffraction (XRD, Cu, D/max-1200, Japan). Using these methods, the authors determined the major minerals and their relative abundances in coal and coal ashes. The results show that the major minerals in raw coals are smectite, illite, kaolinite, chlorite, quartz, calcite and dolomite. Pyrite was not detected on the XRD spectra because the coals are very low in sulfur (averagely 0.56%). New minerals in cluding plagioclase and hematite were formed during the ashing process.

Abstract:It is usually thought that the Mesozoic magmatism in eastern China was related to the westward subduction of the Pacific plate. However, the researches conducted by the author show that eastern China did not belong to circum-Pacific tectonic belt in Mesozoic. It was not in the Andean active continental margin tectonic environment, and there were no island arc basalts and island arc granites. Lots of research work shows that the Pacific plate basically subducted northward in the early Mesozoic and turned to west in the middle early Cretaceous (at about 125 Ma). The large-scale magmatism in eastern China mainly occurred in Jurassic-early Cretaceous period (about 180～130 Ma), and during this period the Pacific plate basically subducted northward. Therefore, the Mesozoic large-scale magmatism in eastern China was not related to the subduction of the Pacific plate. The westward subduction of the Pacific plate only lasted for a very short period, i.e., during 125～110 Ma and 43～0 Ma. During 125～110 Ma, magmatism of eastern China was confined to the east coast of China; during 43～0 Ma, the magmatism in eastern China was almost gone. So the proposition that Mesozoic magmatism in eastern China was related to the westward subduction of the Pacific plate is a wrong unwarranted proposition.

Abstract:Although its concentration is extremely low (about 5% of the volume of nacre) and its research technique is limited, the organic matrix in nacre not only is the most fundamental difference between biominerals and natural inorganic minerals but also has an important effect on biomineralization. In this study, the nacres of pearls and shells cultured in freshwaters and seawaters in Guangxi, Guangdong, Zhejiang and Jiangsu and those in corals were tested by Hitachi 835-50 High speed Amino Acid Analyzer and, as a result, the sorts and content of amino acids of organic matrix in nacre specimens were acquired. In combination with the microtopograpgy of nacre's organics investigated by SEM and HRTEM, the correlation analysis and cluster analysis produced some special amino acid constitutions or categories, which correspond to different organic macromolecules in different spatial positions, structures, kinds, shapes or sizes of nacres. These analyses show that the mineralization effect of organic matrix in nacre is characterized by diversity and complexity, which results in the diversity and complexity of inorganic minerals in species, size, evolution. Hence the unique microstructure of nacre can be formed by inducing and controlling. The conclusion obtained by the authors is significant for understanding the effect of organic matrix on biomineralization in nacre.