Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P
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SHAO Ji''''anPeking University , Beijing LIU Futian , CHEN Hui , HAN QingjunInstitute of Geology , Geophysics , Chinese Academy of Sciences , Beijing
2001, 75(1).
Abstract:High-resolution tomographic images of the belt crossing the Japan Trench-Changbai Mountains-Dong Ujimqin Qi are represented in this paper, revealing the shape of a subducted slab in the western Pacific region and characteristics of the lithospheric structures under the Changbai Mountains and the Da Hinggan Mountains. Studies of the spatial distribution, subduction time and the time-lag between the subduction and magmatism, combined with petrology and isotope geochemistry of the Late Mesozoic volcano-plutonic rocks from the Da Hinggan Mountains-Yanshan Mountains have further proved the independence of magmatic activities from the subduction of the Pacific plate. The Mesozoic tectono-thermal evolutionary history and structural characteristics of the lithosphere in the Da Hinggan Mountains and North China suggest that the formation and evolution of magma have probably a close relationship with the delamination and thinning of the continental lithosphere and the underplating resulting from the consequent upwelling of the asthenosphere. On the other hand, the large-scale strike-slip fault system, resulting from sinistral shearing of the Pacific plate relative to the Asian continent in the Mesozoic, is responsible for the formation and emplacement of magma on the continental margin. It was the intense crust-mantle interaction, together with structural deformation at the shallower levels that led to the large tectono-magmatic belt in the East Asian continental margin.
ZHOU Yong , XU Ronghua , YAN Yuehua , PAN Yusheng , Tsanyao Frank YANG , Wei LO , WU Chunming Laboratory of Lithosphere Tectonic Evolution , Institute of Geology , Geophysics , Chinese Academy of Sciences , Beijing Department of Geology , National Taiwan University , Choushan Road , Taipei - , TaiwanDepartment of Geology , Chinese Culture University , Hwa-kang , Yang-Ming-Shan , Taipei , Taiwan Institute of Geology , Chinese Academy of Geological Sciences , Beijing
2001, 75(1).
Abstract:This paper mainly discusses the timing of the Karakorum strike-slip fault, and gives a brief introduction of its structures, offset, and deformational style. This fault strikes NNW-SSE. Asymmetrical folds, stretching lineation, S-C fabrics, feldspar and quartz σ-porphyroclasts, domino structure, shear cleavages and faults in the fault zone are products of tectonic movements. They all indicate a dextral slip sense of faulting. Mylonitic bands are widely developed along this fault. Phengite appears, indicating rather high deformational pressure. Geochronological data indicate that the Karakorum strike-slip faulting occurred from 6.88±0.36 to 8.75±0.25 Ma. The cumulative displacement from Muztag Ata to Muji is about 135 km.
JIANG Yaohui , ZHOU Xunruo , RUI Xingjian , QUO Kunyi , HE Jurui , YANG Wanzhi State Key Laboratory of Mineral Deposit Research , Nanjing University , Nanjing , Jiangsu Nanjing Institute of Geology , Mineral Resources , Ministry of Land , Resources , Nanjing , Jiangsu China University of Geosciences , Beijing Xinjiang Geophysical , Geochemical Exploration Team , Changji , Xinjiang
2001, 75(1).
Abstract:A systematic geological and geochemical study was conducted for the granitoids of different periods in the western Kunlun erogenic belt. The study indicates that the granitoids belong to tholeiitic, calc-alkaline, high-K calc-alkaline, alkaline and shoshonitic series, and that there are 5 genetic types, i.e., I-, S-, M-, A- and SH-type, of which SH-type is first put forward in this paper, which corresponds to shoshonitic granitoids.
SUN Hongjuan , DENG Wanming , ZHANG YuquanInstitute of Geology , Geophysics , Chinese Academy of Sciences , Beijing Guangzhou Institute of Geochemistry , Chinese Academy of Sciences , Guangzhou
2001, 75(1).
Abstract:The Nangqen basin is one of the Tertiary pull-apart basins situated in the east of the Qiangtang block.Similar to the adjacent Dengqen basin and Baxoi basin, there occurred a series of potassic volcanic and sub-volcanic rocks, ranging from basic, intermediate to intermediate-acid in lithology.Based on the study of petrology, mineralogy and geochemistry, including REEs, trace elements, isotopic elements and chronology, the authors concluded that the Cenozoic potassic volcanic rocks in the Nangqen basin were formed in the post-collisional intraplate tectonic settings. The relations between the basic, intermediate and intermediate-acid rocks are neither differentiation nor evolution, but instead the geochemical variability is mainly attributable to the different partial melting degrees of the mantle sources formed at depths of 50-80 km.The sources of the potassic rocks are enriched metasomatic mantle that has experienced multiple mixing of components mainly derived from the crust. The recycling model can be described as follows: after they had subducted to the mantle wedge, the crust-derived rocks were metasomatized with the mantle materials. In view of the fact that the ratio of crust-derived rocks increases by the age of volcanism, it can be concluded that the sources of the potassic rocks moved upwards progressively with time.The underplating of small scattered magmas upwelling from the asthenosphere may have induced partial melting of the sources of the volcanic rocks in some pull-apart basins in the Hengduanshan area and the intense tectonic movements of large-scale strike-slip belts provided conduits for the ascending melts.
ZHANG Zhaochong , MAO Jingwen , ZUO Guochao , YANG Jianmin , Paul T. ROBINSON Institute of Geology , Chinese Academy of Geological Sciences , Baiwanzhuang Road , Beijing , China Institute of Mineral Deposits , Chinese Academy of Geological Sciences , Baiwanzhuang Road , Beijing , China Institute of Geology , Gansu Bureau of Geology , Mineral Resources , Lanzhou , China Centre For Marine Geology , Dalhousie University , Halifax , Nova Scotia , BH J , Canada
2001, 75(1).
Abstract:The Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. The diabases and basalts show light rare-earth element enrichment and have relatively high TiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. They are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr-spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proteroz
ZHI Xiachen , CHEN PengDepartment of Earth , Space Sciences , University of Science , Technology of China , Laboratory of Chemical Geodynamics , USTC , Advanced Research Center for Earth Science , Astronomy in USTC , Third World Academy of Science , Hefei LIN Chengzhong , CHEN Shuqing , ZHANG GuilanInstitute of Mineral Resources , Chinese Academy of Geology Sciences , Beijing LI Yuzhi , LIN Lei Open Laboratory of Structure Analysis , USTC , Hefei
2001, 75(1).
Abstract:The Mossbauer spectra of natural megacrystal clinopyroxene are usually fitted by 4 sets of symmetric doublets, A-A', B-B', C-C' and D-D', respectively, in terms of increasing Qs value in literature. But the assignments of those doublets are quite different, except the D-D' doublet assigned to Fe3+ at the lattice site Ml in previous papers. Particularly, the assignment and interpretation of the C-C' doublet are diverse.The oxidation experiments of natural megacrystal clinopyroxene collected from the Hannuoba basalt, North China, were performed under controlled conditions of temperature at 1000℃ and oxygen fugacity of FMQ buffer in 1, 2, 3 and 5 days respectively. The oxidized samples were then measured by X-ray diffraction spectrometry and Mossbauer spectrometry. The oxidation of clinopyroxene is characterized by Fe2+→ Fe3+ at Ml under the subsolidus conditions, which is consistent with the increase of the area of the D-D' doublet when the heating time increases. Accordingly, the area of the A-A' and B
Sukru KOC Geology Department , Ankara University , Ankara , Turkeyand Ali RECBER General Directorate of Mineral Research , Exploration , Ankara
2001, 75(1).
Abstract:Fluorite mineralization occurs along fractures and cracks of Middle Eocene and Pliocene limestones and marls in the north and northeast of the Pohrenk region (Qicekdagi, Kirsehir). Tb/Ca - Tb/La and Y/Ho ratios were obtained from REE contents of fluorites which have revealed that mineralization is of hydrothermal type. Negative Ce anomalies and positive Eu anomalies reflect that hydrothermal solutions once had high oxygen fugacity. Fluid inclusion studies indicate that homogenization temperatures of mineralization varied between 90℃ and 200℃, and hydrothermal solutions are composed of NaCl + KCl + MgCl2 + H2O. In addition, salinity measurements show that hydrothermal solutions were mixed with meteoric or rock formation water. Geologic setting, REE geochemistry and fluid inclusion studies suggest that mineralization was deposited from a solution generated by mixing of magmatic and meteoric water under epithermal conditions.
SUN Yuzhuang Hebei Institute of Architectural Science , Technology , Handan , Hebei , ChinaW. PUTTMANNJohann Wolfgang Goethe-Universitaet Frankfurt , FB Geowissenschaften-Umweltanalytik , Georg-Voigt-Str. , D- Frankfurt a. M. , Germanyand H.KUCHAInstitute of Geology , Mineral Deposits , - Krakow , Av. Mickiewicza , Poland
2001, 75(1).
Abstract:Previous studies have shown that the ascending, oxidizing brines play a very important role in Kupferschiefer mineralization. Fractures could be the pathway of the brines. In order to clarify the influences of the brines on bulk organic matter, aromatic hydrocarbons and Kupferschiefer mineralization, one veinlet Kupferschiefer profile from the Lubin mine, southwestern Poland was studied with the microscopic, geochemical and Rock-Eval methods. The microscopic results indicate that organic matter of the veinlet sample consists dominantly of bitumen. Its extract content is higher than in other samples. The dominant aromatic compounds are naphthalene and alkylated naphthalenes (Na-PAH), which have migrated into the veinlet sample from other sediments. The content of phenanthrene and its methylated derivatives (Ph-PAH) is much lower than in other samples. The reason may be due to their heavier mass than Na-PAH. It is more difficult for Ph-PAH to migrate. The Na-PAH was probably removed from the shale by distillation and enriched in fractures because of their relatively low boiling point. The content of biphenyl and alkylated biphenyls (Bi-PAH) indicates the influence degree of oxidizing fluids. Their content in the veinlet sample is higher than in other sample. The high Tmax value of the veinlet sample also reveals a more intense influence of the oxidizing fluids than in other samples. Besides the higher Tmax value, its HI value is higher than in other samples. One can presume that its original hydrocarbon content should be higher than this value because they could be partly depleted by the brines.Five elements (As, Mo, Co, Ni and Bi) are enriched in the veinlet sample, perhaps due to the higher content of extractable bitumen in the fracture, particularly, the high content of Na-PAH. The higher concentration of the five selected elements indicates that the Kupferschiefer mineralization of veinlet type occurred after the Kupferschiefer deposition.
CHEN Bailin , LI Zhongjian , DONG Faxian Institute of Geomechanics , Chinese Academy of Geological Sciences , Beijing ,
2001, 75(1).
Abstract:The Qifengcha-Detiangou gold deposit is a medium-sized deposit recently found in Huairou County, Beijing. It belongs to the altered mylonite type with superimposed quartz vein type and is related to the early Yanshanian magmatic activity. Characterized by multiperiodic activity, the NE-trending Qifengcha fault is a regional ore-controlling structure in the area, and gold mineralization develops only in its southeastern part. Meanwhile, gold mineralization is controlled by the Yunmengshan metamorphic core complex. The nearly N-S- and E-W-trending low-angle detachment faults, reformed by the Qifengcha fault in the northwestern part of the core complex, are the main ore-bearing faults. All discovered gold deposits are located within an area 1.5-4.0 km away from the boundary of the upwelling centre. The N-S- (NNE-) and E-W-trending ore-bearing faults are ductile-brittle structural zones developing in shallow positions and subjected mainly to compressive deformation. The structural ore-controlling effects are as follows. (1) The attitude, shape, and distribution of gold orebodies are controlled by faults. (2) There is a negative correlation between the gold abundance and the magnetic anisotropy (P) of the altered mylonite samples from the deposit, which shows that the gold mineralization is later than the structural deformation. (3) Quartz vein type mineralization is superimposed on altered mylonite type mineralization. (4) In mineralized mylonite, the stronger the ductile shear deformation, the easier the late-stage gold mineralization to occur and the higher the gold abundance. The richest gold mineralization occurs only around the centre of the fault subjected to the strongest deformation.
LIU YuInstitute of Geology , Chinese Academy of Geological Sciences , Baiwanzhuang Road , Beijing
2001, 75(1).
Abstract:Abundant and well-preserved fossil radiolarians found from the Artencasher Formation, Heiyingshan of Baicheng County, Xinjiang Uygur Autonomous Region, are identified, including 15 species and 2 unnamed species in 9 genera. The fauna is dominated by the Family Entactiniidae of Spumellaria. According to the faunal characteristics, the radiolarians may be divided into five assemblages, namely, the Triaenosphaera sicarius, Entatinosphaera palimbola, Entactinia vulgaris, Belowea cf. variabilis and Archocyrtium sp assemblages. The fauna may be correlated with that from the Early Carboniferous of Frankenwald and Rein in Germany. Thus, ophiolite was formed in the Carboniferous, while the age of collision between the Ili plate and the Tarim plate is Early Carboniferous.
2001, 75(1).
Abstract:Over the area between Beipiao City and Yixian County, Hebei Province, there outcrop trachyte-trachyandesite volcanic rocks of the Upper Jurassic Zhangjiakou Formation and sedimentary series of the Dabeigou Formation. The ~(40)Ar-~(39)Ar datings of the volcanic rocks give an age of 143. 9 Ma. The most recently defined basalt member in the lower part of the Cretaceous Yixian Formation was dated at 137-129 Ma, while the andesite member in the upper part at 126-120 Ma. It is ascertained that
HOU Zengqian , QU Xiaoming Chinese Academy of Geological Sciences , Beijing , ChinaTetusro Urabe , Takagi , Naito Geological Survey of Japan , Ibaraki , Japan
2001, 75(1).
Abstract:Boninitic rocks and associated high-magnesian basalt and high-iron tholeiite in the Xiangcheng area constitute the basal horizon of the arc volcanic sequence in the Triassic Yidun Island-Arc, southwestern China. The boninite occurs as pillow, massive and ocellar lavas; the last one possesses well-developed globular structure and alternates with the former two. The boninite is characterized by the absence of phenocrysts of olivine and low-Ca pyroxenes and by low CaO/Al2O3 ratios (<0.67) and high Cr (>1000 ppm) and Ni (>250 ppm). The normalized abundance patterns (NAP) of trace elements to primitive mantle are similar to the NAP of low-Ca modern boninites and SHMB in the Archaean and Proterozoic.As a mechanism of ocellar texture, liquid immiscibility in boninite is supported by the following lines of evidence: (a) sharp contact between ocelli and matrix, (b) constant volumetric ratios of ocelli/matrix and common coalescence of ocelli in ocellar rocks, (c) identical micro-spinifex textures and mineral assemblages with different modal mineral contents in ocelli-matrix pairs, (d) bubbles and acicular clinopyroxene crystal strand over the boundary between ocelli and matrix, and (e) chemical compositions of ocelli and matrix corresponding to high-Mg andesite and komatiitic basalt, respectively. The close association and geochemical similarities between ocellar boninites and pillow boninite/massive boninite suggest that these are comagmatic rocks. The primary features of the ocellar boninite indicated by high Mg/(Mg+Fe2+) ratio and high Cr and Ni abundance show that liquid immiscibility took place in the early evolution stage of the boninitic magma. The miscibility gap in boninite which is smaller than that in tholeiite is likely to be due to the low FeO*/MgO+FeO* ratio and high MgO content of the boninitic magma.The association of komatiite-komatiitic basalt-boninite (or SHMB) and the immiscibility phenomenon in high-Mg lavas in some Archaean greenstone belts and ophiolites is also reexamined. It is considered that liquid immiscibility in parental boninitic magma probably produced komatiitic basalt, which often occurs in close association with boninite (or high-Mg andesite).
Chief Editor:HOU Zengqian
Governing Body:China Association for Science and Technology
Organizer:Geological Society of China
start publication :1922
ISSN:ISSN 1000-9515
CN:CN 11-2001/P