Jun 2007, Volume 1 Issue 2
    

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  • Recent achievements on the research of the Paleozoic-Mesozoic transitional period in South China
    YIN Hongfu, YU Jianxin, HE Weihong, LAI Xulong, FENG Qinglai, XIE Shucheng, HUANG Xianyu, LIANG Handong
    2007, 1(2): 129-141. https://doi.org/10.1007/s11707-007-0017-2
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    This is a review of research achievements on the Permian-Triassic transition in South China. It comprises of five parts: (1) advances on the biostratigraphy and eventostratigraphy of the Meishan Section, the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary (PTB); (2) advances on the PTB research of deep water facies, especially the Dongpan Section in Guangxi; (3) advances on the PTB research of terrestrial facies, especially the Chahe Section in Guizhou; (4) correlation of the global change and biotic extinction between the PTB and modern times and its revelation to the status and future of the earth and mankind; and (5) the pattern and causality of the Permian-Triassic extinction. In the last part, it is concluded that the Permia-Triassic transitional interval constitutes a prolonged crisis period ranging from end-Guadalupian extinction to the end of Early Triassic, totaling 14 Ma. The environmental crisis and mass extinction peaked at the PTB, which displayed multiphase extinction rather than just one phase. Commencement of an extinctions prelude prior to the postulated bolide impact implies that the causes of PTB extinction largely lie in the intrinsic developments of the earth, especially those related with the integration of Pangea.
  • An application of micropaleontology-sequence stratigraphy method in stratigraphic division —An example for the study of the Paleogene in the Guangjiapu area, Chengbei fault-step zone, Dagang
    MENG Peng, LIU Li, GAO Yuqiao, QU Xiyu, SUN Xiaoming
    2007, 1(2): 157-164. https://doi.org/10.1007/s11707-007-0020-7
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    The formation of the Paleogene in the Chengbei fault-step zone of the Dagang off-shore area is very complex and the stratigraphic division and correlation are relatively difficult. A method of micropaleontology-sequence stratigraphy is proposed herein. The study considers Well Zhangcan 1 as an example to prove that the scheme of stratigraphic division is feasible by conducting micropaleontology-sequence stratigraphy in the Guanjiapu area of the Chengbei fault-step zone. The application of micropaleontology-sequence stratigraphy method indicates that Member 1 of the Shahejie Formation in Well Zhuanghai 808×1 and Member 3 of the Dongying Formation of the Paleogene exist.
  • Vertical velocity of mantle flow of East Asia and adjacent areas
    CHENG Xianqiong, ZHU Jieshou, CAI Xuelin
    2007, 1(2): 172-180. https://doi.org/10.1007/s11707-007-0022-5
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    Based on the high-resolution body wave tomo-graphic image and relevant geophysical data, we calculated the form and the vertical and tangential velocities of mantle flow. We obtained the pattern of mantle convection for East Asia and the West Pacific. Some important results and understandings are gained from the images of the vertical velocity of mantle flow for East Asia and the West Pacific. There is an upwelling plume beneath East Asia and West Pacific, which is the earth s deep origin for the huge rift valley there. We have especially outlined the tectonic features of the South China Sea, which is of the ]? type in the upper mantle shield type in the middle and divergent in the lower; the Siberian clod downwelling dives from the surface to near Core and mantle bounary (CMB), which is convergent in the upper mantle and divergent in the lower mantle; the Tethyan subduction region, centered in the Qinghai-Tibet plateau, is visible from 300 to 2 000 km, which is also convergent in the upper mantle and divergent in the lower mantle. The three regions of mantle convection beneath East Asia and the West Pacific are in accordance with the West Pacific, Ancient Asia and the Tethyan structure regions. The mantle upwelling originates from the core-mantle boundary and mostly occurs in the middle mantle and the lower part of the upper mantle. The velocities of the vertical mantle flow are about 1-4 cm per year and the tangential velocities are 1-10 cm per year. The mantle flow has an effect on controlling the movement of plates and the distributions of ocean ridges, subduction zones and collision zones. The mantle upwelling regions are clearly related with the locations of hotspots on the earth s surface.
  • Immiscibility of high salinity fluids in volcanic rocks and the mechanism of magma degassing in the Dongying sag, eastern China
    CHEN Yong, ZHOU Yaoqi, REN Yongjun, WANG Qiang, YAN Shiyong, LIU Chaoying, XIAO Huanqin, SUN Xinian
    2007, 1(2): 206-211. https://doi.org/10.1007/s11707-007-0025-2
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    Fluid inclusions that bear halite daughter minerals were discovered in volcanic rocks at Pingnan area in the Dongying sag. The samples of the fluid inclusions collected from the BGX-15 well drill cores are hosted in quartz of diorite-porphyrite. The daughter minerals are identified as NaCl crystals after being observed under a microscope and analyzed by in situ Raman spectroscopy at -185°C. The results of micro-thermal analysis show that the homogenization temperatures of primary fluid inclusions are between 359 and 496°C, and the salinities of fluid inclusions are from 43.26 to 54.51 wt-%. All fluid inclusions in the studied samples can be divided into five types including primary fluid inclusions and secondary fluid inclusions. The fact that five types of fluid inclusions were symbiotic in the same quartz grain implies that immiscibility happened in magma. Due to the decrease in temperature and pressure during the ascent of magma, the fluids became intensively immiscible. This process accelerates the degassing of CO2 from magma, but the remnant fluids with high salinity are preserved in fluid inclusions. Thus, the primary fluid inclusions are mainly in NaCl-H2O fluids and poor in CO2. The results of our study indicate that the degassing of magma and accumulation of CO2 gas at the Pingnan area are relative to the immiscibility of high salinity fluids. This discovery is important because it can help us have a further understanding of the mechanism of magma degassing and accumulation of the inorganic CO2 in eastern China.
  • Progress in porphyry copper exploration from the Gangdise belt, Tibet, China
    ZHENG Youye, DUO Ji, GAO Shunbao, CHENG Shunbo, DAI Fanghua
    2007, 1(2): 226-232. https://doi.org/10.1007/s11707-007-0028-z
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    Recent mineral exploration in the Gangdise porphyry copper deposit belt, an important component of the Himalaya-Tethyan metallogenic belt, has led to the discovery of a number of deposits, as exemplified by the world-class Miocene Qulong porphyry Cu deposit. This paper reviews major advances in the studies of ore genesis and metallogenic regularity and progresses in mineral exploration of porphyry Cu deposits in the belt. Existing problems and suggestion for future exploration also are given.
  • Fractal characteristics of resource quantity of cobalt crusts and seamount topography, the West Pacific
    ZHANG Weiyan, YANG Kehong, ZHANG Fuyuan, HU Guangdao, YANG Shengxiong, CHENG Yongshou, ZHAO Guojun
    2007, 1(2): 233-240. https://doi.org/10.1007/s11707-007-0029-y
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    This paper presents the fractal distribution of topography of seamounts from the West Pacific and the resource quantity of cobalt crust therein. The cobalt resource quantity has three to four variable fractal dimensions, corresponding to the distinct slopes and water depths of the seamount. The multiple fractal property of resource quantity may have resulted from various factors, such as types and components of cobalt crusts and ages of oceanic crusts hosting the seamounts. Individual seamounts display complex topography and quantity of cobalt crust, both in the same and different regions.
  • Experimental study on water-oil migration and accumulation in a 2D micro-model of carbonate fracture media
    TANG Xuan, JIN Zhijun, YANG Minghui, MING Haihui
    2007, 1(2): 251-256. https://doi.org/10.1007/s11707-007-0031-4
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    Many achievements have been made in experimental studies of hydrocarbon migration in the clastic reservoir. On the other hand, few migration experiments have been reported in the carbonate reservoir simulation realm. This article is a tentative experimental study on hydrocarbon migration and accumulation in the carbonate reservoir, which is a complex media that includes a pore system and fracture system. This microcosmic experiment simulates oil-water displacement using a real core model. Plentiful seepage phenomena were observed in the microcosmic experiments. Three kinds of pathways were found in the plane: parall elpathway, oblique-cross pathway and network pathway. Three types of flow were found: continuous flow, sectioning flow and their combination. Three driving fronts were found in the experiment: piston front, encircle front and impulse front. All these vary with many factors such as fluid pressure, oil saturation, fissure configuration and wettability, and these factors affect each other. The results show that the relation between the fluid pressure and volume of flow is a complex segmenting correlation, instead of a simple positive correlation like the pipe flow that follows Darcy s law. The relation between fluid pressure and the speed of flow also follows the same correlation. Speed of flow relates to the angle and width of the fissure. Speed of flow in the wide fissure that has an acute angle with the pressure gradient is faster than that in a narrow fissure with a high angle with the pressure gradient.