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  • Table of Content
      24 August 1991, Volume 15 Issue 4 Previous Issue    Next Issue
    For Selected: View Abstracts Toggle Thumbnails
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    MODELLING ORE PROSPECTING" AND "NONMODELLINGORE PROSPECTING
    Zhao Wenjin
    Geophysical and Geochemical Exploration. 1991, 15 (4): 241-247.  
    Abstract   HTML   PDF (585KB) ( 573 )

    This paper stresses the importance of studying and summarizing geologi-cal, geophysical and geochemical characteristies of known ore deposits andtheir geological settings so as to establish ore-prospecting models. It is sug-gested that while using such models to guide ore-prospecting work we shouldattach importance to another type of ore-prospecting work, i. e. the search fornew types of ore deposits, new spieces of ore resources and newly-born oredeposits in areas of comparatively detailed geological investigation, or the per-formance of ore-prospecting work in areas of less geological investigation Inthe latter case, characteristics of ore-prospecting targets are not yet clearlyknown, and it is very difficult to choose some concrete model as the basis ofore-prospecting work;the arrangement of geological work only according tothe train of thought of "modelling ore prospecting" is therefore not proper.The author suggests that studies in this aspect should be strengthened andthe characters and regularity of this sort of ore-prospecting work should beinvestigated on the basis of more extensive metallogenic geological settings forthe sake of guiding the ore-searching work. The author names such ore-sear-ching train of thought "nonmodelling ore prospecting" to distinguish it from"modeling ore prospecting".

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    A COMPARISON BETWEEN REGIONAL MODEL ANDGLOBAL MODEL OF THE GEOMAGNETIC FIELD
    An Zhenchang
    Geophysical and Geochemical Exploration. 1991, 15 (4): 248-254.  
    Abstract   HTML   PDF (548KB) ( 543 )

    Spherical harmonic analytical method is usually used to express the globaldistribution of the geomagnetic field (global model), and polynomial method isemployed to express the regional distribution of the geomagnetic field (regionalmodel). In this paper, on the basis of the regional models of the geomagneticfield in China at epoch 1980.0 (CGRF 1980) and the global models of the geo-magnetic field at epoch 1980.0 (DGRF 1980), the differences between CGRF1980 and DGRF 1980 were calculated (diff. =CGRF 1980-DGRF 1980), andcontour maps of the differences were constructed for total intensity (F), verti-cal intehsity (Z), horizontal intensity (H), declination (D) and inclination (I),with some analyses and discussions made. These maps show that the differencesbetween CGRF 1980 and DGRF 1980 are comparatively small in most parts ofChina, but obviously grow larger in border areas of Northwest and Northeast China.

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    THE IMPORTANCE OF FULL SAMPLING INMAGNETIC SURVEY
    Wu Chaojun
    Geophysical and Geochemical Exploration. 1991, 15 (4): 255-262.  
    Abstract   HTML   PDF (1452KB) ( 415 )

    In aeromagnetic survey or ground magnetic survey(whether in total fieldsurvey or vertical gradient survey), full sampling seems extremely importantfor further image processing and image enhancement processing as well asinterpretation of magnetic anomalies. The reason is that all the data obtainedare discrete data set of continuous anomalous field. By applying typical two-dimensional dyke model to conduct theoretical calculation, we used the dis-tance between the field source and the probe to replace buried depth of fieldsource. Based on a series of theoretical calculations and analyses, the authorholds that in large-scale high-precision aeromagnetic survey, the samplinginterval between stations along the survey line should be shorter than orequal to half of the f;ying height, whereas the distance between the surveylines should not exceed the f;ying height.Two application examples are given in this paper.

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    THE ROLE OF SNTRENDING AND EW-TRENDING STRUCTUES OF ENSTERN JIANGHA BASIN INREGIONAL TECTONICS
    Li Zhankui
    Geophysical and Geochemical Exploration. 1991, 15 (4): 263-267.  
    Abstract   HTML   PDF (370KB) ( 498 )

    Based on an analysis of geological and aeromagnetic data,this paper putsforward for the first time the opinion that SN-trending and EW-trending stru-ctures exist in the eastern part of the Jianghan basin.It descrides in detailcharacteristics of geological and geophysical fields of these two sets of stru-ctures,and points out that they came into existence in late Archean-Protero-zoic and controlled basement lithofacies of various times.In the process of theevolution of the basin,they played a governing role in its generation,develop-ment and subsidence.

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    THEORETICAL STUDY OF THE RAYLEIGH-WAVE TECHNI-QUE IN ENGINEERING GEOLOGY
    Huang Jiazheng, Zhou Hongqiu, Guan Xiaoping
    Geophysical and Geochemical Exploration. 1991, 15 (4): 268-277.  
    Abstract   HTML   PDF (627KB) ( 881 )

    In this paper dispersion equations of Rayieigh waves are derived on thebasis of a horizontal layered liquid model. Furthermore, calculation on multi-layered media is made and curves of Rayleigh wave velocity with respect towavelength are drawn. Anomaly characterstics on the curves, which correspondto elastic subsurfaces, agree well with those on curves measured in practice,and reasonably show the mechanism of exploration in layered media by Reyleigh-wave technique. With calculations of the theoretical model, the authors alsooffer comments on the hail-wave-length interpretation method which is cur-rently used in surface wave exploration and explain the anomaly characteristicson curves recorded from solid layered media.

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    THE TECHNIQUE FOR ON-THESPOT DETERMINATIONOF An IN ROCKS
    Liang XingZhong
    Geophysical and Geochemical Exploration. 1991, 15 (4): 278-283.  
    Abstract   HTML   PDF (399KB) ( 503 )

    In this paper the technique for on-the-spot rapid determination of An(219Rn)is studied,and the method for in-situ determination and that for deter-mination in a barrel are presented. With some results obtained in a known ura-nium deposit as all example,the paper also discusses prospects of this technique.

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    THE STUDY OF A NEW METHOD FOR COPPER OREPROSPECTING──X-RAY FLUORESCENCE METHOD
    Zhou Sichun, Xie Tingzhou, Ge Liangquan
    Geophysical and Geochemical Exploration. 1991, 15 (4): 284-289.  
    Abstract   HTML   PDF (421KB) ( 471 )

    Based on element associations in geochemical anomalies from various sortsof copper deposits,this paper discusses the method and techuique in pros-pecting for various sorts of copper deposits using China-made portabl X-rayfluorescence instrument, and describes the effect of usiug the method andtechnique mentioned in this paper in a copper deposits of Northeast China.

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    A STUDY OF THE DfYINITION OF APPARENTRESISTIVITY IN ELECTROMAGNETIC SOUNDING
    Yin Changchun, Piao Huarong
    Geophysical and Geochemical Exploration. 1991, 15 (4): 290-299.  
    Abstract   HTML   PDF (745KB) ( 1107 )

    This paper puts forward the basic principle for definition of apparentresistivity in electrical prospecting, and on such a basis discusses merits anddemerits of various sorts of apparent resistivity definition in MT, TEMS andFEMS methods with some suggestions for improvement made. Studies showthat in MT method the apparent resistivity defined by using real part ofplane impedance or given in time domain is very effective, which can wellrecognize the good conductive layer, while the apparent resistivity defined byusing imaginary part of plane impedance yields the worst result. So far asTEMS method is concerned, the whole-region definition of apparent resistivityis more effective than distant-region or nearby-region approximate definition.Studies also reveal that the whole-region apparent resistivity defined by timederivative of magnetic field sometimes has multi-solutions or even nosolution,whereas the apparent resistivity defined by magnetic field itseif is quiteeffective. For FEMS method, similar discussion is also made concerning thedefinition of whole-region apparent resistivity, and the result obtained, thoughnot so ideal as the result of TEMS method, is somewhat better than the appa-rent resistivity response defined under the condition of commonly-used largeand small induction values. This paper has made physical interpretation of thefalse extremum effect of apparent resistivity response curve that appears inelectromagnetic sounding method.

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    GEOCHEMICAL PRIMARY IODINE ANOMALIES AROUNDDEEP-SEATED CONCEALED POLYMETALLIC DEPOSITS
    Xu Waisheng, Liu Chongmin, Pang Qingheng
    Geophysical and Geochemical Exploration. 1991, 15 (4): 300-306.  
    Abstract   HTML   PDF (489KB) ( 491 )

    Based on geochemical characteristics of iodine, this paper has studied thedevelopment of iodine haloes around deep-seated concealed polymetallic depo-sits. With case history of exploration, it describes in detail distribution patte-rns of geochemical primary iodine anomalies under several different ore-hostinggeological conditions; through statistical study of variation regularity of ave-rage bone content in rocks from different ore districts and in rocks and/orores perpendicular to the ore body, we have determined the dispersion distan-ce of iodine anomaly, and pointed out that this element lies invariably at thehead of the vertical zonation and therefore serves as a distant indicator ele-ment. It is firmly believed that boine anomalies can play a unique indicatingrole in the prospecting for deep-seated concealed ore deposits.

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    ON PRESENT ANALYTICAL SYSTEMATIC ERRORS AND COMPILATION OF GEOCH-EMICAL MAPS
    Ji Lingsi
    Geophysical and Geochemical Exploration. 1991, 15 (4): 307-309.  
    Abstract   HTML   PDF (291KB) ( 458 )
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    TENTATIVE INVESTIGATION OF DISTRIBUTION OF KARST CAVES USING INTEGRATED GEOPHYSICAL PROSPECTING TECHNIQUES
    Huang Lixing, Wang Wulin, Zhang Jie
    Geophysical and Geochemical Exploration. 1991, 15 (4): 309-313.  
    Abstract   HTML   PDF (405KB) ( 437 )
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    THE APPLICATION OF FUZZY APPROXIMATION DEGREE TO THE INTERPRETATION OF ELECTRICAL SOUNDING WATER-PROSPECTING DATA
    Cai Qingxi
    Geophysical and Geochemical Exploration. 1991, 15 (4): 313-316.  
    Abstract   HTML   PDF (296KB) ( 351 )
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    THE EFFECT OF ELECTRICAL METHOD IN URBAN WATER-ROSPECTING
    Dai Aiguo
    Geophysical and Geochemical Exploration. 1991, 15 (4): 317-319.  
    Abstract   HTML   PDF (220KB) ( 469 )
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    THE EFFECT OF VERY LOW FREQUENCY ELECTROMA-GNETIC METHOD IN TRACING GOLD-BEARING FRACTURAL SHATTERED ZONES
    Wei Fuyou
    Geophysical and Geochemical Exploration. 1991, 15 (4): 320-320.  
    Abstract   HTML   PDF (202KB) ( 507 )
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