| Xiangshan volcanic basin,located at the west of the Gan-Hang volcanic-type uranium polymetallic ore belt,is the largest volcanic-type uranium orefiled in China as well as the third in the world.At present,more than twenty uranium orefields have been proven.During the past sixty years's mining history,the total drilling depth is more than 2 million metre.The superficial mineral is gradually diminish,expecilly for the high quallity minerals.Therefore,finding out the deep geological features plays important role in the further deep exploration.In recent years,as the progess in the deep exploration technique and 3D geological modelling technique,3D geological modelling has become a new method for describing geological interface and deep mineralization prediction.This paper chose 11 simbolic orefiled in the northern,western,eastern and souther Xiangshan volcanic basin and establishe 9 3D geological models by GOCAD software based on the application of digital geological mapping data,geological map,prospecting line profile map,middle plane graph and drilling data,displaying the deep geological features of the main areas of the basin in three dimension,analysing the deep mineralization condition,and proposing several favorable mineralization sites for deep uranium polymetallic ore.The main results are listed as follows:(1)First systematiclly applied multi-source data from 232 geological survey routes,19 measured geological sections,9 geological maps of the deposits,257 prospecting line profile maps,28 middle plane maps,1074 drilling cores,and precisly establish 9 3D geological models for 11 orefiles,including Hengjian,Gangshangying,Hongwei,Shazhou,Heyuanbei,Julongan,Penggushan,Zoujiashan,Yunji and Diaoyuan orefields.The toltal modelling area is up to 10.5 km~2.(2)Propose a new method for directly building superficial 3D geolgoical models based on digital geological mapping route PRB data,measured geolgoical section and topographic data.Earth surface geologica mapping data is characterized by high-precision,standard regulation,abundant information,good continuity,easily access and low cost,and can cover the whole data source of the study area,which break the bottleneck of the unsurfficient data for 3D geoloigcal modelling to some extent.(3)Propose block modelling for complex geological interface,which effectivley improve the efficiency and precision of the construction of complex geological interface.Based on the distribution of the modelling data and 3D morphology of geologic body,we divide the complex geological interfaces into several simple geological interfaces,and then chose suitable modelling methods to construct simple geological interfaces,and lastly synthsize the simple geological interfaces into complex geological interfaces by the application of constraint-interpolation and smoothness procesure.(4)Systimatically study the methods of node-conect constraint,control-node constraint,point-line constraint,point(line)-plane,plane boundary constaint,plane boundary-plane termination constraint,distance constraint(line-plane distance constraint,bed thickness constraint),and detailed describe the procedures for the above mentioned constraint methods.Constraint-interpolation method is accompanied by orefiled(site)3D geological modelling,effectively solving the problems of difficulties of multi-data fusion,slowly construction of geological interface and low-precision,and improving the modelling quallity and efficiency.(5)According to the 3D geoloigcal modelling of the polimetallic ore are of the northern Xiangshan volcanic basin,3 EW and 5 NE basement faults divide the metamorphic basement into 8 depressions and differential uplifted diamond blocks.Localized megaphophyric monzonitic granite porphyry intruded along the diamond stractures and formed vertical dyke,which is characterized by“I”,inclined“I”and upper expanded“I”morphology.Magma intruded into the cover straucture and formed small angle(or near horizontal)bed rock(dike)at the intersection of basement faults and cover structure.Colition of dyke and bed rock(dike)in the section shows“flame”,“7”,“T”,“?”,“?”morhphology.The northern orefield are mainly distributed at the megaphophyric monzonitic granite porphyry present at the intersection(nearby)of NE and EW basement faults.Ore body is primarily concentrated at the expanded area of dyke,colition of dyke and bed rock(dike)and iner-outer contact zone.Based on the interpretation of MT section and deep mineralization condition,infering that the intersection of deep dyke and bed rock in the Baquan 11 belt(-1900?-1300m)and Shazhou orefield(-1000?-600m)have good prospecting potential.(6)The Heyuanbei volcanic collapes structure has been found in the wesntern metallogenic province of the Xiangshan volcanic basin.This volcanic collapse trend in EW,and has close relationships with uranium polymetallic mineralization;reconstraint the EW tranded Niutoushan-Julongan-Chuankeng volcanic collpase structure;find out the distribution of the Zoujiashan arc-shaped volcanic collpase structure;infer a volcanic vent of Ehuling period having close relationship with uranium polymetallic mineralization,which is distributed at the intersection of Niutoushan-Heyuanbei fault and Heyuanbei volcanic collapse;find out the 3D morpholog of broom fissure zone present at the base of the fault(strike NS,dip E)which has colse relationship with uranium polymetallic mineralization within the Julongan diamond blocks;fissure zone shows upper convergence,lower spread,southern convergence and northern spread,and display“?”in EW section and inverse“?”in horizontal section.5 deep uranium polymetallic mineralization favorable ore perspective area have been constraint in the Heyuanbei,Julongan and Pingdingshan diamond blocks in western metallogenic province.(7)The Bijiashan-Furongshan megaphophyric monzonitic granite porphyry in eastern and southern Xiangshan volcanic basin is controlled by basement faults and extensional faults present within the volcanic beds,forming dyke and bed rock assemblage,which shows“7”shape in section.Bed rock of this rock mass is characterized by absence of radioactivity,abnomal remote sensing alteration or weak abnomal and not big thickness of the bed rock.Comined with the 3D morphology and favorable mineralization condition of the megaphophyric monzonitic granite porphyry distributed at different areas of the basin,we propose that the bed rock do not has favorable prospecting potential,in contrast,the intersection of dyke and bed rock is favorable prospecting area. |
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