摘要
大塘坡式锰矿成矿后变化程度可从地层抬升程度、氧化程度、构造条件、裂隙与岩溶发育程度、顶底板隔水性、地表及气候等方面进行分析评价。民乐锰矿成矿后受到近地表因素、地下水的以及断层发育的影响,其成矿后变化程度可从地层抬升程度、断裂发育程度以及含锰岩系隔水性3方面进行评价。选取含矿层埋深、距断层距离、矿体上覆及下伏黑色页岩段厚度对3个评价因素进行定量表征,制作单因素等值线图并量化评分,运用层次分析法确定各因素权重,将各单因素加权叠加绘制成矿后变化程度系数等值线图,将成矿后变化程度分区与锰矿形态(品位)、厚度范围叠加,定量分析成矿后变化对找矿的指示意义。研究发现,断裂发育程度对于民乐矿区成矿后变化程度最为重要,地层抬升程度次之,含锰岩系隔水性影响较少;民乐矿区成矿后变化程度具有“两侧高、中心低”的特征,呈现从盆地中心至边缘带递增的趋势,西侧更多受地层抬升影响,东侧则以断裂影响为主;成矿后变化程度较低的区域更有利于找矿,但对于不同形态(品位)的矿体指示性并不明显;对各类地质演化过程的恢复和定量表征应成为今后大塘坡式锰矿成矿后保存改造研究的主要方向。
Objectives:The variation degree after mineralization period is important for the Datangpo-type manganese deposit's exploration and prediction.However,current studies seldom involve the analysis and evaluation of this kind of variation.Some papers exhibit related researches but only focus on the analysis of the phenomenon in some deposits,lacking quantitative evaluations and analyses and studies of the correlation between characteristics of deposits and variation degrees after the mineralization period.To make up the defect of previous studies,this manuscript takes the Minle manganese deposit,which is the typical Datangpo-type manganese deposit in northwestern Hunan,as an example,firstly analyzing possible variations of Minle manganese deposits during and after mineralization and selecting influencing factors according to the various geological features of the Huayuan district,secondly using the Analytic Hierarchy Process model to calculate the weight of factors,finally calculating the index of variation degrees after the mineralization period of the Minle mining area according to results of the score of weightsand combing it with thicknesses and shapes of ore bodies to analyze the relationship between the variation degree after the mineralization period and the preservation of manganese inside the Minle mining area.The study provides a new thought for quantitative evaluation of Datangpo-type manganese deposits.Methods:Choosing proper influencing factors according to previous papers and the data of wells and field works.Using the AHP(Analytic Hierarchy Process)method to calculate the weight of each factor.Analyzing the relationship between manganese ore-bodies'shape and thickness and the variation degree after the mineralization period according to ratios respectively of the area with low variation degree in areas of ore-bodies'various thicknesses(10m,7m,4m,and 1m),amounts of wells with low variation degrees in amounts of wells of orebodies'shapes(compact and massive ores and banded ores),and amounts of wells with low variation degrees in the total amount of wells,which is calculated by the GIS spatial analysis function.Results:The Minle manganese deposit's variation degree after the mineralization period can be divided into two levels according the changing of its coefficient.The coefficient which is bigger than 3.9274 means the strong variation after the mineralization while the coefficient which is smaller than 3.9274 represents the weak variation.The mean and median of variation degree coefficient are respectively 3.8887 and 3.9275,which means the variation degree of Minle mining area is not strong.The amount of wells,the amount of wells develop compact and massive ores and the amount of wells develop banded ores of the weak degree district occupies respectively 64.1%,64.8% and 63.2% of their total amounts of wells.The size ratio of areas with weak variation in the area of which the thickness is over 10m is 97% while the same ratio in the area of which the thickness is over 1m drops to 70%.Conclusions:The developing degree of faults weights the most in producing impacts on the variation degree after the mineralization period,the uplifting degree of stratums weights a little lower and the thickness of manganese-bearing rocks produces less impacts.For the Minle mining area,the variation is strong in two sides and weak in the middle.The western side is mainly influenced by the uplifting of stratums and the eastern side is mainly influenced by faults.The Minle manganese basin has the tendency that the variation degree after the mineralization period is higher and higher from the center to the edge and the area with weak variation is easier to find the manganese deposit.
作者
曹默雷
陈建平
CAO Molei;CHEN Jianping(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing,100083;Beijing Key Laboratory of Land and Resources Information Research and Development,Beijing,100083)
出处
《地质论评》
CAS
CSCD
北大核心
2021年第4期992-1006,共15页
Geological Review
关键词
大塘坡式锰矿
成矿后变化
民乐矿区
断裂发育程度
地层抬升程度
the Datangpo-type manganese deposit
the variation after the mineralization period
the Minle deposit
developing degree of faults
uplifting degree of stratums
