摘要
对大型超大型矿床的找矿与评价,从不同的角度,不少矿床学家已提供很多有益的探讨和意见。本文认为大型超大型矿床的一般成矿条件,与中小型矿床的成矿条件是基本类似的;而在基本类似的成矿条件下能否形成大型或超大型矿床,其特殊条件是成矿区必需有过量的矿源供给。因此,计算预测区内剩余金属总量的丰歉,将是定量评估大型超大型矿床能否出现的关键。坚持找矿实践,实行大中小并举方针。
In the last score of years,the discussions and opinions with regard to the prospection andevaluation of large and super-large ore deposits have been presented by not a few geologistsof mineral deposits.Lots of available results obtained from the different angle and scopeshow obviously that the large and super-large ore deposits are generally found in the metallo-genetic province or the centralized mineralization zones,and occurred in the favourable geo-logical conditions which embrace mainly the geotectonic settings,the regional linear struc-tures,especially those of large deep fractures and thier intersections,the abnormal regions oflithostratigraphy•petro-mineralogy and geochemistry,as well as the areas where show theexistence of geophysical and geochemical anomalies and so on.Considering the above-men-tioned,the author holds that they are not only favourable for the formation of large and su-per-large ore deposits but also for those of the middle and small ones,i,e.the favourable con-ditions for large and small scales are basically,or in the most cases,similar.Thus,there arisesa question,what plays the most important role in forming the large and super-large ore de-posits?As a special condition,it has been realized that the more surpassed amount of sourcesupply is the main,and therefore,to calculate the abundance or shortàge of the total residualproductivity in the prognosticated region should be regarded as the key for the quantitative e-valuation of large and super-large ore deposits.Basing upon the preliminary practising experiences offered from some prospected or ex-plored ore districts of endogenous iron,copper and gold deposits in the provinces of Hebei,Henan and Jiangxi,the author thinks that the calculation may be tentatlvely procceded in twosteps.Firstly,to calculate the total metal productivity from the prirmary anomalies by usingthe formula P=(C.-C,)•A·D,here,P representing the total metal productivity in theforecasted district;C.,the average value of primary anomalies or depletéd field;Cs,the aver-age of background value in the forecasted region;A.the forecasted area,D,the forecasteddepth.Secondly,to calculate the approximate scale of the forecasted ore deposits by the totalresidual metal produetivity using the fortmula S=(P–R)/M,here,S irepresenting the scaleof possibly found ore deposits;P,the total metal productivity(gained from the above),R,the total reserves of prospected and explored ore districts;M,the number of possibly foundore deposits,From here we see that the scale(S)is directly proportional to the total residualproductivity(P–R),but is inversely proportional to the number(M),i.e.the less the numberof the forecasted ore deposits found,the larger tho scale of the forecasted ore depositsformed.It is only in the case of the total residual metal productivity more surpassed the scaleof the expected large or super-large ore deposits,and moreover,under the very favourablegeological conditions that the large or super-large ore deposits could be formed.
作者
沈永和
SHEN Yonghe(Shanzi Depariment of Geology and Mineral Resources)
关键词
超大型矿床
找矿
地质条件
矿床
成矿
super-large ore deposits
prospection and evaluation
total residual metalproductivity
prognostic region
