اصلاح روابط تصحيح رقيق شدگي آنومالي هاي ژئوشيميايي و بهبود تخمين مقدار زمينه واحدهاي ليتولوژيكي در رسوبات آبراهه اي

چكيده انگليسي :

AbstractStream sediment sampling is a well known technique used to discover the geochemical anomalies Geochemical exploration based on stream sediment sampling is one of the most successful tools in regionalexploration of mineral deposits Stream sediment samples commonly represent average chemicalcompositions of lithologic units in the drainage basin upstream of a certain sample location It is why thesematerials are collected in the regional geochemical surveys Various methods have been used ininterpretation of stream sediment data in which geochemical landscapes are proposed to be modeled aseither continuous or discrete fields The sample catchment basin approach SCBA is one of the mostly used discrete field techniques which its theoretical development date back to 1970s and 1980s In SCBA two main processes including correcting the geochemical background due to lithology and dilutioncorrection are applied to avoid the creation of false anomalies and missing true anomalies and to moreeffectively delineation of anomalous catchment basins based on mathematical equation This dissertationaims at presenting the improved equations in both aforementioned scopes Dilution correction process isdone by introducing the geomorphological and physiographical parameters of catchment basins indownstream dilution correction equation and the improvement in estimation of geochemical background isachieved by incorporating relative weathering rate of various lithological units However the metal contentof a stream sediment sample could be linked to several geomorphological sedimentological climatic andgeological factors The area size is not itself a comprehensive representative of dilution taking place in acatchment basin The present study knowing the shortcomings of exploratory geochemical studies tries to take steps toimprove and develop methods of geochemical interpretation of stream sediment data To do these tasks two areas are selected including portions of the1 100 000 Varzaghan and Kohpayeh geological maps Thedatasets used here are a subset of stream sediment geochemical data from the Varzaghan sheets in whichregional geochemical prospecting were conducted by the Geological Survey of Iran while stream sedimentgeochemical data acquisition process including sampling design sampling from stream sediments andupstream lithologies sampling analysis and laboratory test from the Feshark a part of Kohpayeh geologicalmap are in line with the goals of current work In general certain chemical contents of stream sediments have positive relationships with areas of lithologicunits in a catchment basin and have negative relationships with total area of a catchment basin and theserelationships have been used to model background concentrations and dilution effect respectively It shouldbe noted that the area factor applied in all Equations is a horizontal 2D projection of the area whereas inreality chemical composition of stream sediments is influenced by surfaces of lithologic units which varyin three dimensional 3D space as do the surfaces of sample catchment basins To correct dilution effectfrom geochemical anomalies the calculation of the three dimensional area of catchments and rock unitsand its comparison with the results obtained from the calculations based on the two dimensional area of thesame basins in Varzeqan region was studied The study area has 490 samples of stream sediments According to mineral occurrence of copper mineralization and economic value in this study copper wasselected as a reference element to the desired range After calculating the three dimensional area of all rockunits in each basin as well as the True Sample Catchment Basins the residual values of geochemical dilutioncorrection based on the new relation presented by Mokhtari and Grossinejad 2015 based on SDR for n n 0 n 0 25 and n 0 5 were calculated and the geochemical anomalies were separated from thebackground using fractal concentration area The effectiveness of new equation

نجفيان، طاهر

اصلاح روابط تصحيح رقيق شدگي آنومالي هاي ژئوشيميايي و بهبود تخمين مقدار زمينه واحدهاي ليتولوژيكي در رسوبات آبراهه اي

رسوبات آبراهه اي , حوضه ي آبريز , زمينه ي ژئوشيميايي , رقيق شدگي , هوازدگي , آنومالي ژئوشيميايي , انديس معدني , ورزقان , فشارك , ايران