مطالعات آماري چند متغيره بر روي داده هاي ژئوشيميايي منطقه كرويان

Multivariate statistical analysis of geochemical data in Kervian region

در اين مطالعه داده هاي ژئوشيميايي رسوبات آبراهه اي برگه 1:50000 ميرده به روش حوضه آبريز نمونه بررسي شده است. 299 نمونه از رسوبات آبراههاي در مساحتي حدود 617 كيلومترمربع از منطقه مورد مطالعه برداشت شده و تحت آناليز شيميايي قرار گرفته است. به دليل وجود پتانسيل كاني سازي طلا در منطقه روش حوضه آبريز نمونه، بر روي غلظت هاي تك عنصري طلا اعمال شده است. پس از انجام محاسبات مربوط به روش حوضه آبريز نمونه، آناليز PCA بر روي نتايج حاصل انجام شده و نقشه هاي توزيع فضايي آنومالي هاي طلا با استفاده از روش فركتالي عيار- مساحت ترسيم شده است. هدف از اين مطالعه، بررسي قابليت روش حوضه آبريز نمونه در تعيين حوضه هاي آنومال و معرفي مناطق پر پتانسيل در منطقه مورد نظر است. بر اين اساس، مناطق پر پتانسيل معرفي شده توسط روش حوضه آبريز نمونه در جنوب غربي منطقه قرار گرفته است كه با كاني سازي شناخته شده در منطقه مطابقت دارد.

Summary In the present study the sample catchment basin approach has been used in addition to multivariate statistical analysis over geochemical dataset collected in Kervian area in Iran. Sample catchment basin has reasonably detected the favorable zones in the present study and the proven Au mineralization has validated the results. Introduction Stream sediment data application method has been widely used and accepted in exploration of different deposit types in mineral exploration industry and has shown its efficiency in this context. The sample catchment basin approach is a technique for processing of stream sediment data that is employed for removal of lithological impact from existing variation in chemical content of the samples. Methodology and Approaches The target area covers 617 km2 in which 299 stream sediment samples were collected for chemical analysis. In addition, digitized 1:100000 geological and 1:50000 topographical maps were used for creation of sample catchment basins considering the sampling point positions. In order to remove the impact of background contribution to geochemistry of stream sediment by this technique the following procedure has been taken into account: 1- estimation of uni-element background concentration of element of interest for every lithology and then estimation of uni-element background value for every sample catchment basin 2- removal of the background concentration from measured concentration of element for each sample 3- dilution correction of residual values by taking the catchment area size into account 4- analysis of dilution correction values and delineating the anomalous basins. Results and Conclusions The sample catchment basin method was employed and data processing was completed as mentioned above which resulted in delineation of anomalous Au values extended south-westerly. The results are compatible with known gold occurrences located in this part of the map. There are weak to moderate anomalous basins positioned south east and east of the known mineralization covered with the same sedimentary units as mineralization area that could be assumed promising. However, sample catchment basin has successfully highlighted the anomalous basins which were not detected through analysis of raw dataset. Employing this method has led to introduction of more areas for further prospecting, decreasing the chance of false negative anomaly. Comparison between processed dataset with the sample catchment basin approach and raw data set has demonstrated the superiority of the sample catchment basin approach.