بررسي ژئوشيميايي توزيع عناصر نادر خاكي و ساير عناصر استراتژيك در رسوبات آبراهه اي برگه 1:100000 خوي آذربايجان‌غربي بر‌اساس آناليز حوضه‌هاي آبريز و تحليل مؤلفه هاي اصلي

Geochemical investigation of rare earth and other strategic elements in stream sediments of the Khoy 1:100,000 geological sheet area, using catchment basin and principal component analysis methods

روش هاي تحليل مؤلفه هاي اصلي و آناليز حوضه هاي آبريز در بررسي داده‌هاي ژئوشيميايي رسوبات آبراهه اي براي مشخص كردن مناطق داراي پتانسيل معدني از اهميت بالايي برخوردار است و مي تواند سهم ويژه اي در برنامه ريزي هاي پيجويي و مراحل بعدي اكتشاف داشته باشد. در اين مطالعه داده‌هاي حاصل از برداشت 843 نمونه رسوبات آبراهه‌اي در برگه 1:100000 خوي واقع در استان آذربايجان غربي، به وسيله اين روش ها مورد بررسي قرار گرفت. ابتدا با استفاده از روش تحليل مؤلفه هاي اصلي، ابعاد متغيرها كه همان عناصر نادر خاكي (Ce، Eu، Dy، La، Nd، Sc، Sm، Y و Yb) به همراه عناصر مس، سرب، روي، كروم، طلا و نقره هستند، كاسته و مؤلفه هاي اصلي آنها انتخاب شدند و ارتباط هر متغير با فاكتورهاي به دست آمده مشخص گرديد. سپس با استفاده از روش آناليز حوضه هاي آبريز كه از سطح واقعي حوضه آبريز و واحدهاي زمين‌شناسي و به كار بردن ليتولوژي‌هاي بالا دستي در روابط مربوطه استفاده شده است، مقادير زمينه عناصر محاسبه و جداسازي بي‌هنجاري‌هاي محلي صورت گرفت. نتايج به صورت نقشه هاي پتانسيل براي اين عناصر به صورت داده هاي خام و داده هاي حاصل از روش آناليز حوضه هاي آبريز بر روي نتايج به دست آمده از كريجينگ معمولي مؤلفه هاي اول و دوم روش تحليل مؤلفه هاي اصلي، ارائه گرديد. علاوه بر اين كه مشخص شد روش آناليز حوضه هاي آبريز توانايي تفكيك بهتر بي‌هنجاري‌هاي محلي از زمينه را دارا هستند ، اين دو روش ذكر شده نيز به طور محسوسي يكديگر را مورد تأييد قرار مي دهند.

Principal Component Analysis (PCA) and Catchment Basin Analysis (CBA) methods have important role in investigation of stream sediment geochemical data and can have special contribution in prospecting programs and other exploration steps. In this study, the data of 843 stream sediment samples from Khoy 1:100,000 geological sheet area in West Azerbaijan, were investigated using PCA and CBA methods. At first, dimension of variables such as REEs as well as Cu, Pb, Zn, Cr, Au and Ag was decreased using principal component analysis (PCA) and the main principal components were selected for further investigation and finally the correlation of each parameter with achieved factors were given. Then, the background values were calculated and local anomalies were separated using catchment basin analysis on the basis of real area and upstream geological units of catchment. In addition, it is demonstrated that catchment basin analysis is able to better discriminate local anomalies. Consequently two mentioned methods obviously can validate each other.Briefly, in this research, the rare earth and other strategic elements in stream sediments samples of the Khoy 1:100,000 geological sheet area, have been investigated. The background values were calculated and local anomalies were separated using catchment basin analysis on the basis of real area and upstream geological units of catchment. Threshold level method was used for separation of anomalies from background. Also, by principal component analysis (PCA) method, the main factors were delineated. Results obtained from PCA method, were estimated using ordinary kriging and finally these two methods were compared. Consequently two mentioned methods obviously can validate each other. Introduction Aggregation of elements in stream sediments depends on the stream network, area and topography slope of catchment and upstream lithological units. Investigation of these sediments using catchment basin analysis and principal component analysis methods, obviously introduces elements dispersion and prevents demonstrating unreal anomalies. The PCA method is useful in identification of complicated structure, indexing and reduction of data dimension. Because of existence of vast alluvial plains, alluvial fans, coasts and vast basins in Iran, geochemical data analysis by CBA method can lead us to explore the valuable mineral resources to reach sustainable development. The above mention methods will cause to find probable mineralization regions. Methodology and Approaches In this study, for investigation of stream sediments geochemical anomalies, different steps such as data processing, separation of basins, calculation of local anomaly using CBA and PCA methods have been used for REEs and some other trace elements. In CBA method, the basins were separated by ArcGIS software and Archydro tools extension and then, real area of geological units for all catchments were calculated. Finally, using real area and application of upstream lithologies in given equations, the background values were calculated and local anomalies were separated. In PCA method, the main component of each elements were delineated, using ordinary kriging, values of each main factors have been estimated in unsampled regions. Results and Conclusions Results and geochemical maps obtained by BCA and PCA methods demonstrate that catchment basin analysis is able to better discriminate local anomalies and these anomalies have been correlated with the ordinary kriging maps obtained from principal component analysis and these two mentioned methods, obviously can validate each other.