DETECTION OF IRON DEPOSITS BY NORMALIZED FULL GRADIENT METHOD: OJATABAD DEPOSIT, IRAN

7th International Scientific Conference - SGEM2007, www.sgem.org, SGEM2007 Conference Proceedings/ ISBN: 954-918181-2, June 11-15, 2007

ABSTRACT

The Normalized Full Gradient (NFG) method was introduced in the mid of
1960s. This method generally uses for interpretation potential field data in
order to detect gravity and magnetic anomalies. The NFG value represents
the full gradient of the magnetic anomaly at a point divided by the average of
the full gradient at the datum. The closed maxima on a NFG map indicate the
occurrence and the horizontal locations of the centers of magnetic anomalies
related to iron deposits. By means of this map, we can select bore-hole locations
in the field. In this study, we applied the NFG method for detecting Ojatabad
iron deposit (Semnan Province) and determination of its depth by means of
magnetic anomalies. In this paper, after needed corrections, we draw magnetic
anomalies map. In order to calculation the NFG values, a 2D algorithm is
provided and the NFG value map is drown. By applying the NFG method to
the Ojatabad iron deposit, using closed maxima of the NFG method alongside
the other methods, showed that the magnetic anomalies are located in shallow
depths ranged from approximately 10 to 80 meters. Modeling studies show that
the NFG largely depends on number of terms in the Fourier series used to
calculate it, and it closely related to the length and girding of the magnetic
profile or the size of the study area.

Keywords: Ojatabd Fe deposit, Magnetic anomalies, the NFG method, Fourier
series.