New Insights into Interpretation of Aeromagnetic Data for Distribution of Igneous Rocks in Central Iran

—New insights in the aeromagnetic data over the Central Iranian Microcontinent (CIM) have revealed interesting results for future studies and exploration. This work presents the interpretation of different magnetic analyses and the calculated 3D inversion model to provide important insights into the distribution of igneous rocks in the area that may be traced under significant cover. By analyzing several hundred magnetic susceptibility data points and aeromagnetic anomalies of known igneous rocks over the area, it was determined that mafic–ultramafic intrusive rocks generally have a high magnetic susceptibility and produce a strong magnetic response. Intermediate–felsic intrusive rocks have a low magnetic susceptibility and show a smooth gradient variation and commonly regular shape. Volcanic rocks show a wide range of magnetic susceptibility; therefore, the aeromagnetic anomalies are often random or show strong amplitude with high frequency signals and are rapidly eliminated when an upward continuation is applied. Based on the results of analysis of different magnetic maps and 3D inversion of data, and combining this information with known outcropped of igneous rocks, we revealed 1215 concealed intrusive rocks and 528 volcanic rocks in the area. We also renewed the boundaries of tens outcropped igneous rocks. The known and new mapped igneous rocks can be identified as 12 regions (or zones) for intrusive rocks and 4 regions for volcanic rocks. The results indicate that the mafic–ultramafic rocks are mainly located in the Sistan suture zone of eastern Iran along the Nehbandan fault zone. They also show that the many parts of the Lut block as the main structure of CIM have been under magmatic events, so that most of concealed igneous rocks are distributed in the middle and southern part of the Lut block. Volcanic rocks are widespread in the southeastern and northern parts of the area such as the Urumieh-Dokhtar Magmatic Arc, North Lut, and Bam region.

Identification of Buried "Archeological" Objects in the Area around Kedulan Temple using Geomagnetic Methods

Temple is a religion place for ancient culture, Yogyakarta have many incridible temples one of the biggest is Prambanan temple. 2 Km to the north west direction from Perambanan temple located the Kedulans temple who still on renovation projects. Kedulan Temple is located in Tirtomartani Village, Kalasan District, Sleman, Yogyakarta Special Region, at coordinates 7° 44' 28" South Latitude and 110° 28' 5" East Longitude, with an altitude of 168, 45 meters above sea level. Kedulan Temple was found in a collapsed state and buried volcanic material from Mount Merapi. Based on the results of a stratigraphic study conducted by Pramumijoyo, et al., (2005) this temple is covered by 8 meters thick lava which is composed of 14 layers of sediment. To obtain information on the existence of archaeological objects that are still buried around the temple in this study, geophysical measurements were carried out using the geomagnetic method which aims to determine the potential for buried archaeological objects in this case assumed to be igneous rocks that have contrasting susceptibility. Based on the geomagnetic signal analytic map obtained, there is a magnetic anomaly which is suspected to be a hidden temple object which is bordered by a black line which is about 50 meters to the east of Kedulan Temple. This assumption is based on a high magnetic anomaly value >480 nT which is thought to originate from the temple rock object in the form of andesite rock.