Integration and analysis of airborne geophysics and remote sensing data for exploration of porphyry copper deposits in the Central Iranian Volcanic Belt
Department of Mining Engineering, Shahid Bahonar University of Kerman,
Iran. Post box No. 76135-133,
Tel and fax: +98-341-2112764,
M. Honarmand, Z. Moezifar
Department of Geology, Shahid Bahonar University of Kerman, Iran. Post box No. 76135-133
Many of the known porphyry Cu deposits are situated in the Central Iranian Volcanic Belt(Figure 1). This belt has a great potential as far as Tertiary porphyry copper mineralization is concerned. Given the poor soil development, relatively poor vegetation cover but abundant outcrops the arid/semiarid part of the belt is suitable for airborne geophysical survey and remote sensing studies.
Two airborne geophysical surveys were done over the study area. The first airborne geophysical survey (radiometry and magnetometry) over the area was done in 1977 by Prakla-Seismos GMBH on behalf of Atomic Energy Organization of Iran(AEOI). The aim of this survey was exploration for uranium and thorium minerals. The flight line spacing was chosen at 500 meters and nominal terrain clearance was 120 meters. In the second survey a helicopter magnetic/electromagnetic/radiometric survey (HMER) was flown by Geonex Aerodat Incorporated over an area of 7000 km 2, in Kerman Province(in 1992). The aim of the project was mainly for exploration of porphyry and vein-type mineralization in the Kerman region. The survey was conducted over the area in 200 meters flight spacing and constant height at average elevation of 60 meters for spectrometer, 45 meters for magnetometer and 30 meters for electromagnetic coils. The data then, was processed by various filtering and enhancement techniques for noise removal and
data correction(Pitcher et al. 1994). Pitcher et al. (1994) and Ranjbar et al. (2001) have worked on a part of HMER data and concluded that the porphyry copper deposits in the Kerman region are associated with a distinct magnetic low, relative to the host rocks, a potassium high and resistivity low.
Figure 1 : Sketch map(Inset) showing the position of the Central Iranian Volcanic Belt and porphyry-type Cu deposits sub parallel to the Zagros Thrust Zone(Shahabpour, 1994) 1- Bahreasman, 2- Takht, 3- Kuhe Panj, 4- Darrehzar, 5- Sar Cheshmeh, 6- Meiduk, 7- Gowde kolvary, 8- Darre Zereshg, 9- South of Ardestan, 10- Sharif Abad, 11- Songun. Geological map of Sar Cheshmeh area. 1- Recent alluvium(Quaternary), 2- Younger gravel fan(Quaternary) , 3- Calcareous terraces(Quaternary), 4- Neogene sediments, mostly arenites with pebbles and boulders of volcanic and intrusive rocks. Dacites and dacitic pyroclastics, 5- Oligocene-Miocene Granodiorite, quartz diorite, diorite porphyries and monzonite, dikes, 6- Volcanic-sedimentary complex. Trachyandesites, trachybasalts, basaltic andesites, pyroclastics etc.(Eocene), 7- Fault, 8- Working mine and copper deposit, 9- hydrothermal alteration (After, Dimitrijevic et al., 1971).
The integration of multiple data sets is a necessary step in mineral potential mapping. A major focus in modern exploration programs aims at the search for blind ore bodies. Because of the advent of advance computer technologies, various multivariate techniques have been introduced to interpret and synthesize multiple geo-data sets for target selection (Agterberg, 1989). Principal component analysis is a multivariate analysis which can be used for data which are spatially distributed and have common geographical locations. Statistical analysis of geophysical data has been reported by many authors in the recent years (e.g. Duval, 1977; Pan, 1993; Ranjbar et al., 2001).
The previous studies have shown that the elevated potassium in the sericite zone is often observed around the mineralization areas and also acid sulfate conditions resulting from weathering of near surface sulfides can result in eTh mobilization from host rocks and can precipitate with iron in gossan (Dickson et al., 1996).
The integration of satellite and geophysical data, over the Central Iranian Volcanic Belt, has been reported by many workers(e.g. Ranjbar and Roonwal, 1997, Asadi and Hale, 1999, Tangestani and Moore, 2001 and Ranjbar et al. 2002). The integration of geophysical and satellite data can be done either in vector or raster format. A comprehensive literature review of GIS analysis in raster format is reviewed by DeMers(2002). In this study ETM+ data(Acquisition date, 23/6/2001) has been integrated with airborne geophysical data for proposing a model for further exploration activities in the Central Iranian Volcanic Belt.