Evaluation of structural and geological factors in orogenic gold type mineralisation in the Kervian area, north-west Iran, using airborne geophysical data
Alireza Almasi 1 7 Alireza Jafarirad 1 Hasan Kheyrollahi 2 3 Mana Rahimi 4 Peyman Afzal 5 6
+ Author Affiliations
- Author Affiliations
1 Department of Geology, Science and Research branch, Islamic Azad University, Tehran, 1477893855, Iran.
2 Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, 1591634311, Iran.
3 Airborne Geophysics Group, Department of Geomatics, Geological Survey of Iran (GSI), Tehran, 1387835841, Iran.
4 Geoinformatics Group, Department of Geomatics, Geological Survey of Iran (GSI), Tehran, 1387835841, Iran.
5 Department of Mining Engineering, South Tehran branch, Islamic Azad University, Tehran, 1777613651, Iran.
6 Camborne School of Mines, University of Exeter, Penryn, TR10 9FE, UK.
7 Corresponding author. Email: alirezaalmassi@gmail.com
Exploration Geophysics 45(4) 261-270 https://doi.org/10.1071/EG13053
Submitted: 6 June 2013 Accepted: 14 February 2014 Published: 24 March 2014
Abstract
The Piranshahr-Sardasht-Saqqez Zone (PSSZ) in the north-west of the Sanandaj-Sirjan metamorphic zone (SSZ) hosts some major Iranian gold deposits. In the south-east of PSSZ, there is a north-east trending orogenic gold belt which contains three gold deposits/occurrences (Qolqoleh, Kervian and Ghabaghloujeh). In this research, studies are focused on processing and analysing airborne magnetic and radiometric data in order to find applicable indicators for prospecting gold in this area.
Former studies on the gold deposits/occurrences in the study area suggest three essential factors in local orogenic gold mineralisation: (1) intersecting deep bending structures/shear zones, (2) Fe-rich mafic meta-volcanic lithologies (primary source and host rocks) and (3) altered mylonitic granites (secondary host rock). Geological structures and lithological contacts can be mapped based on locating edges in the magnetic field at different depths.
In this study, we extracted the structure from aeromagnetic data by reduction to the pole, upward continuation and applying a tilt derivative filter to the horizontal derivative of the upward continued data. Upward continuation was to several levels from 500 to 4000 m. Afterwards, a 3D architecture was built based on extracted subsurface lineaments in different levels. This 3D model can assist in the visualisation of the underground shape of structures that may influence gold mineralisation.
Moreover, mafic meta-volcanic rocks in the study area, which contain magnetic minerals such as magnetite, titanomagnetite and ilmenite, can be mapped using aeromagnetic data. Mylonitic granites, which are the other host rock in the deposits, were mapped using airborne radiometric data.
Key words: 3D modelling, airborne geophysics, filtering, mineral exploration.
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