تحقيقات ناهمسانگردي خودپذيري مغناطيسي سري هاي رسوبي دزو و داهو در منطقه زرند كرمان

AMS study of the Dezou and Dahou series in the Kerman-Zarand region

Introduction: Red beds have been widely studied by palaeomagnetic methods for what they can tell us about the history of sedimentary basins and their subsequent deformation (Collinson, 1974, Turner, 1979a,b and 1981, McCabe and Elmore, 1989, Elmor, et al, 1993 and 2000). This study has investigated the palaeomagnetism of the Cambrian red sediments (Dezou and Dahou Formation) of the eastern margin of Central Iran. Davoudzadeh and Schmidt, (1984), have done some work on the region which includes these rocks and discuss the few rotations of the Central Iran micro plates. The aim of this study is to consider the AMS results to investigate the palaeo force field on the rock located at the northern side of the Persian Gulf. Geological setting: The sampling sites of this study are situated in the Cambrian E-mail: Darabi@ut.ac.ir -Yf-M ^ } mftS i\ •jU-i 1 and -1 < T < 1 provides information about the shape and the degree of anisotropy on the same plot. T- Pj plot is shown for all sampling sites in the Dahou and Dezou Formations and also site 20 only. Most samples have less than 10% anisotropy but some of the samples tend to be more anisotropic.. Curie temperatures are mostly between 675-700°C and attributed to specularite and pigments of hematite;. In a few examples magnetite with a Curie temperature of about 570°C can be seen as well. The clearest indication of magnetite here is RM ratio (RM ratio is the value of Ms at 100°C on the cooling curve to the value on the heating curve). RM ratio < 1 showing that magnetite has been oxidized to hematite with low Ms Values. Rock magnetic studies show an agreement that both specular hematite and magnetite can occur in these sediments although the effect of hematite is usually dominant. Site 13 that is sample d in red sandstone shows paramagnetic mineral content and hematite pigment with a Curie temperature of 680°C and a saturation field of 2000 mT. Low coercivity of 50 mT shows a low amount of magnetite. Site 14 that is sampled in red sandstone shows a high amount of paramagnetic mineral content and finer grain size of hematite pigments (compare to site 13) with a Curie temperature of 680°C and a saturation field of 3000 mT. Lower coercivity than site 13 shows low amount of magnetite too. Site 15 that is sampled in dolomite breccias shows very scattered results of IRM, hysteresis and Curie curves. And overall look suggest a predominantly diamagnetic mineral. Site 16 that is sampled in red sandstone at its contact with dyke shows an overprinted