R. Pourimani; M. Zahedi; M. Mirzaei
Abstract
In this research magmas (igneous rocks) of 300 hectares area covering of hot springs of Mahallat zone of Iran were studied. Twenty samples of outcrops of magmas were collected. In order to obtain homogeneous fine powder, part of all samples were crushed by jaw and ball milling and dried and passed through ...
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In this research magmas (igneous rocks) of 300 hectares area covering of hot springs of Mahallat zone of Iran were studied. Twenty samples of outcrops of magmas were collected. In order to obtain homogeneous fine powder, part of all samples were crushed by jaw and ball milling and dried and passed through mesh number 40 and packed in Negin containers and sealed. Thin cross section were prepared for all samples and mineral components were determined in mineralogy laboratory. Specific activities of 226Ra, 232Th and 40K of all samples were determined using gamma ray spectrometry method employing high purity germanium (HPGe) detector with its electronic system. Specific activities of these radionuclides in samples obtained from 22.15 ± 1.34 to 62.68 ± 3.76, from 10.69 ± 1.43 to 40.55 ± 2.15 and from 59.99 ± 5.07 to 1467.30 ± 17.48 in Bq/kg respectively. Heat rate generation due to radioactivity decay for samples calculated that varied from 0.69 to 1.82 in µW/m3. The mean Heat production of magma with ten cubic kilometer volume obtained as 13.60 kW and the energy for increasing of water temperature with yields of 35.5 l/s from 15º C to 100º C is necessary 12.7 kW. Therefore consideration level of radioactivity and long life of magma of this region and expansion in conic form under hot springs seem to be the resource of heat due to radioactivity decay of 235U, 238U and 232Th series and 40K.
M Mirzaei; L Soheili; V Ebrahimzadeh Ardestani; A Teymorian Motlagh
Abstract
The main objective of interpretation of acquired gravity data on the Earth's surface is to determine the contrasts in density or shape/dimension of mass anomalies. Interpretation of gravity data can be done through an inversion process. In this research, a block model has been considered for the subsurface ...
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The main objective of interpretation of acquired gravity data on the Earth's surface is to determine the contrasts in density or shape/dimension of mass anomalies. Interpretation of gravity data can be done through an inversion process. In this research, a block model has been considered for the subsurface anomalous mass. By considering a constant initial density (about 2.6 gr/cm3) for all blocks and by using inversion method, distribution of density of the anomalous mass was estimated and interpreted. In this research, Occam method is used to invert 246 gravity data collected in 2007. Results of the gravity data inversion show sufficient fit between observed and calculated gravity data. Using this inversion method, distribution of density in the subsurface layers related to sediments and basement are estimated in this area. Since there is a density contrast between sedimentary layers and basement, the estimated density distribution can help to explore the lithology of formations as well as the discontinuities in them. Densities less than 2 gr/cm3 in horizontal and vertical sections obtained from the inversion are attributed to the alluviums. The depth of these sediments, which include sand, silt and clay of different percentages, is estimated to be less than about 200 m. Unequal density distribution along the layers is taken to indicate fractures. In fact, these fractures are associated with part of the Tabarteh fault in this area, which caused numerous earthquakes (but less than 5 Richters in magnitude) around the Arak and Dawood Abad cities in past years.
A. Nejati Kalateh; M. Mirzaei; N. Gouya; E. Shahin
Abstract
In this paper we used orthogonal basis functions and expansion coefficients for inverse modeling of magnetic data. The basis functions chosen are normalized eigenvectors of second derivation of the objective function (Hessian matrix) calculate for an initial model. Limited number of basis vectors obtained ...
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In this paper we used orthogonal basis functions and expansion coefficients for inverse modeling of magnetic data. The basis functions chosen are normalized eigenvectors of second derivation of the objective function (Hessian matrix) calculate for an initial model. Limited number of basis vectors obtained in this way defines a new subspace in model parameters space. A new objective function is defined in term of these new parameters and minimized in subspace of original space. As in geophysical inverse problems we need to inverse matrixes that are functions data and geometry of data and model parameters. The matrix inversion in new subspace of the original space will be better conditions due to less dimensionality in the inversion. Since the most significant eigenvectors corresponding the largest eigen values in Singular Value Decomposition ( SVD) of matrixes. Others eigenvectors have less influence in fitting data or lead inversion procedures to local minima. With apply subspace method inversion will be fast and stable against the noise. The efficiency of the method is tested with synthetic and real magnetic data (acquired from Moghan area, north-west of Iran). The results proved fast convergence and stability of inversion against the noise.
