فهرست مطالب زهرا فیروزکوهی

Monogenic basaltic cinder cones and lava flows from west of Khash are part of volcanic arc of northern Makran, formed as a result of subduction of Oman oceanic lithosphere beneath the Eurasian plate. The basalts belong to medium-K calc-alkaline series as they contain high Al2O3 (16.5- 19.04 wt. %) and CaO (8.4- 12.0 wt. %) and moderate amounts of K2O (0.5- 1.1 wt. %). They share arc geochemical features such as high LILE/HFSE ([Rb/Zr]N-MORB up to 19) LILE/LREE ([Ba/La]N-MORB up to 4.86) and LREE/HREE ([La/Yb]N-MORB up to 10), and depletion of Ta, Nb, Zr, and Ti relative to N-MORB. Partial melting models indicate that near-primary basalts were derived from an enriched source type mantle wedge peridotite after low to medium degrees (2-10%) of partial melting. This source peridotite was enriched in LREE and LILE, by subduction derived fluids in the supra-subduction zone. Negative correlation of Th/La vs. Sm/La, and relationships between Pb/Ce and Th/Nb values of the studied basalts which are between two end compositions of global subducting sediment (GLOSS) and N-MORB are indicative of significant contribution of subducting sediments to the genesis of the basaltic rocks. Estimates made using binary mixing model are indicative of about 16% of sediment participation in the magma genesis. Low Pb/Ce ratio (1.6 - 11.1), compared to OIB (>20) may be a signature of participation of fluids resulted from dehydration of the subducting slab.

Textural and Geochemical characteristics of plagioclase phenocrysts in Andesitic and basaltic rocks of Bazman volcano (from Makran volcanic arc) show evidence of interaction between basaltic and andesitic magmas. Plagioclase phenocrysts in andesites and basalts are composed of three major parts of core, mantle and rim, with similarity of the anorthite contents in cores and mantles. The cores of the phenocrysts, which seem to be in equilibrium with the andesitic magma rather than the basaltic one (­An39-60), exhibit different styles of oscillatory zoning. The trace element (Fe, Mg, Sr, Ba) concentrations in different zones of the cores also remain constant or change proportional to the anorthite content and may exhibit dynamic processes in the magma reservoir during the core formation in andesitic magma. The engulfed cores and sieve texture in the mantles of plagioclases may have formed in response to changes in temperature and composition of the surrounding melt. Elevated anorthite content of plagioclases (An40-65), accompanied by jump of the Fe, and Mg content, in addition to change in the patterns of Sr, and Ba in the sieve-textured mantle may show the replenishment of magma reservoir by new basaltic magma. Increase of An in the rim of basaltic plagioclases (from An53 to An74) and decrease of An in the rims of andesitic plagioclases (from An69 to An53), indicate that the two magmas gained their contrasting compositional identity most probably as a result of sudden upward movement. These constraints, along with other evidence like weakly-zoned pyroxene microphenocrysts with rounded rims, suggest that the rocks originated in the course of replenishment of mafic melts either with chemical or/and thermal interaction of the melts.

Stock liquidity is one of the criteria that the investors consider in their portfolio decisions. The earning management is one of the other factors that influences stock liquidity. This could examine in terms of discretionary-related earning management and the real earning management. Therefore the main purpose of this study is to estimate earning management based on the Liquidity trading companies and also examine its effect on stock liquidity of companies listed in Tehran Stock Exchange. This study conducted through regression model based on panel data and then hypotheses tested through this. The results of data analysis and hypotheses test indicated that the Liquidity trading companies significantly influence stock liquidity negatively. Also effect of mediator factors on Liquidity trading companies and stock liquidity has been examined. These factors include standard deviation of daily stock returns, the average daily turnover of stocks, the average closing price of stocks traded, the average number of daily transactions of stocks, and market value of company. Also the results indicated that effects of these factors haven’t been accepted.

Stock liquidity is one of the criteria that the investors consider in their portfolio decisions. The earning management is one of the other factors that influences stock liquidity. This could examine in terms of discretionary-related earning management and the real earning management. Therefore the main purpose of this study is to estimate earning management based on the abnormal discretionary costs and also examine its effect on stock liquidity of companies listed in Tehran Stock Exchange. This study conducted through regression model based on panel data and then hypotheses tested through this. The results of data analysis and hypotheses test indicated that the abnormal discretionary costs significantly influence stock liquidity negatively. Also effect of mediator factors on abnormal discretionary costs and stock liquidity has been examined. These factors include standard deviation of daily stock returns، the average daily turnover of stocks، the average closing price of stocks traded، the average number of daily transactions of stocks، and market value of company. Also the results indicated that effects of these factors haven’t been accepted.