GEOSCIENCES
Year:2004 | Volume:12 | Issue:53|Papers Count:11

Arash Syenite is located in central Iran and in Bafq metalogenic province, and has intruded into the Precambrian-Cambrian volcanic-sedimentary sequences. Size and distribution of minerals are not uniform in all parts of the body and vary from chilled margins to the central part of the pluton. Effects of tectonic movements, existence of uncommon textures in plagioclase crystals and the appearance of metasomatic textures are the main evidence for metasomatism. Study of elemental concentration deduced from mass balance calculation reveals the effects of alkaline metasomatism in Arash Syenite. Gain in K2O (and Rb) and Al2O3 with parallel losses in Fe2O3, CaO, Na2O, Ba and Sr are shown. Relative increase in Nb and Zr are due to leaching of mobile cations in this pluton.Decrease in Zr and Nb with parallel increase in SiO2, which is one of the most identical factors for the calc-alkaline differentiation, is remarkable in Arash Syenite. There is a clear change in Y, Th and Nb relative to Zr in this pluton and based on the constant ratio of Zr/Nb, the role of contamination and assimilation of country rock is insignificant in the pertrogenesis of this pluton. Negative anomaly for Nb and TiO2 suggest a subduction-related origin for the Arash Syenite.

Iran has experienced centralized higher education system for the past two decades. Present study employs statistics and information of mining engineering education to demonstrate some of the major obstacles against the engineering education in Iran. During the past 60 years, about 5000 students have been graduated from Mining Engineering Departments of Iran, of which more than 90% fall in the last 20 years. In recent years, about 700 students graduate from 23 mining engineering departments of Iran, annually. About 100 faculty members, which less than 50% of them have a doctorate degree, are teaching mining engineering in 13 institutions of public sector. The present study shows that the number of active mining engineering departments of Iran is more than the sum of similar institutes in USA, Canada and UK. It also shows that the mining engineering graduates of Iran are more than the sum of graduates of USA, Canada, UK and Australia. Based on the global experiences and domestic needs, the present article suggests some remedial measures to relieve the current pitfalls.

Explosion-generated seismic signals have been of interest for many years, especially in connection with geophysical studies for scientific and industrial purposes. Increasing the yield of an explosion in a given type of rock does not necessarily mean a proportional increase in the seismic-signal amplitude. The geological environment in which a nuclear explosive is emplaced has a major influence on the strength of seismic signals. Estimating the yield of underground nuclear explosions from far-field seismic waves is a difficult problem, since accurate estimates require a detailed accounting for source-region and travel-path differences between known and unknown yield events. For short-period P- waves, the first problem is to obtain an unbiased measure of the far-field energy. Conventional mb seems unsatisfactory because of the large scatter in station values. The dominant cause seems to be wave focusing/defocusing by complex earth structure. For yield estimation, it is important to characterize each event by an unbiased measure of the P-wave energy leaving the source region. It is clearly very difficult, and perhaps impossible, to substantially reduce the scatter in conventional mb data. The suggestion with the best theoretical support is to use the “b phase”, since it is least contaminated by pP and other later arriving energy. The data used in this study were taken from 25 Semipalatinsk test site explosions recorded by SRO located at Mashhad. Reasons for selecting 25 records from 50 total records was based on signal to noise ratio and availablity of announced yields. For each event the amplitude of short-period vertical component of the records were read. Also magnification was removed from all records. With attention to epicenteral distance (about 19 degrees) the first arrival is the direct P-wave passed through the mantle. Since with one station we cannot remove focus/defocus effect, it is better to use the amplitude instead of the magnitude in order to estimate the yield. However, the yield-magnitude relationship was calculated. We could obtain better results when using “b phase” rather than the other phases. It is concluded that “b phase” is a good tool for decreasing scattering of the data. The derived relationship is: log(A) = 0.807 log(Y) + 1.049, R2 = 0.8014. So, this formula is recommended for calculating the yield of Semipalatinsk explosions recorded in SRO station, at Mashhad.

The Bayche – Bagh mine area in the northern part of Takab based on lithostratigraphy point of view includes gneisses and amphibolites of Precambrian, which are unconformably overlain by volcanic – volcanoclastic and associated sedimentary rock units of Tertiary and Quaternary age. The volcanic rocks are divided into rhyolitic and andesitic groups in which the rholitic group provides the main host – rock of the deposit. Ore parageneses include copper, lead, zinc, nickel, cobalt and Bismuth mineral occurred in nine veins of main orders and few veinlets. The physico chemical conditions of ore – fluids governing the ore – mineralization, were controlled by fluid inclusion studies and the related obtained parameters are as follows:- Temperature of homogenization (TH) from 2120C to 470C - Salinity (in NaCl-equivalent percent) about 25% - Trapping pressure from 50 to 800 bars The ore-generation processes based on the nature of magmatic host rocks, ore assemblages and thermometric data in the Bayche-Bagh deposit, similar to other hydrothermal five – element vein deposits, seem to be occurred in relation to ore recycling and fluid migrations. These fluids the metals of recycled the deep-seated basic and ultrabasic rocks of the old basement as also adjacent volcanoclastic hosts and deposited the ore minerals in the fault spaces in under suitable conditions.

Misho mafic and ultramafic complex (pre-Permian) is located in 8km southwest of Marand, East-Azarbaidjan, NW Iran, and has intruded in Proterozoic pelletic rocks of Kahar formation developing contact metamorphism. A reverse fault in the northern portion of the study area brought this complex in contact with a series of gypsiferrous marl and sandstone of Miocene age. Based on field, textural, and structural evidence, the mafic and ultramafic intrusives in Misho are divided into two distinct groups, (1) primary gabbros and (2) secondary gabbros (diabases). Primary gabbros crop out in the form of large, rugged, and massive bodies of rocks covering most of the study area, whereas secondary gabbros appear as small and irregular dikes and sill-like bodies intruding the primary gabbros.Based on silicate mineralogy, texture, and sulfide content, the primary gabbros are further divided into three sub-groups: (1) normal Primary gabbros, (2) sulfide-rich gabbroic patches, and (3) pyroxenite patches, and the secondary gabbros are divided into two subgroups: (1) diabases and (2) sulfide-rich micropyroxenite. Opaque mineral phases (sulfides and oxides) in these rocks principally fill as rounded and bent aggregates the interstitial spaces among silicates and occasionally (in sulfide-rich patches) entirely engulf them. In normal primary gabbros, pyrrhotite and ilmenite are the most abundant sulfide and oxide minerals whose modal values are within the range of 0.5-3% and 0.5- 10% respectively. Analytical data shows that the values of Cu, Ni, and Cr in these rocks are <410ppm, <250ppm, and <170ppm respectively.In small Sulfide-rich gabbroic and pyroxenite patches, the modal values of the sulfide and oxide minerals lie within the range of 10-40% and 0.3-3% respectively.Secondary gabbros are mineralogically similar to the primary ones and their opaque phases are mainly ilmenite (3-8%) and pyrrhotite (0.2-2%). The concentration of Cu, Ni, and Cr in these rocks are ~55ppm, ~57ppm, and ~91ppm respectively.Au and Pt values in both Primary and Secondary gabbros are ~5ppb

Well logging Techniques have many important applications in coal exploration, such as determination of coal depth, thickness and quality. Using this method in coal quality investigation is of great importance. In this paper it is tried to investigate the coal ash content in Parvadeh-1 of Tabas region as one of the coal quality parameters. Seven boreholes from the study area have been selected and after lithology interpretation, quality consideration of logs were examined. The region has a normal topography and sequences of shale, sand, silt and coal layers were seen in the area. Well logging was carried out in water filled and open boreholes. Density log shows that gamma emittion in coal layers increases where the ash content of the coal is reduced. In this study statistical analysis indicated a correlation coefficient of 81 percent between chemical ash and density log count rate.

This study is based on six stratigraphic sections of Tarbur formation which names Gondashtlu, Zarghan, Kherameh-1, Kherameh-3, Kherameh-4 and Sarvestan. Over 2500 meters of Tarbur Formation and 850 thin sections are studied. Index microfacies and foraminifers are identified. This study shows that Tarbur Formation is divided by two parts 1- Lower part (well bedded limestone, 2- Upper part (Massive limestone).Index Microfacies include: wackestone, packstone, grainstone and boundstone. Amount of extraclasts in lower part of Tarbur Formation are more than of upper part, and amount of bioclasts are more than of the other of microfacies elements. The index foraminifers which are identified include:Orbitoides media, O.apiculata, O.concavatus, O.tissoti. O.triangularis, Antalyna korayi, Laffitteina sp. Loftusia minor, Omphalocyclus macroporus, Siderolites calcitrapoides, Murciella cuvillieri, Dicyclina schlumbergeri. Coskinolina sp. Rotalia skourensis, Rotalia sp. Dictyconella complanata, D.sp., Sirtina sp., Dictyoconus sp., Vania anatolica, Lepidorbitoides minor, L.socialis, Minaxia sp., Tochospira sp., Subalveolina sp., Bolivinopsis sp., Broeckinella sp., Nezzazatinella sp., Goupillaudina shirazensis, G.sp.,Therefore stratigraphic limits are changed in different stratigraphic sections, but the age of Tarbur Formation is between Campanian to early Paleocene.

The upper Jurassic to lower Cretaceous volcano-sedimentary rocks of Deh-Sard is located in southern part of Sanandaj- Sirjan zone in southern Kerman. It consists of intermittent lava flows (mainly basalt, basaltic-andesite and trachy-basaltic-andesite), pyroclastics (various types of tuffs and bereccias) and sedimentary rocks (limestones and shales).The Deh-Sard basalts composed essentially of plagioclase and clinopyroxene microphenocrysts, set in a matrix of same mineralogy along with opaque and apatite as accessory minerals. The existence of disequilibrium textures in Deh-Sard basalts reveal the rapid changes in the pressure of rising magma.The pyroclastic rocks mainly of crystal litic tuffs, are less common and consists of plagioclases, basaltic-andesites and trachy-basalt-andesites. Lihtologicaly the sedimentary rocks belong to a shallow marine environment. The Deh-sard basalts shows an enrichment in low ionic potential elements (eg., K, Rb, Sr, Ba, Th) and moderate abundances in high ionic potential elements (eg., Nb, Ce, P, Y, Cr) relative to N-type MORB. Based on geochemical data, trace and REE element diagrams the Deh-Sard basalts have characteristics of transitional tholeiitic basalt.The geochemical patterns of the Deh-Sard basalt, normalized to MORB and chonderite, define a pattern more akin to that of basalt from subduction zone in an active continental margin and also to within plate basalt. However creation of a rift type environment in a transitional continental- oceanic crust “off-axis” from the spreading center for the formation of Deh Sard basalt can be also contemplated.In such an “off-axis” environment magmas do not show chemical characteristics of magmas delivered to the axial system, but resemble to those in seamount-type volcanism.

Gandy and Abolhassani epithermal precious-and base-metal deposits occur in the Tertiary calc-alkaline volcanic belt of northeast Iran. The exposed rock units consist of a volcaniclastic sequence of thin-bedded siltstones and sandstones, lapilli tuffs, volcanic breccias and intermediate lava flows at Gandy, and mostly andesitic flows at Abolhassani.Mineralization in Gandy occurs as veins and breccias and can be divided into three main stages. Stage I is economically important in terms of precious metal content. Stage II consists of four substages and contains the majority of base-metal mineralization. The final stage is dominated by quartz and calcite. Mineralization of the Abolhassani veins occurred in three main stages. The first two stages contain similar mineral assemblages, including quartz, calcite, galena, sphalerite, pyrite and chalcopyrite, which are economically important in terms of base-metal content, whereas the final stage is dominated by quartz and calcite.The average homogenization temperatures and salinities of fluid inclusion assemblages from Gandy range from 234o to 285 oC, and 4.2 to 5.4 wt% NaCl equiv. The homogenization temperatures are in a good agreement with isotopic temperatures from two sphalerite and galena pairs (236o and 245oC). The average temperature and salinity of fluid inclusion assemblages from Abolhassani district range from 234o to 340 oC, and 6.7 to 18.7 wt% NaCl equiv. Sulfide pairs of sphalerite-galena do not give reasonable equilibration fractionation temperatures at Abolhassani. Comparison of Th versus freezing (Tm1) values for the two deposits indicates the presence of a moderate salinity fluid (5-6 wt% NaCl) of similar temperature (250 oC) in each deposit, but with a higher salinity component also present at Abolhassani. The Abolhassani district shows higher average Ag/Au (34.7) and Pb + Zn contents (up to 7.6 wt%) than Gandy (Ag/Au 2.1 and 3.9 wt%), consistent with the nearly 4x higher maximum salinity at Abolhassani compared to Gandy.Precious and base-metal mineralization within hydrothermal breccias of Gandy may have deposited under boiling conditions, whereas base-metal mineralization in stage II most likely occurred due to dilution. Based on mixing trends, base-metal sulfides in Abolhassani veins were deposited during periodic injection and dilution of brines. The minimum depth of formation was at least 430 m and 600 m below the paleowater table for Gandy and Abolhassani, respectively.

The Niaz section is located in 22 Km East of Tabas. The thickness of Shishtu Formation is about 14 meters and its lithology consists of coraly biostrome, nodular limestone and marly limestone with abundant fossils (especially brachiopods).Brachiopods of the section were collected and twenty species identified as follows: Schizophoria striatula, Aulacella cf. eifeliensis, Gypidula sp., Coeloterorhynchus tabasensis, Spinatrypina bodini, Spinatrypina chitralensis, Spinatrypina cf. robusta, Desquamatia sp., Athyris chitralensis, Athyris cf. concentrica, Athyris sp., Anathyris sp.,Crurithyris cf. inflata, Cyrtospirifer sp., Cyrtospirifer cf. minor, Indospirifer sp., Warrenella sp., Caucasiproductus sardarensis, Productella e. g. belanskii, Spinulicosta sp.,In addition, conodont specimens were collected from brachioped – bearing beds. Ident lified conodonts are as follows:Palmatolepis winchelli, Palmatolepis sp, Palmatolepis sp, Ancyrodella curvata, Ancyrodella nodosa, Icriodus alternatus alternatus, Icriodus expansus, Polygnathus webbi, Polygnathus capolloci, Polygnathus evidence. As a result, the accurate age for Shishtu Formation (member 1) based on the its brachiopods and conodonts can be proposed as Late Frasnian (linguiformis Zone).