Iranian Journal of Crystallography and Mineralogy
Year:2009 | Volume:17 | Issue:2|Papers Count:17

This study mostly investigated the environmental impact of acid mine drainage (AMD) on the tailing of coal cleaning factory in Mazandaran province. This factory is one of the largest and the oldest in the coal concentration in Central Alborze Coal Basin. So, annually huge amounts of coal tailing will be left. The sampling of coal, coal tailing, drainage water from coal tailing, factory's waste water, secondary surface minerals and river water have been carried out in summer in 2005. On the basis of geochemistry and mineralogy results indicate that the amount of Fe2O3, SO3 and heavy metal have decreased strongly in coal tailing of Zirab coal cleaning factory compare to homogenate coals. This is an indication of oxidation of pyrite and acidic environment formation. This acid reacts with calcite and dolomite and increase the value of pH. The process also decreases the amount of CaO, MgO and MnO in coal tailing. Hydrogeochemical studies demonstrate that drainage and seepaged water from tail dumps are of (Na-Ca-Mg)-SO4 type. In arid seasons, due to evaporation of hydro-sulfates solution, blodite and secondary minerals are formed on the tailing dump surfaces. This drainage water from tailing and Zirab coal cleaning factory into adjacent river has caused the precipitation of hematite, calcite, amorphous iron oxide. Hydrogeochemical modeling proved that hematite goethite and iron hydroxides along with carbonate minerals (cacite, dolomite and aragonite) are forming. According to Gibbs diagram, indicates that lithology is the most important factor in increasing the ionic concentration in drained and seepage water from tailing and river water. The rate of SO4, PO4, Ca, Sr, Sb, and Bi in seepage water from tailing and coal cleaning factory are more than the standard value, which can cause the surfaces and groundwater pollution in this region. By keeping the coal waste material in vicinity of the river, so for prevention of pollution, it is necessary to collect and transform the tailing to a place with a sufficient drainage and treatment systems.

Taftan volcano, is located in about 100 Km South to Southeast of Zahedan, Sistan and Baluchestan province in southeast of Iran. On geological point of view, it is located at the end of Nehbandan-Khash flysch and North Makran structural zones. Field, petrographic and geochemical studies from different samples of rocks show that the volcano mostly composed of andesitic and dacitic rocks. These rocks have no variety in mineralogy and mainly composed of plagioclase, biotite, hornblende and pyroxene minerals. Microanalyses on these minerals show that plagioclases are common minerals with reversal, oscillatory and nonnal zoning and are andesine to labradorite in chemical composition. Plagioclases have 57.2 to 60.2 wt% Silica contents in composition. These mineral shows variation in composition from the core to rim that is correlative with the microscopic evidence and may be resulted by changes in magma composition accompanied with pressure changes during the ascent of magma, magma mixing and variation in water pressure in magma. Structural formulate indicate that amphiboles, micas and pyroxenes minerals are magnesiohornblende, biotite, diopside and hypresthene composition, respectively.

The Kaleybar intrusion with an area of 750km2 is located in the north east Azerbaijan, NW Iran. Based on structural subdivisions of Iran, it is located in the West Alborz-Azerbaijan Zone which is intruded into the Azerbaijan continental crust during Eocene to Oligocene following the Pyrenean Orogeny. It consists of various rock types including nephelinesyenite, syenite, nephelinediorite together with minor diorite and microgranite. The rock forming minerals of the investigated nepheline syenites are plagioclase, orthoclase, nepheline, biotite and amphibole. Clinopyroxene, plagioclase, amphibole and nepheline are dominant minerals in nepheline diorite. Titanian garnet is uncommon accessory phase of the both rock types. Chemically, garnet from the nepheline syenite has TiO2 contents ranging from 1wt% to 5.0 wt%. Its compositions consistent with Ti-Adr67 to 78 mole% Grs 21 to 33 mole%. Ti-garnet from the nepheline syenite is euhedral to subhedral with reddish to deep brown colours which is different from light brown anhedral and fine grain garnet from the nepheline diorite. Magmatic origin of the Ti-garnet from nepheline syenite is suggested on the basis of petrographic studies, mineralogical criteria and chemical properties whereas the secondary garnet in the nepheline diorite seems to originate from metasomatic source.

The Tertiary volcanic rocks in the north and west of Birjand are dacite, andesite, basaltic andesite, trachyandesite and rhyolite. They belong to calc- alkaline from magmatic series. Mineralogcal, petrographcal and geochemical evidence show that they have formed in active continental margins. Most andesites and dacites are appeared as volcanic domes or subvolcanic dykes that injected older unit’s contianing Late Cretaceous ophiolite melange and Late Cretaceous and Paleocene flysch. One of the most important characteristic of these rocks is the presence of enclaves with various compositions. These enclaves are xenolithic types including pelitic hornfels, amphibolitic, tonalitic gneiss and auto lithic types with andesite (diorite) or dacite (tonalite) compositions. The xenoliths are fragments of older flysch and ophiolite melange units that fall to ascending magma and at least bearing two type metamorphism. The first type of metamorphism is dynamothennal that can be related to emplacement of ophiolite upon continental crust. Along with this metamorphism, flysch units change to slate, phyllite and micaschist; basic units change to amphibolite and acidic unit change to granitic geniss. Second type is contact metamorphism resulting from temperature of lava that caused these enclaves metamorphosed to medium or high grade.

The variety of lithologies from Late Precambrian to Quaternary and suitable conditions for mineralization caused formation of Zarshuran gold and arsenic deposit in black schists, shale, limestone and dolomite. The ore paragenesis include As, Sb, Fe, Pb, Zn, Hg sulfides and gold along with fluorite, barite and quartz. The most important alteration is silicification which is more obvious in the ore zone and formed jasperoid. The gold in this deposit is found as very fine grains and is rarely visible. The rare Getchellite occurred in arsenic ore zone of Zarshuran as a red mineral with (001) cleavage. Paragenetically, this mineral is intermediate between As and Sb sulfides. Getchellite found in some epithermal gold deposits,can be used as a gold tracer.

Deylaman area lies on Paleogene volcanic rocks in Western Alborz near the border between Central and Western Alborz structural zones. The succession of Paleogene rocks in the area is comprised of three separate phases each of which representing one stage of volcanic events. The main purpose of this paper is to study the lithologic sequence and geochemical characteristics of phase two volcanic rocks with Oligocene age (?). Rocks from the second phase are made of three separate parts (subunits) which by the order of age from the oldest to the youngest are; subunit one: basalts and basaltic andesite lavas, subunit two: coarse and fine grained tuffs and volcanic breccia, subunit three: andesitic tuffs with andesitic lenses. Geochemical studies on majbr and trace elements of lavas show that these rocks have calc-alkaline characteristic of volcanic arcs. Meanwhile, there are some similarities between REE patterns, for example LREE are more enriched, HREE have flat patterns as well as Eu negative anomalies. Therefore, the magmas of these rocks fonned from a garnet-free but feldspar-bearing source. Immobile trace element data such as Cr and Th confirm their volcanic arc origin.

The Javaherdasht Basalts show compositional range from olivine basalts to quartz basaltic andesites. Petrographic studies indicate that the differentiation of clinopyroxene and olivine minerals has main role for lithologic variety of the basalts. The corosion golf, crenated margins and lack of the same colour in the clinopyroxene phenochrysts margins with matrix Pyroxene grains express a nonequilibrium and are petrographic features for crustal contamination of the basalts. The positive correlation CaO, CaO/Al2O3 and Cr with Mg# and CaO/Al2O3 with Sc and the negative correlation Al2O3 with Mg# are geochemical characters for the differentiation of clinopyroxene and olivine in the magmatic evolution of the area. The high ratios of Ba/Zr and Pb/Nd and low ratio of Ce/Pb and positive correlation of SiO2 and Rb with 87Sr/86Sr and negative correlation of Nd-Sr isotopes display the contamination of these basalts with continental crust.

On the basis of geothermobarometric calculations, amphiboles in volcanic and subvolcanic rocks belong to Upper Jurassic volcanism of Sanandaj-sirjan zone in north of Shahrekord. Using Hamarstrom, Schmidt, Johnson - Rutherford and Hollister methods, amphiboles have crystallized about 635 to 715oc and 2.68 to 7.5 kbar at the depth about 17 to 25km. The result of calculations has moderate accuracy. The lower FET/ (Fet+Mg) ratio in amphiboles is characteristic of calc-alkaline magma suites. Calculated temperatures, pressures and depths for amphiboles is coincide with a subduction tectonical environment. The maximum depth of crystallization of amphiboles is 25km and subduction angle is lower than 45 km on the basis of 35 km distance between this volcanic belt and main Zagros fault. Aliv measures of amphiboles are higher than 1.5 that indicates an island arc suite. The presence of this old island arc had predicted in Zagros orogenic belt.

The results of microprobe analysis indicate four different kinds of amphiboles inAstaneh pluton and its subvolcanic rocks in the Sanandaj-Sirjan zone. The composition of these amphiboles in this area are magnesio hornblende in tonalite and quartz dioritic enclaves, actinolite in granodiorite and monzogranite, pargasite in dacititc enclaves and anthophillite in one tonalitic sample formed by replacement of orthopyroxene at the rim. All of the amphiboles crystallized at high fO2 which imply I-type nature. Application of different barometers and thermometers show that pargasite in dacitic enclave formed at higher pressure and temperature (767°C, 6.6 Kbar) than the magnesio hornblende in quartz dioritic enclave (734°C, 2.8 Kbar) and magnesio hornblende in tonalites (708°C, 1.4 Kbar).

The Khezr-Abad area is located in southwest of Yazd in central Iran at the intersection with the Central Iranian Volcano-Plutonic Belt (Urumieh-Dokhtar Belt). The Darreh-Zerreshk and Ali-Abad porphyry copper deposits are the most important deposits in this district. These deposits are associated with Oligocene-Miocene (18-28 Ma) granitoid intrusions which consisted mainly of quartzmonzonite, quartzdiorite, granodiorite and granite. The aim of this study is to determine the age, thermal history and timing of uplift in the Cu porphyry bearing-granitoid rocks, using Apatite Fission Track (AFT) thermochronology. The result of this investigation shows that mineralized intrusions were formed in a short period approximately 1Ma. Timing of uplift and cooling in all samples are all the same (about 21.5-22.6 Ma; Middle to Upper Miocene).

Zircon is a tetragonal crystal and records different episode(s) of geology in external morphology and internal textures. Factors affecting the shape of the zircon crystals are the composition, possibly the temperature of the crystallization and water content in magma. The zircon typology of the Ghaleh-Dezh granite mostly introduces the fields P5 in classification of Pup in (1990), therefore, show mantle source for the granite. The dominant morphology of the zircon grains reveals a strong dominance of {100} prisms and {101} pyramids over {110} prisms and {211} pyramids. The dominant morphology shows high alkalinity, the temperature of crystallization about 850°C and dry alkalic nature for the granite. Absent of hydrozircon overgrowth indicate dry magma. Also, the Zr saturation temperature based on zircon solubility reflects a mean temperature of 835°C. All of information is corresponded by petrography and geochemical evidences and also with a-type granitic magma that has mantle and crust sources.

Kamar Tallar mineralization zone in Gazik area is engulfed within ophiolitic melange in Sistan suture zone in east of Iran. The Mn-bearing ore bodies of Kamar Tallar are occurred as discontinuouspatches intimately associated with cherts and meta-spilites. Field evidences and study of trenches show that the Mn- bearing patches are principally superficial and laterally limited. Braunite, Bixbyite and Pyrolusite are the major Mn minerals and silica is the main gangue mineral. Mn- bearing minerals mainly occur as veins, veinlets, and podifonn, indicating later remobilization of Mn during operation of hydrothennal fluids, three types of Mn mineralization are recognized in KamarTallar, 1) syngenetic, 2) diagenetic and 3) epigenetic. Mn mineralization occurred in a sedimentary environment as sea floor exhalative process.