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  Economic Geology
The history of economic geology of Iran
Author : Mansour ghorbani
Publisher date : July 2002
Chapter title : Chapter 4 -States, belts, and mining and Metallogenic areas in Iran
Data title : 4-10-1 geology of chrome-bearing Esfandaqe Area

Esfandaqe rock collections area, ophiolitic series of rows that make up the lithology is as follows:
1 - the lowest stone Ultramafic region consists of dunite and harzburgite is such that alternate with a particular rhythm is repeated. In some places, and whose upper part is seen in this series. The main characteristics of this horizon, there strips and lenses are discontinuous chromite in the form of different layers, tapes, compact lens with different textures, leopard skin, grain, etc., can be seen scattered. Stone Mountain Ultramafic Red Mosque south of and mountains are represented this horizon.

 

2 - In many regions, Esfandaqe is previous gradually Ultramafic row of stones which turns alternately characterized dunite, Harzouburgite, lherzolite. Obvious characteristics of the rocks that line its main means of black pyroxenite, major relief and dunite and harzburgite yellow, the bezel form. Rocks of this horizon, in which are accumulated rocks, minerals olivine and pyroxene than will change. Construction layer of profile is typical of this row. In dunite layers of chromite horizons up to a thickness of 2 meters is seen mainly with the regular band is making. Badamu horizon in the region is composed of marl will occupy large area. The amount of horizontal area side is much more thickness in the region east of the mountains and plains Shekar Soughan to find. The minimum thickness is in the mining area to Badamu that gradually goes away. In some cases, these rows Pyroxenite and olivine, with order and layering to determine significance and becomes a Pyroxenite horizon where pyroxene and olivine and plagioclase and Kim to repeats are different than, Repeat layers, but, is not tangible. On the horizon of the earth, it can be called only Pyroxenite. This situation Ultramafic diligent in mass (near the village Razdar) is well evident.


3 - Row Bali dunite and harzburgite that is on the horizon. The thick line, with periodic of dunite and harzburgite and is determined slightly Lherzolith. Several horizons of massive chromite and in some scenarios laid out in this row is formed. Chromite horizons can be seen only in dunite.


Layering in this series was very subtle changes of dunite to harzburgite are very gradual. The row, so that coherent and homogeneous erosion of parts of it to rubble and dust in the steep mountainsides, have created a special prospect, in a sense, the difference of the lower harzburgite with dunite, erosion of the rule of reason and hills collapsed and the relatively flat or bezel comprises is determined. Dunite and harzburgite of the horizon in the upper part of the Duet periodic gradually, and becomes Pyroxenite Harbvrzhyt and the layers and layers in the relative frequency of different pyroxenite. The status of all ultramafic - mafic Esfandaqe be seen. However Pyroxenite and dunite in the upper part of the row, to determine the horizontal occasional one or two chromite horizon appears, like mining chromite with the tower, Garmasulo Valley. Pyroxenitey the horizon in the region have expanded and the Soghan Pyroxenite a blend of different, clinopyroxene and olivine are has been formed. The industrious masses (near Razdar) of this horizon can be seen clearly.

4 - The row Pyroxenite Balafaslh on top of previous row appears, including gabbros are layered with alternating bright and dark layers are specified. Horizons in the collection without making massive gabbro layer also exists. This type of grain textured gabbro and pegmatitic crystals of pyroxene and and Sanite it about 20 meters of reach. Pyroxenite horizons and low horizons and plagioclase, and the rows can be seen small or big ways. In some cases, starting with row is trocolite. In some cases, the upper part of the rocks appears quartz have been formed. These rocks, in fact, last representative products are magmatic differentiation.
5 - Gabbro on line immediately after it, a row of metamorphic rocks appear to be a substantial part (more than 80 percent) of amphibolite and green schist is formed. These rocks with gabbro Contact carefully investigated and found that no unconformity or discontinuity between the major cognitive detachable stone there. In fact is amphibolite a metamorphosed pillow basalt of which the marine environment on diagenesis and gabbro are formed and the eruption game and are in the same medium and lower parts are in differentiation. Among these is amphibolite, metamorphic rocks of the type having wollastonite and other types of marbles, for tapes with thickness of 5 to 200 meters and is more common.


This marbles with amphibolite Contact region, the kind of skarn formation that sometimes have up to about 60 percent wollastonite. The study of rocks and quartzite layers together so they come back on the basaltic lavas (which are later converted to amphibolite) the amount of silica deposits of limestone and chert layers having layer composed of pure limestone and then on the Silica deposits, marble and skarn formation of wollastonite is significant.
On all the marbles and amphibolite, thick rows of green schist and quartzite, and marbles of different layers are located in the upper part, gradually periodic Micaschist of green schist and quartzite and turns. Azmvard interesting one that has had the metamorphic rocks, Period of metamorphic rocks Ultramafic, gabbro, and amphibolite metamorphic marbles that pass, and the region is exposed. Ultramafic this type dunite rocks, and Pyroxenite Harzburgite gradually together, and then the gabbros in the upper layer are on them, amphibolite and quartzite layer thin films and marbles and skarns, and this is situated situation is repeated several times. Of the outcrop, we can conclude that the Ultramafic magma has eruption and sedimentary environment during the process, differentiation is achieved. Contact near gabbro stones Ultramafic this area, a significant Chromite Horizon has been observed. The ophiolitic complex, the eruption of Ultramafic Magma in oceanic basin in a narrow and limited is made.

Ophiolitic complex in the formation, differentiation processes such as magma (In parts Ultramafic - mafic) magma erupts under water and lava formation, deposition (formation of silica and calcareous sediments) are involved. Determine the exact age of different parts of the ophiolitic complex, very difficult. A brunette Studies (1974) and Houshmandzadeh (1977) has been shown that the marbles in the end section along the ophiolite metamorphic complex, the Paleozoic fossils previously (very possibly Devonian) there. Because the fossils between these sectors and sectors having lower metamorphic rocks discharge any stone ground and cognitive hardness there addition between the lower parts of the metamorphic rocks and igneous rocks of the lower (mafic rocks - Ultramafic) detachable ground there is not structural. Therefore, the possibility could be the distance between the ophiolitic series Silurian Late Late Devonian to have been formed. I should note that in recent years, a brunette (1374), the age of the ophiolite probably Late Precambrian to Paleozoic strong as has previously, but not the age of the collection as a controversial issue was discussed and agreement achieved yet. Metamorphism and deformation in some metamorphic rocks can be seen, the underlying igneous rocks such as gabbro and Ultramafic has also appeared. In all outcrops exist in the region, the intensity changes gradually from green schist to amphibolite is the risen gradually layered gabbros has completely changed (so that in many cases, gabbro amphibolite have become de facto. ) peak intensity is ultarmafic Metamorphic the rocks. In these rocks, all the primary magmatic minerals such as olivine and chromite Pyroxene and even finding and re-crystallized crystals that make up their size sometimes reaches 150 m Sanyt. All forms of folding (folds with axes lying east - west) changes can be seen in the same manner and Ultramafic mafic rocks and chromite deposits occur. Layers, lenses and bands of Chromite this region, the transformation and deformation (folding) in the upper rocks can be seen, possess. In many cases, Yazd, in chromite, the cuttings had been asleep and frequent manner and for the general folding area and follow the same cases, chromite is found and re-crystallization of chromite grain and dispersed state, as chromite Patyar of the crystals have become very large. The transformation and deformation to the orogenic phase Hercynian attribute that is finished before the Permian (a brunette, 1980; Houshmandzadeh, 1977).


Ophiolitic rocks of the region, thus pre-Permian are folded, again under the influence of Late Triassic tectonic forces have been broken. Place in fractures, new crevasse is made clear that the samples, the color combination crevasse zone area mine workers. The base rock crevasse, the same Ultramafic of mafic and is the first time on the crevasse area, basaltic pillow lavas have been formed. Along with the lava, the thickness of large rocks and pillow lavas as frequent horizon formed along the lava and in their immediate proximity, silica deposits (radiolarites) and the red rocks and limestone consists of pelagic (e.g. Globotruncana lime).

 Rows in all these rocks during the second high-Triassic to Cretaceous is above the crevasse is formed.
After the Late Cretaceous, orogenic movements caused the closing and folding is the crevasse and the row of stones has changed. During the same movements of the pieces of Ultramafic - mafic old bed manufacturer is the crevasse, the structural among injecting them into blocks and some among them have been driven from each side of the fault is limited and Since the masses during this Ultramafic movements, have been serpentinized, Abs have been heavily de sediments second R. messy and in some cases be with serpentinite and blend the mixture is formed which is called Rainbow which fracture originally caused by crevasse splay color combination are moving again after the Late Cretaceous, and at very cause and making changes, and Magnesite section veins formed by giant said. Movements of these faults, causing the formation of a complex network of minor faults the first order, second and third are each as large as half the tape to 200 meters have been serpentinized.


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