جستجوی مقالات مرتبط با کلیدواژه "کانی سازی رگه ای" در نشریات گروه "زمین شناسی"

The host rock in Chumalu area includes the Eocene volcanic rocks and the Oligocene monzonite intrusive mass that have undergone propylitic-carbonate, silica, and silica-argillic hydrothermal alterations. The hydrothermal activities resulting from the injection of intrusive mass have produced two types of mineralization in the region: the first mineralization type is a silica-shear zone having N70E trend, and the second type is in the form of a bunch of veins with an approximate trend of northwest to southeast, located in the north of the first mineralization type. The mineralization is of the form of vein, veinlet, massive, scattered and replaced, and follows the trend of the faults. The ore contains lead, zinc and fluorine, along with copper, gold and silver, which are formed of chalcopyrite, pyrite, galena, sphalerite, cerussite, calcite and fluorite minerals. Based on the results of the geological studies conducted in this study, the mineralization characteristics of Chumalu area are of the type of lead and zinc hydrothermal deposits. Induced polarization (IP) and resistivity data acquisition were first designed and carried out using rectangular array to determine the anomalous zones, and then, using dipole- dipole array to determine the lateral and depth limits of these anomalies. Then, modeling of IP and resistivity data was done using smooth inversion method. For better representation of the results, all two-dimensional (2D) sections were combined and as a result, a three-dimensional (3D) model was presented. Consequently, an anomaly with an approximate east-west orientation in the south of the area has been extended on the silica-shear zone, and some anomalies with an approximate north-south orientation in the north of the area, in relation to the fractures of the basaltic deposits, which can be linked with metallic mineralization in the area. Anomalous areas with high chargeability and medium to low resistivity values have been determined. High chargeability values for some anomalies in the north of the area are probably due to the presence of scattered pyrites in depth. Finally, 6 points were proposed for drilling.

Application of IP and resistivity geophysical methods and their integration with geological studies is of great importance in the exploration of sulfide metal deposits. The Chumalu area is located 70 km northwest of Zanjan in the Tarom-Hashtjin metallogenic zone, which has possible potential for metal reserves and mineral resources. The purpose of this research is to collect and process raw IP and resistivity data using the smooth inverse modeling, interpretation of the results based on geological studies and finally determining the anomalous limits, depth and thickness of probable mineral masses in the area and at the end, suitable locations for drilling are suggested.

This research is based on field and laboratory studies. In order to conduct geological studies, alteration, mineralization and determination of the genesis of the mineralization, 8 thin sections and 9 polished sections of surface and subsurface samples from the mineralization ore and host rock were prepared and studied. Moreover, field operations of IP and resistivity data acquisition were first made in the form of 4 networks using rectangular array in order to determine the anomalous limits with a current line of 800 meters long, electrode spacing of 20 meters, and the distance between the lines 50 meters. Then, 6 lines using dipole-dipole array were surveyed in order to explore the lateral and depth limits of these anomalies with electrode spacing of 20 meters. Then, modeling of IP and resistivity data was made by 2D smooth inversion method using RES2DINV and ZondRes2D software packages. Furthermore, all 2D sections were combined using RockWorks software and a 3D model was presented. Ultimately, possible mineralization limits were identified and suitable sites for drilling were proposed.

Based on the geological studies, lead and zinc mineralization in olivine basalt volcanic host rock and part of the monzonitic intrusive mass in Chumalu area occurs during hydrothermal processes and in the form of veins along fault structures. Chumalu mineralization is of hydrothermal lead and zinc type. Based on geophysical and geological studies, anomalies have been introduced that have high chargeability and medium to low resistivity, as probable mineralization. Finally, 6 locations were proposed for drilling.

The SW Sorkh-Kuh area makes part of the Tertiary volcanic-plutonic rocks in the west of the Lut Block, SW of Birjand city. Geology of this area consists of andesitic and basaltic volcanic rocks intruded by hornblende diorite, hornblende microdiorite, hornblende diorite porphyry, hornblende quartz diorite porphyry and biotite quartz monzonite, which caused extensive alteration and mineralization. The vein mineralization with a NW-SE trend have been observed in the NW portion of the area which is composed of quartz, chalcopyrite, pyrite and Fe-Cu secondary minerals. This vein is the youngest occurrence of mineralization, related to intrusive rocks, in the Lut Block (after Miocene). Primary fluid inclusions of quartz in paragnesis with mineralization, revealed three types of two phases inclusions with difference in density, which liquid rich phases have an average 270 and 330°C of homogenization temperature. Based on freezing studies, calculated temperature of last melting point of these fluids equals to 12-15 and 16-19% wt eq. NaCl, respectively. Some fluids, which homogenized to gas, have more homogenization temperature and salinity. In evaluation of depth, using homogenization temperature, salinity, density and pressure of fluid inclusion, 700 m depth was calculated for mineralization, corresponding to the present erosion surface. δ18O values of quartz in mineralized vein and fluid in equilibrium with quartz have a range between .66 – .09‰ and .06 – .59, respectively. It could be inferred that the source of ore-forming fluids was magmatic in the mineralized vein. In general, stable isotope and fluid inclusion studies show similarity of mineralization of the SW Sorkh-Kuh with epithermal deposits in which mineralization is related to the dioritic intrusive rocks. The changes in fluid composition and boiling resulted in mineraliztion along a fault as vein.

The study area is located in the central part of the Khaf- Kashmar- Bardaskan volcano-plotunic belt (briefly KKBB). Several IOCG deposits such as Tanourjeh Au-bearing magnetite deposit and Kuh-e-Zar Specularite-rich Au deposit have been explored in KKBB. Geology, alteration, mineralization, geochemistry and fluid inclusion results in Kashmar suggest the IOCG type Au-bearing magnetite mineralization. These IOCG deposits at KKBB form at an active continental arc related to SSZ-type Sabzevar oceanic subduction.
Use of Landsat 7, IRS and Aster satellites.
Petrography and alteration Studies in 150 thin sections of volcanic and intrusive rocks.
Sampling of ore-bearing quartz vein and mineralography.
Preparation of 28 geochemistry samples by the chip composite method of ore-bearing quartz vein and analyzing them in the ACME laboratory by Aqua Regia 1DX1.
Fluid inclusions studies of 14 samples of quartz and barite related to the ore minerals of ore-bearing quartz vein by THM600 stage of Linkam company.
Magmatic events in Kashmar occur at Paleocene-Eocene and include: (1) old mafic - intermediate volcano-plutonic series; (2) felsic volcanic and granitoids; and (3) parallel swarm dykes which are youngest (Almasi et al., 2016). Geochemically, Kashmar rocks are metaluminous to highly peraluminous and Tholeitic to calc-alkaline and shoshonitic in composition (Almasi et al., 2016). The field characteristics, together with isotope and geochemical analyses show that all rock types are essentially co-magmatic and post-collisional I-type (Almasi et al., 2016). Alteration of Kashmar is described in two ways: (1) intense ellipsoidal-linear Argillic-Sillicification and low sericitic with Silica caps and with medium widespread and propylitic alterations in triple regions, next to Dorouneh fault; and (2) Medium Hematite-Carbonate-Chlorite-Silicification alterations in Kamarmard heights. In parts of near the Doruneh fault, sometimes fractures of rocks are filled with tourmaline (Dumortierite type) and iron oxides.
Kashmar surface mineralization is described in the ore-bearing quartz veins. Principal mineralization textures are layered, comb and Brecciation. The most important types of veins are those containing Chalcopyrite - Quartz veins, Specularite-rich veins – Quartz-Galena veins accompany with hydrothermal Breccias. Barren barite veins also exist in the region. The Chalcopyrite - Quartz veins occur on the main fracture zone and next to the Argillic alterations and silica cap in three regions (Bahariyeh, Uch Palang and Sarsefidal). Hydrothermal Breccias, Spicularite- rich veins, Quartz - Galena and barite veins occurred within Hematite- Carbonate-Chlorite-Silicification alterations in the Kamarmard area. Geochemistry of veins indicates anomalies of gold, copper, lead and zinc in them. Most enrichments of gold are accompanied with copper, lead and zinc and they occurs in hydrothermal Breccias and then specularite- rich veins. Gold values up to about 15 ppm and Cu, Pb and Zn each to > 1%.
Temperature – salinity studies of fluid inclusions of ore-bearing Quartz veins in Kashmar show the fluid temperature and salinity values in all veins are close together. Temperatures are moderate to relatively high and between 245° C and 530 ° C and salinities are relatively low to moderate and between 14 to 18 (wt% NaCl). Maximum and minimum of temperatures and salinities are related to fluid inclusions of hydrothermal Breccias and Quartz-Galena vein. Co-existence between two-phase liquid-vapor rich fluids and single-phase gas fluids in the veins indicate that conditions were close to boiling, and maybe a little boiling occurred, which strengthened with brecciaing of rock and view rare CO2-bearing fluid inclusion in veins on the Kamarmard peak. Non-existence of vuggy Quartz in silica caps in the region shows this issue. The frequency of oxide minerals (Specularite, Barite), H2O-NaCl-CaCl2 system, and the low amounts of sulfide minerals in Kashmar, all represent the oxidized conditions of hydrothermal fluid and the impact of CO2-bearing chloride complex in transport, non-interference of meteoric waters and precipitation of metallic elements with reducing of temperature.
Most important IOCG deposits of south America (Candelaria, Mantoverde and Raul Condstable) have Au-bearing massive magnetite bodies accompanied with Potassium (actinolite, biotite and K-feldspar) alterations with high temperatures (500-700 O C) and salinities (>40%wt NaCl) at deepest parts (Sillitoe, 2003). At the upper levels, there are magnetite changes to hematite (Specular) and the possibility of coarse calcite (± silver mineralisation). Hematite zone may display hydrothermal/tectonic brecciation. The hematite-rich veins tend to contain sericite and/or chlorite, with or without K-feldspar or albite, and to possess alteration haloes characterized by these same minerals. Both the magnetite- and specular hematite-rich IOCG veins contain chalcopyrite and generally subordinate Pyrite (Fuller et al., 1965).

Senjedak II & III prospect areas are part of eastern anomalies of the Sangan mine, which is located in northwest of Khaf. The geology of the area consists of Pre-Cambrian schistes, Jurassic and Lower Cretaceous sedimentary rocks, and tuff and biotite monzonite porphyry intrusion with Eocene age. Skarn types in the Senjedak III include pyroxene–garnet skarn, garnet–pyroxene skarn, garnet skarn, pyroxene skarn, and actinolite skarn. Based on EPMA analysis, the garnets belong to grandite (andradite-grassolar) series, pyroxenes are mainly diopside and amphiboles are Fe-rich actinolite. Two different types of mineralization are presented: 1) pyrite and magnetite in skarn zones at the Senjedak III, and 2) magnetite, specularite, barite, hematite, and goethite in vein–type at the Senjedak II. The strike of the veins are NE-SW. The value of iron (37.5%) and manganese (32057 ppm) in vein-type mineralization are more than skarn, whereas the highest contents of arsenic and copper (158 and 332 ppm, respectively) occurred in skarn zones.The Senjedak III iron skarn is calcic-type. The vein type mineralization of Senjedak II can be related to later activity of hydrothermal fluids, which occurs along fault zones.

Shekaste Sabz area is located in eastern Iran, about 96 km north west of Birjand. Preliminary prospecting in the area using ASTER mineral mapping (SAM) detected propylitic, argillic and sericitic alteration which was confirmed by field observation. The area comprises outcrops of Paleocene to Eocene volcanics, which was intruded by intermediate subvolcanic bodies. The main alterations zones are propylitic, argillic and silicified- carbonate. Mineralization is observed as vein (in central and west of area), veinlet and disseminated (in east and west). Veins show North West - South East to North East - South West trend and dip 85 to 90 degrees. Due to the great influence of weathering processes on the hypogene mineralization, secondary sulphide and oxide minerals spread widely and formed malachite, azurite, chalcocite, covellite, goethite and hematite. Relicts of the hypogene minerals such as pyrite, chalcopyrite and magnetite are also seen. Gangue minerals are quartz, calcite and barite. The maximum amount of copper and zinc distribution in stream sediments are located in the areas that vein mineralization and propylitic, argillic- sericitic and silicified alteration zones exist in their upstream. The range of variation for elements in the lithogeochemistry samples are as follows: Cu from o.6 to 2.4 Percent, Mo from 77 to 2290 ppm, Zn from 23 to 2990 ppm, Pb from 24 to 754 ppm, Ag from 1.4 to 8 ppm. The maximum amount of elements in the lithogeochemistry samples are in places which veinlet and disseminated mineralization are associated with andesite.  These are as follows:  Cu 450 ppm, Zn 162 ppm, Pb 309 ppm, Mo 77 ppm. According to alteration type, Anomalous Cu, Zn, Ag and Mo and relation of mineralization with fractures system, Shekaste Sabz mineralization can be placed in the category of vein- type epithermal deposits.

The Roud Gaz area is located 25 km southeast of Gonabad city، Khorasan Razavi province. During Middle Jurassic، shale and sandstone was regionally metamorphosed to slate، schist and quartzite. The Tertiary subvolcanic rocks are mainly monzodiorite to monzonite. These rocks are mostly altered to: argillic، carbonisation، sericitic and silicification- tourmalinisation. Mineralization in the area is mostly as vein type and controlled by fault zones which are trending NW-SE and 85º to 90º dip. The primary minerals are quartz، tourmaline، chalcopyrite، pyrite and the secondary minerals are malachite، azurite and goethite. Lithogeochemical exploration (chip composite method) revealed Cu، Sn، Pb، As (up to 10000 ppm)، Zn (up to 5527 ppm) and Au (up to 325 ppb) anomalies. The least altered rocks are chemically meta-aluminous and medium-potassium. They were formed in a subduction magmatic arc and are strongly enriched in LREE and depleted in HREE and also LILE (K، Rb، Ba، Sr and Th) enriched rather than HFSE (Ti، Nb and Ta)، all features indicate that the magma formed in subduction zone. The positive Eu anomaly، high Sr (411 to 684 ppm) and high (La/Yb) N ratio (more than 21. 55) in all the samples can be attributed to the presence of residual garnet in mantle source. Based on high Sr/Y ratio (more than 67)، Y<8 ppm، Yb<0. 61 ppm and high (La/Yb) N ratio، the parent magma is adakitic type. The magma formed as the result of medium degree of partial melting (25%) from a garnet-amphibolite source. Apparently، these rocks have been only the veins host and have no effect on mineralization. The mineralization of the area is polymetal vein type and related to reduced intrusions in deeper zone.

Roudgaz prospect area is a Cu، Sn، Pb، Zn، and Au polymetal vein system located to the southeast of Gonabad and in the northeast of Lut block. Oxidan subvolcanic Tertiary rocks with monzonite to monzodiorite porphyry composition intruded the metamorphic rocks of middle Jurassic. The majority of intrusive bodies are affected by carbonation، argillic، sericitic، and silicification-tourmaline alteration. Mineralization in the area is controlled by fault and is present as vein with domination of NW-SE direction and 85-90º dip. Primary minerals are quartz، tourmaline، chalcopyrite، pyrite، and secondary minerals are malachite، azurite، and goethite. Geochemical sampling using chip composite method indicated high anomalies of Cu، Sn، Pb، and As (up to 10000 ppm)، Zn (up to 5527 ppm)، and Au (up to 325 ppb). Broad gossan zone is present in the area and is related to the oxidation of sulfide minerals. IP/RS survey was performed over the geochemical anomalies for identification of the location and extension of sulfide mineralization at depth. Generally، chargeability increases in gossan zones، veins، old workings and geochemical anomalies. Resistivity over the quartzite unit and also in locations where mineralized vein is associated with quartz has a high anomaly of up to 425 ohm-m. Due to high geochemical anomaly of Sn and its relation with reduced subvolcanic intrusives، ground magnetic survey was performed to identify the location of magnetite (oxidant) and ilmenite (reduced) series at depth. Variation of Total Magnetic Intensity (TMI) is 335. 1 Gamma in the TMI map. The highest magnetic anomalies in the RTP map are located to the north of the survey area which is related to magnetite series (hornblende biotite monzodiorite porphyry) and extend to the south at depth. The lowest magnetic anomaly is located to the center of the survey area and particularly to the east of the Roudgaz village correlating the highest chargeability and geochemical anomaly. Based on coincidence of geochemical and chargeability anomalies، two holes were drilled in the area and 24 samples were collected from the core drills for geochemical analyses. The highest anomalies are accompanied by silicification and chlorite alteration and locations of extension of secondary Fe oxides.