جستجوی مقالات مرتبط با کلیدواژه "رودگز" در نشریات گروه "زمین شناسی"

Roudgaz granitoid is located in south of Bajestan. In this granitoid body, tourmaline occurred in two forms, as luxullianite and as veins of quartz-tourmaline with a 30 cm width. Based on petrography and electron microprobe analyses data, these tourmalines are schorl-dravite- foitite in composition, with a tendency toward schorl end member, and belongs to alkali and vacancies groups. In comparison with the ideal composition of schorl- dravite, many of tourmaline samples have high Al contents and alkali – site vacancies. The increase of the amount of octahedral aluminum reflects a combination of substitutions in tourmaline involving deprotonation (O-OH exchange) and vacancies in the alkali-site and therefore they have originated from magmatic source. In contrast, the presence of zoning, its occurrence as vein form, having a high Mg compared to samples with high Fe and tendency away from alkali- deficient and proton-deficient tourmaline vectors, shows that tourmaline in the luxullianite as well as the vein tourmalines are hydrothermal in origin. So, based on the evidence described above, tourmaline veins have formed by interaction of boron on-rich magmatic-hydrothermal fluids of the origin of mass granitoid rocks along with various quartz-tourmaline and metapelitic-metapesamitic host rocks.

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.