جستجوی مقالات مرتبط با کلیدواژه « برندق » در نشریات گروه « زمین شناسی »

Barandagh quadrangle (1:50000), a part of Tarom-Hashtjin polymetallic district, is located in NE of Zanjan and SE of Ardabil. The results of preliminary regional geochemical explorations have led to the discovery of anomalous areas for a variety of elements. The anomalies were verified by studies on heavy minerals in stream sediments and mineralized and altered samples taken from the surface outcrops. The identified heavy minerals are hematite, goethite, pyrite, barite, ilmenite, native copper, native zinc, native lead, malachite, molybdenite, micaceous hematite, limonite, cerussite, galena, smithsonite, marcasite, chrysocolla, rutile, zircon, pyroxene, amphibole, and apatite. The identified heavy metallic minerals are principally affiliated with zones of widespread alterations and dispersed veinlet-type mineralization. Chemical analysis of some litho-geochemical samples from the anomalous areas shows noticeable assays for elements such as Ba, Zn, Cu, Sr, Mo, and Be. The majority of anomalous areas are intimately associated with alteration zones in the region. Based on field evidence and mineralogical studies, the alterations are categorized into two discrete types, (1) acid-sulfate alterations (e.g., silisified, alunitized, advanced argillic, phyllic, and propylitic) which are related to shear zones and (2) alterations developed in neutral pH conditions (e.g., argillic, calc-silicate-bearing, and zeolitized) cropped out along the margin of Ghezel-Ozan river. Combination of the overall obtained data from chemical analyses, study of the heavy minerals, petrography of mineralized and altered samples, and field relations led to identification of ten anomalous spots that some, in south and along the margin of the Ghezel-Ozan River, have more potential for ore deposits. The comparison of final anomaly map with the map of fault density depicts that there exists a good correlation between them that may indicate that the fault and shear zones have played a crucial role in creation of these anomalies. Finally the overall results obtained from geochemical investigations in Barandagh show that the identified anomalies belong chiefly to elements such as Sn, Sb, As, Ag, W, Au, Bi, and Pb that can be used as tracer for exploration of epithermal gold and silver and of polymetal (Au, Ag, Cu, Pb, Zn) deposits.

Barandagh quadrangle is located in northeast of Zandjan, and is a part of polymetallic region of Tarem-Zandjan. Field evidence and microscopic studies show an intimate relationship between geochemical anomalies and alteration zones in this area. Based on the field observations and mineralogical studis, these zones, in light of extent, locality, and constituent mineral assemblage, differ from one another, and are scattered along the main shear zone of the area and the margin of Ghezel-Ozan river. The major alteration zones in this area are affiliated with the shear zone, and can be categorized into two discrete alteration types: 1) hypogene acid-sulfate (e.g., silicified, alunitized, advanced argillic, sericitic, and propylitic zones) and 2) supergene acid-sulfate (characterized by minerals assemblage such as jarosite, alunite, goethite, gypsum, and native sulfur). Alteration zone along the margin of Ghezel-Ozan river consists of neutral-pH types of alterations (consisting mainly of argillic, calc-silicate-bearing, and zeolitic zones). In general, these alteration zones were developed by the function of a vast geothermal system during the late Oligocene to Mid-Miocene time. Date gathered indicate that the discrepancy in reaction rate between the fluids and the enclosing rocks caused the development of these two types of alterations. Note the type of alteration zones and the obtained results from geochemical exploration, show that this area possesses suitable potential for prospecting of Ag-Au epithermal and polymetallic (Cu, Pb, Zn, Au, Ag) deposits.