Explanatory note of 1:5000 geological and mineral map of Arghash-Cheshmehzard gold deposit, south of Neyshabour
The Arghesh – Cheshmehzard mining area in a 25 Km2 extension was mapped in two geological – mining sheets with scale 1: 5000. It is located in north part of the khorassan province and 45 km south – west of Neyshabour. This area is a part of relief at the NW Kadkan.
Three main Lithological units have been distinguished in this region :
1)Upper Paleocene – Eocene volcanic unit (Ea)
2)Upper Eocene pyroclastic – volcanic unit (Ebt , Etu , Eap , Eta)
3)Granitoidic bodies and apophyses (gr,di,gd)
The first geological unit consist of andesitic , trachyandesitic and rhiodacitic lava flows, less agglomerate and volcanic breccia . In this interval, basin sedimentary has been involved changes so that other lithologies such as limestone (El) conglomerate (Ec), Middle Eocene Volcanosedimentaries (Et) and so basic volcanic rocks (Esp) are contemporaneous and interlayers with this volcanic unit. In fact, this complex has the main outcrop in the region.
The second unit contains of tuff, tuff breccia, sandy tuff and agglomerate and also a large volume of trachyandesitic and megaporphyr – trachyandesitic (lavas) expanded area are observed specially in northern parts.
The third geological unit contains of gabbro – diorite, granodiorite, granite and acid to basic dykes that contemporaneous with closing and uplifting basin in late Eocene – early Oligocene has intruded to above units and outcropped as the disseminated bodies and apophyses in area.
Granitoidic bodies has been caused to serisitization, argillization and propylitization of the rocks in a wide range and also are the source of hydrothermal waters rich of volatile matters and probably mineralization elements that comming up through the fractures and have altered the host rocks and intrusive bodies.
Antimony, copper, silica with or without gold and calcite, are the products of the hydrothermal activity. Additionally, silisification, carbonation, alunitization, argillization, sericitization and propylitization in margin of veins, joints and fractures are the effects of hydrothermal solutions.
In fact, the igneous units of the mining area are the continuation of post cretaceous magmatic belt, particularly it seen in the inside and around of sabsevar ophiolite zone with NW – SE trend. In the area studied main oxides composition of igneous rocks and compaire to Sabzevar – Quchan – Neyshabour volcanic rooks ( O.Spies, G.Lensch, A.Mihm, 1983), representing the calk – alkaline regime for this rock series that can be a andesitic island arc volcanism. This arc is the result of subduction in the edge Touran plate.
The tectonic studies on the regional faults indicate that the major faulting phases are following the trend of Doruneh and Taknar fauits but the main trend for the most of silica, calcite and antimony veins is concordant to minor fractures.
Following the recent explorations in Arghesh – Cheshmehzard mining area, four gold anomalies and one antimony are present as the target.
So in this stage of exploration Gold anomaly Namber 5 , in addition to a few copper indication were reported. Additionally, contemporaneous to 1:5000 geological – mining mapping of the area, exploration activities contains of trench excavation and its profile mapping, with scale 1:2000 and 1:500, technological test sampling from Arghesh antimony anomalies in 5 km SE Arghesh village and gold anomaly number 3 in 500 meters SW abandoned Cheshmehzard village, had accomplished.