سال:1391 | دوره:17 |تعداد مقالات:8

OROGENIC BELTS SUCH AS ZAGROS EVOLVE THROUGH A NUMBER OF STAGES INVOLVING SUBDUCTION, WITH DEVELOPMENT OF OPHIOLITES AND MAGMATIC ARCS, FOLLOWED BY PROCESSES RELATED TO COLLISION AND IN PART DELAMINATION, WHICH RESULT IN THE BUILDUP OF MAGMATIC COMPLEXES. THE STUDY OF THESE EVOLUTIONARY STAGES COMMENCES WITH MAPPING AND BASIC GEOLOGICAL ANALYSES. ON THAT BASIS GEOCHRONOLOGICAL WORK CAN THEN BE EMPLOYED TO ADVANCE OUR KNOWLEDGE. ...

THE UPPER CRETACEOUS ZAGROS OPHIOLITES OF IRAN HOST A SIGNIFICANT NUMBER OF CHROMITITE DEPOSITS AND OCCURRENCES. PLATINUM GROUP ELEMENT (PGE) ANOMALIES HAVE BEEN PREVIOUSLY REPORTED; HOWEVER, THE AVAILABLE DATA ON THE PGE MINERALIZATION ARE SCARCE. LARGE CHROMITITE PODS AND RESIDUAL TO CUMULATE DUNITIC LENSES ARE RESTRICTED TO THE OUTER ZAGROS NEYRIZ AND HAJI–ABAD OPHIOLITES WITH A HARZBURGITE-DOMINANT MANTLE, BECAUSE THEY HAVE UNDERGONE A HIGHER DEGREE OF PARTIAL MELTING THAN OTHERS WITH LHERZOLITE-DOMINANT MANTLE. VERY LITTLE INFORMATION IS AVAILABLE CONCERNING THE DISTRIBUTION AND MINERALOGY OF PGE IN THE ZAGROS OPHIOLITES. ...

THE ZAGROS-BITLIS SUTURE ZONE WAS EMPLACED IN LATE MIOCENE AFTER THE CLOSURE OF LAST BRANCH OF TETHYS OCEAN, AND MARKS THE TRANSITION FROM CONVERGENCE TO COLLISION BETWEEN THE ARABIAN AND EURASIAN PLATES. IN THE NORTHERN PART OF THIS 1800 KM-LONG BELT, SUTURE EMPLACEMENT DATES BACK TO THE UPPER MIOCENE (E.G. HUSING ET AL., 2009). ...

ALMABULAGE COMPLEX IS LOCATED IN NORTHWESTERN PART OF SANANDAJ-SIRJAN ZONE OF ZAGROS OROGEN IN WESTERN IRAN. THIS AREA IS LOCATED 15 KM TO WEST OF HAMADAN, IRAN, IS AN EXAMPLE OF GEOLOGICAL REGION THAT HAS BEEN SIGNIFICANTLY ALTERED BY METASOMATIC MASS-TRANSFER PROCESSES ASSOCIATED WITH REGIONAL METAMORPHISM. ...

SANDNDAJ-SIRJAN ZONE (SSZ) IS A SUBZONE OF THE ZAGROS OROGENIC BELT (ZOB) OF IRAN. ZOB RESULTED FROM THE ARABIAN–IRANIAN MICROPLATE CONTINENTAL COLLISION FOLLOWING THE SUBDUCTION OF THE NEOTETHYS OCEANIC CRUST UNDERNEATH IRAN (E.G. AGARD ET AL. 2011). SSZ MOSTLY CONSISTS OF A BASEMENT MADE OF LOW- TO HIGH-GRADE METASEDIMENTARY ROCKS INTRUDED BY FELSIC TO MAFIC BODIES SHOWING GEOCHEMICAL ARC AFFINITY (E.G. AHMADI KHALAJI ET AL. 2007).

THE SANANDAJ-SIRJAN ZONE (SSZ) IS A MAGMATIC-METAMORPHIC BELT WITH NW-SE TRENDS WHICH EXTENDS OVER 1200 KM LENGTH AND IS LOCATED BETWEEN THE URMIEH- DOKHTAR VOLCANIC BELT TO THE NORTHEAST AND THE TETHYIAN OPHIOLITE ZONE OF ZAGROS IN THE SOUTHWEST. THE SSZ FORMED IN THE LATE CRETACEOUS DUE TO CLOSURE OF THE NEO-TETHYS AND SUBSEQUENT COLLISION OF THE ARABIAN-IRANIAN PLATE. IT IS A MAJOR METALLOGENIC ZONE IN IRAN, CONTAINING LEAD AND ZINC, COPPER, IRON AND GOLD MINERALIZATION. BASED ON ITS METALLOGENIC CHARACTERISTICS, SSZ CAN BE DIVIDED IN THE NORTHERN, CENTRAL AND SOUTHERN SUBDIVISIONS.

THE ZAGROS MOUNTAINS OF IRAN FORMED BY CONTINENTAL COLLISION FROM CLOSURE OF THE NEO-TETHYAN OCEAN. NEW MAPPING, RADIOMETRIC AGES AND STRATIGRAPHIC ANALYSES HAVE ENABLED ADVANCES IN OUR UNDERSTANDING OF THE JURASSIC TO CENOZOIC TECTONIC HISTORY. THE NORTHWESTERN ZAGROS OROGEN CONSISTS OF THREE BELTS: (1) THE ZAGROS FOLD AND THRUST BELT, DIVIDED INTO THE OUTER ZAGROS SIMPLY FOLDED BELT AND THE INNER HIGH ZAGROS BELT, (2) THE ZAGROS SUTURE ZONE INCLUDING RADIOLARITE, OPHIOLITE AND BISOTUN LIMESTONE THRUST SHEETS, AND (3) THE SANANDAJ–SIRJAN ZONE, WHICH CONTAINS ABUNDANT METAMORPHIC ROCKS. ...

THE ZAGROS OROGENICBELT IS DIVIDED INTO THE SIMPLY FOLDED BELT (ZSFB), THE FOLD-AND THRUST-BELT, THE ZAGROS THRUST SYSTEM AND THE SANANDAJ-SIRJAN METAMORPHIC BELT. THE ZSFBIS CHARACTERIZED BY THE REPETITION OF LONG AND REGULAR ANTICLINAL AND SYNCLINAL FOLDS. THE ANTICLINES ARE NORMALLY MOUNTAIN RIDGES, MOSTLY CONSIST OF LIMESTONE, AND THE SYNCLINES ARE VALLEYS AND PLAINS. THE KARSTICROCKS ARE COMPOSED OF LIMESTONE, DOLOMITE, ANHYDRITE AND HALITE. ...