Writers : Akrami, Mohammad Ali; supervisor:M. Valizadeh
Refference : M.Sc.Thesis _ Tehran university, Tehran
Publishing Year : 1373

Abstract :

Torbat - e - Jam granitoid is located in Binalood structural zone with trending
NW - SE. It is 25 Km northeast from Torbat - e - Jam and its approimate area 6C Km2.
Host rocks include coal bearing shales , siltstones and sandstones which have been metamorphosed in the initial stages of green schist fades. These rocks have suffered two phases of ragional metamorphism. The rock unites are informally named miankuhy Fm. (from Aghdarband group) and infact are SE - extension of Mashhad metamorphic complex, which extend through border line to Afghanistan. Ruttner believe that it is corrolated with Nayband FM. of central Iran and dated as Norian age.
Torbat - e - Jam granitoid and host metamorphic rocks unconformably is over-
lain by basal conglomerate of Kashafrud FM. (Bajocian age). Therefore age of Torbat_ e _ Jam granitoid is post upper Triassic (Norian) and pre Bajocian (a bout 200 M.Y.).
Radiometric age by K - Ar method showes 153 ! 5 M.Y. . But this method is unsuitable for granular rocks(e.g. granite).
Aureole contact metamorphism is shown by occurrence of narrow zone ol hornfels. This contact metamorphism is in albite - epidote hornfels facies and in some places (east of granitoid) with appearnce of cordierite mineral enters into hornblende hornfels fades.
There is wide exposure of paleogene volcanic rocks (andesite and basalt) and Neogen red beds.
�In petrological and geochemical studies in addition to modal analysis used 25 spectrometric analysis (only major elements). Based on above studies , these rocks are recognised as follow: diorite, quartz diorite, quartz md'zodiorite, quartz monzonit with graditional contact) , granodiorite and granite (with graditional contcat) , which are calc_ alkaline to sub alkaline and metalumineous.
The enclaves that are observed in Torbat_ e _ Jam granitoid include pyroxenite, gabbro, hornfels and micro quartz diorite.
Common rock forming minerals are quartz , alkali feldspar , plagioclase biotite, hornblende, allanite, sphene, apatite, zircon and Fe_ oxides , which have been more or less affected by alteration processes . It is noted that muscovite aluminosilicates and surmicaceous enclave are absent in Torbat - e - Jam granitoid. The gold mineralization index in quartz diorites is reported by Williams and Taghizadeh(1965) ,and the presence of Fe - oxide, C02,Si02 solutions in.majoi fault zones can he seen.
Investigations of magmatic origin and tectonic setting show that Torbat - e
Jam granitoid is I - type and continental arc granitoid (CAG) which have beer intruded in late orogenic stage. It is related to subduction of paleo - Tethys II (Indosinid) plate under Turan plate and in effect to activity of Indosinid phasc which is contemporaneous with Early Cimmerian.
Additionally in the number of diagrai!is many samples of Mashhad granites ar ploted to compare with Torbat - e - Jam granitoid.

Subject List : granitoide