Geodynamic Development of Eurasian Active Margin during Closing of Thetys Ocean, Depending on the Scale of Mantle-Crustal Sources Influence at Pre- and Post-collision Settings, Controlled by Geological and Geochemical Indicators

Phanerozoic geodynamic evolution development of Tethys Ocean,its collision and closing,revealed at the Eurasian active margin in pre-and post-collision stages during convergence of Afro-Arabian and Eurasian continents.Subduction of oceanic slab under continental margin revealed in steady state subduction and steepening of subducting slab provoked the incursion of mantle diapir.The steady state subduction is related with island arc setting whereas steepening provoked incursion of mantle diaper interarc-backarc and minor ocean settings.They are controlled by geological indicators—volcagenic,petrochemical,geochemical,tectonic and metallogenic.Each of them is determined by scale of mantle-crustal influence,controlled by intensity and level of mantle diapir incursion in the crust rising from interarc-backarc to minor oceanic setting.The island arc setting is characterized by blocking,which as others by extension of rifting(interarc-backarc)caused spreading out from zone of volcanic activity and mineralization sialic crusts,whereas minor ocean setting caused by spreading out from zone of volcanic activity and mineralization sialic and basaltic crusts.So mantle crustal influence rising from island arc to minor ocean settings controlled type of volcanism and mineralization in pre-collision development.At the closing of ocean occurred the precollision setting which is transferred in post-collision revealed in orogenesis.It is divided in two stages.The first initial stage occurred in penetration hot fluids from the mantle in sialic crust smelted from in granitoid melt and leached the gold and trace melts Sb,W,Mg and Hg from sialic crust.The latter are geochemical indicators of post-collision setting.The second final stage revealed in shoshonite-basalt volcanism activity occurred with penetrated mantle material into deep volcanic chambers and characterized with increasing of mantle influence than initial stage of post-collision activity.

Crustal and Mantle Sources at Various Settings of Phanerozoic Geodynamic Development Expressed in Volcanism and Metallogeny of Eurasian Active Margin

Phanerozoic geodynamic development of the Tethys ocean revealed at Eurasian active margin is manifested in pre-and post-collision stages.The Phanerozoic crust was already divided into sialic and basaltic crusts and rigid upper mantle.The precious and nonferrous metals were redistributed between them.In the sialic crust,precious metals are concentrated: Au,Ag and Pb,in basaltic crust—zinc,the copper mainly rests in the mantle.Phanerozoic plate-tectonics was manifested in the following settings: island arc,inter/backarc and oceanic.Island arc setting correlates with steady-state subduction and controlled by calc-alkaline volcanism.At this stage,the sialic,basaltic crust and mantle material participate in volcanism,whereas the subducted slab plunged in mantle,the metallogenic indicators are Au,Pb,Zn and Cu.The stage of inter/backarc is related to steepening of subducting slab,because mantle diapir incursion provokes the rifting.At the initial stage and at stage of slackening rifting,when the sialic crust is not yet spread out from zone of volcanic activity,mineralization was represented by subalkaline trachydacites,shoshonite and alkali basaltic volcanism(volcanological indicators)and Au and Pb are participated with Zn and Cu in mineralization.The strengthening of steepening with mantle diapir incursion on higher level rifting spread out the sialic crust,volcanism on this stage is tholeiitic and mineralization is represented by zinc-copper-pyrite VMS(Volcanogenic Massive Sulphide)ores.The minor ocean setting is controlled by the most intensive spreading provoked by incursion mantle diapir at highest level,and spread out the basaltic crust as well,and volcanism belongs to ophiolites with dunite-peridotite magmatic activity.The mineralization was represented by copper-pyrite ores and single metallogenic indicator is the copper.The convergence of Eurasian and Afro-Arabian continents and closing of Tethys Ocean resulted in transferring the pre-collision stage in post-collision,characterized by trace elements Sb,W,Mo,Hg,as geochemical and metallogenic indicator of the postcollision setting.

Relation of Tethys Ocean Subduction, Collision and Closure with Regional Metamorphism, Volcanism and Mineralization Exemplified on the Eurasian Active Margin

The geodynamic development of Eurasian active margin is related to subduction,collision and closure of Tethys Ocean.It is divided on pre-collision and post-collision stages.The pre-collision development controlled by subduction,whereas post-collision related by orogenesis,granodiorite magmatism gold base and trace metals(Sb,W,Mo and Hg)metallogeny.The mentioned trace metals association is the geochemical indicator of first stage of post-collision development.The second stage revealed in andesite basalt,shoshonite,olivine basalt and tholeiite volcanic activity.Pre-collision stage is controlled by steady state subduction related with metamorphism and calc-alkaline volcanic activity in subaqual and island conditions of island arc setting.It is lately with steepening of subducting slab and incursion of mantle diapir transferred in interarc-backarc and minor ocean setting with shoshonite-trachyandesite and alkali olivine basalt and tholeiite volcanism and later with ophiolite volcanism,dunite-peridotite magmatism and Cu-pyrite mineralization of minor ocean setting.The pre-collision stage is developed temporally and spacially along dipping of subducted slab in the island arc setting transferring in the backarc-interarc and minor ocean settings.The similar transferring occurs laterally to dipping of slab and ascending succession.The alternation of settings shown the cycling along dipping spatial and temporal alternation of island arc,backarc and minor ocean settings.Laterally to dipping alternation is only spatial,whereas in ascending succession cycling is only temporal,localized spacially.The pre-collision development occurs in subaqual condition,whereas related to orogenesis post-collision development is mainly subaerial.

Geodynamic Development of Eurasian Active Margin at Pre-collision Subduction and at Post-collision Closing of Tethys Ocean

Geodynamic development of Eurasian Active Margin is related to Phanerozoic collision and closure of Tethys Ocean coincided with northvergent movement and stressing of Afro-Arabian continent at the Eurasian margin.The collision coincided with subduction oceanic Slab under margin of continent at pre-collision stage revealed in formation of island arc,inter-arc backarc and minor ocean settings at pre-collision stage.After closure of ocean the subduction is terminated and pre-collision stage transferred in post-collision and orogenesis,caused by stressing Afro-Arabian continent at the Eurasian.Character of subduction determined the settings of pre-collision stage.The island arc setting is related with steady state subduction,interarc-backarc and minor ocean settings are controlled by steepening of subducting slab which caused invasion of mantle diapir extension and spreading the crust revealed in rifting in interarc-backarc and intensive spreading in minor ocean setting,whereas at island arc setting the mantle invasion and spreading did not occur.So,scale of mantle material participation in various settings determined character of volcanism and tectonics.The island arcs are characterized by calc-alkaline rhyo-dacite-andesite-basalt volcanism blocking tectonics,revealed in island uplifting and gold-base metal mineralization.The interarc-backarc settings revealed in tholeiite-olivine basaltic volcanism,rifting and Zn-Cu mineralization the minor ocean setting controlled by ophiolite volcanism ultimatic dunite-peridotite-magmatism and the most intensive spreading of lithosphere and copper-pyrite mineralization confirmed by volcano-petrogenic,metallogenic and tectonic indications and geochemical cryteria.Therefore,type of volcanism,magmatism and mineralization at precollision development are controlled by scale and influence of crustal-mantle participation.The post-collision stage of geodynamic development also is characterized by various scales of crustal mantle influence.Our studied region consists of pre-and post-collision stages,located in Iran,Caucasus,Turkey and Balcan-Carpathian is parth of the Eurasian active margin.At post-collision,as at pre-collision stages the volcanic-magmatic activity,tectonics and mineralization are depended on the crustial-mantle scale of influence and are controlled by volcano-petrogenic,metallogenic,as well as,tectonical and geochemical indicators.