This review work explains some of the most important techniques to detect the occurrence of magma mixing phenomena in the volcanic rocks by using SEM （scanning electron microscope）. In particular, the most useful me...This review work explains some of the most important techniques to detect the occurrence of magma mixing phenomena in the volcanic rocks by using SEM （scanning electron microscope）. In particular, the most useful methods related to the different types of mixing are reviewed： complete mixing （blending） or incomplete mixing （mingling）. For blending, backscattered electron images and EDS （energy dispersive spectroscopy） are the most accurate methods： an example taken from a sample of ash of the 2007 Stromboli volcano eruption was used. For mingling, the best method is given by X-ray elemental mapping （in particular of Ca and Si）, as explained through the example taken from a sample of the 2003 explosive eruption of Soufriere Hills volcano. The aim of this work was to establish whereas would be useful to use backscattered eletron images, EDS, or X-ray elemental mapping techniques, according to the different types of mixing that occur very often in magmatic systems.展开更多
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 ri...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.展开更多
文摘This review work explains some of the most important techniques to detect the occurrence of magma mixing phenomena in the volcanic rocks by using SEM （scanning electron microscope）. In particular, the most useful methods related to the different types of mixing are reviewed： complete mixing （blending） or incomplete mixing （mingling）. For blending, backscattered electron images and EDS （energy dispersive spectroscopy） are the most accurate methods： an example taken from a sample of ash of the 2007 Stromboli volcano eruption was used. For mingling, the best method is given by X-ray elemental mapping （in particular of Ca and Si）, as explained through the example taken from a sample of the 2003 explosive eruption of Soufriere Hills volcano. The aim of this work was to establish whereas would be useful to use backscattered eletron images, EDS, or X-ray elemental mapping techniques, according to the different types of mixing that occur very often in magmatic systems.
文摘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.
