DYNAMICS OF TECTONO-VOLCANO-MAGMATIC EVOLUTION FROM NORTH QILIAN MOUNTAINS,CHINA
Xia Linqi;Xia Zuchun and Xu Xueyi(Xi'an Institute of Geology and Mineral Resources,CAGS,Xi'an,710054)
The relation between paleo-plate tectonics and volcanic magmatism in North Qilina Mountains is explored in this paper on the basis of studies of regional volcanic petrology in view of dynamics of regional tectonics-volcnao-magmatic evolution.The main emphasis in this text is on the petrogenesis of various volcanic rocks,the origins of which can be related directly to their tectonic setting.It has been established by author's studies that from the end of Proterozoic era to Devonian period the North Qilina Mountains underwente complete total process:from continental rift→oceanization→spreading and subduction of ocean basin→formation and development of trench-arc-basin system→closing of ocean basin→collision orogenesis and in each stage there occurred respectively specific marine volcanism. On the basis of tectonic setting we can define five distinct environments in which volcanic magmas may be generated:1.Late Proterozoic-Cambrian continental rift volcanism,2.Late Cambrian-Early Ordovician mid-ocean ridge and ocean island volcanism,3. Ordovician island arc volcanism,4.Middle-Late Ordovician back-arc basin vocanism,5.Late Ordovician-Silurian volcanism during closing of ocean basin.Author's studies reveal that there is clearly a close correlation between the processes of volcanic magma generation in tensional tectonic settings and the formation of sea-floor massive sulfide deposits.Hot brine,which circulates through the sea-floor,plays a fundamental role in the formation of this type of ore deposits.The circulation is driven by the localized high heat fluxes and sea-floor volcanic activity associated with extension tectonic settings.
【CateGory Index】： P548.2