摘要
温都尔庙群产于蒙古地槽褶皱带南缘,其本身又可分南带和北带。前者主要分布于集二线朱日和、哈尔哈达、白音诺尔、乌兰敖包一带,后者则分布于集二线以东苏尼特右旗至苏尼特左旗一带。1958年内蒙古区测队首先建群。
1.The Wundurmiao Group belongs to the ophiolite complex composed of metamorphosed tholeiite,ultrabasic rocks,gabbro,diorite,plagioclase granite,spilitic lavas and dikes and siliceous rocks.They show a pseudosequence of strata and are mostly in faulted contact with each other,spanning a long time interval.Its conception is different from that of conventional stratigraphic groups,so it should be known as a complex.2.The siliceous rocks in the upper part of the group contain Ordovician radiolarians.The greenschist in the mid-lower of the group has a Rb-Sr age of 509±40 m.y.and an initialSr/Sr ratio of 0.70434±0.0001,so it belongs to Mid-Late Cambrian deep-marine tholeiite.The K-Ar amphibole age of residual basalt fragments at the base ranges from 540-630 m.y.The emplacement time of ultrabasic rocks is pre-Silurian.The author doubts about Peng Lihong’s report on the presence of hyolithis fossils in siliceous rocks that have been found in the Meishucun Formation at the base of the Cambrian in southern China.3.The author considers that the absence of early Cambrian(550-600 m.y.)strata was due to Crustal compression before subduction.The Benioff zone was formed 550±30 m.y.ago.In the stable subduction stage when Cambrian-Ordovician strata were deposited on the continental crust,oceanic-crustal fragments of the Wundurmiao Group as well as the Beineimiao island arc were formed.During the Silurian-Devonian,the Sino-Korean plate was obducted northwards,resulting in uplift of continental crust,and so Silurian-Davonian strata were absent and regional metamorphism occurred.Owing to the sledging mechanism of obduction,sialic crust and sima crust were mixed to form a late Caledonian to early Variscan granite zone extending along the convergent zone of plates.Finally the residual sea between plates formed a superposition basin during the Permo-Carboniferous;thus the conversion of oceanic crust to continental crust was completed.
作者
王东方
Wang Dongfang(Shenyang Institute of Geology and Mineral Resources)
出处
《地质论评》
1985年第5期461-468,共8页
Geological Review
