论文部分内容阅读
内蒙古中部温都尔庙群主要由变质基性火山岩夹少量硅铁质岩和石英片岩组成,一直被认为是代表早古生代或更早期的洋壳残片或蛇绿岩套.本文对其中的变质基性火山岩进行了锆石LA-ICP-MS U-Pb定年和岩石地球化学研究.研究结果显示,变质基性火山岩中锆石来源复杂,多为基性岩浆从围岩或其他源区捕获的,锆石年龄变化从晚太古代到早中生代,其中最小年龄为246~261 Ma,限定该变质基性火山岩的原岩形成于晚二叠世-早三叠世或之后.基性火山岩的地球化学特征接近E-MORB,并且有向OIB演化的趋势,可能代表扩张规模有限的陆内洋盆环境.洋盆的形成与该区从早二叠世以来持续发生的伸展作用有关,到早中生代,该洋盆发生闭合.
The Wendu’eriao group in central Inner Mongolia is mainly composed of metamorphic basic volcanic rocks with a few ferrochysites and quartz schist, which have been considered as representative of the Early Paleozoic or earlier oceanic crust or ophiolite sets. U-Pb dating and geochemistry of zircons from the volcanic rocks show that zircons from the metamorphic basement volcanic rocks are complicated in origin and are mostly derived from surrounding rocks or other source areas by the basic magma, The zircon ages vary from Late Archean to Early Mesozoic, of which the minimum age is 246-261 Ma, and the original rocks that define this metamorphic basement volcanic rock were formed during or after the Late Permian-Early Triassic. The basic volcanic geochemistry The characteristics are close to the E-MORB and have the tendency to OIB evolution, possibly representing the expansion of a limited inland ocean basin environment.The formation of the ocean basin is related to the extensional effect of the area from the Early Permian to the continuation of the Early Permian, The ocean basin is closed.