论文部分内容阅读
在Seward半岛蓝片岩相岩石构成了一个构造上连贯的岩带,其出露面积至少有15000km~2。放射性年龄数据表明,高压变质作用多伴发生在侏罗纪,而不象以前推测的古生代或前寒武纪。原岩属内陆盆地或大陆边缘类型的沉积物(Nome Group),并具有早古生代或许是晚前寒武纪的年龄。这样在年龄上就早于高压变质作用的年龄200Ma之多。蓝闪石片岩相矿物组合几乎在Nome Group的所有岩性中都有发育,在富含Fe、Ti的变质基性岩(篮闪石+铁铝榴石+绿帘石)和泥质岩(蓝闪石+硬绿泥石+多硅白云母)中,硬柱石—青铝闪石亚相在Darby山东侧发育,可能在Nome Group岩石中有所发育,半岛西南部钠长石—绿帘岩—角闪岩相组合代表Nome Group岩石的特征。岩带中部地区的变质作用从早期的硬柱石,到后来的绿帘石—铁铝榴石—篮闪石片岩亚相,局部发育有榴辉岩组合(Nome河以东)。高压变质矿物是同构造期的,并拥有中等规模的层内等斜褶皱和方向一致的压扁的叶理,隆起的开始很可能相当于在较早的钠质和阳起石质角闪石环边上有冻蓝闪石的生长,部分构造后绿片岩相的各种交代作用记录了后来的减压阶段,蛇绿岩及混杂岩不与Seward半岛的蓝片岩伴生,高压变质作用是由一个不定成因的外来体所引起的大陆板块的构造负荷所引起的,高压变质作用的P—T 条件大约是 9～11Kb,400～450℃,介于Shuksan和Franciscan岩区的P—T轨逆之间。
Rocks in the Seward Peninsula blue lithofacies constitute a structurally continuous belt with an area of at least 15,000 km 2 exposed. Radioactive age data show that high-pressure metamorphism frequently occurs in the Jurassic, unlike the previously predicted Paleozoic or Precambrian. Protoliths are inland basin or continental margin sediments (Nome Group) and have been dated to by Precambrian age in the Precambrian. This age earlier than the high-pressure metamorphism of the age of 200Ma as much. The glaucophane schist facies mineral assemblages develop in almost all of the Nome Group lithologies. In the metamorphic bedrock (marblesite + almandite + epidote) and argillaceous rocks Glaucophane + chlorite + phengite), the dacite-alluvial-subfacies developed on the east side of Darby Shan and may have developed in the Nome Group rocks. The albite-green curtain Rock-amphibolite combination represents the characteristics of Nome Group rocks. The metamorphism of the Central Belt from the early period to the later epidote-almandine-basketblenzite subfacies, locally developed eclogite assemblages (east of the Nome River). High-pressure metamorphic minerals are isomorphic and have medium-sized isopachic folds and consistent squashed foliage, and the onset of uplift is likely to be equivalent to the earlier calcareous hornblende There is a glaucophane growth on the edge of the ring. After some tectonism, various metasomatism of greenschist facies records subsequent decompression stages. The ophiolites and melanges are not associated with the blue-schist in the Seward Peninsula. The high-pressure metamorphism is caused by The P-T condition of high-pressure metamorphism due to the tectonic load of the continental plate caused by an indefinite causative organism is about 9 ~ 11Kb and 400 ~ 450 ℃, P-T reversal between Shuksan and Franciscan between.