摘要
阿尔泰山南缘原划下石炭统姜巴斯套组实为一套具有洋壳性质的变质岩组成,由玄武岩、辉长岩和少量硅质岩组成,并混杂岩了前寒武纪基底残残块。该洋壳组分位于增生岩楔之中,构造楔形体的形成是俯冲作用一次次"脉冲式"推进的产物,大体可以分为7个岩片,在增生楔下部(南部)见有滑混岩出露。角闪岩相变质的洋壳又经历了退变质作用的影响,显微镜下可见到辉石转变为阳起石、绿帘石交代斜长石的现象。显示折返过程中经历了由角闪岩相绿片岩相的退变质作用演化过程,俯冲的洋壳残片又被仰冲盘携带上升,发生俯冲-折返拼贴式就位,与弧火山岩共同形成了SSZ型蛇绿混杂岩。蛇绿混杂增生岩楔的特征表明洋壳由南向北俯冲,记录了古亚洲洋中支早古生代晚期的演化特点。
The Lower Carboniferous Jiangbasitao formation in south margin of Altay Mountains is actually oceanic crust metamorphic rocks, constituted by basalt, gabbro and minor silicalite, and mixed Precambrian basement residual block. The oceanic crust components are embedded in ac cretionary complexes, which can be divided into seven slices; the formation of the tectonic wedge is the result of repeated pulsed advance of subduction; slide melange was found in the lower part of the accretionary wedge. The oceanic crust with amphibolite facies metamorphism experienced retrograde metamorphism; under the microscope, it is observed that pyroxene was transferred in- to actinolite and epidote plagioclase metasomatic, indicating the retrogressive metamorphism evolution from amphibolite facies and greenschist facies. The remnants of oceanic crust subduction was carried up by the obduction, with a subduction and reentrant collage, and formed the SSZ ophiolitic melange with arc volcanic rocks. Features of ophiolite melange accretionary complex demonstrate the oceanic crust suhduction from south to north, and record the evolution character istics of Paleo-Asian Ocean in late Early Paleozoic era.
出处
《西北地质》
CAS
CSCD
2015年第3期178-184,共7页
Northwestern Geology
基金
中国地质调查局国土资源大调查项目(1212010911055)
