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在泰国北部难河构造带Pha Som变质杂岩中发现保存很好的放射虫硅质岩、玄武岩地层层序.层状硅质岩含放射虫化石Follicucullus porrectus,地质时代为中二叠世晚期至晚二叠世早期.其硅质岩Si O2含量均在92.5%以上,Al/(Al+Fe+Mn)平均比值为0.51,Ce/Ce*比值为1.14,为大陆边缘型硅质岩.玄武岩具有富集大离子亲石元素与高场强元素以及轻稀土富集等洋岛玄武岩的特点.说明难河构造带中-晚二叠世之交存在洋岛型火山岩和靠近大陆边缘的深海盆地硅质岩,代表了小洋盆的沉积组合.该构造带闭合时间应在晚二叠世与晚三叠世之间.
Well-preserved radiolarian chert, basaltic sequence is found in the Phasom metamorphic complex of the Dan River tectonic belt in the northern Thailand. The laminar siliceous rock contains the fossil Follicucullus porrectus, with a geologic age from late Middle to Late Permian In Late Permian, the Si 2 O content of the siliceous rocks is above 92.5%, the average ratio of Al / (Al + Fe + Mn) is 0.51 and the Ce / Ce * ratio is 1.14, which is continental marginal type siliceous rocks. It has the features of enriching large ion lithophile elements and high field strength elements and oceanic basalts such as light rare earth enrichment, indicating that the Yangdao-type volcanic rocks and the deep-sea basins near the continental margin are present in the Middle and Late Permian of the Nahe structural belt The silicalite, which represents the sedimentary assemblage of a small oceanic basin, should have a closing time between late Permian and late Triassic.