迟了二叠早三叠纪( P2-T1 )在 Nan-Uttaradit 地区在海洋山脉和海洋岛的暗岩的东方方面上散布的暴烈的岩石从 petrographic 特征的方面被分析,岩石集合, REE ,踪迹元素,大地构造的背景,等等,显示那些暴烈的岩石拥有特征岛弧展示暴烈的岩石。暴烈的岩石集合是暗岩玄武岩的安山岩安山岩。暴烈的岩石是亚 alkaline,由计算碱的系列统治了,与 tholeiite 系列来下。暴烈的岩石的化学作文被低 TiO2 和 K2O 和高 Al2O3 和 Na2O 描绘。他们的 REE 模式具有扁平的、弱 LREE 丰富使权利倾向的类型。踪迹元素被大阳离子元素例如的丰富描绘 K, Rb 和 Ba, U 和 Th 的普通丰富,和 Nb, Ta, Zr 和 Hf 的弄空。在暴烈的岩石的地以内的石油化学的阴谋下降,在有岛弧的阴谋的一致性在中国的 Jinsha 河地区的暴烈的岩石。这条岛弧暴烈的地区,在 Nan-Uttaradit 地区和 ocean-ridge/oceanic 岛打暴烈的岩石,组成是的暴烈的 rock-island-arc magmatic 岩石地区在对散布了的海洋山脉,显示 Nan-Uttaradit 地区的海洋的外壳曾经具有东方 subduction。这个工作具有在在 Nan-Uttaradit 地区探索 paleo-Tethys 的进化的大意义。
Late Permian-Early Triassic(P2-T1) volcanic rocks distributed on the eastern side of ocean-ridge and oceanic-island basalts in the Nan-Uttaradit zone were analyzed from aspects of petrographic characteristics,rock assemblage,REE,trace elements,geotectonic setting,etc.,indicating that those volcanic rocks possess the characteristic features of island-arc volcanic rocks.The volcanic rock assemblage is basalt-basaltic andesite-andesite.The volcanic rocks are sub-alkaline,dominated by calc-alkaline series,with tholeiite series coming next.The chemical composition of the volcanic rocks is characterized by low TiO2 and K2O and high Al2O3 and Na2O.Their REE patterns are of the flat,weak LREE-enrichment right-inclined type.The trace elements are characterized by the enrichment of large cation elements such as K,Rb and Ba,common enrichment of U and Th,and depletion of Nb,Ta,Zr and Hf.The petrochemical plot falls within the field of volcanic rocks,in consistency with the plot of island-arc volcanic rocks in the Jinsha River zone of China.This island-arc volcanic zone,together with the ocean-ridge/oceanic island type volcanic rocks in the Nan-Uttaradit zone,constitutes the ocean-ridge volcanic rock-island-arc magmatic rock zones which are distributed in pairs,indicating that the oceanic crust of the Nan-Uttaradit zone once was of eastward subduction.This work is of great significance in exploring the evolution of paleo-Tethys in the Nan-Uttaradit zone.