Composition of rocks and minerals from the Bol'shoy Lyakhovsky Island (New Siberian Islands)

In the southeast of the Bolshoi Lyakhovsky Island there are outcrops of tectonic outliers composed of low-K medium-Ti tholeiitic basic rocks represented by low altered pillow basalts, as well as by their metamorphosed analogs: amphibolites and blueschists. The rocks are depleted in light rare-earth elements and were melted out of a depleted mantle source enriched in Th, Nb, and Zr also contributed to the rock formation. The magma sources were not affected by subduction-related fluids or melts. The rocks were part of the Jurassic South Anyui ocean basin crust. The blueschists are the crust of the same basin submerged beneath the more southern Anyui-Svyatoi Nos arc to depth of 30-40 km. Pressure and temperature of metamorphism suggest a setting of "warm" subduction. Mineral assemblages of the blueschists record time of a collision of the Anyui-Svyatoi Nos island arc and the New Siberian continental block expressed as a counter-clockwise PT trend. The pressure jump during the collision corresponds to heaping of tectonic covers above the zone of convergence 12 km in total thickness. Ocean rocks were thrust upon the margin of the New Siberian continental block in late Late Jurassic - early Early Cretaceous and mark the NW continuation of the South Anyui suture, one of the main tectonic sutures of the Northeastern Asia.

在大利亚霍夫岛（Bolshoi Lyakhovsky Island）东南部，出露有由低钾中钛拉斑玄武质基性岩构成的构造残体，该类基性岩以弱蚀变枕状玄武岩及其变质同源岩（角闪岩与蓝片岩）为代表。该套岩石轻稀土元素亏损，其岩浆起源于富集钍（Th）、铌（Nb）与锆（Zr）的亏损地幔源区，且该源区对岩石成岩过程有贡献。其岩浆源区未受俯冲相关流体或熔体的改造。该岩石组合属于侏罗纪南阿纽伊洋壳的组成部分。其中的蓝片岩为同一洋壳的地壳物质，被俯冲到更南侧的阿纽伊-斯维亚托伊诺斯弧下方30~40 km的深度处。变质作用的温压条件指示其形成于‘暖型’俯冲背景。蓝片岩的矿物组合记录了阿纽伊-斯维亚托伊诺斯岛弧与新西伯利亚大陆块发生碰撞的时间，该碰撞过程以逆时针温压轨迹为典型特征。碰撞过程中的压力跃升对应于总厚度达12 km的构造盖层在汇聚带之上的堆叠。洋壳岩石于晚侏罗世晚期-早白垩世早期逆冲于新西伯利亚大陆块的边缘，该构造带为东北亚主要构造缝合带之一——南阿纽伊缝合带的北西向延伸部分。