欧龙布鲁克微地块下奥陶统复理石物源和构造背景研究

利用地球化学测试资料,依据大地构造学理论,对大煤沟剖面石灰沟组碎屑岩物源区性质及构造属性进行研究。结果表明:石灰沟组砂岩具有中等风化、快速堆积的特点,碎屑物质来源于上地壳酸性岩类,形成于活动大陆边缘构造背景;早奥陶世晚期,碎屑物质来自南侧滩间山陆-弧碰撞带的复理石向北的远端超覆,造成欧龙布鲁克微地块南缘大煤沟-城墙沟一带发生沉积岩、沉积相类型乃至沉积体系的转换;研究区不晚于488~471 Ma进入陆-弧碰撞阶段,寒武纪-早奥陶世,欧龙布鲁克海盆处于弧后位置,并非是被动大陆边缘盆地,而是与洋陆俯冲陆-弧碰撞有关的弧后盆地。

Provenance and tectonic background of the Lower Ordovician flysch in Oulongbuluke microplate

Using the geochemistry data, provenance property and structural attributes of Shihuigou formation clastic rocks from Dameigou outcrop were studied under the guidance of the sedimentary geotectonic theories. The results indicate that the provenance of the Shihuigou Formation with characteristics of moderately weathered and rapid accumulation is the upper crust acidic rocks, deposited in the active continental margin tectonic setting. From the early period of Early Ordovician, detrital material from Tanjianshan arc-continental collision zone distal overlapped from the south to the north, leading to the transition of sedimentary petrology types,sedimentary facie types and sedimentary system; By 488-471 Ma, the study area had entered into the stage of continental-arc collision period; During the Cambrian to Early Ordovician period, the Oulongbuluke sea basin was located in the back-arc position, which is not a passive continental margin basin, but a back-arc basin related to the subduction-arc collision.