西昆仑阿什库勒火山群地质特征和活动分期

阿什库勒火山群作为青藏高原内最新期的北部昆仑火山群的典型代表,长期以来一直受到国内外地学界的广泛关注。我们通过对阿什库勒盆地火山区的野外地质地貌考察,研究了阿什库勒盆地内第四纪火山活动历史,完成了阿什库勒火山群重要火山锥体的1∶2000火山机构图。同时,对系统采集于不同火山机构和部位的20个火山岩样品进行了系列Ar-Ar同位素年代测试分析,获得了翔实的研究区不同火山岩石单元的绝对年龄数据。结合野外地质地貌考察结果,讨论了阿什库勒盆地的火山活动的第四纪时期活动历史,并将主要活动时期进一步划分为早更新世早期、早更新世中期、中更新世早期、中更新世晚期、晚更新世期和全新世期六期,取得了与前人有关该研究区火山活动历史和活动期次类似的划分方案,并补充了新的年代学证据。研究成果弥补了藏北高原西部由于恶劣工作环境而造成的第四纪火山学研究的不足。

Geological features and eruption history of Ashikule volcano clusters in western Kunlun Mountain

The high K₂O volcanism of northeastern Tibet in the Cenozoic era, as an "important window", playes the essential roles in studying the composition of plateau lithosphere, the structure of the crust-mantle, and the uplifting mechanism of the Tibetan Plateau. Ashikule volcanic group, which was developed in the western Kunlun Mountain of North Tibet, is composed with 10 major volcanoes and tens of sub-volcanoes, and covers a total area of about 200km² at the average altitude around 5000m, one of the highest volcano groups in the world. Because of the high topographic elevation, inclement climate and inaccessibility this area is one of those poorly-studied geological regions on the earth. In this study, we conducted detailed field investigation of geological and geomophological features of volcanic rocks and volcanic craters in Ashikule basin, and compiled large-scaled geologic map of the study area. We also collected series of samples to carry out high-precision ⁴⁰Ar/³⁹Ar geochronology study of selected lavas from Ashikule volcano group. Finally, based on the field investigation and laboratory dating results, we classified the Quaternary volcanic activity in the basin into 6 periods. The chronostratigraphic framework of the volcanic activity we proposed somewhat differs from the previously adopted ones in the study area. Our work has important implications for understanding the Ashikule eruptive history and, ultimately, for the providing new evidence for the study of tectonic evolution of the northern Tibetan Plateau.