冈底斯西段第四纪钾质火山岩的发现及赛利普组的建立

Discovery of Quaternary potassic volcanic rocks and the establishment of Sailipu Formation in West Gangdis of Tibet, China

冈底斯西段赛利普一带分布有大面积的钾质火山岩,以前曾被划归上新世-早更新世赛利普群。作者对这套火山岩地层进行了详细野外调查并重新测制了火山岩地层剖面,在该套火山岩下伏及层间湖相碎屑沉积层中获得ESR年龄0.268 Ma与0.349 Ma。岩石学、岩石化学研究表明,这套火山岩是以安粗质熔岩为主的钾玄岩系列-钾质碱性玄武岩系列火山岩,岩石类型及岩石组合稳定,岩层产状平缓,岩石新鲜,层位相对清楚,故将其命名为赛利普组,属第四纪早-中更新世。这一发现对研究冈底斯构造带新生代以来岩浆活动、构造演化,进而探讨青藏高原隆升机制有着重要的地质意义。

Large area of potassic volcanic rocks distributed over the Sailipu area of West Gangdis were originally assigned to the Sailipu Group and the age was Pliocene-Early Pleistocene. The volcanic stratum has been investigated in detail and a section of the volcanic rocks has been remeasured by the authors. The ESR ages of 0. 268 Ma and 0. 349 Ma are obtained from the lake sandy gravel under the volcanic layer. Studies of petrology and petrochemistry indicate that such suit of volcanic rocks dominated by lattite belongs to shoshonite series to potassic alkali basalt series. Considering the stability of rocks and their associations, gentle stratum occurrence, fresh degree of rocks and comparatively clarity of horizons, this potassic volcanic stratum distributed over the Sailipu area is named as Sailipu Formation, and the age of which is early-middle Pleistocene of Quaternary. This discovery provides important evidences for the Cenozoic magmatism and tectonic evolution of the Gangdis belt, and is significant for the further study of uplifting mechanism of Qinghai-Tibet Plateau.