Geological and chronological characteristics of the Baiyin'gaolao Formation in Gaoyaowula, Inner Mongolia

Abstract

Based on a regional geological survey at a scale of 1:50000, it reveals that the volcanic rocks from the Baiyin'gaolao Formation of Gaoyaowula in Inner Mongolia could be divided into three lithologic segments by the triple mapping method of "volcanic structure-lithology and lithofacies-volcanic formation". The first lithologic segment is composed of pyroclastic sedimentary rocks, the second intermediate volcanic rocks and the third acidic volcanic rocks. The three lithologic segments constitute a complete depositonal-eruptive cycle, and the early to late magma is characterized by a transition from neutral to acid. The Baiyin'gaolao Formation can be classified into eruptive facies, intrusive facies, overflow facies, volcanic vent facies, eruption-deposition facies and subvolcanic facies, etc. Twelve V-grade volcanic apparatuses are delineated. The Zircon U-Pb LA-ICP-MS dating of the trachyandesite from the second lithologic segment of the Baiyin'gaolao Formation of Gaoyaowula and the rhyolite from the third are 128.2±0.9 Ma and 125.5±0.5 Ma respectively, indicating that the formation age is early-Cretaceous.

Keywords

• baiyin'gaolao formation
• volcanism
• la-icp-ms zircon u-pb dating
• gaoyaowula
• inner mongolia