Provenance analysis by U-Pb dating of detrital zircons of sandstone blocks on the Kenting and Lichi Mélanges

• Main Authors: Yu-Lun Huang, 黃于倫
• Other Authors: Wen-Shan Chen
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/3crsta

碩士 === 國立臺灣大學 === 地質科學研究所 === 107 === The Kenting and Lichi Mélanges formed at the subduction system of Eurasian plate and Philippine Sea plate, located in Hengchun Peninsula and southern Coastal Range, respectively. Mélange is a body of rock characterized by exotic blocks, contained in a fine-grained deformed matrix. The purpose of this study is to analyse provenance of the sandstone blocks on the Mélanges, by using detrital zircon U-Pb dating, petrography, nannofossil biostratigraphy, and Hf isotope analysis. In addiction, in order to understand the sources of ophiolite, and the sandstone blocks of the Kenting and Lichi Mélanges, this study also collected samples from Eastern Taiwan Ophiolite and Miocene strata of Hengchun Peninsula. We analysed 7 Miocene strata samples from Hengchun Peninsula, 28 sandstone blocks from the Mélanges and 4 Eastern Taiwan Ophiolite. According to U-Pb age assemblage analysis, Lilungshan Formation and Shimen Formation have the same character with Central and Norther Taiwan Miocene Strata, but Loshui Formation has a different character. According to paleocurrent data and petrography results, contains argillite, quazite, and ophiolitic lithics, the provenance of Lilungshan Formation and Shimen Formation is the old accretionary wedge. According to U-Pb age assemblage analysis and petrography results, the provenance of Loshui Formation is the Cathaysia. According to zircon U-Pb age assemblage and petrography results, we classified sandstone blocks of the Mélanges into four types. Type 1 sandstone has the same character with Lilungshan Formation and Shimen Formation, the provenance of Type 1 sandstone represent the old accretionary wedge. Type 2 sandstone has the same character with Loshui Formation, the provenance of Type 2 sandstone is the Cathaysia. The provenance of Type 3 ophiolitic sandstone is the old accretionary wedge. The young zircon age population of Type 3 is derived from South China Sea oceanic crust, which been scratched and uplifted by the subduction system, and the old zircons are from continental material. The provenance of Type 4 volcanic lithics sandstone is volcano arc. The young zircon age population of Type 4 is from the volcanic arc, and the old zircons are captured from sedimentary strata, when the original magma upwelling. The Lichi Mélange contains Type 1, Type 2, Type 3 and Type 4 sandstone blocks. The Kenting Mélange contains Type 1 and Type 3 sandsone blocks. The zircon U-Pb age of Eastern Taiwan Ophiolite of the Lichi Mélange, include two age populations (1)17.4~16.3 Ma, and (2)14.8~13.9 Ma, which zircon Hf isotopic data indicated the magmas are from depleted mantal.