Heavy Minerals Characteristics, U-PB Geochronology and Provenance Analysis of Neogene Shawan Formation in Chepaizi Uplift, Junggar Basin

LI Yan1,2, WU Chaodong1,2,†, ZHANG Xuecai3, XIE Lihua1,2, LENG Jiaxuan1,2, GUAN Xutong1,2

1. Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871; 2. Institute of Oil & Gas, Peking University, Beijing 100871; 3. Manage Center of Oil and Gas Exploration of Shengli Oilfield Company, Sinopec, Dongying 257000; † Corresponding author, E-mail: cdwu@pku.edu.cn

Abstract Based on the petrological characteristics, sandstone detrital composition, analysis of heavy minerals assemblages and U-PB zircon age, the sedimentary characteristics and provenance evolution of Sha 1 member of Neogene Shawan Formation in Chepaizi Uplift are discussed. The results show that there were double-provenance systems of north and south in Chepaizi Uplift and Sha 1 member of Shawan Formation was dominated by coarse clastic deposits. In the sedimentary period of first sand group of Sha 1 member, the Zaire Mountains was the northern provenance, with small-scale fan delta deposits. The Central Tianshan and North Tianshan orogenic belts were the southern provenances, with braided river delta deposits. In the sedimentary period of second sand group of Sha 1 member, the sediments derived from the Central Tianshan were weakened, while those from the North Tianshan were strengthened, and the water body of the basin was deepened. Small shore-lake beach bars were distributed in front of the southern braided river delta. The main reason for the variation of the provenance in the south may be that the Tianshan experienced a strong extrusion and uplift process in the middle Miocene due to the remote collision between the Indian plate and the Eurasian plate, resulting in the uplift of the North Tianshan, which provided the provenance for Chepaizi Uplift. Key words provenance analysis; sedimentary characteristics; Shawan Formation; Chepaizi Uplift; Junggar Basin