Abstract

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Title:: Occurrence and Origin of Monazites and Rutiles from Sedimentary Rocks of Chuanlinggou Formation in Changping Area of Beijing

Author(s):: DING Jing; SONG Tian-rui; SHI Yu-ruo; 1. School of Graduates, China University of Geosciences, Beijing 100083, China; 2. Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; 3. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China

Keywords:: genetic mineralogy; Chuanlinggou Formation; monazite; rutile; hydrothermal origin; SHRIMP U-Pb age; EDAX; Beijing

Abstract:: Monazite and rutile grains are found in the contribution by using energy spectrum analysis to study the silty mudstones, which are collected from the lower part of Chuanlinggou Formation in Changping area of Beijing. The maximum particle size of the monazite is up to 88 μm while the largest rutile is 20 μm. According to lots of backscattered images, the monazites show jagged edges and irregular shapes, appeared as fishes, birds, flowers, worms, and so on, while the rutiles are arranged as a string of beads. An overwhelming majority of the monazites and rutiles are distributed in quartz or hematite veins. However, monazites or rutiles are hardly found in the places far away from the veins. These monazites with the age of (152±11)Ma are dated using SHRIMP Ⅱ at Beijing SHRIMP Center. According to the preliminary age data, it is suggested that these monazites belong to secondary monazites, which are associated with the late hydrothermal event, not formed in the diagenetic stage.