Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (3): 386-398.DOI: 10.13745/j.esf.sf.2022.12.57

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Zircon and apatite fission track chronology of intrusive rocks in the Bainaimiao Cu-Au deposit, Inner Mongolia

LÜ Zhao1(), XU Zhan2, PANG Jianzhang3, WANG Jichun2, WANG Jianping1,*(), YUAN Shuopu1   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. Geological Survey Institute of Inner Mongolia, Hohhot 010020, China
    3. Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2021-06-22 Revised:2021-09-19 Online:2023-05-25 Published:2023-04-27

Abstract:

Porphyry copper deposits often experience late-stage uplifting, denudation, destruction and transformation after deposition. The Bainaimiao Cu-Au deposit in Inner Mongolia is one of the few Early-Paleozoic porphyry copper deposits in the orogenic belt of northern China, therefore, it is of both theoretical and practical (in mineral prospecting) significance to study the mineral alteration/preservation processes. According to thermochronological analysis of zircon fission tracks and apatite fission tracks, the total denudation of the Cu-Au mining area since 150 Ma is between 3.11-3.25 km, and the late-stage uplifting and cooling of intrusive rocks in the study area can be characterized by a three-stage process. During the rapid exhumation stage between 150-90 Ma, the tectonic stress is mainly compressional, and the average denudation rate is 0.0457 mm/a; in the stable denudation stage from 90 to 20 Ma, extensional stress dominates, and the average denudation rate is 0.0033 mm/a; and during the rapid exhumation stage from 20 Ma to present, compressional stress again dominates, and the average denudation rate is 0.0388 mm/a. Thus, from the Caledonian to Yanshanian, affected by subduction and collision of the ancient Asian Ocean and intracontinental orogenic activities, the mining area is under tectonic stresses alternating between compressional and extensional, which provides favorable geological conditions for mineral alteration/preservation in the Bainaimiao Cu-Au deposit.

Key words: Bainaimiao Cu-Au deposit, structural-thermal history, fission track age, mineral alteration/preservation

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