Earth Science Frontiers ›› 2021, Vol. 28 ›› Issue (3): 328-337.DOI: 10.13745/j.esf.sf.2021.1.20

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A geochemical method for finding concealed ore deposits in bedrock outcrop area: Application of tectono-geochemical survey

CHENG Zhizhong1(), YUAN Huixiang1,*(), PENG Linlin2, LU Guo’an2, JIA Xiangxiang3, BING Mingming3, LIN Chenggui1   

  1. 1. Development and Research Center of China Geological Survey, Beijing 100037, China
    2. South Jiangxi Geological Survey Team, JBGMED, Ganzhou 341000, China
    3. No.1 Institute of Geology and Mineral Exploration, GBGMED, Tianshui 741020, China
  • Received:2021-01-26 Revised:2021-02-27 Online:2021-05-20 Published:2021-05-23
  • Contact: YUAN Huixiang

Abstract:

Tectono-geochemical survey is effective for collecting information on deep mineralization in bedrock outcrop area. In this article, the basic concepts and the development of tectono-geochemistry are systematically introduced. We propose a multi-point sampling method particularly useful for collecting rock (tectonic rock) samples associated with deep mineralization to ensure proper sample representation and data uniformity. Specifically, within each sampling unit of a survey grid, multiple “sub-samples” are collected mainly from fracture zones, fissures, altered rocks and mineralized rocks, and combined into one sample. For example, in a 1∶50000 tectono-geochemical survey carried out in the Xihe area of Gansu Province, 6-8 “sub-samples” were collected in each 500 m×500 m sampling unit and altogether 2967 samples were obtained from the survey grid. In the final analysis, 19 elements were analyzed, including Au, Ag, Pb and Zn, and the location of Au geochemical anomaly was more accurately determined. The Au orebodies were subsequently discovered through exploration. In another 1∶10000 survey in the periphery of the Jiangxi Yanbei tin (Sn) deposit, we collected 4620 sub-samples from fracture and fissure, using 100 m×100 m grid sampling unit, which resulted in 934 samples for the final analysis to delineate the geochemical anomalies of Sn and other elements. The delineated Sn geological anomaly was verified by drilling and the deep conceal tin orebodies were found. The above results show that the tectono-geochemical survey of different scales can have fruitful application in the discovery of concealed deposits in the bedrock outcrop area, such as in finding Carlin type gold deposits in Southeast Yunnan and volcanic rock covered deposits in the southeast coastal region.

Key words: bedrock cover, concealed deposit, tectono-geochemistry, fissure sampling

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