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ZHAO Chen-hui,WANG Cheng-hui,ZHAO Ru-yi,LIU Shan-bao,RAO Jiao-ping,LIU Wu-sheng,ZHANG Xiong,JIANG Jin-chang,LI Ting-jie.Isotopic Composition and Alteration Characteristics of Dacite Porphyry, and Their Prospecting Significance in the Dabaoshan Copper Deposit of Guangdong Province[J].Rock and Mineral Analysis,2020,39(6):908-920
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Isotopic Composition and Alteration Characteristics of Dacite Porphyry, and Their Prospecting Significance in the Dabaoshan Copper Deposit of Guangdong Province
Received:July 31, 2020  Revised:November 18, 2020
DOI:10.15898/j.cnki.11-2131/td.202007310107
Key words: South China Block|Dabaoshan|porphyry copper deposit|dacite porphyry|X-ray fluorescence spectrometry|inductively coupled plasma-mass spectrometry|major, minor and trace elements|metallogenic epoch
Author NameAffiliationE-mail
ZHAO Chen-hui Key Laboratory of Metallogeny and Mineral Resource Assessment, Ministry of Natural Resources
Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China 
wangchenghui131@sina.com 
WANG Cheng-hui Key Laboratory of Metallogeny and Mineral Resource Assessment, Ministry of Natural Resources
Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China 
 
ZHAO Ru-yi State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China  
LIU Shan-bao Key Laboratory of Metallogeny and Mineral Resource Assessment, Ministry of Natural Resources
Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China 
 
RAO Jiao-ping China University of Geosciences(Beijing), Beijing 100083, China  
LIU Wu-sheng Guangdong Province Dabaoshan Mining Co., LTD, Shaoguan 512127, China  
ZHANG Xiong Guangdong Province Dabaoshan Mining Co., LTD, Shaoguan 512127, China  
JIANG Jin-chang Guangdong Province Dabaoshan Mining Co., LTD, Shaoguan 512127, China  
LI Ting-jie Guangdong Province Dabaoshan Mining Co., LTD, Shaoguan 512127, China  
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Abstract:
      BACKGROUND: The main types of copper deposits are porphyry and skarn types. Dacite porphyry is a rock type commonly developed in the porphyry Cu-Mo-Au system. The rock can be used as a marker clue for ore prospecting and ore-forming rock when there is well-developed hydrothermal alteration. The Dabaoshan deposit is currently the largest copper polymetallic deposit in the South China Block. Previous studies have shown that the dacite porphyry of the mining area is not only the ore-forming parent rock, but also a favorable ore-bearing wall rock. However, there are some debates about the relationship between dacite porphyry and mineralization in this mining area. With the breakthrough of prospecting for medium and large dacite porphyry ore bodies in recent years, the relationship between dacite porphyry and mineralization has once again become a concern.
OBJECTIVES: To understand the relationship between dacite porphyry alteration and mineralization of the Dabaoshan deposit.
METHODS: Based on field work and indoor analysis, X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma-mass spectrometry (ICP-MS) were used to determine copper, tungsten, silicon, aluminum and calcium in Dabaoshan dacite porphyry samples. The isotope composition, metal element contents and alteration characteristics of the dacite porphyry in the mining area were used to discuss the relationship between alteration and prospecting direction.
RESULTS: The copper content ranged from 107 to 6909μg/g, which was consistent with the copper ore grade of 0.3%-0.5% in the mining area. The LOI and other geochemical indicators that can represent the degree of alteration were positively correlated with copper. Hydrothermal alteration was widely developed in dacite porphyry, including potassium, prophyliticition and quartz-sericitization from early to late stage. Among different stages of alterations, the copper content of quartz-sericitization was 2 to 5 times higher than other alteration types, indicating that quartz-sericitization was closely related to copper mineralization and was an important prospecting marker clue.
CONCLUSIONS: The deep alteration intensity of the dacite porphyry (below the 270m elevation) has not been weakened, suggesting a great prospecting potential. In addition, the contact zone between dacite porphyry and the Jurassic strata, and the xenoliths in the dacite porphyry are also important prospecting directions, which may host skarn-type copper-rich deposits.