Characteristics of Devonian hydrothermal dolomite in the Longjie area of Northeastern Yunnan and its mineralization indicative significance
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    Abstract:

    The hydrothermal dolomite (HDS) is a significance ore-bearing wall rock of the MVT Pb-Zn deposit. However, the distribution pattern of hydrothermal dolomite along faults remains unclear, making it as a prospecting indicator of MVT deposit is uncertain. The MVT Pb-Zn ore concentration area in Sichuan, Yunnan and Guizhou on the southwestern margin of the Yangtze platform is generally characterized by HDS ore-endowments. This study focuses on the ore-bearing HDS in the Longjie exploration area of northeastern Yunnan. Through geological mapping and petrographic observation, combined with mineral elemental composition and C-O isotope analysis, and a comparison with buried dolomite, the distribution characteristics of ore-bearing HDS along faults were systematically clarified. The results indicate: ① The ore-bearing HDS is produced along the secondary fracture of the upper disk of the strike-slip normal fault or thrust fault, and the distribution range along the upper disk of the fault is larger than that of the lower disk of the fault. HDS is formed by accounting limestone or dolomite on both sides of the fault. The closer the distance from the fault, the shallower the color, and the larger the crystal size of dolomite. ② The contents of V, Cr, Cu, Zr, Rb and Ba in HDS are higher than those in buried dolomite, and the farther away from the fault, the higher the content is. The distribution pattern of rare earth elements is right-inclined, there are δCe negative anomalies (0.61~0.98) and δEu weak positive anomalies (0.74~1.07), both of which decrease symmetrically away fromt the fault. ③ The dolamitization of HDS in the area occurred in a reduced environment and underwent a process from burial to tectonic hydrothermal alteration, with fluid migrating to both sides along the fault. Therefore, the contents of V, Rb, Zn, Pb and δ13C value of HDS increase from the fault to the surrounding rock, which can sever as effective exploration indicators for MVT Pb-Zn deposits.

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曾毓灿,魏爱英,薛传东,周红琳,马怀昆,陆双交,李徽琪,毛荣威,周发帅,2025,滇东北龙街地区泥盆系热液白云岩特征及其成矿指示意义[J].岩石矿物学杂志,44(1):51~67. ZENG Yu-can, WEI Ai-ying, XUE Chuan-dong, ZHOU Hong-lin, MA Huai-kun, LU Shuang-jiao, LI Hui-qi, MAO Rong-wei, ZHOU Fa-shuai,2025,Characteristics of Devonian hydrothermal dolomite in the Longjie area of Northeastern Yunnan and its mineralization indicative significance[J]. Acta Petrologica et Mineralogica,44(1):51~67.

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History
  • Received:June 24,2024
  • Revised:December 03,2024
  • Adopted:
  • Online: January 15,2025
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