滇东北会泽超大型铅锌矿Re-Os同位素特征及喜山期成矿作用动力学背景探讨

江小均; 王忠强; 李超; 郭忠林; 柴建华; 邱文龙; 王加昇

doi:10.15898/j.cnki.11-2131/td.201805030054

滇东北会泽超大型铅锌矿Re-Os同位素特征及喜山期成矿作用动力学背景探讨

Re-Os Isotope Characteristics of the Huize Ultra-large Lead-Zinc Deposit, Northeastern Yunnan Province: Constraints on the Himalayan Metallogenic Dynamic Background

摘要

摘要: 会泽超大型铅锌矿是滇东北铅锌多金属成矿域中典型的密西西比河谷型（MVT）或会泽型（HZT）矿床，因其独特的成矿系统以及矿床中富锗而被地质学者熟知，由于该类型矿床成矿温度较低且缺少合适的定年矿物，其成矿时代一直存在较大的争议。本文在会泽铅锌矿麒麟厂矿区1584中段0-11号穿脉坑道块状铅锌硫化物矿石中挑选了9件硫化物样品（黄铁矿、方铅矿和闪锌矿），采用负离子热表面电离质谱法进行Re-Os同位素分析，获得Re-Os等时线年龄为40.7±2.6 Ma（n=9），与模式年龄加权平均值40.0±2.6 Ma（n=8）在误差内完全一致，闪锌矿和方铅矿模式年龄分别为38.24±0.41 Ma和36.57±0.40 Ma。上述同位素年龄揭示了会泽超大型铅锌矿的成矿时代可能为始新世。结合滇东北铅锌矿集区NE向逆冲断层和冲断褶皱控矿构造区域构造解析以及断裂、矿体构造-岩相蚀变特征，提出会泽超大型铅锌矿经历了燕山期、喜山期两阶段构造-流体贯入的成矿作用模型。

Abstract:
BACKGROUNDThe Huize ultra-large lead-zinc deposit is a typical MVT or HZT type deposit in the lead-zinc polymetallic belt. This deposit is known as a unique metallogenic system and germanium enrichment. Due to the low mineralization temperature and lack of suitable dating minerals, the age of the ore deposits has been controversial.
OBJECTIVESTo precisely date the mineralization age by Negative Thermal Ionization Mass Spectrometry (NTIMS) Re-Os isotope analyses and discuss the Himalayan metallogenic dynamic process in the Huize ultra-large lead-zinc deposit.
METHODSNTIMS Re-Os isotope analyses were carried out on pyrite, galena, and sphalerite samples collected from the Huize ultra-large lead-zinc deposit. The Re-Os isochron age from the pyrite, galena, and sphalerite samples was used to constrain mineralization age. The initial ¹⁸⁷Os/¹⁸⁸Os values were used to trace the material sources.
RESULTSThe Re-Os isochron age of the pyrite samples is 40.7±2.6 Ma (2σ, n=9) with a model weighted average age of 40.0±2.6 Ma (2σ, n=8). The sphalerite and galena samples have model ages of 38.24±0.41 Ma and 36.57±0.40 Ma, respectively. Furthermore, the initial ¹⁸⁷Os/¹⁸⁸Os values of the pyrite samples vary from 0 to 0.26, whereas those of the sphalerite and galena samples are 0.46 and 0.41, respectively.
CONCLUSIONSThe Re-Os isochron ages indicate that the mineralization for the Huize ultra-large lead-zinc deposit occurred during the Eocene period. Based on regional ore controlling structure, tectono-lithofacies alteration characteristics in Northeastern Yunnan and the isochron ages results, a two-stage (Yanshanian and Himalayan) tectonic-fluid metallogenic model for the Huize Ultra-large lead-zinc deposit is inferred.

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