| 乌日根.大兴安岭北段八分场银矿床的发现及其成矿流体特征[J].地质与勘探,2023,59(1):12-26 |
| 大兴安岭北段八分场银矿床的发现及其成矿流体特征 |
| Discovery of the Bafenchang silver deposit and its ore-forming fluids characteristics in the northern Great Xing’an Range |
| 投稿时间：2022-10-18 修订日期：2022-12-19 |
| DOI：10.12134/j.dzykt.2023.01.002 |
| 中文关键词: 流体包裹体 成矿流体 氢氧同位素 矿床学 八分场银矿床 大兴安岭 |
| 英文关键词: fluid inclusion, ore-forming fluid, hydrogen and oxygen isotopes, ore deposit geology, Bafenchang silver deposit, Great Xing’an Range |
| 基金项目:黑龙江省矿产勘查基金项目“黑龙江省黑河市金水农场八分场530.8高地金银多金属矿普查”（编号：SDKC-2019002）资助 |
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| 中文摘要: |
| 大兴安岭北段多宝山地区是我国重要的铜钼金成矿区，近年来，二道坎和八分场银矿床的相继发现表明该地区银同样具有巨大的找矿潜力。以往研究热点主要集中在铜钼金等矿种，而对银矿床成矿流体性质和矿床成因的认识均极为薄弱，新发现的八分场银矿床为研究该地区银成矿作用提供了可能。本文在开展八分场银矿床地质特征和流体包裹体特征研究工作的基础上，结合与二道坎银矿床的对比分析，总结归纳二者的异同，旨在为区域找矿和深化成矿理论研究提供借鉴和参考。八分场银矿床矿体受NNE向断裂构造控制，呈脉状赋存在构造角砾岩中。矿床的形成主要经历了以下四个阶段：早期石英-磁铁矿阶段、成矿前期石英-黄铁矿阶段、主成矿期石英-银-多金属硫化物阶段和晚期碳酸盐-石英-少硫化物阶段。主成矿阶段石英中流体包裹体的研究显示，流体包裹体类型主要为气液两相包裹体，均一温度峰值集中于190~220 ℃，盐度集中于1.9%~4.1% NaCleqv，密度变化于0.82~0.92 g/cm3。流体成矿压力在9.9~22.6 MPa，估算成矿深度为1.0~2.3 km。氢氧同位素显示，流体δ18O变化范围在1.3‰~1.9‰，δD变化范围在－110.8‰~－89.1‰。总体上，成矿流体显示出中低温、低盐度、低密度和低压的特征，与区域上新发现的二道坎银矿床类似，成矿流体皆为岩浆水和大气降水的混合，所不同的是八分场银矿床由岩浆水主导，且形成深度更深。本文研究表明，多宝山地区具有较大的银成矿潜力，有望成为国内新的银多金属矿产聚集地，银成矿作用不仅发生在地表浅处（以二道坎为代表），深部仍具有较大的找矿潜力（以八分场为代表）。 |
| 英文摘要: |
| The Duobaoshan area, located in the northern part of the Great Xing’an Range, is an important Cu-Mo-Au metallogenic area. The discoveries of the Erdaokan and Bafenchang silver deposits in recent years indicate that there is a great prospecting potential for silver in this area. Most of the studies have been focused on Cu-Mo-Au, whereas the knowledge of silver deposits is not in depth. The newly discovered Bafenchang silver deposit provides an opportunity to study the silver mineralization in this area. Based on the detailed geological characteristics, we have studied the fluid characteristics of the Bafenchang silver deposit. A detailed comparison with the Erdaokan silver deposit has also been conducted to provide reference for regional ore prospecting and improving metallogenic theory. The ore bodies of Bafenchang silver deposit are hosted in structural breccia in the form of veins, which are controlled by the NNE-trending faults. The formation of the deposit was mainly involved in the following four stages: quartz-magnetite stage, quartz-pyrite stage, quartz-silver-polymetallic sulfide stage and carbonate-quartz-less sulfide stage. The study of fluid inclusions in quartz from the main ore-forming stage shows that the fluid inclusions are mainly gas-liquid two-phase inclusions. The peak homogenization temperature of the inclusions varies from 190 ℃ to 220 ℃, the salinity ranges from 1.9% to 4.1% NaCleqv, and the density varies from 0.82 g/cm3 to 0.92 g/cm3. The metallogenic pressure of the ore-forming fluid is at the range of 9.9 and 22.6 MPa, and the estimated metallogenic depth is 1.0~2.3 km. The variation range of fluid δ18O is 1.3‰~1.9‰, and δD is -110.8‰~-89.1‰. In general, the ore-forming fluid has shown medium-low temperature, low salinity, low density as well as low pressure, with similarity to the newly discovered Erdaokan silver deposit in the region. The ore-forming fluids should be sourced from a mixture of magmatic water and atmospheric water for both Bafenchang and Erdaokan. The difference is that the ore-forming fluids from the Bafenchang silver deposit are primarily composed of magmatic water and have been formed at a greater depth. It is inferred that the Duobaoshan area has a great silver metallogenic potential, which could be exemplified by silver mineralization occuring both in the shallow surface (represented by Erdaokan silver deposit) and in deeper depth (represented by Bafenchang silver deposit). |
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