投稿时间：2023-06-16
修订日期：2023-10-30
网络发布日期：2024-03-08
中文摘要:哀牢山金矿带位于三江特提斯造山带的东南部，发育有一系列大型-超大型造山型金矿床，并广泛发育碳质物，但碳质物在金矿成矿过程中的作用还尚不明确。为了确定碳质物在金矿化过程中所扮演的角色，本研究以哀牢山金矿带镇沅超大型造山型金矿发现的不同种类的碳质物和共生黄铁矿为研究对象，对其进行了岩相学、拉曼光谱、傅里叶红外光谱、碳同位素和激光剥蚀电感耦合等离子体质谱（LA-ICP-MS）分析，研究结果表明镇沅金矿中有3类碳质物：CM1、CM2和CM3。CM1呈深灰色不规则形态，拉曼光谱分析显示CM1具有低强度、宽的D1带和高强度、窄的G峰，D2峰较明显，计算显示其形成温度为172~200℃，低于成矿温度（250~330℃）。此外，傅里叶红外分析结果表明CM1石墨化程度低，含较少的CH键和C=O键，表明其未经历热液蚀变。碳同位素分析显示CM1样品的δ13C值为-26.46‰~-26.89‰。与CM1空间上共生的黄铁矿（Py1）呈草莓状分布于碳质板岩中，LA-ICP-MS结果表明Py1的Co、Ni、Zn、Mo、Te元素含量高；CM2呈灰色细长沥青状，拉曼光谱分析显示CM2的D1峰和G峰较CM1更为尖锐，面积近似，且D2峰的光谱分峰程度很低，计算显示其形成温度为358~463℃，高于成矿温度。傅里叶红外分析结果显示，CM2石墨化程度高，在2925 cm-1和1705 cm-1处有明显的谱峰，含有较多的CH2+CH3、C=O和C=C键。CM3呈灰色细小颗粒状，拉曼光谱分析显示CM3的光谱特征与CM1的相似，但CM3的D2峰具有独立的峰段，计算显示其形成温度为258~322℃，与成矿温度一致。碳同位素分析显示CM3的δ13C值为-9.09‰~-14.12‰。与CM3空间上共生的黄铁矿（Py2）呈自形分布于含金石英脉中，LA-ICP-MS结果表明Py2的As、Au元素含量高。综合以上结果，笔者认为CM1来源于有机质，形成于碳质板岩的早期成岩阶段，属于变质成因，与其共生的Py1形成于成岩期，属于沉积成因的黄铁矿。CM2的形成温度高于成矿温度，也为变质成因。CM3源于成矿流体，形成于围岩中的含铁矿物和成矿流体发生反应，属于热液成因，而Py2与CM3从流体中同时沉淀。其中CM1和CM3在金矿化过程中起到重要的作用。CM1作为还原剂能够有效和成矿流体中金的硫氢络合物发生水岩反应促使金的沉淀，而CM3在硫化过程中和Py2共同沉淀导致成矿流体中H2S的大量消耗，进一步破坏了金的硫氢络合物稳定性，导致金沉淀和再富集。
Abstract:The Ailaoshan gold belt is located in the southeastern part of the Sanjiang Tethys orogenic belt. It consists of a series of large and super-large orogenic gold deposits. Moreover, carbonaceous materials (CM) are widely recognized in those deposits. However, the role of carbonaceous materials in the deposit formation is still unclear. In order to determine the role of carbonaceous materials in the gold mineralization, different kinds of carbonaceous materials and symbiotic pyrites found in Zhenyuan super-large orogenic gold deposit in Ailaoshan gold belt were analyzed by petrographic observation, Raman spectroscopy, Fourier Transform infrared spectroscopy, carbon isotope and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. The results show that there are three types of carbonaceous materials in Zhenyuan gold deposit, namely CM1, CM2 and CM3. CM1 has a dark gray irregular shape. Raman spectroscopic analysis shows that CM1 has a low-intensity, wide D1 band and a high-intensity, narrow G peak, and D2 peak is more obvious. Calculation shows that its formation temperature is 172~200℃, lower than the metallogenic temperature (250~330℃). In addition, the FTIR shows that CM1 has a low degree of graphitization, contains less CH and C=O groups, indicating that it has not undergone hydrothermal alteration. The δ13C values of CM1 samples range from -26.46‰ to -26.89‰. Framboidal pyrite Py1 and CM1 are spatially associated and distributed in carbonaceous slate. The LA-ICP-MS results show that Py1 has high content of Co, Ni, Zn, Mo and Te. CM2 is gray slender asphalt. Raman spectroscopy shows that the D1 and G peaks of CM2 were sharper than CM1. The area of D1 peak and G peak of CM2 are similar, and D2 peak has a low degree of spectral separation. The calculation shows that its formation temperature is 358~463℃, which is higher than the metallogenic temperature. The Fourier analysis shows that CM2 is highly graphitized, with obvious spectral peaks at 2925 cm-1 and 1705 cm-1, containing more CH2+CH3, C=O and C=C groups. CM3 is gray and fine granular. Raman spectroscopic analysis shows that the spectral characteristics of CM3 are similar to those of CM1, but the D2 peak of CM3 has an independent peak segment. The calculation shows that the formation temperature of CM3 is 258~322℃, which is consistent with the metallogenic temperature. The δ13C values of CM3 range from -9.09‰ to -14.12‰. Euhedral Pyrite (Py2), symbiosis with CM3, is distributed in the auriferous quartz veins, and LA-ICP-MS results show that Py2 has high content of As and Au. Based on the analytical results mentioned-above, we proposed that CM1 is derived from organic matter and formed in the early diagenetic stage of carbonaceous slate, which belongs to metamorphic origin. The symbiotic Py1 is formed in the diagenetic stage, belonging to sedimentary pyrite. The formation temperature of CM2 is higher than that of mineralization, which is also of metamorphic origin. CM3 comes from ore-forming fluid, which is due to the reaction between iron-bearing minerals in wall rock and ore-forming fluid, belonging to the hydrothermal origin, while Py2 and CM3 co-precipitate from the fluid. CM1 and CM3 play important roles in gold mineralization. CM1 acts as a reductant and effectively reacts with the sulfur hydrogen complex of gold in the ore-forming fluids to promote gold precipitation. While CM3 co-precipitates with Py2 in the sulfide process, resulting in a large amount of H2S consumption in ore-forming fluids, which further destroys the stability of the sulfur hydrogen complex of gold, resulting in gold precipitation and reenrichment.
keywords:orogenic gold deposits carbonaceous materials Raman spectroscopy Zhenyuan gold deposit Ailaoshan gold belt
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基金项目:本文得到国家自然科学基金项目（编号：91855213、41972070、41672071和U1302233）资助
引用文本：
武中洋,孙晓明,丁正鹏,高显青.2024.云南哀牢山金矿带镇沅超大型造山型金矿床碳质物特征及其成矿意义[J].矿床地质,43(1):43~59WU ZhongYang,SUN XiaoMing,DING ZhengPeng,GAO XianQing.2024.Characteristics and metallogenic significance of carbonaceous materials in Zhenyuan super-large orogenic gold deposit in Ailaoshan gold belt, Yunnan Province, China[J].Mineral Deposits43(1):43~59
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