The Enrichment Characteristic and Mechanism of Gold-Silver Minerals in Submarine Hydrothermal Sulfides from the Ultra-Slow-Spreading SWIR
WANG Yan1, SUN Xiao-ming1，2，3*, WU Zhong-wei1，2, DENG Xi-guang4, DAI Ying-zhi2, LIN Zhi-yong2
1. School of Marine Sciences, Sun Yat-sen University, Guangzhou 510275, China 2. Department of Earth Sciences, Sun Yat-sen University, Guangzhou 510275, China 3. Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510275, China 4. Guangzhou Marine Geological Survey, Guangzhou 510760, China
Abstract：In the present study, content and occurrence of Au, Ag in three submarine hydrothermal sulfide samples from the ultra-slow-spreading Southwest Indian Ridge (SWIR) were studied by using inductively coupled plasma-atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of ICP-AES show that all of the samples have signs of Au-Ag enrichment. By SEM/EDS, we discovered a mass of gold-silver minerals in the samples. In S27-4, gold occurs as irregular-shaped native gold and electrum grains in sulfides or between crystal particles. However, we discovered lots of Au-independent silver minerals except parts of electrum in S35-22. EDS results of silver minerals indicate that silver minerals closely related with halogen element, inferring that silver minerals may be silver halides. Electrum in S35-22 can be absorbed at the surface or crystal edge of pyrite besides occurring in or between sulfides as S27-4, supposed to be related to surface defect in pyrite. Electrum is the only Au-Ag mineral discovered in S35-17. These electrum gains occur as inclusion gold, absorbed gold or fissure gold. In addition, there are different Au-Ag mole ratios of electrum in three samples, indicating distinct hydrothermal conditions. In the base of research before, we consider that AgCl-2 is the dominant complex of silver in ore-forming fluid of S27-4, however, gold is transported as AuCl-2 transforming to AuHS0, indicating that hydrothermal fluids decreased from high-moderate to moderate-low temperature and conductive cooling played an important role in this process. Similar enrichment mechanism happened in S35-22, but silver halides discovered in S35-22 suggest a higher temperature and chloride in the early stage. However, The enrichment of electrums in black smoke sample(S35-17) relates to mixing of hydrothermal fluids and seawater.
王 琰1，孙晓明1，2，3*，吴仲玮1，2，邓希光4，戴瑛知2，林志勇2. 西南印度洋超慢速扩张脊海底热液硫化物中金银矿物的富集特征及富集机制研究 [J]. 光谱学与光谱分析, 2014, 34(12): 3327-3332.
WANG Yan1, SUN Xiao-ming1，2，3*, WU Zhong-wei1，2, DENG Xi-guang4, DAI Ying-zhi2, LIN Zhi-yong2. The Enrichment Characteristic and Mechanism of Gold-Silver Minerals in Submarine Hydrothermal Sulfides from the Ultra-Slow-Spreading SWIR . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2014, 34(12): 3327-3332.
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