In-situ sulfur isotope and trace element of pyrite constraints on the formation and evolution of the

• 作者: Jinxiang Li Chenghai Zhao Yong Huang Yuzhou Zhuo Jinwei Li
• 来源期刊: 地球化学学报(英文）
• 关键词: Nibao Carlin-type gold deposit Pyrite NanoSIMS LA-ICP-MS Sulfur isotopes
• 年，卷（期）: 2019,（4）
• 页码范围: 555-575
• 页数: 20页
• 语种: 英文
• DOI: 10.1007/s11631-019-00342-0

摘要

The fault-controlled Nibao Carlin-type gold deposit, together with the strata-bound Shuiyindong deposit, comprise a significant amount of the disseminated gold deposits in southwestern Guizhou Province, China. Five main types and two sub-types of pyrite at the Nibao deposit (Py1a/Py1b, Py2, Py3, Py4, Py5) were distinguished based on detailed mineralogical work. Py1, Py2 and Py3 are Au-poor, whereas Py4 and Py5 are Au-rich, corresponding to a sedimentary and hydrothermal origin, respectively. Through systematic in situ analyses of NanoSIMS sulfur isotopes, the framboid pyrite Py1a with negative δ34S values (- 53.3 to - 14.9‰) from the Nibao deposit were found to originate from bacterial sulfate reduction (BSR) processes in an open and sulfate-sufficient condition while the superheavy pyrite Py1b (73.7–114.8‰) is probably due to the potential influence of closed-system Rayleigh fractionation or the lack of preservation of deepsea sediments. Data of Py2 and Py3 plot within the area of S isotope compositions from biogenic and abiogenic sulfate reduction. In view of few coeval magmatic rocks in the mining district, the near zero δ34S values of the Au-rich pyrites (Py4 and Py5) may discount the potential involvement of magmatic but metamorphic or sedimentary origin.LA-ICP-MS and TEM work show that Au in ore-related pyrite is present as both nanoparticles and structurally bound. LA-ICP-MS analyses show that the Au-rich pyrite also contains higher As, Cu, Sb, Tl and S than other types of pyrite, which inferred a distal manifestation of deep hydrothermal mineralization systems.