Colloform pyrite with core-rim texture is commonly deposited in carbonate platforms associated with the sulfide ores such as the Caixiashan Pb-Zn deposit.However,the genesis of colloform pyrite in Pb-Zn deposits,its g...Colloform pyrite with core-rim texture is commonly deposited in carbonate platforms associated with the sulfide ores such as the Caixiashan Pb-Zn deposit.However,the genesis of colloform pyrite in Pb-Zn deposits,its growth controls and their geological implication are insufficiently understood.Integration of in-situ trace element and SIMS sulfur isotopes has revealed geochemical variations among these pyrite layers.These colloform pyrite occur as residual phases of core-rim aggregates,the cores are made up of very fine-grained anhedral pyrite particles,with some rims being made up of fine-grained and poorlycrystallized pyrite,while the other rims were featured with euhedral cubic pyrite.which are cemented by fine-grained calcite and/or dolomite with minor quartz.Sulfur isotope analysis shows that some wellpreserved rims have negative δ^34 S values(-28.12‰to-0.49‰),whereas most of the cores and rims have positive δ^34 S values(>0 to+44.28‰;peak at+14.91‰).Integrating with the methane and sulfate were observed in previous fluid inclusion study,we suggest that the 34 S depleted rims were initially formed by bacteria sulfate reduction(BSR),whereas the positive δ^34 S values were resulted from the sulfate reduction driven by anaerobic methane oxidation(AOM).The well-developed authigenic pyrite and calcite may also support the reaction of AOM.Combined with petrographic observations,trace element composition of the colloform pyrite reveals the incorporation and precipitation behavior of those high abundance elements in the pyrite:Pb and Zn were present as mineral inclusion and likely precipitated before Fe,as supported by the time-resolved Pb-Zn signal spikes in most of the analyzed pyrite grains.Other metals,such as Hg,Co and Ni,may have migrated as chloride complexes and entered the pyrite lattice.Arsenic and Sb,generally influenced by complex-forming reactions rather than substitution ones,could also enter the pyrite lattice,or slightly predate the precipitation of colloform pyrite as mineral inclusions,wh展开更多
Colloform pyrite is a special form of nano-micro polycrystalline aggregation growth, for which a suitable term is ＂aggregates of nano-micro crystals＂. This kind of colloform texture is observed in various geological...Colloform pyrite is a special form of nano-micro polycrystalline aggregation growth, for which a suitable term is ＂aggregates of nano-micro crystals＂. This kind of colloform texture is observed in various geological bodies, such as ancient sedimentary rocks, modern marine and lake sediments, various types of ore deposits, and modern seafloor hydrothermal vents. This paper summarizes the latest developments and research into the definition, formation mechanisms, and environmental indications of colloform pyrite. There appears to be three main formation mechanisms of colloform pyrite： pseudomorphic replacement; biogenic precipitation; and inorganic precipitation. The morphology, particle size, trace element content and preferential growth orientations of coUoform pyrite microcrystals can be important indicators for sedimentary environments, hydrothermal activity, and ore-forming processes. We suggest that the microscopic features of nano-micro crystals in colloform pyrite and their aggregation growth patterns need further investigation. The relationships between formation mechanisms of colioform pyrite, organic activity and depositional environments require further exploration. To reveal the nature of nano-micro grain aggregation growth in colloform pyrite and analyse its growth environment and evolutionary history, it is supposed to apply nanoscientific and nanotechnological methods, further integrate consideration of macroscopic geological backgrounds and microscopic mineral growth phenomena, combine high-resolution imaging systems and in situ quantitative microanalysis methods and constitute a mergence of earth science, thermodynamics and kinetics, life science, material science, and chemistry in the study.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41702067 and 41602067)National Key Research and Development Program of China(Grant No.2018YFC0603603)+1 种基金Natural Science Foundation of Guangdong Province(Grant No.2017A0303113246)the Fundamental Research Funds for the Central Universities(171gpy63 and 181gpy25)
文摘Colloform pyrite with core-rim texture is commonly deposited in carbonate platforms associated with the sulfide ores such as the Caixiashan Pb-Zn deposit.However,the genesis of colloform pyrite in Pb-Zn deposits,its growth controls and their geological implication are insufficiently understood.Integration of in-situ trace element and SIMS sulfur isotopes has revealed geochemical variations among these pyrite layers.These colloform pyrite occur as residual phases of core-rim aggregates,the cores are made up of very fine-grained anhedral pyrite particles,with some rims being made up of fine-grained and poorlycrystallized pyrite,while the other rims were featured with euhedral cubic pyrite.which are cemented by fine-grained calcite and/or dolomite with minor quartz.Sulfur isotope analysis shows that some wellpreserved rims have negative δ^34 S values(-28.12‰to-0.49‰),whereas most of the cores and rims have positive δ^34 S values(>0 to+44.28‰;peak at+14.91‰).Integrating with the methane and sulfate were observed in previous fluid inclusion study,we suggest that the 34 S depleted rims were initially formed by bacteria sulfate reduction(BSR),whereas the positive δ^34 S values were resulted from the sulfate reduction driven by anaerobic methane oxidation(AOM).The well-developed authigenic pyrite and calcite may also support the reaction of AOM.Combined with petrographic observations,trace element composition of the colloform pyrite reveals the incorporation and precipitation behavior of those high abundance elements in the pyrite:Pb and Zn were present as mineral inclusion and likely precipitated before Fe,as supported by the time-resolved Pb-Zn signal spikes in most of the analyzed pyrite grains.Other metals,such as Hg,Co and Ni,may have migrated as chloride complexes and entered the pyrite lattice.Arsenic and Sb,generally influenced by complex-forming reactions rather than substitution ones,could also enter the pyrite lattice,or slightly predate the precipitation of colloform pyrite as mineral inclusions,wh
基金funded by the National Natural Science Foundation of China(41272062)the Fundamental Research Funds for the Northeastern University(N150106001)+1 种基金the Open Foundation Of State Key Laboratory Of Ore Deposit Geochemistry(Institute Of Geochemistry,Chinese Academy Of Sciences,Guiyang)(201308)the Open Foundation Of Key Laboratory Of Mineralogy and Metallogeny in Guangzhou Institute of Geochemistry,Chinese Academy of Sciences(KLMM20150101)
文摘Colloform pyrite is a special form of nano-micro polycrystalline aggregation growth, for which a suitable term is ＂aggregates of nano-micro crystals＂. This kind of colloform texture is observed in various geological bodies, such as ancient sedimentary rocks, modern marine and lake sediments, various types of ore deposits, and modern seafloor hydrothermal vents. This paper summarizes the latest developments and research into the definition, formation mechanisms, and environmental indications of colloform pyrite. There appears to be three main formation mechanisms of colloform pyrite： pseudomorphic replacement; biogenic precipitation; and inorganic precipitation. The morphology, particle size, trace element content and preferential growth orientations of coUoform pyrite microcrystals can be important indicators for sedimentary environments, hydrothermal activity, and ore-forming processes. We suggest that the microscopic features of nano-micro crystals in colloform pyrite and their aggregation growth patterns need further investigation. The relationships between formation mechanisms of colioform pyrite, organic activity and depositional environments require further exploration. To reveal the nature of nano-micro grain aggregation growth in colloform pyrite and analyse its growth environment and evolutionary history, it is supposed to apply nanoscientific and nanotechnological methods, further integrate consideration of macroscopic geological backgrounds and microscopic mineral growth phenomena, combine high-resolution imaging systems and in situ quantitative microanalysis methods and constitute a mergence of earth science, thermodynamics and kinetics, life science, material science, and chemistry in the study.
