Geneticmineralogy And Sources Of Metallogenic Materials Of Liaoshang Gold Deposit In Shandong Province

Liaoshang Gold Deposit is a gold deposit with obvious structural control characteristics located in the lower plate of Guocheng fault zone.There are many stages of carbonate veins in it.These carbonate veins are the main gold-bearing ore bodies.The rock types are mainly monzonitic granite and marble.Previous people's understanding of Liaoshang gold deposit has gradually changed from SKARN-TYPE gold deposit to special"Liaoshang-type gold deposit".This paper rely on the Project“mineral and petrology characteristics of Liaoshang Gold Deposit”.It use optical microscope,Nano-SIMS and other devices to study the mineralogy and the source of ore-forming materials in Liaoshang gold deposit.We gain the following understandings:?1?The fineness of gold mineral particles is from 800.00 to 891.48.The average value is 865.04.The number of Ag/Au is from 0.143 to 0.167.The average value is 0.16.It is far less than 1.So it can be concluded that ore-forming fluids are related to regional magmatic activity.The ore-forming fluids is alkalinous.It forms in the medium-shallow depth.The metallogenic environment is relatively stable.It may form in Mesozoic-Cenozoic.?2?The 80 percent of the data about the sulfur isotope is from 0 to 20‰.43 records is from0 to 30‰.The record of?³⁴S is from 4.6 to 151.2‰.The range is 147‰.The average value is21.4‰.The sulfur isotopes of pyrite show the characteristics of lower core value and higher boundary value.Based on this,it is inferred that the ore-forming fluids originated from Jingshan Group and Mesozoic Laiyang Group.?3?Carbon,hydrogen and oxygen isotopes of gold-bearing carbonates in the metallogenic period of Liaoshang are determined,and the data obtained are mapped and analyzed.It is understood that the carbon source of Liaoshang gold deposit is characterized by multiple sources.Part of it comes from deep carbon dioxide and part from marble of Jingshan Group.The fluid source of Liaoshang gold deposit is a mixture of mantle-derived primary water,atmospheric precipitation and construction water.?4?The metallogenic model of Liaoshang gold deposit is inferred by integrating and analyzing the above data:Fluids mixed with mantle-derived primary water and atmospheric precipitation flow through the Paleoproterozoic Jingshan Group and Mesozoic Laiyang Group to form carbon dioxide-rich fluids.A large number of gold complexes were dissolved in the fluid.Temperature and pressure decrease gradually as fluid migrates along Guocheng fault and secondary fault.Carbon dioxide precipitates in the form of carbonate,which leads to a sudden drop in alkalinity and oxygen fugacity of ore-bearing hydrothermal solution.As a result,Au is supersaturated in the fluid and precipitates as a single substance.