Characteristics Of Pyrite Zoning And Gold Remobilization In The Yangshan Gold Belt,West Qinling,China

The Yangshan gold belt is located in the Mianlue suture zone,west Qinling orogenic belt.It is a multistage mineralization and developed pyrite zoning.It is a ideal district to study the formation and evolution of pyrite zoning in orogenic gold deposits.The paper used BSE and LA-ICP-MS to conduct mineragraphy and geochemistry studies on the structure and composition characteristics of the pyrite in the Yangshan Gold Belt.The main results were as follows:The hydrothermal mineralization period was divided into four stages:M1 pyrite-quartz stage,M2pyrite-arsenopyrite-quartz stage,M3 arsenopyrite-pyrite-quartz stage,M4 stibnite±natural gold±calcite-quartz stage,where M2 stage includes a large number of pyrite,arsenopyrite less,M3 stage includes a large number of arsenopyrite.The core to the edge of the pyrite is py1a,py1b,py2,and py3.Py1a are riched in mineral inclusions,weaker dissolution reprecipitation reaction,compared to other stages of pyrite enriched in Co,Ni,Pb,Bi trace elements,which is an order of magnitude higher than py2,py3,poor As,Au,Cu,which is 1-2 orders of magnitude lower than py2 and py3,and As is strongly positively correlated with Au,and Pb is weakly positively correlated with Bi.Py2 often has an As-rich oscillation zoning.There is often a small amount of arsenopyrite coexisting in the zoning.It is mainly enriched in As,Au,Cu,depleted Co,Ni,Bi,and Pb,and As is weakly positively related to Au,and Pb is strongly positively related to Bi.The Py3 characteristic is similar to py2,mainly enriched in As,Au,Cu and lack of Co,Ni,Bi,and Pb,and there is an As-rich zone between py2 and py3.Au is weakly positively correlated with As,and Pb is strongly positively correlated with Bi.Py1b is an illusion of py1a,which is formed when py1a is subjected to strong dissolution reprecipitation reaction.The trace element content is between py1a and py2,and differently degree enriched Co,Ni,Pb,Bi,As,Au,Cu.As is weakly positively related to Au,and Pb is strongly positively related to Bi.There was no significant change in Sb and Ag content at all stages and there was a strong positive correlation.Since the M2 stage,the regional cyclic brittle deformation increased,part of py1a dissolved and reprecipitated,and a larger range of element remobilized and redistributed in the regional strata,making Au,As,Cu,Co,Ni,and Pb remobilization.And Au,As,and Cu are more easily remobilization and redistributed than Co,Ni,Pb,and Bi.Finally in the M2 stage,a part of Au enters the py1a,py1b lattice by dissolution and precipitation reaction,and a part of gold enters the py2 lattice.No gold remobilization occurred in the pyrite and arsenopyrite after the M2 stage.The nature gold appearing in the M4 stibnite±natural gold±calcite+quartz vein stage may be directly precipitated in the fluid.The temperature is 271.3 to288.3? and is rich in CO₂.