Study Of Geological Characteristics And Metallogenic Mechanism Of Wangjiaping Gold Deposit,Shanyang County,Shannxi Provice

Shanyang-Zhashui ore concentration area locates in the late Paleozoic fault belt of the north section of the eastern Qin ling orogenic belt,tectonic belt occurs in nearly E-W direction along the tectonic lineament experienced complex tectonic evolution and extensive development of magmatism,Wang Jiaping gold deposit is a rare Carlin type gold deposit located in the south of Shanyang-Fengzheng fault which is the South boundary of Shanyang-Zhashui ore concentration area.This area experience complex tectonic setting,and this ore concentration area involved various kinds of deposits.This paper is based on the "12th Five-Year" National Science and technology support program,Wang Jiaping gold deposit was selected as the research object,we carried out a detailed geological investigation,like the geological characteristics,ore geochemistry,stable H-O-S isotope study and so on.We discuss the ore forming minerals,the source and property of ore-forming fluid and their metallogenic mechanism of the deposit.The main achievements are as follows:(1)Wang Jiaping gold deposit is hosted in Xinghongpu Group formation,it's about the Devonian silt slate.The ore-controlling structure is a series of reverse faults which strikes in a nearly E-W direction,and the distribution of the orebody is controlled by catallactic alteration zone.The types of mineralization is carline type,and the main gold-bearing mineral is pyrite?limonite?railcar?orpiment and so on.The main wall-rock alteration is pyritized?salinification?decalcification and so on.Mineralization can be divided into three phases: quartz-calcite-pyrite stage?calcite-quartz-gold-polymetallic sulfide stage and quartz-calcite-railcar-orpiment stage.(2)By micro thermometry fluid inclusions of different mineralization stages,we can found that Wang Jiaping gold deposit was formed in 100-120?,and its mineralization salinity is 15.96wt% NaCl.The densities of ore-fluids are 1.06g/cm~3,and the pressure of the deposit mineralization is 133 MPa.The depth of Wang Jiaping gold deposit is 4.9km,which is a epithermal deposit.(3)The rare earth and trace elements test results showed that not only the rare earth elements distribution curve type and characteristics of surrounding rock and ore of Wang Jiaping gold deposit are similar,but also the rare earth and trace elements distribution curve type and characteristics of the pyrite in surrounding rock and ore are similar.It means the main source of ore-forming materials is from the surrounding rock.The ratio of Y/Ho and the abnormal high value of Tl indicates that the component of the deep part of earth is provided minerogenic materials in the mineralization process.(4)H-O isotope and trace element results showed that the ore-forming fluid changes between the rich Cl fluid and the rich F fluid,and it indicated that the ore-forming fluid has multi-period evolution characteristics during the whole mineralization stage.The distribution of S isotopes further proved that the ore-forming materials have the addition of deep source materials.(5)Based on the comprehensive regional data and the geological characteristics of Wang Jiaping gold deposit,it is concluded that the metallogenic mechanism of the deposit is strong tectonic movement in the region,and the gold in the original di spersed state of the surrounding rock layer is constantly activated?transported and enriched.With the increase of geothermal and tectonic stress,a large amount of thermal dehydration and formation sealing water are released.The fluid flow into the void structure extraction of surrounding rock minerals in the heat and f orce at the same time along,mixing with the deep fluid from mantle deep to shallow crustal movement,leading ore components of liquid substances by the deep crustal fluids carrying contamination and fluid properties change.Finally,under the participation of atmospheric precipitation,the ore bearing hydrothermal fluid is precipitated by seepage at all levels of the fault,forming the Wang Jiaping gold deposit.