Geochemistry And Significance Of Research On Lamprophyre In Hongshiquan Area, Gansu Province

There are many typical granite-type uranium deposits in China,including several lamprophyre dykes.Lamprophyre is a"window"to study changes in the mantle and mantle,and has an important relationship with gold,uranium,diamond and other deposits.Prior to the 1980s,some predecessors carried out some geological prospecting and research work in the Hongshiquan area,but the study on the basic vein rock?lamprophyre?is weak.In this paper,the lamprophyre in Hongshiquan area of Gansu Province was taken as the research object to carry out the field geological survey,lithofacies,geochemistry,Sr-Nd-Pb isotopes and so on.The characteristics of lamprophyre in Hongshiquan area were systematically determined.Based on the discussion of its magma source area nature,tectonic environment,magmatic evolution and uranium mineralization.By studying the petrological and mineralogy of lamprophyre,it is found that the lamprophyres in this area have the same features,such as gray-green,lamprophyric texture structure and massive structure.The amphiboles are mainly amphiboles and the matrix is mainly composed of plagioclase Rock and biotite composition,deputy minerals are mainly magnetite,apatite and zircon,named blinking lamprophyre.According to the geochemical analysis of the lamprophyre,the main elements are SiO₂=45.46%⁴8.96%,K₂O+Na₂O=3.26%⁴.45%and the Ritman???=2.67⁷.24.Calcareous alkaline lamprophyres,MgO as a reference factor in the Harker diagram,MgO and other oxides there is a positive correlation and negative correlation,indicating the evolution of the magma experienced crystallization separation.In terms of trace elements,the lamprophyre enriches large ion lithophile elements such as K,Rb and Pb relative to the original mantle rocks;the relatively weak loss of Sr;the relatively depletion of high field strength elements such as Ta,Nb,Th and Ti;the U content is obviously high The average lithospheric and mainland crustal average values in mainland China.For rare earth elements,?REE=159.652×10^-6241.866×10^-6;LREE/HREE=6.91¹1.67;?Eu=0.79⁰.97;For the Sr-Nd-Pb isotopes,¹⁴³Nd/¹⁴⁴Nd=0.511279⁰.511994,which lies between the mantle of Scotland and the mantle of eastern China,indicating that the Hongshuquan lamprophyre came from the mantle;(⁸⁷Sr/⁸⁶Sr)_i=0.706042⁰.706930,The lamprophyre magma in Shiquan area came from the mantle.The ²⁰⁸Pb/²⁰⁴Pb,²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb contents were high,especially 206Pb anomalously high,indicating that the lamprophorite has a high original uranium content.The diagenetic age of lamprophyres in Hongshuquan area is 237.2±2.6Ma by ⁴⁰Ar-³⁹Ar whole-rock determination,belonging to the Triassic period.The study suggests that the lamprophyre magma originated from the EMII-rich mantle source area and has the characteristics of evolving basalts.Magma formed in the plate tension environment,in the crystallization process may also have undergone a slight part of the melting effect of crustal material contamination,the origin of the model for the"mantle source+continental crust mixed"type.The relationship between the lamprophyre and uranium mineralization at time and space shows that the uranium enrichment in the lamprophyre is related to the re-enrichment of uranium deposits in the Hongshuquan deposit,providing a theoretical basis for the study of Hongshuquan uranium mineralization.At the same time,uranium The re-enrichment played a geochemical barrier.