Vertical Alteration Zoning And Element Distribution Characteristics Of Porphyry Metallogenic System

The Jiama copper-polymetallic deposit is one of the most complex porphyry metallogenic systems in the Gangdise metallogenic belt of the Qinghai-Tibet Plateau.It develops various types of ore bodies such as porphyry ore bodies,skarn ore bodies,and horny ore bodies,and The value of scientific research and the significance of exploration and evaluation.In this paper,through the detailed geological catalogue of the first 3000m scientific deep drilling(JMKZ-1)in the Jiama deposit and the analysis and testing of 63 elements of the full-hole core samples,Combined with the vertical alteration zoning characteristics of the metallogenic system,the distribution characteristics of representative elements in different types of alteration zones were identified,The reasons for element enrichment or depletion are discussed in order to provide reference for the metallogenic mechanism of porphyry metallogenic system and deep ore prospecting.Through the detailed geological cataloging of the drill cores and the identification of the samples under the optical thin section microscope,the vertical core geological features of the Jiama deposit are mainly as follows:The vertical lithology from top to bottom is biotitisation and silicified hornstone,skarnized hornstone,skarn,skarnized marble,Sericitized,weakly sericitized(kaolinite)porphyry and weakly potassium silicated porphyry,porphyry-like granite without mineralized alteration(no ore core).According to the vertical alteration and mineralization characteristics of the cores,the drill cores are roughly divided into three alteration zones:horny alteration zones,skarn alteration zones and sericite(kaolinite)alteration zones.At the same time,the horny alteration zones dominated by biotized altered horns and strongly silicified altered horns,a skarnized alteration zone dominated by skarn in the progressive alteration stage and skarn in the regressive alteration stage and the sericite(kaolinite)alteration zone dominated by monzonitic granite porphyry and granodiorite porphyry without obvious(weak)mineralization alteration,intra-and inter-alteration elements were analyzed.characteristics were studied.The study of element geochemical characteristics shows that the shallow horny alteration zone is rich in Au,Se,Cs,Cu,Mo,Tl,W,K₂O,Rb elements,and depleted in Fe₂O₃,Mn O,Hg,Zn,Te,Pb elements,and the content of rare earth elements is relatively large,showing a weak negative Eu anomaly;The central skarnization zone is obviously enriched with elements such as Ca O,Au,Se,Bi,Cu,Mo,W,Sn,Be,Cs,In,Mn O,etc.At the same time,in the stages of progressive alteration and regressive alteration,the The characteristics of the relatively large difference in rare earth element content;The deep sericitized porphyry belt is enriched with Sr,W,K₂O,Cs,Te,U,Ca O,P₂O₅,Se,Be,Tl,Rb,and strongly depleted of Fe₂O₃,Ni,Sc,Te,Pb,Cd and so on.During the alteration and mineralization of hornstones,skarns and porphyries,ore-forming fluids brought in a large amount of ore-forming elements such as Cu,Mo,Pb,Zn,and W,These metal elements and volatiles form complexes that dissolve in the ore-forming fluid,and precipitate out and form corresponding sulfides due to changes in temperature,p H,and sulfur concentration.In the process of porphyry alteration,the metasomatism of hornblende,biotite,plagioclase,etc.is mainly through hydrothermal fluid,or filling cracks in the form of hydrothermal veins,resulting in the introduction of elements.