The "Three-in-one" Deposit Characteristics And Metallogenic Mechanism Of Luoyang Iron Ore Inin Zhangping City,Fujian Province

The Luoyang iron polymetallic ore deposits in Zhangping City is located in the east of the southwestern Fujian basinin late Palaeozoic and in the southeast of Zhenghe-Dapufrcture.It has been experienced EarlyDevonian basement formation,evolution of the Late Paleozoic basin and tectono-magmatic progress since Mesozoic with corresponding mineralization associated with different periods.Luoyang iron ore deposits has a great researching significance as the represe,geochemistry,mineral deposits,study of orefield structure and so on,this article researches ore-controlling factors through thrntation of the “Makeng type” iron deposits.Based on “three in one”,which means ore-forming geological body,metallogenic tectonic and metallogenic structural plane,mineralization marks,discusses ore genesis and mineral-forming and ore-forming age,finallywe establish metallogenic mechanism and prospecting modle.The granite rock mass is compound rock mass mainly composed of medium-fine grain porphyritic granite and granite porphyry in Luoyang iron deposits area.Its intrusive period is 153±1Ma and 129±1 Ma.In Geochemical composition,the rock mass has the I type granite's characteristics of the high silicon and alkali,high potassium calc alkali,weakly peraluminous,enrichment of large iron lithophile elements,loss of high field strength elements.It is the lower crust remelting type granitewith a small amount of mantle source materia,and it is shown as after collision environment which reflects the lithospheric stretching tectonic setting under the tectonic domain environment from extrusion to stretch transformation during the period from late late Jurassic to early Cretaceous.The main forming age of molybdenite in Luoyang iron deposits was 133.0±1.9Ma~134.0±4.2Ma.We conclude Luoyang iron ore metallogenic epoch is the early Cretaceous.Combined with the geochemical characteristics,so we infer granite rock mass in the early cretaceous(130Ma±)is closely related to mineralization.In a word,the granite rock is the metallogenic geological body.Luoyang iron deposits strictly controlled by the tectonic and calcium-silicon surface.Anticline fold structure,thrust nappe structure and decollement structure serve as good migration pathway and ore-forming space for diagenesis and mineralization.The mainly ore-bearing beds of the main orebody is the fracture zone between clastic rocks in Lindi formation(C1l))and limestone in Chuanshan-Qixia formations(C3c-P1q),it is also near the contact zone of granite porphyry and carbonate rocks.So we think Luoyang iron deposit is a stratabound skarn type deposit.At deposit genesis aspect,in this paper,we carry out the hydrogen-oxygen isotope on quartz vein and sulfur isotope on pyrite and molybdenite.The results of hydrogen-oxygen isotope is ?D points fall into magma water scope,it reveals luoyang iron deposit has the characteristics of the magma source.Characteristics of sulfur isotope belongs to the deep magmatic sulfur scope.it indicates the ore-forming fluid comes from deep magma.Through Re isotope determination,magma has the characteristic of crust-mantle mixed source.So,Luoyang iron ore-forming materials derived from the crust-mantle mixed source of deep magmatic hydrothermal.Through the study of ore-forming elements,it reveals that the luoyang iron deposit is stratabound skarn type ore deposit which is strictly controled by the formation,structure and granite.At the same time,we establish the metallogenic model and prospecting model,it has great significance of “Makeng type” iron deposits genesis and metallogenic mechanism.