Late Jurassic-early Cretaceous Magmatism And Its Mineralized Potentiality In The Gongqiongzuobo Fe-Cu Ore Occurrence In The Western Bangong-nujiang Metallogenic Belt,Tibet

This paper has systematicaly researched about LA-ICP-MS zircon U-Pb age,zircon trace element features,whole-rock geochemistry（major and trace element,Sr-Nd-Pb isotope composition）,in-situ zircon Hf isotope composition of main intrusives from the Gongqiongzuobo Fe-Cu ore occurrence.The result of Geochronology testing shows:the weighted average age are 147.0Ma（Granite porphyry）,146.1 Ma（Quartz diorite porphyrite）,143.6 Ma（Monzonitic granite porphyry）and 142.8 Ma（Syenogranite）respectively,means there are at last four periods of magma activity in Gongqiongzuobo area during late jurassic-early cretaceous epoch.The result of geochemistry characteristics shows:（1）Granite porphyry belongs to aluminum-weakly peraluminous I-type granite;（2）Monzonitic granite porphyry is high potassium calc-alkine series and belongs to weakly peraluminous I-type granite;（3）Syenogranite has experienced strong crystallization differentiation and belongs to high differentiation I-type granite;（4）the rare earth element of those rocks all enriche in Rb,Th,U,Pb and deplete in Nb,Ta,Ti,P.All features imply that the rock-forming materials are mainly coming from the crust-source:（1）Nb/Ta ratio of the Granite porphyry is 12.1,Monzonitic granite porphyry’s is 13.5,all are closed to continental crust;（2）the ratios of ⁸⁷Sr/⁸⁶Sr_（i）of Monzonitic granite porphyry are ranged from 0.709613 to 0.711233,the ratio of¹⁴³Nd/¹⁴⁴Nd_（i）are ranged from 0.511955 to 0.511989,ε_Nd（t）are ranged from 9.1 to-9.7,T_DM2-Nd are ranged from 1.70 to 1.76 Ga;（3）the ratios of ²⁰⁷Pb/²⁰⁴Pb_（i）of Monzonitic granite porphyry are ranged from 15.684 to 15.714,the ratios of ²⁰⁶Pb/²⁰⁴Pb（i）are ranged from 18.610 to 18.666,all those shows the source characteristics of upper cruste/middle lhasa base materials;（4）the zircon’sε_Hf（t）of Granite porphyry are ranged from-8.50 to-5.14,the zircon’sε_Hf（t）of Quartz diorite porphyrite are ranged from-10.51 to-6.26,the zircon’sε_Hf（t）of Monzonitic granite porphyry are ranged from-8.57 to-4.32,the zircon’sε_Hf（t）of Syenogranite are ranged from-9.88 to-6.15,all those zircons have a negativeε_Hf（t）value.There are various types of skarn,including garnet skarn,wollastonite skarn,tremolite（actinolite）skarn,epidote-chlorite skarn.Fe-Cu mineralization is primarily occurred in the skarn,mainly including magnetite,malachite,covellite,chalcopyrite.Observing from the distribution of mineralization-alteration and the structure contact relationshio of intrusives-skarn-marble,we conclude that the Granite porphyry is the ore-forming body.The main mineralizing element（Au Cu Mo W TFe）texts of five skarnized ore sample shows that the highest-grade of TFe is nearly 27.9%and the highest-grade of Cu is nearly 1.37%,both are above the industrial-grade.Gongqiongzuobo Fe-Cu ore occurrence is the first disvovery of the late Jurassic mineralizing event in the southern edge of the Bangong-Nujiang metallogenic belt.It has important significances for consummating regional metallogeny,directing regional prospecting and opening a new direction for mineral exploration.