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,?_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's?_Hf?t?of Granite porphyry are ranged from-8.50 to-5.14,the zircon's?_Hf?t?of Quartz diorite porphyrite are ranged from-10.51 to-6.26,the zircon's?_Hf?t?of Monzonitic granite porphyry are ranged from-8.57 to-4.32,the zircon's?_Hf?t?of Syenogranite are ranged from-9.88 to-6.15,all those zircons have a negative?_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.