Mesozoic Magmatism And Metalogeny Geodynamics Of Linglong Gold Deposit In Jiaodong Peninsula, Eastern North China Craton

Jiaodong peninsula, located in the east margin of north China craton, is the mostimportant gold producer in China. This article, through the sampling of Linglonggranite, Guojialing granodiorite and mafic enclaves, melanocratic dykes, meltingbasement rocks and ores systematicly in linglong gold deposite and surrounding areas,and adopting the methods of zircon U-Pb isotope dating, in situ Lu–Hf isotopeanalyses, whole rock analyses of major, trace and rare earth elements and Rb, Sr, Sm-Nd isotope compositions and the40Ar-39Ar dating of potassium feldspar, combiningto the previous studies in the tectonic background, devotes to discuss Petrogenesis,source materials of gold mineralization and magmatism and the metallogenicdynamics in Jiaodong Peninsula.Zircon U-Pb and Lu-Hf isotopes show that the linglong granite age is150-160Ma, epsilon Hf (t) values are between-34.0to-23.8, indiacating the source derivedfrom the recycle of archean basement; the ages of Guojialing granodiorite and itsmafic enclaves are betwwen123-127Ma, epsilon Hf (t) value of-19.3~-16.8,indicating the magmatic origin of crustal source, meanwhile the existence of maficenclaves illustrates the Guojialing granodiorite also derived from deep source (mantlesource) mixing with crustal magma; the emplacement ages of melanocratic dykes arebetween126to166Ma, their epsilon Hf (t) values (-44.6and9.8) further confirm amixture of recycled ancient crust and younger juvenile components. In addition, inthese rocks, young zircons (120ma) have higher Th/U ratios than old inheritedzircons, indicating that the lithosphere’s destruction is with the mantle materialsupwelling and then joining in the crust. The40Ar-39Ar dating results of potassiumfeldspar show that the plateau age is117.5±1.0Ma, consistent with the timing of goldmetallogeny (110-120Ma)Whole rock analyses of Rb-Sr, Sm-Nd isotope composition and geochemicalcharacteristics show that epsilon Nd,T=122Mavalues range from-21.3to-15.6,obviously among the areas of mantle-derived melanocratic dykes, granite and metamorphic rocks of epsilon Nd (t) values. The standardized distribution patterns ofrare earth elements on all these rocks and ores analysed are tilted to the right, and themelanocratic dykes relatively enrich the heavy rare earth elements. The evidencesabove indicate that the source materials for gold mineralization and magmatism in theJiaodong Peninsula thus show multiple origins involving Precambrian basement rocks,Mesozoic granitoids and mantle-derived mafic magmas.Our study reveals a mixing of crustal, lithosphere mantle and asthenosphericcomponents in gold metallogeny. We present and integrated tectonic model for thegenesis of gold mineralization which involves delamination, mantle upwelling,subduction-related metasomatic enrichment and recycling of ancient components.An integrated model explains the processes of delamination, slab subduction,lithospheric thinning and gold metallogeny in the Shandong Peninsula. The collisionbetween the North China Craton and the Yangtze Craton is marked by the formationand exhumation of the Su-Lu ultrahigh pressure metamorphic belt. The mantlemagmas migrated through structural pathways and were emplaced as a series ofmelanocratic dykes of varying compositions, depending on the degree of melting atthe source and the extent of compositional modification during ascent. Themelanocratic dykes probably acted as ‘stoppers’(impermeable barriers) to focus themineralization at their contacts. The Tan-Lu fault served as a major corridor tochannelize the magmas and fluids.