Petrogenesis Study Of The Biotite Diorite And Monzogranite Of The Mangling Pluton In The North Qinling Tectonic Belt

The Mangling pluton is one of the large regional plutons in the North Qingling tectonic belt,and has various rocks types with the biotite diorite and monzogranite being the representatives.There are biotite diorite enclaves hosted in the medium-to coarsed-grained monzogranite in the local exposures of the Mangling pluton.Therefore,a comparative study on the biotite diorite and monzogranite in the Mangling pluton can clarify the petrogenesis and magmatic nature of the related rock types of this pluton.In this paper,a detailed comparative study on the biotite diorite enclave,biotite diorite,medium-to coarsed-grained and fine-grained monzogranite of the Mangling pluton has been done through geological observation,petrography,zircon U-Pb dating,whole-rock geochemistry,zircon Hf isotope and geochemistry,with main recognitions as follows:(1)In the Mangling pluton,the biotite diorite enclave and biotite diorite formed at 149.6±0.9Ma and 147.3±0.6 Ma,whilst the medium-to coarsed-grained and fine-grained monzogranite formed at 144.0±0.7 Ma and 142.3±0.9 Ma,with the former two types of rocks emplacing earlier than the latter two types of rocks.(2)The biotite diorite and monzogranite of the Mangling pluton have similar characteristics in their whole-rock geochemistry,viz.,high-K calc-alkaline series and metaluminous to weakly peraluminous,LILE and LREE enrichment,HFSE depletion and having minor to negligibly negative Eu anomalies.But in the petrogenesis,the biotite diorite enclave,biotite diorite and monzogranite of the Mangling pluton have different petrogenesis,viz.,the biotite diorite enclave having A₁-type granitiods characteristics,the biotite diorite being I-type granitiods,whilst the medium-to coarse-grained and fine-grained monzogranite being fractionated ?-type granite.(3)In the magma sources,the biotite diorite enclave and biotite diorite of the Mangling pluton were mainly soured from melting of lithospheric mantle,with contamination of some old crustal materials,whilst the medium-to coarse-grained and fine-grained monzogranite of the Mangling pluton were mainly derived from re-melting of the Pale-to Mesoproterozoic crust,with minor mixing of mantle-derived magma and some crustal contamination during the rock formation.(4)In the formation temperature,the biotite diorite enclave and biotite dioriteof the Mangling pluton are higher than that of the medium-to coarse-grained and fine-grained monzogranite of the Mangling pluton.However,in the oxygen fugacity of magma,the biotite diorite enclave and medium-to coarse-grained monzogranite of the Mangling pluton are higher than that of the biotite diorite andfine-grained monzogranite of the Mangling pluton.(5)The medium-to coarsed-grained monzogranite has many similarities with the Taoguanping ore-related small intrusion,indicating that the magma of the medium-to coarsed-grained monzogranite may have potential for mineralization.