Geochronology and geochemical characteristics of magmatic rocks and their rela-tionship with mineralization in Taoxiba deposit,southern Jiangxi Province
The Taoxiba large tin deposit is located at the junction of Wuyishan Metallogenic Belt and Nanling Metallo-genic Belt in South China.Its deposit type,genesis,magmatism and relationship between magmatism and mine-ralization are very complex,and has been lack of effective constraints.This article conducts systematic petrology,zircon U-Pb chronology,and rock geochemistry research on magmatic rocks developed in the ore deposit.The magmatic rocks in the Taoxiba deposit exhibit multi-stage and multi-phases evolution characteristics,ranging from early to late:tuff→medium to coarse-grained porphyritic granite→fine-grained granite→granite porphyry.LA-ICP-MS zircon U-Pb dating studies show that it has two main magmatic periods:140～148.4 Ma(intermedi-ate-acid volcanic rocks)and 122.3～138 Ma(granitoid).The Taoxiba granite has the characteristics of high sili-con,rich potassium and poor calcium,belongs to A-type granite,and the tuff has the characteristics of being rich in silicon and calcium.Although they both are relatively enriched in incompatible elements such as Rb,Th,U,Nb,and depleted in Ba,Sr,etc.,they have different sources and evolutionary processes.The former mainly comes from old crustal materials,with a significant addition of mantle derived materials,and has undergone the fractional crystallization of potassium feldspar.The latter mainly comes from partial melting of old crustal mate-rials,and has undergone the fractional crystallization of plagioclase.In addition,the forming age of the Taoxiba granite is consistent with the mineralization age,while the tuff age is significantly older than the mineralization age,and the granite has a higher degree of evolution and lower oxygen fugacity conditions compared to tuff,which is more conducive to the enrichment of tin.The mineralization of the Taoxiba tin deposit is more closely related to granite,and the metallogenic parent rock is medium to coarse-grained porphyritic granite and fine-grained granite,formed in the context of large-scale continental extension in southern China during the late Yan-shanian period.
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