Geochronological constraints and geochemical insights into the Late Paleozoic-Early Mesozoic evolution of the Baimaxueshan pluton,Deqin,Yunnan
To better understand the geological evolution history and its temporal framework of the Jinshajiang tectonic zone,this study conducted a systematic analysis of geological phenomena in the western section of the Jiangda-Deqin-Weixi magmatic arc,focusing on the genesis and age of the Ninong tonalite and Baimaxueshan granodiorite.High-precision zircon U/Pb geochronological results indicate that these two types of rocks were formed in the early(279±2.9 Ma)and late(255.8±5 Ma)stages of the Permian period,providing a new temporal framework for the geological evolution of the Jinshajiang tectonic zone.Whole-rock analysis shows that the rock bodies belong to a high-K calc-alkaline intermediate-acid intrusive rock series,with quasi-aluminous to peraluminous properties,enriched in large ion lithophile elements(LILEs),and strongly depleted in high field strength elements(such as Nb,Ta,Ti),representing typical arc magmatic characteristics.These rock bodies exhibit similar geochemical characteristics to the Jiaren and Ludian diorite-type rock bodies,suggesting similar magma sources but undergoing different magma evolution processes.Combined with published data,this study suggests that the Jinshajiang tectonic zone may have undergone at least five episodes of granitic magmatism since the Paleozoic era:347～340 Ma,292～279 Ma,261～249 Ma,237～235 Ma and 232～214 Ma.The formation of the Ninong tonalite(279±2.9 Ma)is associated with the initial stage of westward subduction and consumption of the ancient Jinshajiang Tethys Ocean,while the Baimaxueshan granodiorite(255.8±1.8 Ma)may have formed during the end of the subduction stage or the transition from subduction to collision.The orogenic collision in the Jinshajiang tectonic zone occurred in the Middle Triassic and ceased in the middle of the Late Triassic.These findings provide new insights and constraints for understanding the tectonic evolution and plate dynamics of the Jinshajiang tectonic zone and even the entire eastern region of the Qinghai-Tibet Plateau.
万方数据
维普
