The W-Sn Metallogeny And Its Geodynamic Setting, Eastern Guangdong Province, Southeast Coast

There is an episode of W-Sn metallogenic event occurred in coastal eastern Guangdong Province.In this study,we present a detailed investigation of the mineral deposit geology and geochemistry,the timing of magmatism and mineralization,and the metallogenic mechanism from the Xiling Sn,the Feie'shan W-Sn and the Lianhuashan W deposits,in order to summarize the metallogenic regularity and understand the metallogenic geodynamic setting.The new obtained findings and conclusions can be summarized as follows:1.Three metallogenic series can be summarized as follows:?1?the porphyry Cu-Au/Cu-Mo metallogenic series associated with Middle-Late Jurassic quartz diorites and granodiorites;?2?the W-Sn/Sn-Pb-Zn-Ag metallogenic series associated with Early Cretaceous highly fractionated I-or A-type granitic rocks;?3?the porphyry-epithermal Cu-Au-Mo and porphyry Cu-Mo metallogenic series associated with Late Cretaceous granodiorites.2.In conbination with the field works,the geochemical characteristics of volcanic rocks and the highly precise geochronology,we propose that the volcanic-subvolcanic rocks werve as the host rocks for the Xiling mineralization,and the related granitic intrusions might be hidded at depth in the Xiling deposit.The study of fluid inclusions suggests that the mixing of magmatic and meteoric fluids is the deposition mechanism of the Xiling Sn deposit.Combined with geochronlogical evidence,we propose that the Xiling Sn deposit is a product of multiple magmatic-hydrothermal pulses.3.We propose that the Feie'shan W-Sn deposit is a typical greisen deposit in the region.The ore-forming fluid has low salinity and reduced features,the alkali metal saturation in the early ore-forming stage is critical to W deposition,and the fluid-rock reaction is the deposition mechanism in the main ore-forming stage.Moreover,the mineralization and related magmatism formed in the Early Cretaceous,and the granite associated with W-Sn mineralization belongs to A₂-type granite,which was most likely derived from magma hybridization between anatectic granitic and mantle–derived magmas with following highly fractional crystallization.4.We propose that the Lianhuashan is a typical porphyry W deposit in the region,and the mineralization and related magmatism formed in the Early Cretaceous.The quartz porphyry is associated the Lianhuashan W mineralization,which was derived from a Mesoproterozoic crustal source with some contributions of mantle components.5.Combined with recent studies,we suggest there is an episode of Early Cretaceous W-Sn metallogenic event related to highly fractionated I-or A-type granitoids in eastern Guangdong Province,which is related to a geodynamic setting of large-scale lithospheric extension and thinning.The geodynamic mechanism is that the subduction orientation became highly oblique with respect to the Eurasian continental margin,whilst the upwelling of asthenosphere likely caused by a slab window rollback forming during the Middle-Late Jurassic in the Nanling Range.The ascending mantle–derived mafic magmas led to remelting of the crust in southeast coast.Then,the granitic melts underwent strong fractional crystallization during ascend,resulted in formation of I–or A–type granitic intrusions.