诸广中部鹿井铀矿田大场坪矿点花岗岩成因及其对铀成矿的启示OA

Granite-related uranium deposits exhibit a close spatial and genetic association with granitic intru-sions.Investigating the relationship between magmatic evolution and uranium mineralization is essential for a deeper understanding of uranium metallogenic regularities and for elucidating the regional metallogenic mecha-nisms.At the Dachangping uranium deposit,the medium-to coarse-grained two-mica granite is the principal ore-hosting wall rock.In this study,drill core samples from various depths at Dachangping were analyzed using petrography,LA-ICP-MS zircon U-Pb dating,major and trace element geochemistry,and Sr-Nd isotopic compo-sitions to explore the magmatic evolution.Analytical results indicate that the crystallization age of the medium-to coarse-grained two-mica granite is(230.4±1.0)Ma.Geochemically,the granite is silica-rich,has a high to-tal alkali content with K＞Na,and a Rittmann index of less than 3.3,classifying it as a high-K calc-alkaline granite.With A/CNK values greater than 1,it belongs to the peraluminous granite category.Trace element data reveal enrichment in high field strength elements(HFSEs),such as Th and U,and significant depletion in large-ion lithophile elements(LILEs),including Ba and Sr.These granites are characterized by low Nb/Ta,high Rb/Sr,and high Rb/Nb ratios.Rare earth element(REE)patterns,normalized to chondrite,show a pro-nounced"seagull-shaped"distribution with a distinct negative Eu anomaly.In addition,the granite exhibits high initial 87Sr/86Sr ratios((87Sr/86Sr)i)and low εNd(t)values.These geochemical signatures are consistent with crust-derived granites and uranium-bearing granites in South China.Moreover,the granite displays low CaO/Na2O and CaO/Al2O3 ratios,along with a high(Na2O+K2O)/CaO ratio,indicating that the source re-gion was dominated by metamorphosed argillaceous-siliciclastic sedimentary rocks-characteristic of S-type gran-ites.Integrated with geochronological data and the regional tectonic framework,the formation of the medium-to coarse-grained two-mica granite is interpreted to have occurred shortly after the peak of the collision between the South China-Indochina block and the North China block.It was emplaced in a post-collisional extensional tec-tonic setting associated with crustal thickening and thinning,driven by a combination of radiogenic heat accumu-lation in the crust and thermal input from mantle-derived magmas.