Petrology, Geochemistry and Petrogenesis of Wolonggu granites and Tongchang granodioritic porphyries: Constraints on copper metallogenic geological settings in northeastern Jiangxi Province

Northeastern Jiangxi Province is a major polymetallic ore-forming area in northeastern segment of the Jiangnan orogenic belt. Wolonggu granitoid pluton is a typical nonmineralized granite pluton and consists chiefly of monzogranites. LA-ICP-MS zircon U-Pb isotopic dating yields a weighted mean 206Pb/238U age of 133Ma±1Ma, which represents the age of magmatic crystallization and reveals that the granitic pluton was emplaced in Early Cretaceous. Combined with their high initial 87Sr/86Sr values ranging from 0.716079 to 0.719392 and low εNd(t) values ranging from -6.51 to -5.14, the authors hold that the Wolonggu granites were probably derived from partial melting of metamorphic pelitic rocks from the crustal source region. However, Tongchang granodioritic porphyric intrusion is a classic mineralized granitic pluton and consists mainly of granodioritic porphyries. Emplaced in Middle Jurassic (with crystallization age of 171Ma±3Ma), the Tongchang granodioritic porphyries display low initial87Sr/86Sr values ranging from 0.704403 to 0.704475, high εNd(t) values ranging from -1.14 to +1.80 and higher Mg# values of 28-53, suggesting that the magma was possibly derived from partial melting of subducted oceanic slabs and relative sediments, and was polluted by mantle materials during its upward migration. The comparison of features between the nonmineralized granite pluton and the copper mineralized granitic pluton can detect the constraint of the Mesozoic granitoid magmatism on copper metallogenic geological settings, which may provide the essential geological data of the geodynamic setting for regional mineralization.