地质科学2025，Vol.60Issue(4)：991-1013,23.DOI:10.12017/dzkx.2025.066
徐淮地区旗杆楼铁矿早白垩世花岗岩成因及其成矿意义
Petrogenesis and metallogenic significance of the Early Cretaceous granites in the Qiganlou Fe deposit,Xuzhou-Huaibei area
摘要
Abstract
The skarn-type deposits of the Xuzhou-Huaibei area are closely related to the Early Cretaceous magmatism,and the Early Cretaceous magmatic rocks widely distributed in the area are excellent objects for studying igneous and ore-forming processes.This study focused on the investigation of petrography,isotopic chronology,whole-rock geochemistry,and Hf isotopic compositions of zircon from the Early Cretaceous granite of the Qiganlou region in the Xuzhou-Huaibei area.Additionally,we examined the petrography and geochronology of skarn from the Qiganlou Fe deposit.Based on the research above,we analyze the petrogenesis of these granites and their source area properties,and discuss the restricting effect of the Qiganlou granites on the formation of skarn type iron ore.Zircon LA-ICP-MS U-Pb isotopic dating results indicate that the Qiganlou granites formed at 105.4±0.9 Ma.The U-Pb isotopic age of garnet in the skarn is 102.2±1.6 Ma,representing the mineralization age of the Qiganlou Fe deposit.These results suggest that both the igneous and ore-forming activities occurred during the late Early Cretaceous.The Qiganlou granites are primarily composed of plagioclase,potassium feldspar,and quartz,with low P2O5(0.14％～0.19％),A/CNK(0.68～0.97),(Na2O+K2O)/CaO(2.11～6.53),and TFeO/MgO(1.13～2.54),which is consistent with the geochemical characteristics of Ⅰ-type granites.Zircon εHf(t)values of the Qiganlou granites range from-18.3 to-14.7,significantly lower than those of Early Cretaceous mafic intrusions and high-Mg adakites in this area,suggesting a probable origin from ancient mafic lower crust,with minor or without contribution of the mantle-derived materials.Zircon Hf isotopic compositions of the Early Cretaceous magmatic rocks in the Xuzhou-Huaibei area are significantly more depleted than those of the adakites in the Dabie orogenic belt,implying that the source of the Early Cretaceous magmatism in this area is not the lower crust of Yangtze Craton,but derived from partial melting of mafic lower crust of the North China Craton.The Qiganlou granites show the geochemical characteristics of low contents of Sr(108.5×10-6～460×10-6),Y(7.9×10-6～10.8×10-6),Yb(0.79×10-6～0.96×10-6),low ratio of Sr/Y(10.05～44.23),and high ratio of(La/Yb)N(10.96～54.53),indicating the presence of residual plagioclase and garnet in the magmatic source area,corresponding to a melting pressure of 1.0～1.5 GPa.The transition from high-Mg adakites to Ⅰ-type granites of the Early Cretaceous magmatism in the Xuzhou-Huaibei area is attributed to lithospheric thinning triggered by westward subduction of the Paleo-Pacific slab.Additionally,the magmatic oxygen fugacity(logfo2=-18.76～-9.32)of the Qiganlou granites is notably lower than that of the metallogenic magmatic rocks(logfo2=-15.10～-2.12)of the Yangqiaozi Cu-Au deposit in the Xuzhou-Huaibei area.Comprehensive analyses suggest that the differences in magmatic oxygen fugacity and magma source both contributed to the contrasting mineralization types between the Qiganlou Fe deposit and the Yangqiaozi Cu-Au deposit.关键词
旗杆楼铁矿/早白垩世/花岗岩/岩石成因/氧逸度Key words
Qiganlou Fe deposit/Early Cretaceous/Granites/Petrogenesis/Oxygen fugacity分类
天文与地球科学引用本文复制引用
杜东旭,牛漫兰,刘航,王磊,朱光,产思维,徐干干,衡哲,詹润..徐淮地区旗杆楼铁矿早白垩世花岗岩成因及其成矿意义[J].地质科学,2025,60(4):991-1013,23.基金项目
国家自然科学基金项目(编号:41772228,42272241)、中央高校基本科研业务费专项资金项目(编号:JZ2023HGTB0237)、安徽省重点实验室自主创新专项(编号:PA2024GDSK0158)和安徽省公益性地质工作项目(编号:2016-g-3-34)资助 （编号:41772228,42272241）
