CAJ | 학술논문

85~90 Ma是班公湖-怒江构造带一个重要的成矿期。目前对该期矿床的形成环境和矿床成因还存在争议，而且该带西段的研究比较薄弱。通过区域地质矿产调查，我们在班公湖-怒江构造带西段日土县西侧扎隆琼娃发现与近南北走向的伸展构造和晚白垩世富镁石英二长岩密切相关的富铁矿。通过锆石LA-ICP-MS U-Pb测年法获得石英二长岩的成岩年龄和成矿年龄分别为85.60±0.48 Ma 和85.51±0.77 Ma。地球化学特征显示石英二长岩类似埃达克质花岗岩，却具有较高的Mg#(52.9~56.8)、Cr(106.8×10-6~597.1×10-6)、Ni(60.6×10-6~78.2×10-6)，岩石富集轻稀土和大离子亲石元素Rb、Th、U等，亏损重稀土和高场强元素 Nb、Ta、Ti等。据此初步认为：晚白垩世中期班公湖-怒江构造带在陆内地幔软流圈底辟及相关的地壳热隆伸展构造背景下，通过壳幔相互作用形成了富镁石英二长岩及其相关的富铁矿。
85~90 Ma시반공호-노강구조대일개중요적성광기。목전대해기광상적형성배경화광상성인환존재쟁의，이차해대서단적연구비교박약。통과구역지질광산조사，아문재반공호-노강구조대서단일토현서측찰륭경왜발현여근남북주향적신전구조화만백성세부미석영이장암밀절상관적부철광。통과고석LA-ICP-MS U-Pb측년법획득석영이장암적성암년령화성광년령분별위85.60±0.48 Ma 화85.51±0.77 Ma。지구화학특정현시석영이장암유사애체극질화강암，각구유교고적Mg#(52.9~56.8)、Cr(106.8×10-6~597.1×10-6)、Ni(60.6×10-6~78.2×10-6)，암석부집경희토화대리자친석원소Rb、Th、U등，우손중희토화고장강원소 Nb、Ta、Ti등。거차초보인위：만백성세중기반공호-노강구조대재륙내지만연류권저벽급상관적지각열륭신전구조배경하，통과각만상호작용형성료부미석영이장암급기상관적부철광。
85-90 Ma is an important metallogenic period for the Bangong Lake-Nujiang River tectonic zone. So far, the metallogenic geological background and genesis of this period are still controversial, and the western part of the tectonic zone is less well documented. Based on the regional geological and mineral investigations, we found a high-grade iron deposit at Zhalongqiongwa in the west of Ritu County, west part of the Bangong Lake-Nujiang River tectonic zone. The deposit is closely associated with the nearly north-south extensional tectonics and the late Cretaceous magnesium-rich quartz monzonite. The diagenetic age and mineralization age are 85.60±0.48 Ma and 85.51±0.77 Ma, respectively, using LA-ICP-MS zircon U-Pb dating method. Geochemical characteristics show that the quartz monzonite is suspected to be adakitic granite, with high SiO2 (62.09%~65.54%), Al2O3 (15.08%~15.92%), Sr (385×10-6~453×10-6) and low Y (14.8×10-6~17.9×10-6), Yb (1.40×10-6~1.70×10-6), LREE enrichment (19.56<(La/Yb)N<26.69), weak negative Eu anomaly (0.72<δEu<0.81). However, the quartz monzonite has high contents of Mg# (52.9~56.8), Cr (107×10-6~597×10-6), Ni (60.6×10-6~78.2×10-6) and is rich in LREE and LILE (e.g. Rb, Th, U) and poor in HREE and HFSE, such as Nb, Ta, Ti. It is suggested that under the background of asthenosphere diapirism and related thermal-uplift extensional tectonics in the crust, the crust-mantle interaction led to the formation of the magnesium-rich quartz monzonite and the relevant magnetite deposit.