从同位素年龄看白云鄂博稀土-铌-铁矿床区域 地质演化历史

内蒙古白云鄂博稀土-铌-铁矿床是世界上著名的巨型多金属矿床,但对其区域地质演化历史的认识至今仍不统一,而同位素年龄是解决矿床区域地质演化历史的有效手段。本文基于测年方法对白云鄂博矿床同位素年龄数据收集整理,结合矿床地质背景对矿床区域地质演化历史进行讨论:白云鄂博矿床发育在上太古界-下元古界结晶基底色尔腾山群之上,中元古代白云鄂博裂谷期的海底火山喷发-同生沉积作用发育了层状的含稀土铌铁矿层,同时发育了广泛的碳酸岩墙群和基性岩墙群,这是白云鄂博矿床最主要的成矿事件。白云鄂博矿床还经历过至少三次后期成矿热事件叠加或改造成矿,主要包括:(1)新元古代南华期热事件(约720Ma);(2)早古生代志留纪晚期叠加成矿事件(约440Ma);(3)晚古生代二叠纪岩浆岩侵入事件(约280Ma)。白云鄂博矿床是中元古代裂谷成矿事件为主并叠加了后期多次热事件的结果。

The regional geological evolution history of the Bayan Obo REE-Nb-Fe deposit derived from isotopic ages

The Bayan Obo REE-Nb-Fe deposit in Inner Mongolia is one of the most famous polymetallic deposits in the world. However, its regional geological evolution history remains controversial. This work attempts to address this issue using isotopic ages in combination with the geological background of this area. Data suggests that this deposit developed on the crystalline basement of the Upper Achean to Lower Proterozoic Seertengshan Group. During the submarine volcanic eruption-synsedimentary stage of the Mesoproterozoic Bayan Obo rifting period, formed a layered REE-bearing niobium-iron ore bed with a widespread carbonatite dikes and mafic dyke swarms. This was the most important metallogenic event in the Bayan Obo deposit. It has also undergone at least three late ore-forming thermal events to superimpose or transform the ore-forming process: 1) the Neoproterozoic Nanhua period thermal event (ca. 720 Ma); 2) Late Silurian superimposed metallogenic event in early Paleozoic (ca. 440 Ma); and 3) Late Paleozoic Permian magmatic intrusion event (ca. 280 Ma). Thus the Bayan Obo deposit is primarily the result of the Mesoproterozoic rift metallogenic event superposed by many thermal events in the later period.