赣南珠兰埠岩体锆石U-Pb年代学研究及其含矿性评价
U-Pb Dating of Zircons and Ore-bearing Potential of Zhulanbu Intrusions in the Southern Jiangxi Province
-
摘要: 珠兰埠岩体是南岭地区大面积出露的岩体之一, 也是缺少精确年龄数据的复杂岩体之一, 在以往工作中被认为是燕山期早期岩体, 此后相关研究较少, 由于时代和方法的限制未见确切的同位素年龄数据发表。本文采用LA-(MC)-ICPMS锆石U-Pb法对珠兰埠复式岩体的粗粒斑状黑云母花岗岩、中细粒含斑黑云母花岗岩进行同位素年代学研究, 探讨其成矿可能性。获得粗粒斑状黑云母花岗岩、中细粒含斑黑云母花岗岩等时线年龄分别为228.7±2.0 Ma和231.0±1.2 Ma, 表明珠兰埠复式花岗岩体主体形成于印支期, 而不是前人认为的燕山早期, 由此修正了岩体成岩时代, 同时结合珠兰埠岩体的地球化学特征与印支期花岗岩的成矿特点, 较好印证了目前在该岩体及其周边, 并未发现钨矿床的现象。本研究成果为赣南地区花岗岩研究提供了新的实例。Abstract: Zhulanbu granite is located in the Nanling district with a large exposed area, but its formation age is still unknown. It was previously considered to have formed at the Yanshanian, but no precise isotopic age was reported, as a result of the limitation of time and method. LA-(MC)-ICPMS was used to determine the ages of zircons from coarse grained prophyritic bioxite granite and medium-fine grained prophyritic biotite granite, which were used to discuss the ore potential, and is reported here. These two types of rocks have ages of 228.7±2.0 Ma and 231.0±1.2 Ma, indicating Zhulanbu composite granite was formed in Indosinian. Combined with the geochemistry of Zhulanbu composite granite and ore-forming characteristic of Indosinian granite, these ages explain the phenomenon that tungsten deposits are not found within the granite and its surroundings. This study provides a new example for the study of granite in southern Jiangxi.