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江西九(江)-瑞(昌)地区是长江中下游铜-铁-金(硫)成矿带的一个重要的矿集区,位于成矿带的西段。本文选取了区内研究程度相对薄弱的丁家山、洋鸡山、宝山、铜岭和大浪等5个与Cu-Au成矿作用密切相关的花岗质岩体,首次进行了锆石LA-ICP-MS U-Pb年龄测定,并讨论其地质意义。测年结果显示,上述岩体分别形成于145.4±1.2 Ma、144.8±1.3 Ma、143.6±1.2 Ma、141.2±1.3 Ma和146.4±1.2 Ma,为晚侏罗世-早白垩世岩浆活动的产物。结合区域地质资料,认为九瑞矿集区内这一成岩-成矿地质事件可能与古太平洋板块俯冲挤压造山作用后期整体向弧后伸展环境过渡的地球动力学机制有关。是否为区域性加厚下地壳、拆沉下地壳部分熔融或洋脊俯冲作用的产物,还有待进一步研究。
Jiangxi Jiujiang-Ruichang-Changjiang is an important ore-gathering area of the copper-iron-gold (sulfur) metallogenic belt in the middle and lower reaches of the Yangtze River, located in the western part of the metallogenic belt. In this paper, we selected five granitic intrusions closely related to Cu-Au mineralization such as Dingjiashan, Yangjishan, Baoshan, Tongling and Dalang in the study area. The zircon LA-ICP -MS U-Pb dating, and discuss its geological significance. The dating results show that the above-mentioned rock masses were formed at the intervals of 145.4 ± 1.2 Ma, 144.8 ± 1.3 Ma, 143.6 ± 1.2 Ma, 141.2 ± 1.3 Ma and 146.4 ± 1.2 Ma, respectively, which are the product of Late Jurassic-Early Cretaceous magmatism. According to the regional geological data, it is considered that this diagenesis-metallogenic event in Jiurui ore-gathering area may be related to the geodynamic mechanism of the overall transition to the post-arc extensional environment in the latter part of the subduction of the Paleo-Pacific plate. Whether it is a product of regional thickening of the lower crust, partial crustal melting or subducting subduction of the oceanic ridge remains to be further studied.