LA-ICP-MS/FT方法在矿床保存研究中的应用——以赣东北德兴铜矿和银山铅锌矿床为例

矿床保存是成矿系统研究的重要组成部分,其中裂变径迹研究是揭示矿床保存条件和程度的有效手段之一。本文建立了LA-ICP-MS/FT方法,该方法获得磷灰石裂变径迹年龄值与已有外探测器法分析结果对比表明这一方法是可行的。基于此方法,对赣东北德兴铜矿与银山铅锌矿进行了磷灰石裂变径迹分析,得到了德兴成矿岩体的磷灰石裂变径迹年龄71.4±8.6 Ma,银山地区英安斑岩的磷灰石裂变径迹年龄为77.1±8.3 Ma。这一结果表明,在区域整体抬升背景下,两个矿区均以较低的剥蚀抬升速率抬升至地表。两个矿区样品磷灰石平均裂变径迹围限长度分别为12.32±1.77μm和12.56±1.91μm,对应Dpar值为2.45±0.19μm和1.84±0.17μm,径迹长度频度分布属于单峰型,证实两个矿区为单向冷却过程且没有遭受后期明显的热扰动。进一步温度?时间热模拟路径显示,德兴和银山在70 Ma前经历了快速隆升过程,然后开始缓慢抬升,到约20 Ma开始再次快速隆升。结合前人报道的U-Th/He定年结果,100 Ma以来,德兴可能比银山具有相对更高的隆升量(~1 km)。

LA-ICP-MS/FT Application in Preservation Evaluation of Ore Deposits——Case Studies of the Dexing Copper Deposit and Yinshan Pb-Zn Deposit,Northeastern Jiangxi Province

Deposit preservation is an integral part of the ore-forming system;and fission track is one of the effective tools to evaluate deposit preservation.In this paper,apatite fission track age of reference sample obtained by LA-ICP-MS/FT is similar to that of external detector method,indicating that LA-ICP-MS/FT dating technique is reliable.The technique is thus performed on apatite from the Dexing copper and Yinshan Pb-Zn deposits in order to evaluate the preservation of these deposits.The AFT ages of the Dexing granodiorite porphyry and Yinshan dacite porphyry are 71.4±8.6 Ma and 77.1±8.3 Ma,respectively,with mean measured confined track length of 12.32±1.77μm and 12.56±1.91μm,respectively.Thermal modeled time-temperature path indicates that both deposits experienced fast uplift before ca.70 Ma and after 20 Ma,respectively.Combined with previous U-Th/He dating results,the Dexing deposit might have experienced more uplift than the Yinshan deposit(ca.1 km).