研究生知识库

矿床保存是成矿系统不可或缺的组成部分。对矿床、矿区及更大尺度区域的剥蚀抬升情况的研究，不仅有助于矿床保存情况的了解，还可以为区域找矿提供一定的信息。低温年代学是研究剥蚀抬升的理想手段，其中磷灰石裂变径迹法在得到其热年龄值（120~60℃）的同时，根据磷灰石裂变径迹长度频度分布和基于裂变径迹长度和Dpar值模拟出的热史曲线可为热演化认知提供助益。传统裂变径迹方法（外探测器法）受限于方法原理，需要漫长的热中子照射和繁琐的裂变径迹选数工作。基于LA-ICP-MS的裂变径迹方法则可省去该步骤并有效的减少选数裂变径迹的工作量，本文初步建立了磷灰石LA-ICP-MS/FT方法。该方法在获得裂变径迹密度后，使用LA-ICP-MS测得238U/43Ca，基于Zeta常数校正法，即可得到磷灰石裂变径迹年龄值。相关的成果如下： （1）对磷灰石年龄标样Durango分析得到Zeta值为2474±179Ma/μm2，为测试方法可信性，选取已完成外探测器法样品GD1210进行测试，得到LA-ICP-MS/FT年龄值为51.2±6.3Ma，对应外探测器法年龄值57.3 ± 3.6 Ma，测值相较于外探测器法测值偏小, 误差数值偏大。但就低温热年代学研究而言, LA-ICP-MS/FT是接受的。 （2）对GD1210再次分析测试中得到年龄值为51.6±4.6Ma，与初次测量结果很好的吻合。此外，增大选数矿物点数可有效的降低误差。（3）德兴花岗闪长斑岩和银山英安斑岩磷灰石裂变径迹年龄分别为71.4 ± 8.6Ma和77.1 ± 8.3Ma，磷灰石围限径迹长度统计分别得到平均长度为12.32 ± 1.77 μm和12.56 ± 1.91 μm，对应Dpar值为2.45 ± 0.19 μm和1.84 ± 0. 17 μm。使用HeFTy软件模拟所得热史曲线显示27 Ma以前德兴矿区相较于银山矿区的抬升剥蚀作用, 表现为一定的滞后性和相对较小的冷却速率，但整体而言，德兴具有更大的剥蚀抬升量。（4）石门寺矿区样品LK-02铀含量分布不均匀，且其径迹密度与238U/43Ca未呈现出相关性，LA-ICP-MS/FT未能获得其磷灰石裂变径迹年龄。LK-07磷灰石裂变径迹年龄为49.6±3.7Ma。（5）矿区尺度样品裂变径迹研究受蚀变作用的影响较大，表现为磷灰石矿物颗粒较多的晶格缺陷和包裹体，对裂变径迹的选数和U的测量均存在影响。

Preservation of ore deposit is an indispensable part of the mineralization system. The understanding of the erosion and uplift of deposits, mining areas and larger scale areas not only contributes to the understanding of deposit preservation, but also provides certain information for regional deposits prospecting. Low temperature chronology is an ideal method to study denudation. The apatite fission track method obtains thermal age (120~60 °C), and its apatite fission track length frequency distribution, and the thermal history curves simulated by the length and Dpar values can help the thermal evolution cognition. The traditional fission track method (such as external detector method) is limited by the principle of the method and requires long thermal neutron irradiation and cumbersome fission track selection task. The fission track method based on LA-ICP-MS can eliminate this step and effectively reduce the workload of selecting fission track. This paper preliminarily established the apatite LA-ICP-MS/FT method. After obtaining the fission track density, 238U/43Ca was measured by LA-ICP-MS, and the apatite fission track age value was obtained based on the Zeta constant correction method. The relevant results are as follows: (1) With the apatite age standard sample Durango analysis, the Zeta value is 2474±179Ma/μm2. In order to test the credibility of LA-ICP-MS/FT method, the completed external detector method sample GD1210 is selected for LA-ICP-MS/FT age. The value is 51.2±6.3Ma, which corresponds to the external detector method age value of 57.3 ± 3.6 Ma. The measured value is smaller than the external detector method, and the error value is larger. However, LA-ICP-MS/FT is feasible for low temperature thermochronology studies. （2）The value of the GD1210 retest was 51.6±4.6 Ma, which was in good agreement with the initial measurement. In addition, increasing the number of grains can effectively reduce the error.(3) The fission track ages of Dexing granodiorite porphyry and Yinshan dacite porphyry are 71.4 ± 8.6 Ma and 77.1 ± 8.3 Ma, respectively, and the average length of the apatite fission track length is obtained separately. It is 12.32 ± 1.77 μm and 12.56 ± 1.91 μm, corresponding to Dpar values of 2.45 ± 0.19 μm and 1.84 ± 0.17 μm. The heat history curve obtained by HeFTy shows that the Dexing mining area before 27 Ma has a certain hysteresis and a relatively small cooling rate compared with the uplift and denudation of the Yinshan mining area, but overall, Dexing has a larger amount of erosion lifted.(4) The uranium content of sample LK-02 in Shimensi mining area is inhomogeneous, and its track density has no correlation with 238U/43Ca. LA-ICP-MS/FT failed to obtain its apatite fission track age, which indicates that uranium inhomogeneity is a challenge for LA-ICP-MS/FT. The LK-07 apatite fission track age is 49.6 ± 3.7 Ma.（5）The fission track study is deeply affected by alteration, on the selection of the fission tracks and the measurement of U concentration, which is characterized by the lattice defects and inclusions of the apatite mineral particles.