西秦岭阳山金矿带成矿热年代学:锆石和磷灰石裂变径迹研究

阳山金矿带因其独特的构造位置、超大型金资源量以及成矿后区域发生大规模隆升剥蚀事件，成为矿床学领域研究热年代学的理想选区。本文针对金矿带成矿后热历史演化开展锆石和磷灰石裂变径迹研究，获得如下成果：（1）锆石裂变径迹年龄值分布范围为(287.0±21)～(101±3) Ma(1σ)，且不同岩性的年龄值各有特征，砂板岩锆石裂变径迹年龄值跨度最大(287～107 Ma)，千枚岩锆石裂变径迹值分布范围为177～101 Ma，斜长花岗斑岩中锆石裂变径迹年龄值为193～185 Ma；（2）磷灰石裂变径迹年龄值分布范围为(69±7)～(46±14) Ma(1σ)，径迹长度及其分布特征显示金矿带在晚白垩世—古新世的地层冷却表现为单调且缓慢地通过磷灰石裂变径迹的封闭温度。根据金矿带热历史演化分析，结合研究区古地温梯度、成矿深度数据，得出泥山矿段先于葛条湾矿段剥蚀，阳山金矿带自白垩纪以来地层总剥蚀厚度约为12.24 km，矿体剥蚀厚度上限约为880 m，推测阳山金矿带北部地层剥蚀少的矿段有较大的找矿潜力。

Geochronology of mineralization in the Yangshan gold belt,West Qinling:a study on zircon and apatite fission track

The Yangshan gold ore belt has become an ideal place for studying geochronology of mineral deposits because of its unique tectonic location, ultra-large gold resources, large-scale uplifting and post-mineralization erosion events. Based on the previous studies, we carried out zircon and apatite fission track analysis on the thermochronology of the Yangshan gold ore belt. The results show that the distribution range of zircon fission track age was from 287.0±21 to 101±3 Ma (1σ), with the following characteristics based on lithology: (1) The zircon fission track ages of sandstone and slate had the largest age span, ranging from 287 to 107 Ma; (2) The distribution range of phyllite zircon fission track was between 177 and 101 Ma; and (3) plagio granite porphyry zircon fission track age ranged from 193 to 185 Ma. The apatite fission track age ranged from 69±7 to 46±14 Ma (1σ), and fission track length and its distribution characteristics show that the Yangshan gold ore belt moved monotonously and slowly through the closure temperature of apatite fission track, between the Late Cretaceous to Paleocene. Based on the thermal history analysis of apatite fission track lengths and age inversion, combined with paleogeothermal gradient and ore body metallogenic depth in the study area, we concluded that the Nishan ore body was denuded before the Getiaowan ore body section. From the Cretaceous Period, in the Yangshan gold ore belt, the total thickness of the eroded stratum was about 12.24 km, and the upper limit on the eroded ore body thickness was about 880 m. We speculated that the less eroded ore-zone in the northern Yangshan gold belt may have large prospecting potentials.