胶莱盆地郭城-崖子断裂带金矿集区剥蚀程度及深部找矿潜力

Denudation degree and deep prospecting potential of gold deposits in Guocheng-Yazi fault zone,Jiaolai basin

胶莱盆地郭城-崖子断裂带是国内近年来发现的一个重要金成矿区,陆续探明了一批大中型-超大型金矿床。然而,该矿集区的深部找矿勘查工作一直没有取得重大突破。本文通过系统采集成矿岩体样品,挑选磷灰石单颗粒矿物,采用裂变径迹热年代学方法,揭示研究区岩体(矿体)温度-时间演化关系,反演岩体(矿体)热演化历史,解析成矿后构造对矿床的改造,定量计算岩体(矿体)抬升-剥蚀速率,总结矿床变化保存规律。结果表明:郭城-崖子断裂带金矿集区主要经历了110~20 Ma和20~0 Ma两个阶段的成矿后热史,两阶段不均匀的隆升冷却过程受到了太平洋多期增生扩张过程的影响。根据对磷灰石裂变径迹热历史演化分析,结合区域古地温梯度、成矿深度以及侏罗纪和白垩纪陆相沉积地层厚度,计算得出研究区内白垩纪至今地层总剥蚀深度约为5.33 km,金矿带矿体成矿深度为5.62 km,表明郭城-崖子断裂带内矿体遭受了较大程度的抬升剥蚀,推测断裂带南西向地层剥蚀少的部位有较大的找矿潜力,并建立了郭城-崖子断裂带深部金矿体定位模型,评价了深部找矿潜力。

The Guocheng-Yazi fault belt in the Jiaolai basin is an important gold metallogenic area discovered in recent years,and a number of large and medium-sized to super-large gold deposits have been discovered continuously.However,n the deep prospecting and exploration work in the ore concentration area has not made a major breakthrough.In this paper,through the systematic collection of ore-forming rock and ore samples,the apatite single mineral was separated.The fission track thermochronology method was used to reveal the temperature-time evolution of the ore body in the study area.We inversed the thermal evolution history of the rock mass and ore body,analyzed the structural transformation of the deposit after mineralization,quantitatively calculated the uplift denudation rate of the rock mass and ore body,and summarized the denudation and preservation law of the deposit.The results show that the Guocheng-Yazi fault zone gold concentration area mainly experienced two stages of post-mineralization thermal history of 110−20 Ma and 20−0 Ma,and the two-stage uneven uplift and cooling process was affected by the multi-stage proliferation and expansion process of the Pacific Ocean.Based on the analysis of the thermal history evolution of apatite fission track,combined with the regional paleogeothermal gradient,metallogenic depth and the thickness of Jurassic and Cretaceous continental sedimentary strata,the total erosion depth of the strata in the study area from Cretaceous to now is calculated to be about 5.33 km,and the metallogenic depth of the ore body in the gold belt is 5.62 km,indicating that the ore body in the Guocheng-Yazi fault zone has been subjected to a large degree of uplift and denudation.It is speculated that the part of the fault zone with less erosion of the southwest strata has great prospecting potential,and the deep gold ore body positioning model of the Guocheng-Yazi fault zone is established to evaluate the deep prospecting potential.