胶西北金成矿系统热年代学

发布时间：2018-04-09 00:12

本文选题：热年代学　切入点：成矿作用年代与时限　出处：《中国地质大学(北京)》2016年博士论文

【摘要】：胶东是由前寒武纪基底岩石和超高压变质岩块组成、中生代构造-岩浆作用发育的内生热液金矿集区。该区中生代经历了华北与扬子板块陆陆碰撞造山作用和大洋板块俯冲构造体制的叠加/转换,发生了多幕式的大规模成矿作用和巨量金的工业聚积,其中90%以上探明储量集中于胶西北地区。论文以胶西北金矿床(体)时空分布、蚀变-矿化特征与矿物组合及控矿构造变形研究为基础,开展系统的蚀变矿物40Ar/39Ar、锆石和磷灰石裂变径迹与锆石(U-Th)/He热年代学研究,结合锆石U-Pb,角闪石、白云母和黑云母40Ar/39Ar年代学工作,构建区域晚中生代构造-金成矿热年代学模式,获得以下主要认识:1、玲珑变质核杂岩是胶西北矿集区重要的控矿构造,拆离断层下盘玲珑黑云母花岗岩侵位于~163-155Ma,于~155-134Ma沿着玲珑拆离断层发生快速剥露和冷却,并在拆离断层内形成了超糜棱岩-糜棱岩带;~134Ma玲珑变质核杂岩隆升和剥蚀减缓,区域韧-脆性变形转换;郭家岭花岗岩于132-123Ma侵位于玲珑花岗岩中,并经历了同剪切韧性变形,~123-120Ma区域大规模脆性变形叠加。2、区域前寒武纪变质基底岩石中晚侏罗世金成矿作用发生于约~162Ma,黄铁矿显微褶皱等韧性变形特征说明,该期金成矿作用受控于高绿片岩相环境的韧性变形,与新太古代胶东群TTG片麻岩部分熔融、混合岩化作用和晚侏罗世玲珑花岗岩侵位结晶时间一致,均发生于区域大规模伸展作用初始阶段。3、胶西北矿集区早白垩世发育了两期重要金成矿事件:伴随变质核杂岩隆升减缓和郭家岭花岗岩侵位,在玲珑拆离断层带韧-脆性转换域内发生了~130Ma金成矿作用;伴随断裂构造的递进变形过程,在脆性变形和热液蚀变叠加部位发生了~120Ma的大规模金成矿作用,于紧靠区域主控矿断层下盘,形成浸染状/网脉状黄铁绢英岩型矿体,远离主断裂的下盘高角度正断层中形成石英-硫化物脉型矿体。4、变质核杂岩的快速隆升和剥蚀导致晚侏罗世金矿床大部分被剥蚀;早白垩世金成矿深度为5-10km,成矿后主控矿断裂的正断活动导致了其上下盘差异化的隆升和剥蚀,夹持于玲珑拆离断层与焦家断裂间的地块剥蚀约3-7km,深部找矿潜力巨大,区域大规模脆性变形和热液蚀变叠加部位是有利的找矿靶区。
[Abstract]:Jiaodong is composed of Precambrian basement rocks and ultrahigh pressure metamorphic rocks, and the Mesozoic tectonic-magmatism is a concentrated area of endogenic hydrothermal gold deposits.During the Mesozoic Mesozoic, the continental collision orogeny between North China and Yangtze plate and the superposition / transformation of oceanic plate subduction tectonic system occurred, resulting in a multi-scene large-scale mineralization and industrial accumulation of huge amounts of gold.More than 90% of the proven reserves are concentrated in the northwestern region of Jiao.On the basis of temporal and spatial distribution of gold deposits (bodies) in northwestern Jiao, alteration and mineralization characteristics, mineral assemblage and ore-controlling tectonic deformation, a systematic study of 40 Ar39 Ars of altered minerals, fission tracks of zircon and apatite and thermo chronology of zircon U-ThU / he is carried out.Combined with zircon U-Pb, hornblende, Muscovite and biotite 40Ar/39Ar chronology, a regional late Mesozoic tectonic-gold metallogenic thermochronology model was constructed. The main understanding is that the Linglong metamorphic core complex is an important ore-controlling structure in the North Jiaoxi ore concentration area.The Linglong biotite granite intrusion in the lower face of the detachment fault was located at Guang 163-155 Ma. The rapid exfoliation and cooling occurred along the Linglong detachment fault at 155-134 Ma, and the uplift and denudation of the Linglong metamorphic core complex of 134Ma in the ultramylonite-mylonite belt were formed.The regional ductile-brittle deformation transformation, the Guojialing granite in the 132-123Ma transgression is located in the Linglong granite,And experienced the same shear ductile deformation, 123-120Ma regional large-scale brittle deformation superposition. 2, the regional Precambrian metamorphic basement rocks occurred in the late Jurassic gold mineralization about 162Ma. the characteristics of ductile deformation, such as pyrite micro-fold, etc.The gold mineralization in this period is controlled by the ductile deformation of the high-greenschist facies, which is consistent with the partial melting, mixing lithology of the TTG gneiss of the NeoArchean Jiaodong Group and the emplacement crystallization time of the Linglong granite in the late Jurassic.Both occurred in the initial stage of regional large-scale extension. 3. Two important gold mineralization events occurred in the early Cretaceous in the North Jiaoxi ore concentration area: along with the slowing down of the metamorphic core complex and the emplacement of the Guojialing granite.Gold mineralization occurred in the ductile-brittle transition region of the Linglong detachment fault zone, followed by progressive deformation of the fault structure, and large-scale gold mineralization occurred at the brittleness deformation and hydrothermal alteration superposition at 120Ma.At the bottom of the main ore-controlling fault adjacent to the area, the disseminated / net-vein yellow tierite orebody was formed.The quartz-sulfide vein type orebody .4 is formed in the high-angle normal fault far from the main fault. The rapid uplift and denudation of the metamorphic core complex results in the denudation of most of the late Jurassic gold deposits.The gold mineralization depth of the early Cretaceous is 5-10km. The positive fault activity of the main ore-controlling fault after mineralization resulted in the uplift and denudation of the upper and lower face differential, and the erosion of the block between the Linglong detachment fault and the Jiaojia fault was about 3-7km, and the deep prospecting potential was great.Large scale brittle deformation and superposition of hydrothermal alteration are favorable ore-prospecting targets.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.51

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