安徽东至兆吉口铅锌矿床岩浆岩及断裂构造研究

发布时间：2018-11-22 17:09

【摘要】：东至兆吉口铅锌矿床是近年来在安徽省南部新发现一铅锌多金属矿床,其累计探明的铅锌资源量已达50万吨以上,并有望进一步扩大。本文通过对兆吉口地区野外地质考察及钻孔岩芯观察,着重开展该矿床的岩浆岩和断裂构造研究。首先,选取合适的岩浆岩石样品,结合岩相学、岩石地球化学、同位素分析及年龄测定,确定岩石类型、成岩物质来源、成岩构造环境、并探讨岩浆活动对成矿的控制因素；其次,选取断裂活动中产生的断层泥样品进行K-Ar同位素年代学分析,确定构造运动的时限,结合区域构造演化既区内断裂构造的地质特征及其应力场分析,探讨断裂构造对成矿的影响,确定成矿和控矿的关键因素。本文取得成果如下：区内侵入岩以花岗闪长斑岩、花岗斑岩及闪长玢岩为主。侵入岩总体属于过铝质钙碱性系列岩石,侵位较浅。花岗闪长斑岩和花岗斑岩岩浆可能以壳源岩浆为主并混染了一定的幔源岩浆,而闪长玢岩岩浆以壳幔混源岩浆为主。侵入岩经历了较为明显的分离结晶作用,岩浆作用发生于由挤压和挤压向拉张过渡的地球动力学背景之下。区内存在两期岩浆活动,花岗闪长斑岩与花岗斑岩的形成年龄在145Ma左右,而闪长玢岩在129Ma左右形成。闪长玢岩中见及含矿石英脉穿切的地质事实说明,该期岩浆作用与区内铅锌矿床成矿作用关系密切。区内侵入岩中均发育大量继承锆石核,反映岩浆岩成岩物质中有大量壳源物质参与。继承锆石同位素年龄集中于740～890Ma,与皖南地区新元古代花岗岩及新元古界青白口系铺岭组安山玄武岩及安山岩的年龄一致,揭示了晋宁期华夏板块向扬子板块之间的构造-岩浆事件。大于1000 Ma的锆石年龄反映该区可能存在古元古代-太古代陆壳基底。兆吉口铅锌矿床发育于东至断裂带及其西侧,矿体呈脉状和透镜状分布于东至断裂带内及其西侧北北西向次级张性断裂和裂隙中,矿石呈角砾状、脉状和网脉状。受断裂带中的泥质充填物控制,东至断裂东侧上盘未见矿化。东至断裂中的断层泥K-Ar拟合年龄为是126.6和138.3Ma,指示东至断裂于燕山早期-晚期的均有活动。
[Abstract]:East to Zhaojikou Pb-Zn deposit is a new Pb-Zn polymetallic deposit discovered in the south of Anhui Province in recent years. The accumulative amount of Pb-Zn resources has reached more than 500000 tons and is expected to be further expanded. This paper focuses on the study of magmatic rock and fault structure of the deposit through field geological investigation and drilling core observation in Zhaojikou area. Firstly, the appropriate samples of magmatic rocks are selected, combined with petrography, geochemistry, isotopic analysis and age determination, to determine the types of rocks, the source of diagenetic material, the diagenetic tectonic environment, and to discuss the controlling factors of magmatic activity on the mineralization. Secondly, the samples of fault gouge produced by fault activity are selected for K-Ar isotopic chronology analysis, and the time limit of tectonic movement is determined, combined with the geological characteristics and stress field analysis of fault structures in the regional tectonic evolution area. The influence of fault structure on mineralization is discussed, and the key factors of ore-forming and ore-controlling are determined. The results are as follows: granodiorite, granodiorite and diorite-porphyrite are the main intrusive rocks in the area. The intrusive rocks generally belong to peraluminous calc-alkaline series rocks with shallow emplacement. Granodiorite porphyry and granodiorite magma may be dominated by crust-derived magma and mixed with mantle-derived magma, while diorite-porphyrite magma is dominated by crust-mantle mixed magma. The intrusive rocks experienced distinct separation and crystallization and magmatism occurred in the geodynamic background of the transition from compression and compression to tension. There are two stages of magmatic activity in the area. The age of formation of granodiorite porphyry and granodiorite porphyry is about 145Ma, while diorite porphyrite is formed at 129Ma. The geological facts of diorite porphyrite and ore-bearing vein perforation indicate that the magmatism in this period is closely related to the mineralization of lead-zinc deposits in the area. A large number of inherited zircon cores are developed in the intrusive rocks in this area, indicating that a large number of crustal materials are involved in the diagenetic material of magmatic rocks. The inherited zircon isotopic age is 740U 890 Ma, which is consistent with the age of Neoproterozoic granite and Neoproterozoic Qingbakou Puling formation andshan basalt and andesite in southern Anhui. The tectonic-magmatic events between the Cathaysian plate and Yangtze plate in Jinning period were revealed. The zircon age of more than 1000 Ma indicates that there may be Gu Yuan-Archean continental crust basement in this area. The Zhaojikou lead-zinc deposit is developed in the east to the fault zone and its west side. The orebody is vein-like and lenticular distributed in the secondary tensional fracture and fissure in the Dongzhi fault zone and its west side, and the ore is breccia, vein and reticular vein. Controlled by the muddy filling in the fault zone, no mineralization was found in the upper disc of the east to the east of the fault. The K-Ar fitting ages of fault gouge in Dongzhi fault are 126.6 and 138.3 Ma.This indicates that the Dongzhi fault occurred in the early to late Yanshanian period.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.4;P542

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