长江中下游成矿带黄梅尖复式岩体年代学特征:成岩成矿的启示  

Geochronology of Huangmeijian Composite Pluton in Middle-lower Yangtze River Valley Metallogenic Belt,China:Implications on the Petrogenesis and Metallogeny

作　　者：张舒[1,2,3] 周涛发[3] 张赞赞[2] 吕博[2] 施立胜 汪晶[2] 吴明安[1,2] ZHANG Shu;ZHOU Tao-fa;ZHANG Zan-zan;LYU Bo;SHI Li-sheng;WANG Jing;WU Ming-an(MNR Technology Innovation Center of Coverage Area Deep Resource Exploration Engineering,Geological Survey of Anhui Province,Hefei 230001,Anhui,China;Anhui Institute of Geological Sciences,Hefei 230001,Anhui,China;School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,Anhui,China;Anhui Nuclear Exploration Technology Central Institute,Wuhu 241000,Anhui,China)

机构地区：[1]安徽省地质调查院自然资源部覆盖区深部资源勘查工程技术创新中心,安徽合肥230001 [2]安徽省地质科学研究所,安徽合肥230001 [3]合肥工业大学资源与环境工程学院,安徽合肥230009 [4]安徽省核工业勘查技术总院,安徽芜湖241000

出　　处：《地球科学与环境学报》2022年第2期220-242,共23页Journal of Earth Sciences and Environment

基　　金：安徽省公益性地质调查项目(2016-g-2-16);安徽省重点研发计划项目(201904a07020077);安徽省自然资源科技项目(2016-k-3,2020-k-13)。

摘　　要：黄梅尖复式岩体是长江中下游成矿带A型花岗岩的代表,亦是区内重要的产铀岩体,其由早到晚可划分为黑云母石英正长岩、正长斑岩、石英正长岩、碱性长石花岗岩4个侵入阶段,黑云母石英正长岩与碎屑岩地层的接触带是主要的铀矿化部位。对黄梅尖复式岩体各阶段锆石的显微结构进行了详细研究,并开展了锆石稀土元素分析及U-Pb定年。结果表明:黑云母石英正长岩、正长斑岩、石英正长岩中的锆石为岩浆成因锆石,形成时代分别为(131.8±1.1)、(129.7±1.6)、(124.7±1.6)Ma。碱性长石花岗岩的锆石具有明显的核边结构,核部为岩浆成因锆石,经历了蜕晶质化作用,锆石U-Pb年龄为(111.5±1.3)Ma,代表了岩体就位时间;边部锆石受到流体的交代溶蚀并发生了变质重结晶作用,锆石U-Pb年龄为(107.6±2.1)Ma,代表了流体的活动时间。结合以往区域A型花岗岩的年代学数据,将长江中下游燕山期A型花岗岩活动初步划分为3个阶段。早阶段集中在132~129 Ma,岩性以黑云母石英正长岩、正长斑岩为主;主体阶段集中在128~124 Ma,岩性以石英正长岩与正长花岗岩为主;晚阶段集中在115~110 Ma,岩性以细粒碱性长石花岗岩为主。碱性长石花岗岩的成岩年龄及随后的热液活动时间同热液脉状铀矿床成矿年龄接近,结合铀矿床稳定同位素特征,推断末阶段碱性长石花岗岩可能为铀成矿提供了热液及驱动力。Huangmeijian composite pluton is a uranium-bearing A-type granite in Middle-lower Yangtze River valley metallogenic belt. Huangmeijian composite pluton can be divided into four emplacement stages from earliest to latest, including stage Ⅰ biotite quartz syenite, stage Ⅱ syenite porphyry, stage Ⅲ quartz syenite and stage Ⅳ alkali feldspar granite. The vein-type uranium mineralization predominantly occurs along the contacts between the stage Ⅰ biotite quartz syenite and the clastic rocks. The study on the micro-textures, REE characteristics and U-Pb dating of zircons in Huangmeijian composite pluton was carried out. The results show that the zircons of biotite quartz syenite, syenite porphyry and quartz syenite are of magmatic genesis, and yield zircon U-Pb ages of(131.8±1.1),(129.7±1.6),(124.7±1.6)Ma, respectively. The cores of zircons in alkali feldspar granite are of magmatic genesis and undergo metamictization, while the rims of zircons in alkali feldspar granite are altered by hydrothermal fluid, and probably undergo recrystallization. The zircon U-Pb dating of alkali feldspar granite yields the crystallization age of(111.5±1.3)Ma and the hydrothermal activity age of(107.6±2.1)Ma. Based on the previous geochronological studies, the A-type granites in Middle-lower Yangtze River valley metallogenic belt can be divided into three periods. The early period is represented by biotite quartz syenite and syenite porphyry with crystallization age of 132-129 Ma;the main period is represented by quartz syenite and syenogranite with crystallization age of 128-124 Ma;the late period is represented by alkali feldspar granite with crystallization age of 115-110 Ma. The crystallization ages of alkali feldspar granite and hydrothermal activity time are close to the uranium mineralization ages;combining with the stable isotope studies, it probably indicates that stage Ⅳ alkali feldspar granite of Huangmeijian composite pluton has provided the ore-forming fluid and heat for the uranium mineralization.

关 键 词：复式岩体 A型花岗岩 锆石U-Pb年龄 年代学 铀矿床 侵入岩 长江中下游成矿带 安徽 

分 类 号：P571[天文地球—矿物学] P597[天文地球—地质学]