【作者】 覃永军；

【导师】 曾键年；

【作者基本信息】 中国地质大学 ， 矿产普查与勘探， 2010， 硕士

【摘要】 安徽庐枞盆地是长江中下游铁铜金成矿带的一个重要矿集区,夹持在郯庐断裂与长江断裂之间,属于中国东部中生代燕山期发育的一个继承式火山岩盆地。盆地内金属成矿作用与燕山期岩浆大爆发密切相关。本文在收集、整理前人大量研究资料的基础上,通过野外地质矿产调查、系统的样品采集和显微观察、测试分析,以“构造-岩浆-成矿作用”的时空演化为主线,从三维角度和矿田尺度对庐枞盆地不同期次、不同序次控岩控矿构造形迹的系统解析和对盆地内不同类型矿床的控矿构造规律、岩浆作用及其时空关系的系统厘定,即查明研究区在全球构造体系下深部断裂构造体系-岩浆继承活动的地球动力学过程与浅表构造-成矿作用响应。运用“应变菱形分析技术”方法,解析庐枞盆地构造体系。建立盆地成矿作用的空间结构；通过测试含矿岩浆岩的成岩时代来约束成矿作用的时限,建立庐枞盆地成岩成矿作用的时间结构；进而系统分析成矿地球动力学背景,探讨盆地燕山期成矿动力学机制,最终建立地球动力学成矿模式。本文取得了以下主要认识和进展：1.含矿岩浆岩岩石学和岩石化学分析结果表明,区内岩浆岩发育埃达克质钙碱性侵入岩系列和橄榄安粗岩系的火山岩-侵入岩系列。前者主要分于沙溪地区及其盆地深部；后者主要分布于盆地内部；它们均为同一深部过程、不同性质源区的岩浆作用产物。综合微量元素和同位素资料,认为盆地火山岩主要来源于EMI富集地幔；结合板块环境判别和古地理演化,岩浆喷发环境为弧后裂谷环境,并非典型的陆内裂谷；2.对区内典型矿床矿石的显微观察和黄铁矿电子探针、含矿岩浆岩及矿石稀土、微量元素以及稳定同位素地球化学研究,认为区内的玢岩型铁矿、沉积-热液叠加改造型铁矿、脉状热液型铜-金矿床和斑岩型铜矿在成因上均与燕山期岩浆活动密切相关；前三类成矿作用类型受橄榄安粗岩系列火山-侵入岩控制,斑岩型成矿作用则受埃达克质钙碱性侵入岩系列控制；3.综合成矿地球化学、岩相学和成矿年代学研究成果,提出了罗河铁矿的成矿岩体属于砖桥组(火山旋回)期后火山活动间隙期的次火山辉石粗安玢岩,并非前人认为的火山熔岩；对比分析龙桥铁矿和罗河-泥河铁矿的磁铁矿单矿物稀土微量元素特征,结果表明沉积热液改造矿床和玢岩型矿床在成因上存在联系,为龙桥铁矿提供成矿热液的岩浆可能与罗河-泥河次火山岩类相似；拔茅山矿床可能属于沉积改造成因,其层位可以与龙桥进行对比；矿化特征研究结果显示,井边热液脉型铜矿床可能与朱家凹、雨坛卧龙矿床成因存在差异,应当进一步与沙溪斑岩型铜矿床进行对比研究；4.利用高精度LA-ICP-MS锆石U-Pb同位素定年技术,获得沙溪、雨坛、拔茅山侵入岩和泥河、罗河次火山含矿岩浆岩的成岩年龄分别为134.0±1.5Ma、129.6±0.8Ma和129.7±1.4Ma以及132.8±2.6Ma、133.3±0.6Ma和133.2±1.1Ma,建立了盆地成岩成矿作用的时间结构；对比长江中下游地区大规模成矿作用集中在200～160 Ma、140 Ma左右和130～110Ma的三个时期的岩浆成矿规律,认为庐枞盆地成矿作用对应140 Ma左右和130～110Ma两个时期,分别对应构造体制转折的过渡背景和大规模岩石圈的伸展拆沉背景；5.运用“应变菱形分析”方法对庐枞构造体系和动力机制解析,结果显示成岩成矿作用受燕山期太平洋板块的俯冲和深部壳幔作用的双重因素控制,属于中生代燕山期新华夏系力场；区内的深大断裂及其基底断裂属于太平洋板块与欧亚板块动力场产生的第一序次结构面：S4(NE40°)、S2(NE280°)、S3(NE310°),这些结构面控制盆地燕山期大规模岩浆喷发-侵入活动,制约区内成矿带的分布；第一序次结构面与以第一序次结构面断裂(NE40°及NNW350°)为边界形成的规模较小的第二序次结构面中的扭张性或张扭性结构面和区域,对火山喷发晚期的脉状热液型Cu-Au成矿作用的空间分布具有一定的控制作用：6.运用“应变菱形分析”方法解析盆地控矿构造规律建立了盆地成矿的空间结构：(1)3个成矿带：沙溪-东顾山Cu-Au成矿带、龙桥-罗河Fe-Cu-(Au)成矿带、黄屯-枞阳Cu-Au-(Fe)成矿带；(2)3个成矿环：高温Fe、S成矿内环、中低温Fe、Cu成矿中环、中低温Cu、Zn、Pb多金属成矿外环；(3)三维尺度上的两大成矿块体,一是分布于沙溪地区和盆地深部的与斑岩型成矿作用相关的埃达克质钙碱性岩浆岩成矿块体；一是分布于盆地内部与玢岩型、沉积-热液叠加改造型、脉状热液型成矿作用相关的橄榄安粗岩火山-侵入岩成矿块体；7.根据岩浆地球化学的深部信息、古地理构造格架、板块环境判别、区域的岩浆活动规律和“应变菱形解析”的综合认识,认为庐枞盆地在华北与扬子板块对接时期就已经形成了NE方向深大断裂的基本格架；燕山早期构造主要属于太平洋与欧亚板块形成的新华夏构造体系,是成岩成矿的有利就位空间；进入白垩纪以后印度洋板块对本区产生了一定的影响,迁就、利用新华夏系的构造形迹形成引张为主的构造。8庐枞盆地燕山期的成矿地球动力学背景属于岩石圈的大规模拆沉减薄。在该动力机制下,形成了大规模的金属矿产。在此基础上,构建了庐枞盆地燕山期的岩浆-成矿动力学模式；更多还原

【Abstract】 There is an inherited-type volcanic basin developed during Yanshan period in Luzong volcanic basin on the Lower Yangtze region, and an important role for the sub-ore-forming unit of large scale mineralization collection, which is holded between Tan-Lu fault and Yangtze fault. On the basis of the collection and secondary development on the number of previous studies data, throngh field geological investigation, sample collection and microscope oberservation, emphasising on space-time evolution of tectonic-magmatism-mineralization, from the view of three-dimensional and ore field scale, the strcture feature of different time and order are analysised systematically,and ore-controlling structure、magmatism and their space and time relationship are investigated in order to ascertain the deep geodynamic processes of deep faulting-magmatic activity under global tectonics system and the surfacial response of tectonic-mineralization.Using the method of "diamond-shaped strain analysis",through identifying the strcture orders of rock-and ore-controlling,analysising the structure system,the mineralization space texture in Luzong basin is established.By geochronologically studyting on magatic rocks related mineralization, restrict the times of mineralization,the time texture of mineralization in Luzong bansin is established.Further, Mineralization dynamic setting and dynamic process in Luzong basin during Yanshanian period are probed and metallogenic geodynamic model are established.We get some improvements and understandings as following:1.Petrological and geochemical results of magmatic rocks related to mineralization showed that the igneous rocks belong to adakitic calc-alkaline intrusion series and shoshonitic volcanic-intrusion series.The former mianly distributes in Shaxi region and the latter in the interior of basin.They are derived from the different magama sources by the same deep magmatiam process. The results of trace element and isotope indicate that the volcanics is mainly derived from EMI mantle.Its eruption environment is back-arc rift,not typical of intracontinental rift.2.Combined the information including ore microcope observation,EPMA of pyrites,REE and trace elements of magmatic rocks and ore,it indicates that the metal mineralization including porphyry-type iron, sedimentary hydrothermal-transformation-type iron, hydrothermal vein-type Cu-Au deposits are all related to Yanshanian magmatism.Adakitic calc-alkaline intrusive magmatiam resulted in the formation of porphyry copper deposit,and shoshonite magmatism controlled the porphyry-type, sedimentary hydrothermal-transformation-type, hydrothermal vein-type mineralization. 3. Integrated the results of research geochemical, petrographic and metallogenic chronology, presented Luo River iron ore rock is subvolcanic coarse pyroxene porphyry between the period of volcanic activity,which belongs to Zhuanqiao group,not the volcanic lava of previous view. We contrast and analysis the characteristics of trace element and rare earth of single mineral magnetite from Longqiao Iron deposit and Luohe-Nihe Iron deposit,and it show that there is a link between the sedimentary hydrothermal-transformation-type and the porphyry-type in genesis.The magma of hydrothermal mineralization for the Longqiao Iron deposit is similar with subvolcano rock in Nihe-Luohe; The genesis of Bamaoshan Iron deposit may belong to reworked sedimentary, and its horizon could compare to the Longqiao Iron deposit; The hydrothermal vein-type Copper deposit of Jingbian is different with Zhujiaao,Yutan,Wolong deposit in genesis from the research of mineralization characteristic,it Should be a further comparative study with Shaxi porphyry copper deposit.4. By using high-precision LA-ICP-MS zircon U-Pb isotopic dating technique, The ages of main ore-forming rock are obtained,134.0±1.5Ma of Shaxi,129.6±0.8Ma of Ba Maoshan, and 129.7±1.4Ma of Yutan, and 132.8±2.6Ma of Nihe,133.3±0.6Ma and 133.2±1.1Ma of Luohe respectively.The time texture of rock-and ore-forming in Luzong basin are established. Combined magmatism evolution in Luzong basin and neihbouring area,it can concluded that the large scale mineralization in area of the middle and lower of Changjiang Rive occurred at 200～160 Ma、140 Ma or so and 130-110Ma,and the mineralization in Luzong occurred in the latter two periods,corresponding to impression(thickening)-extension(thinning) and large scale lithosphere delamination resultede from extension respectively.5.The results of analyzing of the structural controlled mineralization and dynamic mechanism by "diamond-shaped strain analysis"show that the rock-and ore-forming in Luzong bain are controlled by double factor including deep subduction of Pacific plate and crust-mantle interaction. The discordogenic fault and the foundational fault in the area belong to first sequence of structural surface which come from the dynamic field of Pacific plate and the Eurasian plate: S4(NE40°)、S2(NE280°)、S3(NE310°);These structural surfaces control large-scale eruption-intrusive activities in Yanshan period,and they also restrict the distribution of metallogenic belt region. First sequence of structural surface and its rupture(NE40°and NNW350°) form the boundary which shape into smaller scale transtensional or face-shear structures and regional of second sequence of structural surface,and they have some controlling effect on the spatial distribution of mineralization of hydrothermal vein-type Cu-Au deposit in late eruption.6.The space texture of mineralization in Luzong basin is eatablished,which is as followings:(1)three metallogenic belts:Sahxi-Dong Gushan Cu-Au,Longqian-luohe Fe-Cu (Au)and Huang tun-Zongyang Metallogenic belts;(2)three metallogenic rings:inner ring of high temperature Fe,S mineralization,middle ring of middle-low temperature Fe,Cu mineralization and outer ring of middle-low temperature Cu,Pb,Zn mineralization. (3) We divide two ore blocks in the view of three dimensions:one is calc-alkaline intrusion ore block found in Shaxi region and deep basin which is related toporphyry-type mineralization,the other is shoshonitic volcanic-intrusion ore block found in basin which is related to porphyry-type, sedimentary hydrothermal-transformation-type, hydrothermal vein-type mineralization. 7. A comprehensive understanding of deep magma geochemical the information,structural framework of ancient geography, plate setting discrimination, laws and activity of regional magmatic, "Analysis of strain Diamond",we get the kownledge that the basic framework of NE directional deep fault was formed during North China and Yangtze plate docking; Early structure of Yanshan period was a great space to diagenetic mineralization,which belong to Pacific and Eurasian tectonic plate system, the formation of new China. After the Indian plate into the Cretaceous in this area had a certain impact, accommodation, use of the new Chinese system of structural features form the main structure of tensile. However,large scale of oceanic crust fragments(Ancient oceanic crust)joined into lithosphere mantle and mantle basaltic magma raised during lithosphere thicked in deep。8. Then large-scale delamination of lithospheric thinning occurred in the weak region of plate suture zone. On this basis, Yanshanian magma-metallogenic dynamics model of Lu-zong was constructed.更多还原