【作者】 侯明金；

【导师】 朱光；

【作者基本信息】 合肥工业大学 ， 矿物学、岩石学、矿床学， 2005， 博士

【摘要】 本博士论文得到国土资源部地质调查项目“中国成矿体系与区域成矿评价”专题“中国东南地区(大别山-台湾走廊带)Cu,Au,Ag,Pb,Zn,Fe成矿作用与资源潜力-成矿区带形成的四维结构”的亚专题“江南隆起带成矿作用、深部过程与资源潜力”(专题编号:K1. 4-2) 项目的资助。笔者经过两年的系统学习,结合上述专题研究,选择江南隆起带安徽部分为研究区域,同时包括北侧的江南过渡带即皖南印支-早燕山期褶皱带,本文内简称研究区。重点研究江南隆起带(安徽部分)及江南过渡带的印支期以来的古构造应力场特征、构造演化;燕山晚期的岩浆活动、岩浆岩岩石地球化学特征、岩浆岩成岩作用、岩浆岩的成岩深部过程以及成岩区域地球动力学背景等,内容包括:研究区的古构造应力场特征、构造演化;区域地球物理场特征,包括重磁特征和地震结构等;燕山晚期岩浆岩的时空分布、类型、演化;燕山晚期岩浆岩的地球化学,岩浆作用过程与机制;成岩作用的构造和地球动力学背景、壳-幔结构及相互作用,地球动力学过程。取得的主要认识如下:1、 岩浆活动期次:首次通过精确同位素测年分析,认为江南隆起带(安徽部分)燕山期的岩浆活动主要发育于晚期,本次取得了两个岩体的黑云母40Ar/39Ar坪年龄,分别是靠背尖黑云母花岗闪长岩40Ar/39Ar坪年龄为133. 97±0. 48Ma;逍遥花岗闪长斑岩40Ar/39Ar坪年龄为141. 46±0. 62Ma。统计分析,皖南地区燕山期侵入岩浆作用发生的时间集中在130～142Ma和120～130Ma之间,反映燕山晚期主要岩浆活动可分为两次即早白垩世的早期和晚期。2、 岩石圈拆沉、伸展活动的开始时间:通过区域对比分析,上述两个岩体具有一定的区域代表性,岩浆活动的发育反映了岩石圈拆沉、软流圈上涌,下地壳部分熔融,地幔底侵作用的发育。本次通过同位素年龄精确测定,获得了142Ma的最大年龄,从逍遥岩体的野外地质特征与区域上同类型岩体对比分析,综合前人的同位素资料,本次获得的同位素年龄乃代表了江南隆起带上的最可靠的最老的燕山期岩浆活动年龄,因此指示了江南隆起带岩石圈拆沉的开始时间,即从142Ma开始岩石圈减薄。3、 岩浆岩类型及成因:研究区燕山晚期侵入岩基本上均属于高钾钙碱性系列岩石。研究区燕山晚期的花岗斑岩体、花岗岩体的成岩物质以壳源为主,源岩中混染有一定的幔源物质,皖南燕山期花岗岩和斑岩体与陆壳改造系列类似,CPG型的花岗岩。已有的研究表明,皖南燕山期花岗岩、斑岩体成岩物质以壳源为主,但是稀土元素、微量元素、Pb、Nd、Sr同位素还反映出其又具有一些同熔系列花岗岩的特点,成岩物质来源具有一定壳、幔混合特点,这可能与源区物质存在一些幔源组分有关。从岩浆岩的Nd模式年龄上看,研究区燕山晚期花岗岩(除冯村、黄山、谭山外)燕山晚期花岗斑岩体TDM值较低(<1. 6Ga),而皖南冯村、黄山、谭山岩体花岗岩TDM值较高(>1. 6Ga)。采用两阶段TDM计算,则TDMⅡ全部较低,都小于1. 6Ga。侯明金江南隆起带(安徽部分)燕山晚期岩浆活动与深部过程同时,研究区的燕山晚期花岗岩、花岗斑岩体Is;值普遍较高,在0.708以上。因此,其侵入岩浆作用主要发生于陆壳内,为壳源物质部分熔融作用的产物,少量慢源物质的混染加入。 4、印支期以来的区域构造应力场演化特征:印支一燕山早期NNW-SSE、近N一S向挤压,陆内造山作用发育,属古特提斯构造域;燕山晚期即早白至世早期,NW-SE向挤压,北东向断裂发生左行走滑运动,中国东部处于西环太平洋构造域;早白坚世晚期一古新世(始新世),Nw-SE向伸展作用,研究区及其周边处于强烈的伸展断陷作用阶段;新生代,受区域上近E一W向的挤压作用影响,研究区发生挤压逆冲作用。 5、印支一早燕山期:陆内造山阶段。区域地质资料和构造应力场统计测量结果分析,认为江南中生代陆内造山作用始于与大别造山作用的同时,在南陵湖组内发育有初始水平挤压应力场,方向为NW3 100一3400。此乃江南隆起带隆升的开始时间即早三叠世末。中三叠世一中侏罗世,区域上的应力场统计测量表明:盆地属于总体NW-SE向挤压背景下的前陆盆地。江南隆起带大部分处于古陆环境,湖泊相沉积主要发育于屯溪一休宁盆地内。陆内造山使岩石圈加厚大于1 IOkm,当时没有发生岩石圈拆沉或俯冲板片的断离,因此没有陆内同造山的岩浆活动发育。 江南隆起带与大别一苏鲁造山带的区别可能是江南隆起带为陆内造山带,大别一苏鲁造山带为陆间造山带。江南隆起带在中生代已经为一近乎刚性的陆块,而大别一苏鲁造山带为华北和扬子两地块的俯冲、对接和碰撞形成的.当华南地块向北碰撞推挤,首先在大别地区发育俯冲碰撞型陆间造山带,俯冲碰撞到一定程度时,则不再能消减来自南部的强大的推挤力,使得推挤力向后退缩,从而在江南隆起带发生陆内造山作用,形成一系列切入中下地壳的逆冲推搜厚皮构造为主要特征的江南中生代(印支一燕山早期)叠置山系。 6、早白里世早期:走滑作用阶段。早白呈世早期为构造体系转换的时间,随着古特提斯构造域的关闭,研究区陆内造山作用的结束,中国东部转入环太平洋构造域.由于西伯利亚板块、华北板块及华南板块的汇聚,中国东部区域上处于NW-SE向的挤压作更多还原

【Abstract】 This Ph.D thesis is supported by the geological survey project of the Ministry of Land and Resources （Grant No.K1.4-2-2）. It is "the Mineralization, the depth process and resources potential in Jiangnan Uplift Zone". It is a branch project of "the Mineralization of Cu,Au,Ag,Pb,Zn,Fe in the southeastern part of China （the Dabieshan-Taiwan Profile Zone） and its resources potential and the 4-dimention structure of the Mineralization Zone".After systemic study during two years, and based on the project research, I selected the Jiangnan Uplift Zone （Anhui segment） as the research region, including the north part of the folding and thrusting belt of forland. The major aim is studying on the magmatism, petrology, geochemistry, magmatism, its depth process and regional geodynamic basement of the later stage of Yanshanian. The main contents are such as the tectonic property and its evolution, the characteristic of its physical geography of gravitation and magnetism and seismic structures; the magma distribution, types, evolution of the later stage of Yanshanian. The main progresses in this thesis are as below.1. The stages of the magmatism. It is decided that the main magmatism was happened in the later stage of Yanshanian based on the first accurate isotopic dating. We obtained two isotopic data by the dating of two biotites with the method ⁴⁰Ar/³⁹Ar, they are 133.97±0.48Maof the Kaobeijian biotite-granodiorite and 141.46±0.62Ma of Xiaoyao granodiotite porphyry. After statistically analysis, we can found that the isotopic data of the magmatism in the region are mostly located between 130 142Ma or 120¹30Ma. So it indicated that there were two stages of the magmatism of the region during the later stage of Yanshanian, they are the middle stage and later stage of Cretaceous.2. The time of the lithosphere delamination and extention. After regional correlating, we supposed that the two intrusive bodies of Xiaoyao granodiotite porphyry and Kaobeijian biotite-granodiorite have a certain regional representation of the magmatism. The magmatic activities indicated that the lithosphere delamination, the asthenosphere uplifting and lower crust partly melt and mantle underplating to the crust. The 142Ma isotopic data is the oldest precise age in the region until now, considering the regional geological information; we supposed that age was precise one that it is the representation of the regional magmatism. So it indicated that the beginning time of the lithosphere delamination, i.e. the lithosphere had been delaminated since 142Ma in Jiangnan Uplift Region.3. The magma petrology and its cause of formation. The most of the intrusive bodies of the Later Yanshanian are belong to the HK calc-alkalite granite. The mother sources of the granite-porphyry and granite are from the crust, and mixed with somecomponents of the mantle. They are similar to the crustal rebuilt serials granite, such as CPG type granite. But according to the characteristic of the REE, micro elements, Pb, Nd and Sr isotopes show the type of syntactic magma series, and the diagenetic matter show a mixed pattern of the crust and mantle. It indicated that there were some mantle components in the sources of the magma. According to the Nd model age of the magma, it shows that the granite （except Fencun, Huangshan and Tanshan） and granite-porphyry exhibit younger Nd model ages （<1.6Ga）, Fencun, Huangshan and Tanshan granites show elder Nd model ages （>1.6Ga）. But if we take the equation of the two stages of Nd model age, all of the granites exhibit younger Nd model ages （<1.6Ga）. and also, the granites exhibit that the higher /Sr, above 0.708. Concerning those mentioned above, it indicated that the magmatism was happened mainly in the crust, it was formed by partly molten of the crust, but some mantle components have been put in the petrogenetic processes.4. The evolution of the regional tectonic paleostress field since Yindosinian. It exhibit the compression which strikes NW-SSE, nearly N-S; the inner-continental orogeny developed, it belonged to in the paleo-Tethyan更多还原