辽东半岛大营子拆离断层系及其区域构造意义

华北克拉通晚中生代发生了大规模岩石圈减薄并伴随着地壳层次区域性伸展作用的发生.在此伸展背景下,华北克拉通区发育有一系列的伸展构造,大营子拆离断层系即为一个典型实例、大营子拆离断层系位于华北克拉通东部（辽东半岛东南部）,主要由上盘火山-沉积盆地,大营子-黄花甸拆离断层带以及下盘古元古代变质岩系和侵入岩体三部分组成.依据拆离断层带中构造岩组合、构造岩变形显微构造和石英EBSD组构分析揭示出下盘岩石主要经历了从高绿片岩相到低绿片岩相的变形变质过程.基于火山-沉积盆地中火山岩的SHRIMP和LA-ICP-MS锆石U-Pb测年结果,推断伸展构造开始活动于（135±1.2）Ma之前,结束于（127±1）Ma.通过与辽南变质核杂岩及辽东半岛其他伸展构造的对比,以及这些伸展构造的分布及影响深度,可充分说明辽东半岛岩石圈破坏和减薄的不均一性,从而显示出其破坏程度的差异,并藉此探讨了华北克拉通破坏和伸展减薄的不均匀性.     

组构对花岗质岩石流变影响的实验研究

正华北克拉通减薄是近年来地学界的热点问题,拆离断层形成与地壳伸展减薄是华北克拉通岩石圈减薄的浅部响应,而拆离断层内岩石的流动及变形机制直接受控于岩石流变学状态。对于华北克拉通地壳流变研究,流变实验和天然样品流变分析多数集中在下地壳,对于与拆离断层对应的中上地壳流变实验研究比较少。目前为止,有关于地壳伸展和拆离断层形     

内蒙古赤峰安家营子金矿成矿时代以及对华北中生代爆发成矿的意义

安家营子金矿位于华北克拉通北缘金矿成矿带的中部, 其北紧邻兴蒙造山带. 华北陆块与兴蒙造山带之间的边界断裂即赤峰-开原断裂从附近经过, 是区域性控矿断裂. 安家营子金矿为一中型矿床, 矿体主要赋存于安家营子花岗岩体中. 与金矿化相伴生广泛分布着流纹斑岩、煌斑岩等岩脉. 对安家营子花岗岩、穿切矿体的流纹斑岩岩脉的锆石U-Pb年龄测定表明, 安家营子花岗岩的侵位时代为132~138 Ma, 流纹斑岩的成岩时代为124.9~126.5 Ma. 根据矿体与花岗岩、脉岩之间的穿切关系将安家营子金矿成矿时代限定在126~132 Ma, 即早白垩世. 这一年龄与华北克拉通上其他主要金矿集中区的成矿年龄是一致的, 也与华北克拉通中生代动力学体制发生转折的时间相吻合. 这表明华北克拉通上绝大多数金矿床, 包括安家营子金矿床形成的动力学背景是相同或相似的, 即形成于中生代大规模的岩石圈减薄的构造背景下.     

“长江深断裂带”的构造性质:深地震反射证据

长江深断裂带自20世纪50年代提出以来,因其在区域控岩、控矿、工程地质和灾害地质研究中的重要意义,一直受到广泛关注和研究,但由于缺乏深部资料,对长江深断裂带的构造性质、空间展布众说纷纭.本文通过分析穿过长江河床及两岸的六条深地震反射剖面,讨论了长江中下游成矿带及长江深断裂带的构造性质及演化,获得如下认识:(1)长江中下游成矿带是燕山期的陆内俯冲带,上地壳发生强烈挤压变形,以大型逆冲、叠瓦、褶皱和推覆构造为特征;下地壳及岩石圈地幔俯冲或叠置到相邻块体之下,在宁芜火山岩盆地和沿江凹陷下形成了"鳄鱼嘴"构造.(2)白垩纪以来,长江深断裂带(CJF)由一系列拆离断层组成,大致沿长江河床分布.该断裂带在燕山期陆内造山阶段为一组逆冲断裂,伸展垮塌阶段反转为正断层或拆离断层,同时控制了沿江凹陷的形成和演化.(3)陆内俯冲或叠置导致地壳加厚、拆沉,引发大规模岩浆活动."鳄鱼嘴"构造或是沟通深部岩浆向上迁移的主要通道,控制了沿江成矿岩浆岩的分布.正是这种特殊的深部过程和构造特征,导致了燕山期长江中下游地区的大规模成岩、成矿作用.     

鄂尔多斯块体-华北地区地壳上地幔P波三维速度结构

本文利用华北地震科学台阵、鄂尔多斯及周缘地震台网和区域地震台网记录的62736个远震P波走时数据,获得了鄂尔多斯块体中部与华北地区之间400km深度范围内的P波三维速度结构.考虑到研究区的复杂地质结构,本文采用FMM算法和子空间反演算法进行地震层析成像.成像结果表明:1)研究区的地壳速度分布与地质构造格局的相关性显著,随着深度的增加相关性减弱;断裂带多为高速异常区和低速异常区的分界线.2)研究区东部的速度结构与鄂尔多斯块体相比存在明显的不均一性,上地幔高速异常具有南北不均匀性.表明华北克拉通破坏时东、西部的岩石圈可能经历了不同的构造变形过程,东部岩石圈受到大规模破坏,破坏后的上地幔物质呈南北向不均匀分布,西部鄂尔多斯块体岩石圈保持着相对稳定的克拉通特征,不存在大规模破坏的证据.3)华北克拉通的岩石圈厚度由东向西整体逐渐增加.东部在100km深度附近出现大范围的低速异常,表明在该深度已进入软流圈,西部鄂尔多斯块体的岩石圈厚度约为250km.4)鄂尔多斯块体的东边界在黄河以东的离石断裂带.     

华北克拉通地区基于程函方程的面波层析成像

利用布设在华北克拉通地区的流动和固定地震台站记录到的地震波数据,使用基于程函方程的面波成像方法获得了整个华北克拉通地区瑞利波15～150 s周期的相速度,并反演了研究区S波速度结构.中长周期相速度结果显示,在上地幔及岩石圈深度范围内,燕山地区表现为高速特征,华北克拉通中部大同盆地及其以南地区、太行山等区域的低速体与华北盆地的低速体相连,呈现大面积的低速异常,低速体的速度值比青藏高原东北缘的速度值更低;S波速度显示鄂尔多斯岩石圈厚度较厚,克拉通中部和华北盆地岩石圈厚度相差不大,燕山地区岩石圈厚度要厚于华北盆地.本文认为华北克拉通岩石圈破坏存在分区性,克拉通中部和燕山地区均存在一定的克拉通破坏,但破坏程度不同,鄂尔多斯地块北部存在局部克拉通改造,但克拉通稳定性特征依然存在;破坏的主要动力学来源更可能是太平洋板块的西向俯冲.研究发现克拉通中部和东部的强震分布区与克拉通破坏区域重合,大部分强震发生在岩石圈强度边界上,分析认为岩石圈强度的差异是岩石圈强度边界上显示出较高的强震活动性的原因.     

胶东大型黄金矿集区及大规模成矿作用

研究表明，胶东矿集区的东界与华北克拉通的东界吻合，金矿以华北克拉通变质岩及其有关的侵入岩为控矿围岩．主成矿期成矿时代为 １２１．６～１２２．７ Ｍａ，约在 １个１００万年的短时限内．成矿物质具有多源性，既来自于控矿围岩－花岗岩和变质岩，又来自于幔源的岩浆岩，特别是与中基性脉岩、偏碱的钙碱性花岗岩的侵入关系密切．胶东大规模成矿的动力学过程受华北东部中生代构造转折体制制约，是周围板块共同作用下的大规模壳幔相互作用的直接结果．     

四川盆地—大巴山结合带地壳构造特征:深反射地震约束的重磁解释

大巴山位于四川盆地北部、秦岭南缘,以发育大规模的中生代逆冲推覆构造为世人瞩目,其地壳尺度结构与构造特征对于理解扬子克拉通和华北克拉通的碰撞过程有重要意义.本文基于深反射地震剖面和宽角反射与折射地震数据的约束,结合地质与钻井资料,通过重磁场分析拟合解释,对四川盆地北部—大巴山地壳尺度的构造进行综合研究,建立了地壳断面结构与构造模型.模型显示,四川盆地北部基底和沉积盖层变形差异较大,且上下地壳具有解耦性,上地壳向北延伸至紫阳断裂一带;而下地壳与上地壳拆离,向北延伸远至安康断裂一带.研究区莫霍面起伏较大,自南向北先加深后抬升,在大巴山下出现Moho的构造叠置,这种现象源于大陆地块(扬子克拉通)下地壳向大巴山—秦岭造山带下的俯冲.类似的现象也出现在西昆仑山下,即塔里木盆地下地壳向西昆仑山下俯冲,俯冲板片前缘出现Moho的叠置.     

华北克拉通中东部基底构造单元的重磁特征

系统收集并重新处理了华北克拉通中东部的重磁资料,利用处理结果,结合近年来华北克拉通前寒武纪结晶基底构造研究的进展,重新将华北克拉通中东部划分为2个一级重磁异常单元和7个二级重磁异常单元;重点描述了7条分划性断裂的重磁特征,特别指出中国东部重力梯度带正是华北克拉通中部带的集中表现,而郯庐断裂带和兰考～聊城～盐山～台安-大洼断裂带是燕山期陆内不同刚性块体调整的重要边界,所以也是重磁特征的变异带．据此,对华北克拉通断裂与构造单元的重磁异常特征赋予了新的地质意义．研究表明,华北克拉通现今的地球物理特征能够反映结晶基底构造,其原因是华北克拉通现今构造格局是中新生代构造继承结晶基底构造的结果．     

辽东地区金矿床成因与资源潜力

华北东部广泛分布着与晚中生代克拉通破坏相关的金矿床,但不同地区金矿床在研究程度、成矿特征、探明储量等方面存在显著差异.华北东部的辽东具有与胶东相似的区域地质特征,并共同经历了晚中生代克拉通破坏作用,但其金成矿的理论研究和探明的黄金资源量却存在巨大差异.本文在分析研究辽东区域地质、中生代岩浆-构造演化和矿床地质基础上,通过深部-浅部综合地球物理探测和大数据AI资源量预测,提出了辽东晚中生代金元素富集主体来自于克拉通破坏诱发的幔源熔流体,金矿床主要受北东-北北东向断裂控制,金矿类型以破碎带蚀变岩型和含硫化物石英脉型为主.明确了鸭绿江主断裂带及相关的次级断裂、已知矿集区外围与深部是未来金矿资源勘查的重要区域,预测鸭绿江成矿带黄金资源潜力巨大,具备新增数千吨级黄金资源的潜力.     

Gold mineralization age of the Anjiayingzi gold deposit in Chifeng County,Inner Mongolia and implications for Mesozoic metallogenic explosion in North China

The Anjiayingzi gold deposit in Chifeng County, Inner Mongolia is located in the central part of the gold mineralization belt of the northern margin of the North China Craton (NCC), and is adjacent to the Paleozoic Inner Mongolia-Da Hinggan Mountains orogenic belt in the north. The Chifeng-Kaiyuan fault, which separates the NCC from this orogenic belt, is considered to be a regional ore-controlling structure. The Anjiayingzi gold deposit is a mediate-size quartz lode-gold deposit and is hosted by the Anjiayingzi quartz monzonite that was emplaced into the basement composed of early Precambrian gneisses. Rhyolitic and porphyritic dikes are generally associated with the gold mineralization. Zircon U-Pb analyses suggest that the Anjiayingzi granite was emplaced from 132 Ma to 138 Ma, while the rhyolitic dikes that occupy the same fracture system as the gold-bearing quartz veins and locally crosscut the gold lodes crystallized from 125 Ma to 127 Ma. These results constrain the mineralization age between 126     

Metallogenesis of superlarge gold deposits in Jiaodong region and deep processes of subcontinental lithosphere beneath North China Craton in Mesozoic

The study of ore-forming chronology indicates that the superlarge gold deposits in the Jiaodong region were formed in 120±10 Ma. Sr-Nd-Pb isotopic compositions from typical gold deposits suggest that ore-forming materials were derived from the multisources, mantle component was partly involved in mineralization, the deep dynamic processes are the major geological background of large-scale metallogenesis in the Jiaodong region in Mesozoic. The deep pro- cesses mainly include the effect of post deep-subduction of continental crust of the central orogen belt and the distant effect of subduction of the paleo-Pacific plate underneath the Eurasian continent. However, lithosphere thinning, crust-mantle interaction, crustal extension and formation of large-type ore-controlling structures would be the comprehensive consequences of the above- mentioned geodynamic processes in the region.     

Metallogenesis of superlarge gold deposits in Jiaodong region and deep processes of subcontinental lithosphere beneath North China Craton in Mesozoic

The study of ore-forming chronology indicates that the superlarge gold deposits in the Jiaodong region were formed in 120±10 Ma. Sr-Nd-Pb isotopic compositions from typical gold deposits suggest that ore-forming materials were derived from the multisources, mantle component was partly involved in mineralization, the deep dynamic processes are the major geological background of large-scale metallogenesis in the Jiaodong region in Mesozoic. The deep processes mainly include the effect of post deep-subduction of continental crust of the central orogen belt and the distant effect of subduction of the paleo-Pacific plate underneath the Eurasian continent. However, lithosphere thinning, crust-mantle interaction, crustal extension and formation of large-type ore-controlling structures would be the comprehensive consequences of the above-mentioned geodynamic processes in the region.     

Three-dimensional distributed DC/IP method for altered tectonite-type gold ore deposits exploration: a case study of the Jiaojia gold metallogenic belt,Eastern China

To develop an effective method to identify ore-controlling faults, we studied the Jiaojia gold metallogenic belt, a most typical altered tectonite-type gold metallogenic belt in the Jiaodong Peninsula, China, and conducted experiments using the 3D distributed direct current-induced polarization (DC/IP) method. Firstly, we tested the ability of using 3D distributed DC/IP method to identify altered tectonite-type gold ore deposits by 3D synthetic modelling. We then collected real data of the Sizhuang gold deposit using the 3D distributed DC/IP method. The resistivity model obtained of this region is generally consistent with the known geological setting. Moreover, to obtain the information about the southern extension of the Jiaojia gold metallogenic belt, we conducted a 3D distributed DC/IP experiment in the Shijia area in the southern segment of the Jiaojia fault. The southern extension of the Jiaojia fault and tectonic evolution of shallow magma in this region were inferred from the 3D resistivity and chargeability models. Based on all the information above, we concluded that the 3D distributed DC/IP method has the advantages of 3D observations, high spatial resolution and great detection depth and will be one of the most effective methods for detecting altered tectonite-type gold ore deposits.     

利用背景噪声和接收函数研究华北克拉通地壳结构

收集华北克拉通地区188个宽频带流动台站观测资料进行处理.通过背景噪声面波数据和接收函数双重资料约束联合反演,得到了研究区沉积层厚度、地壳厚度及地壳S波速度结构.结果显示:(1)沉积盖层厚度与地质构造相对应,盆地区与隆起区分界明显.(2)研究区地壳厚度变化范围约29~46 km,自西向东逐渐变薄.(3)中、上地壳华北盆地S波速度偏高,可能与新生代以来多次沉降所造成的相对高的岩石强度有关;(4)下地壳S波速度显示研究区主要存在三个低速区,分别是唐山—天津周边、张北及太行山造山带地区;华北盆地存在显著高速异常,推测可能是由于华北盆地经历下地壳拆沉后,大规模的伸展作用相伴随的幔源基性铁镁质岩浆底侵至下地壳结晶所造成的.(5)多个发生过强震的区域表现出沉积层下方存在较大范围的(约10 km)高速体,并且高速体又被其下低S波速度包裹,壳内岩石强度的差异为应力积累及地震发生提供条件.     

利用爆破地震揭示华北克拉通基底的高分辨速度结构——大丰—包头折射剖面的探测结果

大丰—包头剖面以"高密度观测点距与炮距"为特点,我们在1334 km测线上获得了21炮高信噪比的地震资料.在对Pg波震相特点分析基础上利用反演方法处理、构建了基底的精细结构图像,揭示了沿剖面不同构造地块基底结构的差异.苏北盆地基底埋深4.5~9.0 km、苏鲁隆起1.5~2.0 km,基底埋深与速度结构的强烈起伏变化可视其为华北与扬子板块碰撞、挤压构造环境下形成复杂的构造格局在地震学上的体现;鲁西隆起区基底埋深浅、速度高,结构稳定;华北盆地Pg波到时滞后、视速度低,基底埋深7.0~10.km,速度结构与基底面存在局部的起伏变化.诸多现象揭示出该区为新生代沉积巨厚、规模较大的基底坳陷区.同时在盆地内不同构造单元基底结构呈局部分块、凹陷与凸起并存的构造格局,显示出新生代沉积活动显著、变化强烈、结构不稳定的构造特点;太行山前断裂、聊兰断裂是具有显著地震学标志的断裂构造带,断裂两侧基底界面呈现出"断崖式塌陷"和速度结构的强烈横向非均匀性.综合研究认为,太行山前断裂是华北地区一条重要的构造带,它的复杂性不仅体现在两侧地形地貌、地层介质的截然不同,其基底埋深及速度结构、地壳及地幔岩石圈结构均存在显著的差异,其重要的标志是太行山以东不仅地壳厚度发生了相当规模的减薄,岩石圈的厚度也明显减薄,亦即形成了华北克拉.通破坏在东西部其基底一地壳一岩石圈的结构在空间上具有明显的差异性及强烈的横向非均匀性.     

The big mantle wedge and decratonic gold deposits

The Circum-Pacific subduction zone is a famous gold metallogenic domain in the world, with two important gold metallogenic provinces, the North China Craton and Nevada, which are related to the destruction of the North China Craton and the Wyoming Craton, respectively. Their ore-forming fluids were possibly derived from the stagnant slab in the mantle transition zone. The oceanic lithospheric mantle usually contains serpentine layers up to thousands of meters thick. During plate subduction, serpentine is dehydrated at depths of 200 km and transformed into high-pressure hydrous minerals, known as Phases A to E, which carries water to the depth of 300 km. The overlying big mantle wedge is hydrated during the breakdown of these hydrous facies in the mantle transition zone. The dehydration of the subducted slab in the big mantle wedge releases sulfur-rich fluid, which extracts gold and other chalcophile elements in the surrounding rocks, forming gold-rich fluid. Because the cratonic geotherm is lower than the water-saturated solidus line of lherzolite, the fluid cannot trigger partial melting. Instead, it induces metasomatism and forms pargasite and other water-bearing minerals when it migrates upward to depths of less than 100 km in the cratonic lithospheric mantle, resulting in a water-and gold-rich weak layer. During the destruction of craton, the weak layer is destabilized, releasing gold-bearing fluids that accelerate the destruction. The ore-forming fluids migrate along the shallow weak zone and are accumulated at shallow depths, and subsequently escape along deep faults during major tectonic events, leading to explosive gold mineralization. The ore-forming fluids are rich in ferrous iron, which releases hydrogen at low pressure through iron hydrolysis. Therefore, decratonic gold deposits are often reduced deposits.     

Large clusters of gold deposits and large-scale metallogenesis in the Jiaodong Peninsula, Eastern China

The Jiaodong Peninsula is the largest repository of gold in China based on the production in history. It covers less than 0.2% of China’s territory, but production of gold accounts for about one fourth of the whole country. Thus, the Jiaodong Peninsula is a typical area or case of large-scale metallogenesis and a large clusters of mineral deposits in China. It is characterized by the large clusters of gold deposits in large scale, high reserve and short mineralizing stage. In this study, we suggest that the eastern boundary of the large clusters of gold deposits is as same as that of North China Block, the gold deposits are hosted by Archean metamorphic rocks or Mesozoic granites, and the age of gold mineralization is 121.6 to 122.7 Ma. Gold and related ore-forming materials are derived from multisources, i.e. Archean metamorphic rocks, granites and intermediate-mafic dikes, especially, intermediate-mafic dikes and calc-alkaline granites. The metallogenic geodynamic process is constrained by the tectonic evolution of eastern North China Block during Late Mesozoic, and it is the result of the interaction between mantle and crust as the boundary plates are playing role on the block.     

基于背景噪声和地震面波联合反演华北克拉通中部岩石圈结构

基于ChinArray三期项目布设于华北克拉通中部的流动台阵观测数据,利用背景噪声互相关和地震面波层析成像获取了研究区内6—140 s周期的瑞雷面波频散,使用蒙特卡罗非线性反演方法获得了华北克拉通中部岩石圈的高分辨率三维S波速度结构。结果显示华北克拉通不同地块的岩石圈速度结构存在显著的横向差异:其中鄂尔多斯盆地腹地整体表现为高速特征,延伸至200 km以下,但其东南缘存在小范围的低速异常;东部的华北盆地整体表现为低速特征,具有较薄的地壳和岩石圈厚度;中部造山带南北两端以及南北重力梯度线下方存在相连接的低速区域,在深处延伸至华北盆地下方;在下地壳和上地幔顶部,大同火山群区域的低速体逐渐向西偏移至鄂尔多斯盆地东北角下方;而在上地幔中,该区域的低速异常随深度增加而逐渐减弱,低速体延伸至东南方向的华北盆地下方。基于本研究获得的S波速度模型,我们认为:鄂尔多斯盆地腹地保持了克拉通特性,但其东南缘存在局部的岩石圈改造作用;华北盆地发生了强烈的岩石圈破坏减薄和地壳伸展变形;中部造山带南北端以及南北重力梯度线下方的岩石圈发生了局部的改造减薄,其机制可能都来源于华北盆地下方地幔热物质的上涌;大同火山群下方上涌的热物质从鄂尔多斯盆地东北角下方侵入下地壳,在地壳内上升过程中受到上地壳的阻挡,向东流动至大同火山群下方,形成了大同火山群的岩浆活动,其深部来源可能与西向俯冲的太平洋停滞板块有关。      

Conditions and processes leading to large-scale gold deposition in the Jiaodong province,eastern China

The gold deposits in the Jiaodong Peninsula constitute the largest gold mineralized province in China. The mineralization shows common characteristics in their tectonic setting, ore-forming fluid and metallogenic system. Sulfidation and fluid immiscibility are two important mechanisms controlling gold precipitation, both of which consume sulfur in the oreforming fluids. The escape of H_2S from the main ore-forming fluids and the decrease of total sulfur concentration not only lead to the efficient precipitation of gold, but also result in the crystallization of reducing minerals such as pyrrhotite and oxidizing minerals such as magnetite. Quartz solubility shows strong dependence on temperature, pressure, and CO_2 content. The dependence of quartz solubility on pressure is weak at low temperatures, and progressively stronger at higher temperatures.Similarly, the temperature dependence of quartz solubility is relatively low at low pressures, but becomes gradually stronger at high pressures. The results of solubility modeling can constrain the dissolution and reprecipitation behavior of quartz in the oreforming veins and the formation mechanism of different types of quartz veins. The multi-stage mineralization fluid activity resulted in the complex dissolution structure of quartz in the Jiaodong gold veins. Pyrite in the main metallogenic period in the Jiaodong gold deposits shows complex microstructure characteristics at single crystal scale. The trace elements(mainly the coupling of As-and Au-rich belt) and sulfur isotope composition also display a certain regularity. The As-rich fluids might have formed by the initial pulse of ore-forming fluids through As-rich metasedimentary strata, while the As-Au oscillation zone at the margin of pyrite grains is related to the pressure fluctuation caused by fault activity and the local phase separation of fluids. There is a temporal and spatial evolution of gold fineness in the Jiaodong gold deposits. Water/rock reaction(sulfidation) was the main ore-forming mechanism of early gold mineralization, forming relatively high fineness gold, while significant pressure drop in the shallow part accompanied by fluid phase separation promoted the late gold mineralization, forming low fineness gold. Under cratonic destruction setting, dehydration of the amphibolite and granulite facies metamorphic lower-crust resulted in the formation of Au-CO_2-rich ore-forming fluids, which rose along the deep fault and secondary structure, and formed the largescale fault-controlled gold deposits in Jiaodong.