黔南坳陷及邻区盆地演化和海相沉积的后期改造

黔南坳陷是扬子克拉通内由3组不同方向的断裂围限的一个相对稳定的区块。分4个阶段（新元古代,早古生代,晚古生代—三叠纪,侏罗纪—古近纪）重塑了贵州南部及邻区与周边造山作用耦合的盆地演化。广西运动形成北东向构造,是海相沉积建造阶段中的一次重要改造。印支运动使贵阳—镇远断裂和紫云—罗甸断裂反转,奠定了其成为黔南坳陷的北界和西南界断裂的基础。中侏罗世后的逆掩—冲断可分为两期：早期称燕山运动,以北东走向的断裂向北西逆冲和扩展为特征;晚期称燕山末期—喜马拉雅运动,区域上表现为北北东走向的断裂向南东东逆冲,铜仁—三都断裂成为黔南坳陷的东界,印支运动形成的近南北向—北北东向断层向西（偏北）逆冲,构成铜仁—三都断裂的背冲构造。近南北向断层上盘发育的开阔背斜是黔南坳陷内海相油气勘探的最有利靶区。     

鄂西地区燕山期古构造应力场初步定量研究

鄂西地区主要的构造变形为一系列NNE向褶皱,该区域主要构造形迹已经得到比较系统的研究,但对于发生褶皱时期的古构造应力场则至今尚无较深入的研究,前人仅根据褶皱构造形态特征和断层滑动方向进行过一些古构造应力场的定向研究,导致对齐岳山、利川等燕山期构造演化有了一些不同的观点。本文对燕山期古构造应力场的应力作用方向和作用力大小进行了比较系统的研究。根据研究区地层接触关系,侏罗系与三叠系为同一构造层,而白垩系与该构造层的角度不整合接触关系指示发生构造事件的时间为侏罗纪之后、早白垩世之前;根据野外测量的共轭剪切节理的产状、褶皱两翼地层产状等数据,结合区域整体构造形变特征来判断压缩区,确定了当时最大主压应力轴方向,总体上均为NW SE向;依据野外采集侏罗系、三叠系的石英砂岩标本进行实验测试,在透射电子显微镜下对采集标本进行晶内位错构造的观测统计,使用晶体内自由位错密度与差应力值的经验关系公式,计算出古差应力值的大小,为定量研究该区古构造应力场打下了扎实的基础。     

高铁网络化时代旅游地理学研究新命题审视

交通是推动旅游发展的重要"引擎".伴随中国进入高铁网络时代,高铁"时空压缩"效应对区域交通可达性格局产生重大影响,进而引致"哑铃型"旅游系统或旅游"人地关系"体系中一系列区域旅游要素产生"多米诺"效应,尤其是高铁对旅游空间行为,旅游市场需求和客源结构,旅游资源吸引力格局,与其他交通系统竞合,旅游产业结构,旅游空间格局等方面产生的影响更加凸显,由此催生出旅游地理学研究的20个新命题.梳理这些新命题既能为系统性开展高铁旅游研究提供思想启示,又有利于推动旅游地理学学科发展和理论创新.     

江西修水县梅子坑钼矿床地质特征及成因初探

梅子坑钼矿位于九岭钨钼成矿带,为中型石英脉型钼矿床。矿区内地层和岩浆岩钼元素含量分别是克拉克值的43倍和21倍。矿体赋存于双桥山群修水组浅变质岩系中及北西向断裂控制的裂隙密集带中;矿石主要类型为石英脉型,矿石有益组分为辉钼矿,形成于石英-黄铁矿-辉钼矿-黄铜矿早期矿化阶段。矿床可能与隐伏的燕山期细粒花岗岩、花岗斑岩岩脉有成因关系,属与燕山期岩浆活动有关的中-高温热液矿床。北西向断裂密集带,硅化、云英岩化、黄铁矿化围岩蚀变,燕山期花岗岩类及双桥山群浅变质岩系,是其主要找矿标志。     

大兴安岭区古生代优地槽褶皱带质疑

根据火山岩、绿片岩发育等特征 ,中国著名的地质学家认为 ,大兴安区是古生代优地槽褶皱带。最近 ,笔者识别出其台型沉积岩建造 ,如石英砂岩、含磷岩系、红层、石灰岩含燧石结核和夹有燧石条带等。按大地构造学理论 ,台区沉积岩建造与槽区火山岩系不能共生。为此 ,置于古生界中的大部分火山岩不该属古生界 ,而应属中生界。额尔古纳河组和佳疙疸组为整合接触 ,都夹有绿片岩 ,皆属元古宇。本区古生代地层是盖层 ,元古宙地层为结晶基底。因此 ,该区为地块 ,而不是古生代优地槽褶皱带。     

Reconstruction of Ore-controlling Structures Resulting from Magmatic Intrusion into the Tongling Ore Cluster Area during the Yanshanian Epoch

The Tongling ore cluster area experienced intensive compression and associated shearing during the Indosinian-Yanshanian Epoch, which formed a trunk ore-controlling fold and fault system in the caprock. The magmatic intrusion in the Yanshanian Epoch induced a multi-stage unmixing of poly-phase fluids, resulting in mineralization characterized by multi-layer, wide-range, and multiform styles. The magmatic intrusion in the Tongling area not only supplied the essential ore-forming materials, but also reconstructed the ore-controlling structures according to a trend surface simulation of the following five strata boundaries： Silurian-Devonian, Devonian-Carboniferous, Carboniferous- Permian, Middle Permian-Upper Permian and Permian -Triassic. The result of this simulation shows that there exists a significant difference between the strata in the upper part and those in the lower. The lower trend surfaces are antiform whereas the upper trend surfaces are synform. In addition, superposing of the trend surfaces of adjacent bed boundaries （such as, Silurian-Devonian boundary superposed upon Devonian-Carboniferous boundary） shows that the lower trend surface always pierces the one above. Moreover, the position and orientation of the pierced parts of the different superposed trend surfaces are similar and show E-W-trending zonal distribution in accordance with the distribution of the regional E-W-trending magmatic-metallogenic belt. Based on comprehensive analysis of the mechanical properties of the strata, structural deformation mechanisms, and field phenomena, it seems that the special characteristics of the stratal trend surface resulted from jacking due to magmatic intrusion into the caprock previously controlled by an E-W-trending basement fault. Therefore, it is deduced that the major ore-controlling structures, which formed during regional horizontal compression, were reconstructed by the vertical jacking function of ore-forming magmas during the Yanshanian Epoch. During the ore-forming process, the local vertical jacking of magmas, coupled with the regional horizontal compression, optimized an extensive environment in the fluid- conduit network and accelerated the unmixing of poly-phase fluids following magmatic emplacement. Jacking also strengthened the vertical and lateral fluid-guiding structures, supplying more suitable physical conditions for multi-layer emplacement and wide-ranging transport of poly-phase fluids.     

Petrology and geochemistry of Mesozoic granitic rocks from the Nansha micro-block, the South China Sea: Constraints on the basement nature

There are several micro-blocks dispersed in the South China Sea (SCS), e.g., Xisha-Zhongsha block, Nansha block and Reed-Northeastern Palawan block, etc., but detailed petrological constraints on their basement nature were previously lacking. The magmatic ages for granitic rock samples from two dredge stations in the Nansha micro-block vary from 159 to 127 Ma, which are comparable to magmatic activities occurred in the northern margin (Pearl river mouth), HongKong and East China. Petrographic characteristics, major-, trace element and Sr–Nd isotopic data of nine samples from two dredged station performed in the Nansha micro-block, the SCS, are reported. Petrographically, these granitic rocks can be divided into two groups which underwent a complex history of magmatic process, i.e., tonalitic rock (Group I) and monzogranitic rock (Group II). The Rittmann index (σ) for these rocks (1.9–3.1) suggest that they belong to calc-alkaline rocks. Group I rocks which is of typical I-type, have higher contents of TiO₂, Al₂O₃, FeO, MgO, CaO, Na₂O and P₂O₅, but lower values of SiO₂ and K₂O, when compared with those of Group II with I-type characteristics. Group I rocks are produced by partial melting of older Precambrian basement with the variable influence of mantle-derived magma which results from the interaction of released fluids from the subducted slab and the overlying mantle wedge in a general convergent margin setting, and Group II rocks result from partial melting of lower crustal basic rocks (amphibolite) and/or further partial melting of the Group I rocks associated with the variable influence from the underplating mantle-derived magma resulting from lithospheric extensional regime. Both Groups I and II have undergone assimilation and fractional crystallization (AFC) processes during its petrogenesis. This study therefore demonstrates that there exists a continental basement within micro-blocks in the South China Sea, and further supports the idea that a Middle Jurassic to Mid-Cretaceous subduction zone existed across the temporary Taiwan, Palawan to Southern Vietnam, which was associated with westward to northestward convergence of the Pacific Plate during Late Mesozoic. We suggest that this subduction zone may have been connected with the paleo-Pacific plate subduction zone offshore eastern China during Mesozoic era. This study provides petrologic data for the pre-Cenozoic tectonic evolution of the South China Sea.     

广东省22个燕山期花岗岩的源区特征及成因：元素及Nd-Sr同位素研究

根据主要元素组成,将所研究的22个广东省燕山期花岗岩分为强过铝花岗岩和弱过铝花岗岩两类,后者又区分出分异和未分异两种。它们总体具有较为相似的微量元素和稀土元素组成,即都是以大离子元素明显富集、Ba,Sr,Nb,Ta,P与 Ti 呈负异常、Eu 亏损为特征,但分异弱过铝花岗岩(包括禾洞、大埔、荷泗、白浆岩体)的 Ba、Ti 呈负异常和 Eu 亏损更为明显。强过铝和弱过铝花岗岩的 Nd 同位素组成区别明显:象头山等6个强过铝花岗岩体具有低的ε_(Nd)(t)值(-13.4～-10.0,平均为-12.1)和较老的 Nd 模式年龄(1.76～2.08Ga,平均为1.96Ga),是由成熟度较高的陆壳部分熔融形成;在弱过铝花岗岩中,石背岩体以及禾洞和大埔两个分异岩体具有高的ε_(Nd)(t)值(-3.6～-4.9,平均为-4.4)和年轻的 Nd 模式年龄(1.23 ～1.34Ga,平均为1.3Ga),反映其源区存在一定数量的地幔物质;佛冈等其余12个弱过铝花岗岩体(包括荷泗、白浆2个分异花岗岩)的ε_(Nd)(t)值(-12.3～-8.1,平均为-9.7)和 Nd 模式年龄(1.56～1.94Ga,平均为1.74Ga)都介于上述两类花岗岩之间,但相对较接近于强过铝花岗岩,主要是由成熟度不同程度地低于强过铝花岗岩源区的陆壳变质岩部分熔融形成。广东省燕山期花岗岩主要是在伸展构造及玄武岩底侵条件下,由以沉积变质岩为主的中下陆壳部分熔融形成。     

晋东北燕山期岩浆活动与金多金属成矿作用动力学

晋东北燕山期岩浆活动受区域性构造控制,具有北东成带,带内成区的分布规律,时间上可划分为150~160Ma、130~140Ma和85~127Ma三个高峰期。岩浆岩可划分为以花岗闪长岩—二长花岗岩—中细粒-粗粒斑状黑云母花岗岩等和以闪长岩—花岗闪长斑岩—花岗斑岩—石英斑岩等为主体的两大岩石组合,后者与金多金属矿床成矿关系密切。主要岩浆岩为过铝质碱性岩类,具有埃达克质岩石的亲和性;成因上属于I型,具同源演化关系。其形成可能与华北板块中生代岩石圈大规模减薄所引发的壳幔相互作用密切相关。与燕山期岩浆活动相对应,区域金多金属成矿也具有集中分布和多期成矿的特点。在类型上,主要包括斑岩型Mo-Au矿床、矽卡岩-热液脉型Au、Fe矿床和爆破角砾岩-热液石英脉型Au或Cu-Ag,Ag-Pb-Zn等矿床。有时在同一个成矿集中区内可见有多型一体的复杂组合,并在空间上具有明确的元素分带关系;在时间上,150~160Ma,主要与(二长)闪长岩或石英闪长岩、花岗闪长岩等有关,形成以钼-金为主的矿化;130~140Ma,主要与石英闪长岩、石英斑岩等有关,形成大规模金矿化;85~127Ma,主要与花岗斑岩、石英斑岩、隐爆角砾岩等相关,形成了强烈的银多金属矿化。不同类型矿床成矿热液主要源自相关的岩浆体系。华北板块中生代发生区域性构造体制转折,岩石圈大规模减薄及在此背景下发生的陆内造山作用是区域大规模岩浆活动和成矿作用的重要动力学机制。     

卡而却卡地区新元古代变质侵入岩体的发现及其地质意义

卡而却卡地区地处东昆仑祁漫塔格成矿带内。通过对卡而却卡地区花岗片麻岩的岩石学、地球化学、同位素年代学的研究表明,区内原厘定的花岗片麻岩应为新元古代花岗岩。LA-ICP-MS锆石U-Pb同位素定年研究结果显示岩体侵位时代为910Ma±3Ma,时代为新元古代青白口纪;岩石具高SiO_2、Al_2O_3、K_2O,贫FeO、MgO、CaO特点;稀土元素分布模式为轻稀土富集,Eu中等亏损;岩石中不相容微量元素K、Rb、Ba、Th等强烈富集,Nb、Zr、Ce、Ta、Hf等富集一般,Y弱亏损。以上特征表明,岩石属于高钾钙碱性S型花岗岩,岩浆来源于陆壳部分熔融,形成于同碰撞环境,是东昆仑地区响应Rodinia超大陆汇聚事件的物质记录。