Distinguishing tectonically-and gravity-driven synsedimentary deformation structures along the Apulian platform margin (Gargano Promontory,southern Italy)     

《Marine and Petroleum Geology》2016

The assessment of deformation types within the slope of a carbonate platform can be complicated by the possible interaction of rooted (tectonically-induced) and superficial (gravity-driven) structures. An ideal case study to document and distinguish tectonically- and gravity-driven structures is provided by the Cretaceous slope-to-basin carbonates exposed in the Gargano Promontory, southern Italy. These carbonates formed adjacent to the Apulian platform margin, which was oriented approximately NE–SW to NW–SE along the southern and northern edges of the promontory, respectively. Slump-related folds are characterised by axial planes typically oriented either sub-parallel or at small angles to the strike of the inferred paleoslope. In fact, the strike of folds is roughly NE–SW in the southern portion of the study area, whereas it is NW–SE in the northern part. Correspondingly, gravity-driven normal and reverse faults strike sub-parallel and at acute angles to the adjacent Apulian paleoslope. Cretaceous tectonic faults in the slope-to-basin carbonates form two principal sets striking NW–SE and WNW-ESE. The former set is made up of normal faults and the latter one includes mainly oblique-slip normal faults. Neither normal nor oblique-slip normal faults show any relationship with the geometry of the paleoslope. The results obtained from this study may help the interpretation of subsurface data in those geological contexts in which the interplay of gravitational and tectonic processes is responsible for deformation.  相似文献   

砂岩型铀矿地震勘探中可控震源激发参数试验     

吴曲波  潘自强  李子伟 《铀矿地质》2016,(6):371-375

针对鄂尔多斯盆地东胜地区砂岩型铀矿成矿特点,开展可控震源的震源台数、震动次数、扫描时间、扫描频率、驱动电平、扫描信号斜坡等激发参数试验,确定了较适用于该区的激发参数取值:震动台次2台×6次,扫描时间12s,扫描频率15~100Hz,驱动电平60%,扫描信号斜坡0.3s。采用这些参数可提高该区砂岩型铀矿地震原始资料的信噪比和分辨率。  相似文献   

黔西北地区铅锌矿床流体包裹体与硫同位素地球化学研究   总被引：4，自引：2，他引：2  

朱路艳  苏文超  沈能平  董文斗  蔡佳丽  张正伟  赵海  谢鹏 《岩石学报》2016,32(11):3431-3440

黔西北铅锌成矿区位于扬子地块西南缘,矿床产于不同时代的碳酸盐岩建造中,其矿物组合和热液蚀变特征类似于MVT型铅锌矿床。本文通过对该区部分铅锌矿床的矿石显微岩相学结构、矿物学与地球化学、脉石矿物和闪锌矿中流体包裹体岩相学与显微测温学以及硫同位素地球化学等研究,确定了该类型矿床成矿流体的性质及其成矿过程。结果表明,黔西北地区不同赋矿层位铅锌矿床具有相似的成矿流体特征,为中低温(160~260℃)、较高盐度(10%~22%NaCleqv)、含有低密度的CO_2、CH_4和N_2的卤水,不同于MVT型铅锌矿床成矿流体特征;硫同位素地球化学研究揭示,这些铅锌矿床硫化物的δ~(34)S范围均落在对应赋矿地层时代蒸发岩中的硫酸盐和生物成因硫化物的δ~(34)S演化曲线上或其附近,表明这些铅锌矿床硫化物中的S可能主要来源于对应地层本身。结合地球化学热力学分析,认为Pb、Zn等成矿元素的Cl络合物是成矿元素的主要搬运形式,富含Pb、Zn的成矿流体与赋矿地层中富含H_2S还原性流体的混合是铅锌富集成矿的重要机制之一。  相似文献   

四川天宝山铅锌矿床的锌-硫同位素组成及成矿物质来源   总被引：5，自引：4，他引：1  

何承真  肖朝益  温汉捷  周汀  朱传威  樊海峰 《岩石学报》2016,32(11):3394-3406

四川天宝山铅锌矿床位于扬子板块西南缘,赋矿地层为上震旦统灯影组白云岩。尽管这个地区已有大量的科研工作,但其成矿物质来源仍然存在争议。本文主要测定了闪锌矿微区样品的锌和硫同位素组成,以及三个中段的闪锌矿单矿物、上震旦统灯影组白云岩和会理群天宝山组砂岩的锌同位素组成。闪锌矿微区样品的δ~(66)Zn值介于0.39‰~0.52‰之间,平均值为0.46‰,δ~(34)SCDT值介于4.24‰~4.87‰之间,平均值为4.59‰。同一块手标本上闪锌矿微区样品具有均一的锌同位素组成表明小尺度上(10×10cm~2)热液流体具有均一的锌同位素组成。在大尺度上(矿体),三个中段的闪锌矿的锌同位素组成范围变化较大,其δ~(66)Zn值介于0.15‰~0.73‰之间。同一块手标本上早期阶段的闪锌矿具有更重的锌同位素组成表明早期阶段的成矿流体可能具有更重的锌同位素组成。三个中段闪锌矿的锌同位素组成变化主要受成矿流体中锌同位素组成和成矿流体的迁移就位途径控制。上震旦统灯影组白云岩的δ~(66)Zn值介于0.06‰~0.35‰之间,平均值为0.21‰,暗示热液淋滤控制了灯影组白云岩的锌同位素组成。会理群天宝山组砂岩的δ~(66)Zn值为0.62‰,可能代表了未经热液淋滤的沉积端元的锌同位素组成。本次研究表明天宝山铅锌矿床的锌主要来源于上震旦统灯影组白云岩,但不能排除白云岩之上的沉积盖层、基底和更深物质的贡献;硫主要来源于上震旦统灯影组地层中的蒸发岩(主要通过热化学还原作用形成还原硫)。  相似文献   

右江盆地酸性脉岩继承锆石成因及地质意义   总被引：1，自引：1，他引：0  

朱经经  钟宏  谢桂青  赵成海  胥磊落  陆刚 《岩石学报》2016,32(11):3269-3280

卡林型金矿与岩浆作用的关系一直以来是矿床学家关注的热点。右江盆地发育众多卡林型金矿床,但由于区内岩浆岩出露十分有限,岩浆活动对金成矿有无贡献目前还无定论。火成岩中的继承锆石常常可以用来指示早期的、隐伏的岩浆活动。桂西北地区晚白垩世巴马、料屯和下巴哈石英斑岩脉中含有大量的继承锆石。其中,料屯和下巴哈两处脉岩分别与料屯和明山金矿在空间上紧密相关。脉岩中锆石的LA-ICP-MS和SIMS原位U-Pb定年表明,其主要集中于130~140Ma、242Ma左右、400~450Ma、700~1000Ma和1700~1800Ma等五个年龄段。关于较年轻的两个时间段,来自料屯和下巴哈石英斑岩脉的继承锆石分别获得两组谐和年龄,即136.3±3.9Ma(2σ)和242.3±1.7Ma(2σ)、128.2±2.3Ma(2σ)和243.1±3.6Ma(2σ)。这些脉岩侵入的最年轻地层为中三叠统百逢组,因而前三叠纪继承锆石可能捕获自地层,而晚于三叠纪的130~140Ma锆石则应来自于深部隐伏岩体。关于242Ma左右锆石,尽管其与围岩地层百逢组1~2段近于同期,但其晶形较差且多呈不规则碎片状,暗示其更可能源自百逢组中的沉积碎屑锆石。结合区域地质背景,认为该期锆石所代表的岩浆事件可能与古特提斯洋闭合有关。以上130~140Ma和约242Ma左右的两组年龄,与初步确定的右江盆地卡林型金矿的两次成矿的时代基本一致,据此推断金矿化与岩浆作用可能有一定成因联系。  相似文献   

湘南粤北铅锌矿床闪锌矿的标型特征及指示意义     

徐接标  张术根  左亚飞  冯雨周  卢敏晨 《岩石矿物学杂志》2016,35(2):283-296

湘南粤北位于南岭成矿带中段,是我国最重要的铅锌矿集区之一。本文选取湘南粤北地区MVT和岩浆热液型两类铅锌矿床的闪锌矿样品,对闪锌矿的形态、结构、化学成分、硫同位素组成、流体包裹体成分等进行系统研究,分析其成矿温度、硫的来源和成矿流体特征,为揭示成矿作用提供可靠依据。研究结果表明:MVT铅锌矿床成矿作用发生在中低温、氧化-弱还原、较低压力环境,硫主要来源于容矿地层,成矿流体主要来自于热卤水和沉积物变质脱水;岩浆热液型铅锌矿床成矿作用发生在中高温、弱还原、较高压力条件下,硫源主要以岩浆硫为主,成矿流体早期以岩浆热液为主,晚期为混合流体。结合矿体与岩体的形成时间、空间分布、大地构造背景,认为岩浆热液型铅锌矿床由燕山早期(180~150 Ma)古太平洋向大陆俯冲、岩石圈加厚,爆发大规模花岗质岩浆岩侵位,导致铅锌成矿;MVT铅锌矿床由燕山晚期(130~90 Ma)欧亚大陆岩石圈伸展减薄产生的岩浆热液叠加改造泥盆系的原始矿源层形成。  相似文献   

Effects of Material Composition and Water Content on the Mechanical Properties of Landslide Deposits Triggered by the Wenchuan Earthquake   总被引：3，自引：0，他引：3  

ZHOU Jiawen  CUI Peng  YANG Xingguo 《《地质学报》英文版》2016,90(1):242-257

Abundant landslide deposits were triggered by the Wenchuan earthquake, providing a rich source of material for subsequent debris flows or slope failures under rainfall conditions. A good understanding of the physical and mechanical properties of the landslide deposits is very important to the research on slope failure mechanisms and the initiation of debris flow. Laboratory biaxial compression tests are used to study the material compositions and water content impacts on the mechanical properties of landslide deposits, and a discrete element method (a bond-contact model) is used to study the particle stiffness, bond force, friction coefficient and confining stress impact on the mechanical behaviors and the relationships between the numerical and experimental parameters. The experimental results show that the failure stress of landslide deposits is decreased with increasing content of fine particles and also with increased water content, especially at the initial increasing stage. Cohesion of the saturated landslide deposits is increased, but the friction angle is decreased with the increase in the fine particle content. Shear strength parameters (the cohesion and friction angle) are decreased with the increasing water content at the initial increasing stage, and then, they slowly decrease. There is a critical value of the water content at 5%–7% (in weight) for the failure stress and shear strength parameters of the landslide deposits. Quadratic equations are presented to describe the relation between the bond force and cohesion, and the numerical friction coefficient and the experimental friction angle.  相似文献   

Geology and Isotope Geochemistry of the Yinchanggou-Qiluogou Pb-Zn Deposit, Sichuan Province, Southwest China   总被引：1，自引：0，他引：1  

LI Bo  ZHOU Jiaxi  LI Yingshu  CHEN Aibing  WANG Ruixue 《《地质学报》英文版》2016,90(5):1768-1779

The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD_(H2O-SMOW) and δ~(18)O_(H2O-SMOW) values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H_2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ~(13)C_(PDB) values ranging from-6.2‰ to-4.1‰ and δ~(18)O_(SMOW) values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ~(34)S_(CDT) values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.  相似文献   

Sulfur isotopic geochemistry of the huize Pb-Zn ore field in yunnan province北大核心CSCD     

Wang L.  Han R.-S.  Zhang Y.  Wang J.-S. 《矿物岩石地球化学通报》2016,(6):1248-1257

In order to constrain sulfur isotope compositions of ore-forming fluids, ore-forming temperature, source of sulfur and mechanism of sulfur reduction in the Huize lead-zinc ore field, based on sulfur isotope compositions from previous studies, new data of sulfur isotopic composition of primary sulfide of upper ore-bodies in Qilinchang and newly-found sulfate outside the deposits were utilized in this study. It show that 5 values of primary sulfide vary from 8. Oft∗ to 17. 68 ft∗ , and sulfur isotopes in ore-forming fluid have reached equilibrium; S'lS values of sulfur out side the deposits vary from 17. 95ft∗ to 24. 30ft∗ with average value of 20. 14ft∗ , yielding sulfur isotopic composition of ore-for ming fluids as 14. 14ft∗ by the Pinekney method for mineral association. The value is close to 5'4S of marine sulfate. Ore-forming temperature is calculated as 1 34 - 388by isotope geological thermometer. The results of fluid inclusion thermometer indicate that barites were crystallized from hydrothermal fluid, which is suggested that sulfur in ore-forming fluid probably originates from marine sulfate of stratum in and outside the deposits or hydrothermal barites found in ore district. Reduction mechanism of sulfate is likely to be themio-chemical sulfate reduction.  相似文献   

长江口的台风浪及其对崇明东滩的冲淤作用   总被引：1，自引：0，他引：1  

茅志昌 《海洋学研究》1993,11(4):8-16

本文分析了多年的台风和波浪资料得到如下的结果:对崇明东滩有较大影响的台风路径主要有两类:即在浙江中部至长江口登陆的台风和在长江口外侧海域转向北上的台风;佘山岛海洋站百年一遇的最大波高为5.6m;台风期间偏北、东北、东南的强风向均能引起长江口较大的增水现象。 本文还以8310号台风为例,阐明了台风前后的冲淤变化及台风浪塑造的滩地地貌形态。指出东旺沙和北八效高潮滩冲淤甚微,中低潮滩冲刷严重,奚东沙高潮滩冲刷严重,中低潮滩呈微淤状态。波浪对东滩塑造的主要地貌形态有冲刷坑和浪蚀泥坎。  相似文献