务正道铝土矿基底古地貌与矿石品质的关系——以务川大竹园铝土矿床为例   总被引：2，自引：0，他引：2  

翁申富 《地质与勘探》2013,49(2):195-204

本文以贵州务正道地区务川大竹园铝土矿床为例,对其岩相古地理进行总结,并对基底古地貌与铝土矿品质的关系进行分析。研究认为,务正道铝土矿受沉积环境的制约,呈环状分布于滨湖相、三角洲相和浅湖相的沉积环境中,其中以浅湖相环境下形成的铝土矿质量较优,而滨湖相和三角洲相环境下形成的铝土矿则质量欠佳。铝土矿含矿岩系赋存在基底页岩或碳酸盐岩准平原化地貌之上,铝土矿的品质不仅受物源供给、沉积环境的制约,而且还与准平原化地貌特征密切相关,在基底古地貌低凹处三氧化二铝含量较高,铝硅比值较大;基底古地形地貌即坑洼形态、大小、深度控制了铝土矿体的展布范围、产出形态、贫富变化及其形成规模。  相似文献   

Correlation of Devonian rocks     

K. S. W. Campbell Convener 《Australian Journal of Earth Sciences》2013,60(4):423-425

The Mount Black lead‐zinc deposit at Cooleman Plains, southern New South Wales, occurs in the uppermost part of the moderately folded, weakly metamorphosed, Upper Silurian Cooleman Limestone. A joint‐controlled collapse‐breccia zone interpreted as a palaeokarst structure has been partly replaced by quartz, sphalerite, galena, and a little chalcopyrite, pyrite, marcasite, tetrahedrite, arseno‐pyrite, and mackinawite. These minerals show evidence of having encrusted and replaced limestone fragments in the breccia. Oxidic Zn, Pb, Cu, and Fe minerals have formed by the near‐surface oxidation of the sulphides.

Petrographic and field evidence indicates that the quartz and sulphides were deposited mainly by encrustation and precipitation from saline solutions (possibly diagenetically expelled connate brines) in cavities, probably at low temperature at shallow depth. The deposit has many similarities to Mississippi Valley‐type lead‐zinc deposits.  相似文献   

内蒙古扎赉特旗辉长岩-闪长岩地球化学特征和LA-ICP-MS锆石U-Pb年龄   总被引：1，自引：0，他引：1  

汪岩  付俊彧  那福超  刘英才  张广宇  康庄  杨帆 《中国区域地质》2013,(10):1525-1535

扎赉特旗地区发育的辉长岩-闪长岩属钙碱性岩石系列。岩石相对富集LREE、大离子亲石元素（K、Rb、Ba和Sr）及u,亏损高场强元素（Th、Ta、Nb和Ti）,类似于岛弧环境产物。推测其源区为岩石圈地幔,原生岩浆为幔源物质部分熔融产生,在上升过程中遭受微弱地壳混染。用LA-ICP-Ms同位素测定方法．测得其中变辉绿岩、角闪辉长岩和辉长闪长岩的锆石206Pb／238U年龄平均值分别为317．3Ma±1．1Ma（30个数据点）、328．1Ma±1．3Ma（29个数据点）、325．2Ma±0．9Ma（32个数据点）,为首次在扎赉特旗地区中基性岩体中获得较早的高精度岩体侵位年龄,指示扎赉特旗-带在早石炭世末期存在洋壳俯冲作用,为进一步研究二连浩特-贺根山碰撞拼合带东延至扎赉特旗-带的形成与演化提供了新的证据。  相似文献   

张英1，郭依群2，莫午零3，胡玉波4     

张英  郭依群  莫午零  胡玉波 《现代地质》2013,(5)

南海北部神狐海域钻探获得的水合物中天然气组分以甲烷为主,为典型干气,气体甲烷碳氢同位素组成揭示天然气为典型的生物成因,为二氧化碳还原形成。南海北部地区在硫酸盐-甲烷还原界面（SMI）以下进入生物甲烷生成阶段,盐度适中,适宜产甲烷菌等菌群的生存和生物甲烷气的生成,埋深200～1500 m层段是生物甲烷的主要生成阶段。中新世中晚期、上新世和第四纪沉积物以泥为主,部分层段为砂泥岩互层,有机质丰度较高,类型好,热演化程度低,生物气生成条件优越,可为浅部天然气水合物的形成提供充足的气源。  相似文献   

Deep-water Depositional Features of Miocene Zhujiang Formation in Baiyun Sag,Pearl River Mouth Basin     

LI Yun  ZHENG Rongcai  YANG Baoquan  ZHU Guojin  GAO Boyu  HU Xiaoqing 《《地质学报》英文版》2013,87(1):197-210

Eleven lithofacies and five lithofacies associations were indentified in the Miocene Zhujiang Formation on the basis of detailed core analysis.It could be determined that three depositional types developed,namely submarine fan,basin and deep-water traction current.Six microfacies were further recognized within the fan,including main channels in the inner fan,distributary channels in the middle fan,inter-channels,levees and the outer fan.The lower Zhujiang Formation,mainly sandstone associations,was inner fan and inner-middle fan deposits of the basin fan and the slope fan. The middle part,mainly mudstone associations,was outer fan deposits.With the transgression,the submarine fan was finally replaced by the basinal pelagic deposits which were dominated by mudstone associations,siltstone associations,and deep-water limestone associations.During the weak gravity flow activity,the lower channels,the middle-upper outer fans and basin deposits were strongly modified by the deep-water traction current.The identification of the deep-water traction deposition in Miocene Zhujiang Formation would be of great importance.It could be inferred that the deep-water traction current had been existing after the shelf-break formation since the Late Oligocene (23.8 Ma) in the Baiyun sag,influencing and controlling the sediment composition,the distribution, and depositional processes.It would provide great enlightenment to the paleo-oceanic current circulation in the northern South China Sea.  相似文献   

U–Pb Zircon Geochronology, Geochemistry and Geodynamic Significance of Diabase Porphyries from the Jianchang Area, Northern North China Craton     

FENG Guangying  LIU Shen  FENG Caixi  YANG JingSui 《《地质学报》英文版》2013,87(Z1):125-125

  相似文献   

The Southward Extension of Cathaysia Block: Evidence from Zircon UPb Dates of Borehole Volcanics in the Northern South China Sea   总被引：1，自引：0，他引：1  

XU Changhai  QUE Xiaoming  SHI Hesheng  ZHOU Zuyi  MA Changqian 《《地质学报》英文版》2013,87(5):1370-1386

Five Paleogene volcanics sampled from the northern South China Sea were analyzed via LA-ICP-MS zircon U-Pb dating,including basalt and andesite from Borehole SCSV1 and volcanic agglomerate from Borehole SCSV2,respectively.A total of 162 zircon U-Pb dates for them cover an age range from Neoarchean to Eocene,in which the pre-Paleocene data dominate.The Paleogene dates of 62.5±2.2 Ma and 42.1±2.9 Ma are associated with two igneous episodes prior to opening of South China Sea basin.Those pre-Paleocene zircons are inherited zircons mostly with magmatogenic oscillatory zones,and have REE features of crustal zircon.Zircon U-Pb dates of 2518–2481 Ma,1933– 1724 Ma,and 1094–1040 Ma from the SCSV1 volcanics,and 2810–2718 Ma,2458–2421 Ma,and 1850 –993.4 Ma from the SCSV2 volcanics reveal part of Precambrian evolution of the northern South China Sea,well comparable with age records dated from the Cathaysia block.The data of 927.0±6.9 Ma and 781±38 Ma dated from the SCSV2 coincide with amalgamation between Yangtze and Cathaysia blocks and breakup of the Rodinia,respectively.The age records of Caledonian orogeny from the Cathaysia block are widely found from our volcanic samples with concordant mean ages of 432.0±5.8 Ma from the SCSV1 and of 437±15 Ma from the SCSV2.The part of the northern South China Sea resembling the Cathaysia underwent Indosinian and Yanshannian tectonothermal events.Their age signatures from the SCSV1 cover 266.5±3.5 Ma,241.1±6.0 Ma,184.0±4.2 Ma,160.9±4.2 Ma and 102.8±2.6 Ma,and from the SCSV2 are 244±15 Ma,158.1±3.5 Ma,141±13 Ma and 96.3±2.1 Ma.Our pre-Paleogene U-Pb age spectra of zircons from the borehole volcanics indicate that the northern South China Sea underwent an evolution from formation of Precambrian basement,Caledonian orogeny,and Indosinian orogeny to Yanshannian magmatism.This process can be well comparable with the tectonic evolution of South China,largely supporting the areas of the northern South China Sea as part of southward extension of the Cathaysia.  相似文献   

北祁连龙王山晚志留世花岗岩LA-ICP-MS锆石U-Pb测年及其地球化学特征     

王国良  叶占福  祁生胜  李杰  刘建栋 《矿产与地质》2013,(6):462-470,508

通过对龙王山灰白色细粒石英闪长岩和灰白色细粒二长花岗岩样品进行LA-ICP-MS锆石U-Pb测年结果属于晚志留世侵入岩。岩石地球化学特征表明,为高钾过铝质-准铝质碱钙性岩;稀土元素Eu具有弱负异常特征;微量元素中Ta、Nb、gr、Sr、Ti、P相对贫化,Rb、Th、Hf、Ba、Sc、K、Ce、Nd、Sm含量相对富集。Rb／Sr平均值为0．30,介于上地幔值与地壳值之间,反映出壳幔源的特点,为s型花岗岩。综合分析该期花岗岩是弧陆碰撞向陆陆碰撞转化阶段构造背景下形成的同碰撞花岗岩。  相似文献   

南海北部沉积物特征及其对珠江演变的响应   总被引：1，自引：0，他引：1  

邵磊  赵梦  乔培军  庞雄  吴梦霜 《第四纪研究》2013,33(4)

采用沉积地球化学、沉积物矿物成分分析等手段研究发现,自渐新世以来,南海北部沉积物成分具有阶段性改变的特征.在早渐新世,沉积物反映出其母岩以花岗岩和区域变质岩为主;到晚渐新世,母岩中区域变质岩类型消失,而以花岗岩、沉积岩和接触变质岩为特征;进入中新世,沉积物主要反映出碳酸盐岩等沉积岩为主的源区特点.这种沉积物成分演变特征与南海北部盆地基底及珠江流域不同区域物质组成特征极为一致,反映出珠江流域演化与南海北部沉积充填之间的对应关系.因此,通过这种研究方法,可以更好地理解32Ma以来南海北部沉积物成分发生改变的原因.同时,可以通过对比南海北部古珠江来源沉积物各时期的成分特点,建立珠江流域的侵蚀-搬运-沉积过程,探讨珠江流域演化历史.  相似文献   

40Ar‐39Ar and K‐Ar age constraints on the Early Proterozoic Tennant Creek Block,northern Australia,and the age of its gold deposits∗     

D. M. Compston  I. McDougall 《Australian Journal of Earth Sciences》2013,60(6):609-616

⁴⁰Ar‐³⁹Ar age spectra on minerals from granitic, metamorphic and hydrothermal rocks confirm that the Early Proterozoic Tennant Creek Block was affected by two thermal events during its evolution. Although extensive alteration of biotite and feldspar within the granites precludes the direct determination of their cooling history, ⁴⁰Ar‐³⁹Ar analyses for hydrothermal muscovite from several nearby gold‐copper deposits indicate that regional cooling to below ～ 300°C was not prolonged. Flat, uniform muscovite age spectra were obtained from gold deposits east of the Tennant Creek town site and indicate a minimum age of 1825–1830 Ma for their formation. These ages are within error of those for the felsic volcanism of the Flynn Subgroup, and a genetic relationship between the two may exist. Samples from gold deposits elsewhere in the area indicate disturbance of the K‐Ar isotope system. The second thermal event to affect the region occurred at around 1700 Ma, and is confirmed by the ⁴⁰Ar‐³⁹Ar muscovite ages for the ‘Warrego’ granite (1677 ± 4 Ma) and for the metamorphism of the Wundirgi Formation (1696 ± 4 Ma).  相似文献