Sedimentary records of natural and artificial Huanghe (Yellow River) channel shifts during the Holocene in the southern Bohai Sea   总被引：4，自引：0，他引：4  

Shuqing QiaoXuefa Shi  Yoshiki SaitoXiaoyan Li  Yonggui YuYazhi Bai  Yanguang LiuKunshan Wang  Gang Yang 《Continental Shelf Research》2011,31(13):1336-1342

Two gravity cores collected off the modern Huanghe (Yellow River) delta in the southern Bohai Sea were analyzed for grain size, the total organic carbon (TOC)/total nitrogen (TN) ratio, color diffraction, magnetic susceptibility, ¹⁴C dating and ¹³⁷Cs and ²¹⁰Pb isotope contents to clarify changes in the sedimentary environment during the Holocene. In particular, the effect of natural and artificial river-course shifts of the Huanghe on the Bohai Sea sediment was investigated. A peat layer, scouring surface and sharp changes in the grain size, TOC/TN ratio, sediment color (L^?, a^?) and magnetic susceptibility were identified and are likely to be due to the early-Holocene sea-level rise resulting in environmental changes from coastal to shelf environments in the Bohai Sea. After the sea level reached its maximum at 6-7 ka BP, the lateral shifts in the river course of the Huanghe formed 10 superlobes, and superlobe 7 (11-1048 AD) and superlobe 10 (1855-present) of the Huanghe delta affected the core sites. The northern site of BH-239 has been more affected by the Huanghe since the middle Holocene. Notably, in the superlobe 10 period, the reshaping of the northern Huanghe delta due to an artificial river-course shift from northward to eastward in 1976 (e.g., a∼10 km shoreline retreat due to coastal erosion) was recorded in the core sediments, particularly in terms of the TOC/TN ratio, sediment color (L^? and a^?) and magnetic susceptibility, owing to the huge sediment supply from coastal erosion of the former river mouth area.  相似文献   

贵州大竹园大型铝土矿稀土元素地球化学特征及其意义   总被引：2，自引：0，他引：2  

李沛刚  王登红  雷志远  翁申富  高兰 《地球科学与环境学报》2012,(2):31-40

贵州大竹园大型铝土矿是中国近年来取得重要找矿进展的大型铝土矿之一。以采自大竹园矿区栗园向斜不同部位铝土矿、铝土岩和黏土岩的样品为研究对象,分析了这些样品的稀土元素含量(质量分数)特征及空间分布特征,研究了稀土元素含量与铝土矿质量及成矿过程的关系,最后就稀土元素对于成因和环境的指示意义进行了讨论。结果表明:铝土矿、铝土岩和黏土岩稀土元素总含量(不包括Y)分别为107.07×10-6、185.00×10-6和246.28×10-6,依次增高,说明铝土矿的成矿过程是一个稀土元素贫化的过程,也是Eu异常和Ce异常趋于增大的过程,即相对于黏土岩来说,铝土矿具有高Eu异常、Ce异常的特征;相对于重稀土元素来说,无论是栗园向斜西翼还是东翼,铝土矿轻稀土元素相对富集,且轻稀土元素含量以及La与Yb含量之比均随深度变浅而增加;单纯利用稀土元素图解不能有效反映成矿物质的来源,但可以大体反映含矿岩系形成于海相或海陆过渡相环境;大竹园大型铝土矿与黔北其他铝土矿一样,总体上属于沉积型,可能与古喀斯特化过程、古风化过程有关。  相似文献   

云南兰坪盆地北部东缘铅锌矿床喷流沉积成因的厘定———来自矿物学和硫同位素证据   总被引：1，自引：0，他引：1  

黄玉凤  曹殿华  王志军  李以科  王安建 《地质力学学报》2011,17(1):91-102

通过详细的野外地质工作和显微镜下观察,对云南兰坪盆地东北部维西—乔后断裂带上三叠统石钟山组(T₃s)中产出的铅锌矿床成因进行厘定。研究结果表明,测区内存在大量典型的同生沉积矿床标志,如:纹层构造、条纹条带构造、网脉构造、黄铁矿条带软沉积构造、黄铁矿草莓状结构、黄铁矿胶状构造、闪锌矿同心环状构造等。青甸湾矿床金属硫化物硫同位素测试结果显示,黄铁矿的δ34 S介于3.7‰ ~ 8.1‰,均值5.34‰; 闪锌矿的δ34 S介于5.2‰ ~ 10.0‰之间,均值为7.18‰; 方铅矿的δ34 S介于5.2‰ ~ 9.9‰之间,均值为7.275‰,铅锌矿床硫来源于海水硫酸根无机还原。结合矿床形成时代及大地构造背景,认为该区铅锌矿为喷流沉积作用形成。   相似文献   

柴达木盆地马海钾盐矿床沉积环境与开发   总被引：2，自引：0，他引：2       下载免费PDF全文

马金元  胡生忠  田向东 《盐湖研究》2010,18(3)

马海钾矿床是柴达木盆地内重要的盐类矿床之一。从盐类矿床沉积物的物相分析入手,着重揭示该成盐盆地沉积环境和古地理变迁特征,论述湖盆由形成、发展至老化衰亡的演变规律,反映了从上新世末期以来新构造运动在矿区地质构造上的典型表现,由这些成矿因素构建的矿床地质构造特征也得到总结。依照持续稳定发展的要求,就矿床开发过程中出现的急功近利局面,提出调整产品结构和重新布局开采对象的新策略,对企业生产实践具有指导意义。  相似文献   

Sedimentary impacts from landslides in the Tachia River Basin, Taiwan   总被引：1，自引：0，他引：1  

Chien-Yuan Chen   《Geomorphology》2009,105(3-4):355-365

A case study of coseismic landslides and post-seismic sedimentary impacts of landslides due to rainfall events was conducted in the Tachia River basin, Taichung County, central Taiwan. About 3000 coseismic landslides occurred in the basin during the M_L 7.3 Chi-Chi earthquake in 1999. The deposits from these landslides provided material for numerous debris flows induced by subsequent rainfall events. The estimated 4.1 × 10⁷ m³ of landslide debris produced in the upland area caused sediment deposition in riverbeds, and flash floods inundated downstream areas with sediment during torrential rains. The landslide frequency-size distributions for the coseismic landslides and the subsequent rainfall-induced landslides were analyzed to determine the sediment budgets of the post-seismic geomorphic response in the landslide-dominated basin. Both the coseismic and the rainfall-induced landslides show a power–law frequency-size distribution with a rollover. It was found that the rainfall-induced landslide magnitude was smaller than the coseismic one, and that both have comparable negative scaling exponents in cumulative form, of about − 2.0 for larger landslides (> 10^− 2 km²). This may be attributed to ongoing movement or reactivation of old landslides, and a natural stabilisation of small landslides between 10^− 4 and 10^− 2 km². It is proposed that the characteristics of geological formations and rainfall as well as changes in landslide area are reflected in the power–law distribution.  相似文献   

Empirical site-specific response-spectra correction factors for the Gubbio basin (central Italy)     

S. Parolai  F. Cara  D. Bindi  F. Pacor 《Soil Dynamics and Earthquake Engineering》2009

Providing quantitative microzonation results that can be taken into account in urban land-use plans is a challenging task that requires collaborative efforts between the seismological and engineering communities. In this study, starting from the results obtained by extensive geophysical and seismological investigations, we propose and apply an approach to the Gubbio basin (Italy) that can be easily implemented for cases of moderate-to-low ground motion and that takes into account not only simple 1D, but also more complicated 3D effects.  相似文献   

川东地区嘉陵江组四段膏盐岩分布的沉积环境分析          下载免费PDF全文

张奇  徐亮  金小林  王坛 《盐湖研究》2009,17(4):1-5

四川盆地东部地区嘉陵江组嘉四段沉积环境是局限海台地蒸发岩相,水体封闭,有利成盐。以川东地区油气勘探的500余口实际钻井资料为基础,通过岩性微相的研究,探讨川东地区的古地貌特征,寻找成盐的微环境因素,有助于从区域上预测盐类的分布。T1j4盐湖主要分布在蒸发岩沉积中心——膏盆相,但位于膏盆相的周缘地带和膏盆内部堤坝周围,少部分分布在膏盆边缘相,区域上则主要分布在宣汉、达州、万县、云阳、垫江及渠县等地区,有一定的继承性。  相似文献   

桂西二叠系沉积型铝土矿鲕粒成因机制探讨     

张启连  韦访  邓军  李活松  陈文伦  宫研  覃洪锋  辛晓卫  黄尚恒  王学恒  苏可 《岩石矿物学杂志》2024,43(1):21-36

已有研究表明铝土矿中鲕粒的Al含量普遍高于基质,但鲕粒富集Al过程尚不清楚。本文通过对桂西地区铝土矿进行宏微观观察以及电子探针测试(EPMA)和X粉晶衍射分析,研究了矿石构造和元素地球化学变化规律,试图分析铝土矿中鲕粒生长机制。含矿岩系层序多变特征表明桂西铝土矿为陆相成因;鲕粒内部圈层Al含量大于50%,而Si含量小于1%,Fe含量波动于1%左右,证明矿石中鲕粒Al的含量比基质的高,同时硬水铝石的结晶程度亦较高;与鲕粒生成有密切关系的构造主要为凝胶和裂隙,两者为正反馈关系;胶体在分离过程中出现分凝,主要形成富铝、富硅和富铁凝胶,分凝过程中Fe、Si亲和性强,两者的迁移能力均高于Al。分析认为鲕粒形成于浅埋阶段,是一种凝胶的反复分凝过程,受控于湿润-干热气候,成鲕可大致分为3个阶段,即充水阶段、湿润阶段和干热阶段,成核机制为脱水收缩,圈层增长机制为成胶-凝胶老化交替。铝土矿型风化壳的物质搬运过程使鲕粒的圈层停止生长,形成夭折鲕,若条件有利则形成再生鲕。首次引入磁场的概念解释了鲕粒保持浑圆形习性的原因。  相似文献   

桂西平果教美矿区堆积型铝土矿形成过程中矿物转化与元素迁移     

章颖  吴功成  刘学飞  张起钻  管涛  王庆飞 《现代地质》2015,29(1):20-31

桂西地区铝土矿为典型喀斯特型,包括二叠系沉积型和第四系堆积型两亚类。堆积型铝土矿是沉积型铝土矿经抬升、破碎、风化,最后堆积于喀斯特洼地中形成。以平果教美铝土矿为研究对象,探索堆积型铝土矿形成过程中矿物的变化与元素迁移。沉积型矿石的矿物组成包括硬水铝石、鲕绿泥石、锐钛矿及少量针铁矿、金红石和高岭石;堆积型矿石的矿物组成主要为硬水铝石、锐钛矿、高岭石及少量三水铝石和鲕绿泥石。转化过程中堆积型矿石中的硬水铝石含量明显增加,鲕绿泥石含量明显减少。沉积型铝土矿的主要化学组成为Al₂O₃、SiO₂、FeO和TiO₂;堆积型为Al₂O₃、SiO₂、TiO₂和Fe₂O₃。两类矿石中元素Zr 、Ba、Nb、V含量均较高,稀土总量变化大,富集轻稀土。质量平衡计算表明堆积型铝土矿形成过程中Al、Ba、Sr、Y等元素增加,而Si、Fe、Ti、Nb、V、Ce等元素减少,其余元素变化不明显。  相似文献   

广西扶绥—崇左地区铝土矿矿产远景调查主要进展及成果          下载免费PDF全文

邓军  陈粤  黄宏伟  梁裕平  何海洲  陈胜  吴天生  杨志强  韦访  罗立营 《中国地质调查》2015,2(4):8-12

在龙州地区首次发现早石炭世的堆积型铝土矿矿源层,提出广西堆积型铝土矿至少存在早石炭世和晚二叠世两个时代的矿源层。探索运用高密度电阻率法寻找古风化壳沉积型铝土矿的有效性试验工作。提交新发现矿产地4处,探获新增铝土矿(334₁)资源量5 289.15万吨。重新厘定区域地层岩性及岩相特征,系统总结区内铝土矿矿床(点)的时空分布特征、控矿地质条件、成矿规律及找矿标志,建立了区域成矿模式和预测找矿模型,圈定成矿远景区5处,找矿靶区6处,开展区域矿产预测,初步评价了本区铝土矿资源潜力。为该地区下一步地质调查、矿产勘查规划和开发提供了丰硕的基础资料和有益参考。  相似文献