多金属结核瞬时生长速率及其意义

本文用Ｘ射线荧光光谱分析，沿结核壳层的生长方向逐点扫描测定铁锰含量，计算结核壳层的瞬时生长速率，划分结核壳层的生长阶段，计算各生长阶段的生长速率，并在结构壳层中建立高分辨率的时间标尺，重建多金属结核生长历史。     

四川盆地东部茅口组白云岩成因: 来自岩石学、矿物学和地球化学的证据*

四川盆地中二叠统茅口组白云岩中蕴藏丰富的天然气资源,但是这套白云岩的成因多年来一直存在争议。盆地东部茅口组白云岩储集层多发育在茅三段中下部,纵向上厚度介于3.0~46.8 m之间,平面上沿北西—南东向基底断裂呈带状展布。野外和钻井岩心观察发现,白云岩内发育交织状张性裂缝,将岩石切割呈角砾状,裂缝多被粗晶方解石、白云石充填或半充填。根据围岩和裂缝中白云石晶体形貌和产出状态,在显微镜下识别出4类不同组构的白云石: 第1类为灰泥基质中“星散状”自形粉晶—细晶白云石; 第2类为半自形面状组构细晶白云石,呈他形—半自形镶嵌状; 第3类为具“雾心亮边”的自形晶面状组构细晶—粗晶白云石,具糖粒状结构,晶间孔隙发育; 第4类为脉体充填的粗晶鞍状双晶白云石。背散射照片显示前3类白云石的“雾心”部分晶面混浊、表面分布方解石残斑及微孔, 而第3类白云石的“亮边”部分与第4类鞍状粗晶白云石脉则晶体明亮、洁净、致密,属新生矿物。上述4类白云石的成分均具有富Ca和贫Fe、Mn、Sr的特点,MgO含量变化较大,其中前两类白云石MgO含量总体低于白云石标准计量,而后两类白云石的MgO含量则接近或略高于标准计量。岩石学、矿物学和地球化学特征表明:茅口组白云岩主要经历了2期白云化作用,初次白云化作用形成第1类、第2类白云石及“雾心”白云石,二次白云化作用形成“亮边”白云石和粗晶白云石脉体; 2期白云化作用均发生得很早,可能始于同沉积期至浅埋藏期。白云石原位微量元素和原位锶同位素分析表明,白云化作用流体具有混源的特点,流体可能由富Ca地下水以及与火山活动有关的热液混合而成。推测中二叠世末期峨眉山地幔柱的喷发引起四川盆地内基底断裂再次活动,造成茅口组内张性构造裂缝发育,这为白云化流体混合及运移提供了通道。     

Reconstruction of the Yangtze Ramp during Floian to Darriwilian (Ordovician) in South China: Its Morphology, Controlling Factors and Significances

A robust stratigraphic framework and a coherent depositional ramp model for the Zitai, Dawan, Meitan and Ningkuo formations of Floian–Darriwilian age (Early–Middle Ordovician) in the Yangtze (Daoba, Xiangshuidong, Daling, Gudongkou and Honghuayuan sections) and Jiangnan regions (Nanba section) was created based on lithofacies and major element analysis. Three siliciclastic (LF1–3) and six carbonate (LF4–9) lithofacies are recognized representing sediments that were deposited in mixed siliciclastic and carbonate ramp environment. The intensity of mixed sedimentation and terrigenous input were evaluated using the elemental proxies Intensity of Mixed sedimentation (IM) and Aluminum Accumulation Rate (AlAR), as well as their mean values during certain time intervals. Mixed sediments are most well-developed along the marginal Yangtze region, strongly impacted by recurrent influx of westerly derived terrigenous materials in response to global eustatic changes and regional tectonic movements, shaping the gently southeast-dipping morphology. Regular terrigenous influx resulted in periods of enhanced primary productivity on the Yangtze Ramp as evidenced by matching biodiversity peaks in planktonic organisms, i.e., chitinozoans and acritarchs. Brachiopods and other shelly fauna were also able to proliferate as new niches developed along the gently dipping ramp floor with substrate changes. The biodiversification patterns suggest that terrigenous influx controlled in part by regional tectonics played a more important role than previously thought in the development of Great Ordovician Biodiversification Event in South China.     

四川盆地北部中二叠统茅口组孤峰段优质烃源岩特征及其油气地质意义

二叠系是四川盆地海相烃源岩发育的重要层系,对天然气勘探具有重要意义.基于钻井、测井与露头剖面资料综合分析,厘定了四川盆地北部重点钻井中二叠统与上二叠统界线,证实在盆地北部广泛发育茅口组孤峰段薄层状碳硅泥岩,揭示了孤峰段优质烃源岩分布、地球化学特征与发育环境,评价了其生烃潜力及成藏贡献.结果表明:①四川盆地北部孤峰段优质烃源岩厚度在5～40 m,呈北西-南东向带状展布,存在4个厚值区;②孤峰段烃源岩TOC整体极高、变化范围大,分布在0.5％～31.04％,均值5.08％,为一套优质烃源岩,有机质类型主要为Ⅱ型,有机质成熟度处于成熟—过成熟阶段;③拉张构造背景下形成的台内裂陷深水沉积环境、强还原条件与高古生产力共同控制了孤峰段优质烃源岩发育与分布;④孤峰段优质烃源岩生烃潜力较大,生烃强度主要在5×108～25×108m3/km2,对研究区内海相常规天然气和页岩气勘探均具有重要意义.     

基于波动方程正演对九龙山地区茅口组地震响应特征识别研究

九龙山构造位于四川盆地西北部旺苍县和苍溪县境内,该构造具有构造规模大、隆起幅度高、保存条件好、纵向上多产层、钻井显示丰富等特点。本文主要针对九龙山构造范围内下二叠统茅口组储层的地质模型和正演结果,明确储层发育位置,找到对应的地震相特征,并对储层进行分级评价。通过测井响应特征、储集空间、储层厚度、曲率等综合分析,用波动方程正演模拟预测下二叠统茅口组地震响应特征。正演结果表明茅口组孤立溶洞型储层的地球物理响应特征为同相轴串珠状上拉、振幅减弱;茅口组缝洞系统储层的地球物理响应特征为茅口组顶界同相轴"扭曲断续、下拉"。在此基础上总结了孤立溶洞和缝洞系统两种地震响应识别模式,为储层的预测提供了参考依据。     

湖南弗拉阶地层的分布特征和页岩气有利区

湖南上泥盆统弗拉阶佘田桥组泥页岩是重要的页岩气勘探目的层。由于区域上具有岩相分异显著、变化快的特征,佘田桥组存在多个同期地层,容易造成引用和野外识别困难,严重制约其页岩气调查工作进程。通过梳理佘田桥组及其同期地层的历史沿革,明确和圈定了它们的分布区域和使用范围。基于佘田桥组的岩石组合特征、有机碳含量的区域变化和已有调查成果,提出受陆缘碎屑输入影响较强的新化-涟源、邵东地区为页岩气有利勘探区的设想,同时认为找准台盆范围是页岩气调查发现的关键。     

滇东北乌蒙山地区峨眉地幔柱活动与火山-沉积盆地的响应关系

为加深滇东北乌蒙山地区峨眉地幔柱演化的认识,对该区的峨眉山玄武岩及下伏的栖霞组—茅口组开展了详细地质调查工作,并对峨眉山玄武岩进行了岩石学、同位素年代学研究,结果显示:峨眉地幔柱活动导致的地壳抬升形成了研究区栖霞组—茅口组西薄东厚、峨眉山玄武岩西厚东薄的地质特征,地壳开始隆升的时限为(273.1±3.1)Ma,地壳抬升...     

The last interglacial sea-level high stand on the southern Cape coastline of South Africa

The continental margin of southern South Africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long-term eustatic sea-level changes. We report a suite of optical luminescence ages and supplementary amino acid racemization data, which provide paleosea-level index points for three sites on this coastline. Deposits in the Swartvlei and Groot Brak estuaries display tidal inlet facies overlain by shoreface or eolian facies. Contemporary facies relations suggest a probable high stand 6.0-8.5 m above modern sea level (amsl). At Cape Agulhas, evidence of a past sea-level high stand comprises a gravel beach (ca. 3.8 m amsl) and an overlying sandy shoreface facies (up to 7.5 m amsl). OSL ages between 138 ± 7 ka and 118 ± 7 ka confirm a last interglacial age for all marginal marine facies. The high stand was followed by a sea-level regression that was associated with the accumulation of eolian dunes dating to between 122 ± 7 ka and 113 ± 6 ka. These data provide the first rigorous numerical age constraints for last interglacial sea-level fluctuations in this region, revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far-field locations.     

钢锚墩在锦屏一级水电站地下厂房的运用

锦屏一级水电站地下厂房地应力高,分层开挖完成后随着地应力的释放及重新分布,局部岩体出现压碎、层状劈裂破坏,围岩松弛深度及变位不断加深、加大。为了尽快实现锚索锚固支护效应以确保地下厂房洞室群围岩稳定和工程安全,施工时将部分原设计现浇混凝土锚墩调整为钢锚墩进行施工,取得了较好的质量、进度效果。主要介绍了钢锚墩的施工工艺、质量控制要点及其与混凝土锚墩的工效对比分析。     

哀牢山造山带构造演化及其两侧盆地耦合

哀牢山造山带的崛起和盆地耦合,对东西两侧沉降盆地的构造-沉积性质起关键性作用。转换构造性质不仅形成了逆冲推覆与走滑剪切联合作用的构造共生组合,形成两类不同性质的沉积盆地。