Hydrothermal Dolomite: A Review and PerspectiveEI北大核心CSCD     

Li Q.  Bao Z. 《大地构造与成矿学》2018,(4):699-717

Hydrothermal dolomite commonly closely associates with oil-gas reservoirs and sediment-hosted Pb-Zn deposits, the Mississippi Valley-type (MVT) Pb-Zn deposits in particular. Host rocks of MVT deposits usually experienced extensive dolomitization, and indeed, hydrothermal dolomite is considered as a useful prospective indicator for MVT mineralization. However, genetic link between the hydrothermal dolomitization and MVT Pb-Zn mineralization is a matter of debate. This paper briefly reviewed the nomenclature and research history of hydrothermal dolomite, introduced the major geological, geochemical characteristics, and distribution of hydrothermal dolomite, spatial and possibly genetic relationship between hdyrothermal dolomite and hdyrothermal ore deposits and oil-gas reservoirs based on case studies including the occurrence of hydrothermal dolomites in MVT deposits in Southwest China. The temporal and genetic relationships between dolomitizaiton and thermal sulfate reduction, sulfide precipitation and thus the location of ore mineralization well worthy more attention, and comprehensive geological and isotope geochemical and state of art in situ techniques will contribute to understanding of the genesis of hydrotherml dolomite and the spatially related ore deposits and oil-gas reservoirs. © 2018, Science Press. All right reserved.  相似文献   

Characterization of hard‐to‐differentiate dune stratification types in the Permian Coconino Sandstone (Arizona,USA)     

Sarah A. Maithel  Leonard R. Brand  John H. Whitmore 《Sedimentology》2021,68(1):238-265

Dune stratification types, which include grainfall, grainflow and ripple lamination, provide a record of the fine‐scale processes that deposited sediment on palaeo‐dune foresets. While these facies are relatively easy to distinguish in some cross‐bedded sandstones, for others – like the Permian Coconino Sandstone of northern and central Arizona – discrete stratification styles are hard to recognize at the bedding scale. Furthermore, few attempts have been made to classify fine‐scale processes in this sandstone, despite its renown as a classic aeolian dune deposit and Grand Canyon formation. To interpret depositional processes in the Coconino Sandstone, cross‐bed facies were characterized using a suite of sedimentary textures and structures. Bedding parameters were described at multiple scales via a combination of field and laboratory methods, including annotated outcrop photomosaics, strike and dip measurements, sandstone disaggregation and laser‐diffraction particle analysis, high‐resolution scans of thin sections, and scanning electron microscopy. Cross‐beds were observed to be laterally extensive along‐strike, with most dip angles ranging from the mid‐teens to mid‐twenties. While some cross‐bed sets are statistically coarser near their bases, others exhibit no significant vertical sorting trends. Both massive and laminated textures are visible in high‐resolution scans of thin sections, but laminae contacts are commonly indistinct, making normal and reverse grading difficult to define. Diagenetic features, such as stylolite seams and large pores, are also present in some samples and might indicate alteration of original textures like detrital clay laminae and carbonate minerals. Observed textures and sedimentary structures suggest that the cross‐beds may consist of grainflow and grainfall deposits, but these remain difficult to differentiate at outcrop and thin‐section scales. This characterization of fine‐scale processes will play a critical part in the development of depositional models for the Coconino Sandstone and elucidate interpretations for similar cross‐bedded formations.  相似文献   

Geology and mineralization of the Sanshandao supergiant gold deposit (1200 t) in the Jiaodong Peninsula,China: A review     

《China Geology》2021,4(4):686-719

The Jiaodong Peninsula in Shandong Province, China is the world’s third-largest gold metallogenic area, with cumulative proven gold resources exceeding 5000 t. Over the past few years, breakthroughs have been made in deep prospecting at a depth of 500–2000 m, particularly in the Sanshandao area where a huge deep gold orebody was identified. Based on previous studies and the latest prospecting progress achieved by the project team of this study, the following results are summarized. (1) 3D geological modeling results based on deep drilling core data reveal that the Sanshandao gold orefield, which was previously considered to consist of several independent deposits, is a supergiant deposit with gold resources of more than 1200 t (including 470 t under the sea area). The length of the major orebody is nearly 8 km, with a greatest depth of 2312 m below sea level and a maximum length of more than 3 km along their dip direction. (2) Thick gold orebodies in the Sanshandao gold deposit mainly occur in the specific sections of the ore-controlling fault where the fault plane changes from steeply to gently inclined, forming a stepped metallogenic model from shallow to deep level. The reason for this strong structural control on mineralization forms is that when ore-forming fluids migrated along faults, the pressure of fluids greatly fluctuated in fault sections where the fault dip angle changed. Since the solubility of gold in the ore-forming fluid is sensitive to fluid pressure, these sections along the fault plane serve as the target areas for deep prospecting. (3) Thermal uplifting-extensional structures provide thermodynamic conditions, migration pathways, and deposition spaces for gold mineralization. Meanwhile, the changes in mantle properties induced the transformation of the geochemical properties of the lower crust and magmatic rocks. This further led to the reactivation of ore-forming elements, which provided rich materials for gold mineralization. (4) It can be concluded from previous research results that the gold mineralization in the Jiaodong gold deposits occurred at about 120 Ma, which was superimposed by nonferrous metals mineralization at 118–111 Ma. The fluids were dominated by primary mantle water or magmatic water. Metamorphic water occurred in the early stage of the gold mineralization, while the fluid composition was dominated by meteoric water in the late stage. The S, Pb, and Sr isotopic compositions of the ores are similar to those of ore-hosting rocks, indicating that the ore-forming materials mainly derive from crustal materials, with the minor addition of mantle-derived materials. The gold deposits in the Jiaodong Peninsula were formed in an extensional tectonic environment during the transformation of the physical and chemical properties of the lithospheric mantle, which is different from typical orogenic gold deposits. Thus, it is proposed that they are named “Jiaodong-type” gold deposits.©2021 China Geology Editorial Office.  相似文献   

基于变分客观分析方法的青藏高原试验区夏季对流降水过程热动力特征分析     

庞紫豪  王东海  姜晓玲  张明华 《大气科学》2019,43(3):511-524

本文利用基于变分客观分析方法的物理协调大气分析模型,构建了青藏高原试验区大气热力—动力相互协调的数据集,并通过该数据集对青藏高原试验区夏季深厚及浅薄对流降水过程的热动力特征进行分析,结果表明:变分客观分析后的垂直速度场能更好地与实际观测的对流降水过程相吻合;深厚对流降水期高云含量多,整层大气为较强的上升运动,上升运动可达100 hPa左右,浅薄期高云含量少,上升运动仅能延伸到300 hPa左右;两种对流降水过程中视热源Q₁在低层为冷却作用,高层为加热作用,在深厚期中高层Q₁存在两个加热中心,中层受较强的水汽凝结释放潜热加热所影响,高层主要受过冷云水凝结成冰晶形成高云时释放的热量所影响;在浅薄期中高层Q₁只存在一个加热中心,大气的加热主要来源于水汽的凝结潜热释放;深厚对流降水期视水汽汇Q₂的加热作用可以延伸到200 hPa,而浅薄期仅到340 hPa左右。  相似文献   

2017年6月一次华南沿海强降水的对流性特征及热动力机制研究     

曾智琳  谌芸  朱克云 《大气科学》2019,43(6):1295-1312

在华南北部或长江流域有锋面雨带活动时,华南沿海常常会出现对流性强降水,突发性很强,给预报造成很大的困惑。文章采用多种观测资料、ERA-Interim 0.125°×0.125°逐6 h再分析资料,对2017年6月15～16日华南北部的锋面雨带及沿海强降雨过程开展分析,对比了二者降水特征与环境条件,重点探讨了该次过程华南沿海强降雨的对流触发与维持,揭示了一种由边界层风切变强迫造成涡度持续发展的动力效应。结果表明:（1）锋面雨带与华南沿海强降雨在降水特征上有显著差异,并各有特点。锋面雨带以大尺度层状云降水和弱对流性降水为主,降水强度东段弱西段强。沿海强降雨以对流性降水为主,局地性强、落区集中、强降雨持续时间长、夜发性明显。（2）水汽方程诊断发现沿海强降雨在边界层水平水汽平流项、垂直水汽输送项比锋面雨带东段具有更大量级,大气层结反映出更深厚的暖层、湿层与对流不稳定,是二者降水强度及性质差异的主要原因。（3）莲花山、峨眉嶂造成气流侧向摩擦与正面阻挡促使漯河河谷内垂直涡度发展,暖湿空气堆积上升并达到自由对流高度,触发了华南沿海最初的降水。夜间建立的西南风急流使边界层垂直风速切变增强,水平涡度倾斜部分转化为垂直涡度发展,与风速水平切变造成的垂直涡度叠加,是强降雨持续时间长的动力机制。海陆边界摩擦差异造成水平、垂直两个方向的风切变增强,共同强迫垂直涡度发展是此次强降雨过程对流维持的动力效应。（4）方程诊断表明华南沿海强降雨由对流潜热释放造成的垂直上升速度占总垂直上升速度的39%～75%,持续、稳定的对流潜热释放是强降雨持续时间长的热力驱动因素。  相似文献   

基于ENVI-met的福州大学校区冬季热环境模拟与热舒适度变化分析     

庄莉娟  蔡芫镔  祁娟娟 《气象与环境学报》2021,37(6):44-52

选取福州大学校园教学区为研究区域,基于典型冬季日背景,运用三维非静力微气候模型ENVI-met,分析模拟校园热环境的差异变化及其热舒适度响应。结合实地勘测,对模型进行校准和验证。结果表明：ENVI-met模型能较好地表征室外热环境,准确预测温度和相对湿度的日变化趋势。混凝土路面、灰色地砖路面行人高度的日平均气温分别比草地高出0.1 ℃和0.3 ℃,逐时最大温差分别为0.68 ℃和0.65 ℃。建筑物阴影和树阴可降低行人高度的气温1.1—1.9 ℃;同一组团在有无遮阴的条件下,平均辐射温度（T_mrt）相差最大可达30 ℃;树木附近和建筑物组团内部生理等效温度（PET）值较小,比硬质路面低2—3个等级。无植被方案下,高温低湿区范围有所扩张,在垂直方向上的增温效应可伸展至10.5 m;风速最大增幅可达1.23 m·s^-1,平均辐射温度较高区域的面积增加了69.25%;热舒适区和热不适区面积分别增加了19.78%和2.03%。  相似文献   

非均匀介质热蠕变流动的数值求解   总被引：5，自引：1，他引：4       下载免费PDF全文

刘洁  刘启元  宋惠珍 《地球物理学报》2006,49(4):1029-1036

针对非均匀介质中热蠕变流动问题,给出了有限单元方法与网格－粒子方法联合求解新技术,即有限单元方法求解欧拉网格节点上的未知量,分布于单元内部作为物质成分标记的粒子反映变形过程.有限元法求解动量方程和连续性方程时引入了速度场和压力场等阶插值的压力场稳定的Petrov Galerkin方法,求解能量方程时采用了流线迎风Petrov Galerkin方法,网格－粒子算法中采用双线性插值与有限单元插值函数对应.有限单元计算与网格－粒子计算相对独立,两种方法计算的数据通过有限单元节点传递.同时,实现了三角形单元的算法和程序,解决了复杂结构条件下不规则网格计算的问题.通过经典方腔热对流问题验证了程序,给出了不规则形态块体沉降算例,并分析了数值解的稳定性.  相似文献   

1617号鲇鱼台风登陆后引发不同性质暴雨的成因对比分析          下载免费PDF全文

王毅  张晓美  杨寅  曹勇  张芳华  周庆亮 《大气科学学报》2019,42(2):245-254

2016年9月28日1617号台风"鲇鱼"登陆后由台风本体环流和外围环流引发了不同性质的暴雨,这是本次秋季登陆台风暴雨预报的难点。利用常规气象观测资料以及NCEP的1°×1°再分析资料等,对不同性质暴雨的成因进行了诊断对比分析。结果表明:浙江东南部对流性降水和江西南部稳定性降水的大气层结结构具有明显的差异。中高纬度低槽距离台风较远,冷空气主要从低层入侵台风西北侧,破坏台风低层的暖心结构。台风外围中层干冷空气随东南风向浙江东南部输送,并叠加在低层暖湿气流之上,形成上冷下暖的不稳定层结,同时在对流层上层有干冷空气下沉至台风环流中下层(干侵入),导致浙江文成附近出现了局地特大暴雨。江西南部由于低层被湿冷空气占据,层结较为稳定,降水发展平缓。低空东南急流为台风外围环流暴雨提供了充足的水汽,浙江东南部地形对降水起到了增幅作用。不稳定层结及中层冷空气的输送对对流性暴雨的激发作用可以为登陆台风降水性质和强度预报提供参考依据。  相似文献   

南海中部海域障碍层特征及其形成机制   总被引：2，自引：0，他引：2  

潘爱军  万小芳  许金电  郭小钢  吴日升 《海洋学报》2006,28(5):35-43

南海中部海域(10°~19°N,108°~122°E)存在显著的季节变化的障碍层.障碍层发生概率夏季最大(52.8%),秋季次之(41.0%),春季最小(10.5%).夏季(2000年8~9月)障碍层最显著,平均厚度约为14.2m;除114°E以东、吕宋岛以西海域为障碍层的多发区外,中南半岛东南海域(12°~14°N,110°~114°E)也存在显著的障碍层;春季(1998年4~6月)和秋季(1998年12月)障碍层平均厚度分别为6.8和11.2m,障碍层多位于114°E以东、吕宋岛以西海域.此外,吕宋岛以西海域(12°~16°N,116°~120°E)及中沙和西沙群岛附近(16°~18°N,110°~116°E)海域障碍层年发生几率超过20%,相对而言,其他海域障碍层年发生几率偏小.降水机制和层结机制分别是南海中部海域春、夏季和秋季障碍层形成的主要原因.其中,降水机制及东南向的Ekman平流较好的解释了春、夏季吕宋岛以西附近海域成为障碍层多发区的原因;此外,强降水是夏季中南半岛东南海域(12°~14°N,110°~114°E)障碍层产生的关键,反气旋涡(暖涡)有助于形成更强的障碍层,上升流对障碍层的影响有待进一步研究.  相似文献   

The impact of northern Indian Ocean rivers on the Bay of Bengal using NEMO global ocean model     

Srivastava Atul  Gera Anith  Momin Imran M.  Mitra Ashis Kumar  Gupta Ankur 《海洋学报(英文版)》2020,39(3):45-55

The effect of river runoff over the northern Indian Ocean(NIO) especially over the Bay of Bengal(Bo B) has been studied using global Nucleus for European Modelling of the Ocean(NEMO). Two sensitivity experiments, with and without river runoff are conducted and the influence of river runoff on the Indian Ocean hydrography,stratification and circulation features are studied. It is found that due to river runoff surface salinity over the northern Bo B decreases by more than 5 and the East India Coastal Current strengthens by 2 cm/s during post monsoon season. The fresh river water reaches up to 15°N in the Bo B and is the main cause for low salinity there.Sea surface temperature in the northwestern Bo B increases by more than 0.2℃ due to the river runoff in summer monsoon while surface cooling upto 0.2℃ is seen in north-west part of Bo B in winter season. The seasonal mixed layer depth in the region is found to be dependent on river runoff. The effect of vertical shear and Brunt Vaisala frequency on stratification is also examined. The ocean water becomes highly stratified up to 3 035 m due to the river runoff. It is found that the energy required for mixing is high in the northern and coastal Bo B.  相似文献