Placers in the System of Sedimentogenesis

Boundary conditions of the placer formation environment are discussed on the basis of a comprehensive study of approximately 40 placer-forming minerals and examination of the following features of minerals: stability under different conditions of migration and redeposition; capacity to be concentrated in a certain grain size class; and industrial requirement of the raw mineral quality. It is suggested that the migration capacity of placer-forming minerals is realized in a wide range of conditions. The work discusses specific features of the transformation of placer mineral assemblages during the scattering and relative concentration in local structural-sedimentation traps (denudation cycle) and the absolute concentration and development of new parageneses in terminal sedimentary basins. The role of structural-sedimentation traps in the formation of large and superlarge placers is demonstrated. It is shown that all types of continental lithogenesis are valid for placer formation, although each type can contribute some specific features to the placer-forming process. Five megaepochs of placer formation are identified in the Earth's history. The duration of Phanerozoic megaepochs, except the last (incomplete) one, is approximately 100 Ma. In terms of placer productivity during the Phanerozoic, the second half of the Paleozoic ranks below the Cenozoic megaepoch.     

Watershed Controls on the Geomorphology of Small Coastal Lagoons in an Active Tectonic Environment

This study investigates the relations between watershed precipitation, upstream channel slope, and the geomorphology of 19 small (40 to 18,658 m²), fluvial-incised lagoons in the actively uplifting piedmont near Santa Barbara, CA. Lagoons in the study are funnel-shaped, shallow (<2 m), river-dominated, and enclosed by a sandy to cobble-sized beach barrier for much of the year. Results indicate a strong link between watershed processes and lagoon geomorphology, such that a significant portion of the variability in lagoon area, length, volume, average width, circularity, and lagoon width expansion can be explained by the variability of watershed precipitation and channel slope upstream of the lagoons. Performing multiple regression analysis with watershed precipitation and channel slope as independent variables, coefficients of determination for the power function regressions are 0.88 (lagoon area), 0.88 (lagoon volume), 0.83 (lagoon volume), and 0.74 (average width). Upstream slope is the best single predictor of lagoon geomorphology.     

Titanium–Zirconium Placers of the Stavropol Region

Lithofacies analyses and paleogeographic reconstructions of the middle Sarmatian sequence in the central Ciscaucasus, which hosts the most promising titanium–zirconium placers of the Stavropol region, indicate that ore components (rutile, ilmenite, leucoxene, and zircon) were mainly delivered to the Stavropol placer basin by the paleo-Volga River from a northern land. Bryozoan organogenic edifices played a significant role in the formation of placers. The organogenic edifices appeared under anomalous (for bioherm formation) conditions of terrigenous sedimentation on the western and northwestern slopes of the Stavropol Uplift, hampered the transport of ore material to the deep-water zone of the basin, and promoted its differentiation in the paleouplift.     

Problem of the Formation of Eolian Gold Placers on the East European Platform

The distribution of eolian gold in various Proterozoic–Cenozoic sediments on the East European Platform is considered. Eolian placers of the Timan Ridge are characterized by specific features: significant areal distribution and consistent strike of the thin (0–30 cm) productive bed. Prospecting criteria of eolian gold placer in the study territory can be the presence of gold flakes and other minerals with signs of eolian reworking, specific structure of productive bed, deflation structure of relief, and characteristic lithological composition of sediments. It is concluded that since gold flakes with eolian reworking make up high metal concentrations, such as placer deposits in the Timan Ridge, eolian placers of different age may be found on the East European Platform.     

辽东地区砂金矿控矿因素的初步研究

论述了辽东地区砂金矿控矿因素,揭示了砂金矿矿规律,并指出了在具备物源,气候,水动力,地貌,等条件下,形成一个有工业意义的砂金矿床,对其含金层必须要有一定适宜的封存条件。     

The Mineral Composition of Rare-Metal Placers of the Lovozero Massif

Geology of Ore Deposits - The new original data on the mineralogy of the Sergevanskii section of the Revdinskaya placer of the Lovozero placer area are reported in the paper. Glacial and tectonic...     

Miocene Placers and Ceramic Clays of the Central Russian Upland

Geology of Ore Deposits - Abstract—Miocene rocks within the eastern slope of the Central Russian Upland are represented by the rocks of the Berekskaya (Oligocene–Miocene),...     

准噶尔盆地乌夏地区二叠纪构造控扇作用

乌夏前陆冲断带二叠系构造层序特征、沉积相特征及断裂特征研究表明,二叠纪乌夏地区系受到推覆体严格控制的周缘前陆盆地,主要发育水下扇-扇三角洲-冲积扇-湖泊沉积体系,其中扇体发育代表了最典型的沉积特征.受海西运动晚期的影响,构造演化经历了强烈俯冲碰撞造山期、弱冲断夹短暂伸展火山期和强烈冲断复活期3个阶段,并形成了众多走向不同却又彼此相互切割叠加的逆冲断裂,影响了地层的沉积与剥蚀,控制了断裂带的形成和演化.由早至晚扇体由山前向盆内呈前展式夹短暂退覆式叠置迁移,相应地,二叠纪以北东东向断裂为主,并从山前向盆地方向依次发育,其间夹杂短暂后展式发育,构造活动强度逐渐由西向东、由北向南迁移,因此,绝大多数同生断裂控制了扇体的沉积边界和分布,部分控制了其厚度和发育方向,扇体的迁移与控扇断裂的活动迁移具有很好的吻合性,断裂活动是控制乌夏地区沉积的主要因素.     

The First Find of Silver Nuggets in Gold Placers of the Subpolar Urals

Doklady Earth Sciences - In the gold placers of the Subpolar Urals, silver nuggets have been found for the first time. Galena, cassiterite, wolframite, cosalite, tetradymite, ferberite, cobaltine,...     

海岸带城市地下水分布特征

我国城市海岸带地下水类型和分布主要受控于陆地地质作用,尤以大地构造作用和河流地质作用为主导。松散沉积物类海岸带地下水为孔隙水,含水介质单一,空间变化大,地下水的赋存和分布规律亦相应复杂。以距今78万年晚更新世为界线,可将第四纪松散沉积物含水层组划分为上（浅）下（深）两层（部）。下部的全新统（Q4）和上更新统（Q3）含水岩组以微咸水、咸水多见;上部的中更新统（Q2）和下更新统（Q1）分布有淡水,部分地下淡水资源有一定的供水意义。基岩类海岸带地下水主要为裂隙水和岩溶水,多为淡水,其水资源量与当地的降水量和基岩入渗系数的大小有直接关系。除砂砾石台地的基岩类海岸带、少数溺谷型泥质海岸带的河谷内和碳酸盐岩分布区外,一般无集中供水意义。     

基于生态工程的海岸带全球变化适应性防护策略

在全球变化导致的海平面上升和灾害性气候等压力下,我国海岸带风暴潮、海岸侵蚀、地面沉降等灾害发生频率和强度正在增加,对海岸防护体系的需求日益提高。传统海岸防护工程维护成本高,更新困难,而且可能造成地面沉降、水质恶化、生态退化、渔业资源衰退等后果。基于生态工程的海岸防护提供了抵御海岸带灾害的新理念。修复和重建沙滩、红树林、沼泽湿地、珊瑚礁等海岸带生态系统,可以起到消浪、蓄积泥沙、抬升地面的作用,有效应对全球变化引发的灾害风险,形成更可持续的海岸防护体系。通过分析不同海岸防护技术的优势和限制,认为以生态工程为核心理念构建和管理我国海岸防护体系,才能起到保障社会经济发展和维持生态健康的最佳效果。     

Features of the Impurity Composition of Diamonds from Placers of the Northeastern Siberian Craton

Doklady Earth Sciences - Diamond crystals from the Istok (25 crystals) and Mayat (49 crystals) placers were studied using the EPR, IR, and luminescence methods. The total content of impurity...     

冻土带砂金矿再生机理的初步模拟实验研究——含Au(Ⅲ)、Au(0)的NaCl溶液单向冻结实验

文章首次报道了含不同价态金的ＮａＣｌ溶液在单向冻结条件下，其中的Ａｕ（Ⅲ）、Ａｕ（０）浓度及盐度的变化特征。实验结果表明，冻结过程中，由于“盐析作用”的结果，金元素及盐分离子发生强烈迁移，大量富集在未冻液中。在常温及零温条件下，Ａｕ（Ⅲ）稳定，Ａｕ（０）最不稳定，极易发生沉淀。表明冻土带砂金矿再生的关键可能就在于如何使金的价态发生变化，从而导致未冻液中金元素的沉淀，以及使分散在沉积物中的微细粒金进一步富集、长大。     

玻璃砂矿评价新方法的研究

在综合分析福建滨海玻璃砂矿主要化学组分赋存状态基础上，根据石英砂矿采样工艺特点，分析了玻璃砂原矿评价方法的不足。结合国内外玻璃工业对硅质原料(玻璃砂)的质量要求，提出滨海玻璃砂矿新的评价方法——精矿评价法。并介绍了新的评价方法在玻璃砂矿勘查实践中的应用成果。     

Direct and Indirect Effects of Estuarine Reclamation on Nutrient and Metal Fluxes in the Global Coastal Zone

We demonstrate that land reclamation in estuaries is resulting in very large-scale loss of intertidal area and disconnection of stored sediment with the water column. This process is not just causing loss of estuarine ecosystem services, it is also having a major deleterious impact on the ability of estuaries to retain nutrients and trace metals. The global scale of loss of estuarine wetlands and subtidal sediments has reached the point where the impact of this loss of estuarine retention is likely to be affecting coastal seas worldwide and possibly global element cycles.     

山东省沿海岸带矿产资源分布特征

山东省沿海岸带矿产资源分布广泛,资源储量丰富。由于地壳演化历程的差异,决定其岩石建造和含矿建造的差异,从而导致了各大地构造单元内分布着各具特色的矿产;各个地质历史时期中形成的岩系都分布着一定的矿产。山东省沿海岸带属环太平洋Ⅰ级成矿带,分属于济阳（华北）成矿区、胶北（辽宁胶东半岛）成矿区和胶南威海成矿区3个Ⅱ级成矿区。由于山东省区域成矿作用的发生、发展和矿床的形成都受区域地质的发展演化控制,矿产在时间上的分布具有不均一性和规律性。     

被动大陆边缘构造演化对深水区烃源岩形成的控制

以世界被动大陆边缘含油气盆地构造演化、油气田资料为基础,采用地质综合分析方法,探讨了不同类型被动大陆边缘盆地在不同构造演化阶段深水区烃源岩的形成条件:开阔海型被动大陆边缘盆地群裂谷阶段发育大型局限湖盆,区域分布的厚层湖相富生油黑色泥页岩为主力烃源岩;边缘海型被动大陆边缘盆地群裂谷阶段发育受河流—波浪控制的大型三角洲,海陆过渡相富生气炭质泥页岩和煤系为主力烃源岩;被动大陆边缘阶段盆地群发生持续性海侵,在高水位体系域缺氧环境下的富有机质海相泥页岩为盆地重要的烃源岩。     

大港千米桥潜山储层形成对油气分布的控制

位于黄骅坳陷北大港构造带之下的千米桥潜山是一个深埋的奥陶系碳酸盐岩潜山油气藏。潜山形成经历了中—新生代褶皱抬升—埋藏改造等复杂的地质过程,碳酸盐岩储层成因复杂,有效孔隙分布具有极强的非均质性,严重影响了晚期油气的充注。对碳酸盐岩储层成岩过程的解析表明,中生代强烈构造变形事件之后的大气水岩溶作用形成了潜山储层基本格架,而第三纪埋藏过程中发生的选择性溶蚀与胶结作用则使储层结构复杂化,储集空间分割性进一步加强。在潜山油气充注过程中,缝洞系统与供烃窗口的对接关系决定着油气主疏导网络分布,而疏导网络与储集空间的连通与否则控制潜山油气分布。千米桥潜山油气藏应属于成岩封闭的裂缝性油气藏,而非块状油气藏。     

福建沿海地区表层土壤铅来源及分布特征

在福建省沿海经济带生态地球化学调查的基础上,应用富集因子法对福建省沿海地区表层土壤中铅的来源进行了分析,并对其自然来源和人为来源的分布特征及影响因素做了初步探讨。结果表明,福建沿海地区约98.2%的土地面积表层土壤中铅属于自然来源,其余地区含有人为来源铅,且集中分布于个别市县城区;铅自然来源区呈现广域性分布特征,人为来源区则呈现零星的斑点状分布特点;铅自然来源区和人为来源区的空间分布特征在很大程度上受到土壤类型、森林植被分布以及人为活动等因素的影响。