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961.
Huan-Xin Weng Ya-Chao Qin Xiang-Wei Sun Hailiang Dong Xiang-Hua Chen 《Estuarine, Coastal and Shelf Science》2007,73(3-4):501-509
Based on lab-culture experiments analyzing limitation and combination of iron and phosphorus on the growth of Cryptomonas sp. (Cryptophyceae), and the study of accumulation and release of Fe-bound P in sediment cores collected from the marine region of the Pearl River Estuary, China, reasons for the high frequency of phytoplankton bloom therein are discussed. Results show that the combined effect of Fe and P can obviously accelerate algal development, and the optimum culture conditions maintaining maximum growth rate are 0.05 μM Fe and 50 μM P. Cellular contents of Fe and P is consistent and the P:Fe molar ratio is 159:1. The optimum range of the P:Fe molar ratio in culture experiments for cell incubation is 500–1400. The vertical trends of total Fe and total P variations in sediments are parallel. Fe-bound P is the main species of inorganic sedimentary P. Through continuous leaching with agitation, 34–80% of exchangeable P and 4–23% of exchangeable Fe are concurrently released from the surficial sediments. This is a possible way by which nutrients are made available to phytoplankton. These factors might be responsible for a high frequency of harmful algal blooms in the Pearl River Estuary. 相似文献
962.
The problem of ore-bearing potentiality of the strata involves metallogenic theory and ore-search orientation. Studies of
the spatial distribution of endogenic Au-Ag polymetallic ore deposits in North Hebei indicated that the strata in which ore
deposits occurred range in age from Paleozoic, Proterozoic to Mesozoic. In addition the ore deposits are characterized as
being strata-bound in nature. The arise and establishment of “extracting” viewpoint may be attributed to the following three
reasons: 1) influence by the idea of “ore-source bed”; 2) limitation of analytical techniques in the 1980s’ (especially gold
element); and 3) a small number of samples (sampling locations were mostly disturbed by mineralization). Studies have shown
that ore-forming materials would most probably come from the deep interior of the Earth. Deep-seated ore-bearing materials
including Au-Ag polymetals were brought to the shallow levels by way of mantle plume-mantle sub-plume-mantle branch structure
multi-stage evolution, finally leading to the formation of ore deposits. 相似文献
963.
Behavior of REE Fractionation during Weathering of Dolomite Regolith Profile in Southwest China 总被引:3,自引:0,他引:3
<正>REE fractionation during the weathering of dolomite has been recognized for decades.A regolith profile on dolomite in southwest Yunnan of China was selected to investigate the behaviors of REE during weathering.The weathering of dolomite is divided into two stages:the pedogenesis stage and soil evolution stage,corresponding to the saprolites and soils respectively in the regolith profile. SiO_2,TiO_2,P_2O_5,Zr,Hf,Nb and Ta were immobile components during the weathering by and large, while Al_2O_3,K_2O and Fe_2O_3 were lost during the soil evolution stage in the physical form(clay minerals probably).REE were fractionated during the whole weathering of dolomite.The field weathering profile and the lab acid-leaching experiments on dolomite indicate that MREE were enriched clearly relative to other REE during the pedogenesis stage in a "capillary ascending-adsorption" mechanism, but they did not fractionate clearly in the soil evolution stage.REE were lost and accumulated in the weathering front of dolomite during the soil evolution stage in a "physical-chemical leaching" mechanism. 相似文献
964.
安徽南部桃冲地区铁矿床控矿构造分析 总被引:2,自引:0,他引:2
通过对桃冲地区典型铁矿床的赋存环境及构造特征的研究和控矿因素分析,认为红花山背斜两翼的铁矿体产于背斜的层间断裂带中的次级褶曲内,受"碳酸盐岩地层+次级褶曲+层间断裂带"三个控矿因素的制约,环滨江岩体的铁矿床受厚层状矽卡岩接触带的制约。综合桃冲地区控矿因素的特点,提出了找矿有利部位。 相似文献
965.
同震地表破裂带是地震破裂最直观的表现。地表破裂带的精细填图对理解地震破裂过程及发震机理有着重要意义。我们对5.12汶川地震映秀-北川同震破裂带南部的虹口乡区段开展了较为精细的填图工作,该区段地表破裂带的平面几何和同震位移特征沿走向均显示出公里尺度的横向变化和复杂性。根据同震破裂不连续性特征可把地表破裂分为4段,自南向北依次为深溪沟段、庙坝段、高原新村段和八角庙段。其中,深溪沟段和八角庙段同震垂直位错较大,达.5~6m;庙坝段同震垂直位移量普遍较低,1~2m或更低; 在高原新村附近,地表破裂带分为近平行的南北两支,北支以右旋走滑为主,南支以南东盘逆冲抬升为主,这与与映秀-北川同震破裂总体北西盘抬升的性质相反。本文对高原新村附近的反向陡坎进行了深入的探讨,并综合前人的研究结果,认为是破裂在从深部往上扩展的过程中,在浅表部位顺着发育在虹口东南部的大鱼洞-龙溪飞来峰后缘的具南东倾向的断面继承而成。与北川沙坝附近的反向陡坎一样,说明老断裂带构造几何特征对单次地震破裂的扩展有牵引作用。最后,讨论了八角庙有切割关系的两组断层擦痕的地震学和地质学意义,指出可能指示了映秀-北川断裂面上局部区段震前的初始应力水平较低。 相似文献
966.
炭屑化石的显微结构研究是根据木材的解剖特征(组成木材的细胞与组织的形态和排列方式)确定燃烧植物的类型,重建古植被和古环境,探讨人类活动对环境的影响。火石梁和缸缸洼青铜冶炼点位于河西走廊西北部、黑河流域下游巴丹吉林南缘沙地中,散布了大量的炭屑化石遗存。通过炭屑化石3个切面(横切面、径切面和弦切面)显微结构特征研究,比对现代切片标本和木材解剖图版,识别和确定炭屑化石的木材种属,确定 2100~1860BC期间的青铜冶炼所用木材为柽柳、杨属、柳属、蓼科4种乔灌木植物,火石梁和缸缸洼地区大量乔、灌群落生长要比目前荒漠生态环境优越的多。先民的青铜冶炼活动导致乔木和灌木植物被大量砍伐,植被盖度急剧降低,对生态环境产生重大影响,是1900BC左右杨属、柳属和蓼科乔灌木植物基本消失的主要原因。 相似文献
967.
968.
通过对永定河冲洪积物的研究发现,永定河形成前后的沉积环境明显不同。钻探资料表明永定河形成前本地区沉积环境主要为湖泊相,当时湖水宁静,沉积物主要为泥岩和粉砂。永定河形成时洪水裹携大量碎屑形成巨厚的泥石流堆积,沉积环境为冲洪积相,主要为砂砾石、砂、粉砂和粘土互层,形成巨大的冲洪积扇。通过新5孔钻孔岩芯273块古地磁样品的系统剩磁测试,获得了该钻孔岩芯的古地磁极性序列,对比国际地磁极性年表,认为该钻孔岩芯剖面 0~96.59m以正极性带为主,对应布容正极性时,其地质时代为0~0.78Ma; 96.59~246.79m则以反极性带为主,对应松山反极性时,其地质时代为0.78~2.58Ma; 246.79~413.64m以正极性带为主,则对应高斯正极性时,其地质时代为2.58~3.58Ma,属于新近纪上新世。研究推测永定河最早的沉积物为上新世形成,距今3.33~3.58Ma。
相似文献
通过对永定河冲洪积物的研究发现,永定河形成前后的沉积环境明显不同。钻探资料表明永定河形成前本地区沉积环境主要为湖泊相,当时湖水宁静,沉积物主要为泥岩和粉砂。永定河形成时洪水裹携大量碎屑形成巨厚的泥石流堆积,沉积环境为冲洪积相,主要为砂砾石、砂、粉砂和粘土互层,形成巨大的冲洪积扇。通过新5孔钻孔岩芯273块古地磁样品的系统剩磁测试,获得了该钻孔岩芯的古地磁极性序列,对比国际地磁极性年表,认为该钻孔岩芯剖面 0~96.59m以正极性带为主,对应布容正极性时,其地质时代为0~0.78Ma; 96.59~246.79m则以反极性带为主,对应松山反极性时,其地质时代为0.78~2.58Ma; 246.79~413.64m以正极性带为主,则对应高斯正极性时,其地质时代为2.58~3.58Ma,属于新近纪上新世。研究推测永定河最早的沉积物为上新世形成,距今3.33~3.58Ma。
相似文献
969.
Up to now,there were no systematic studies of geochemistry and isotopic age for the Yixian(义县) fluorite deposit,western Liaoning(辽宁) Province,China.Based on the analysis of metallogenic geological setting,we studied the REE,Rb-Sr and Sm-Nd isotopes.The chondrite-normalized REE patterns of fluorite are characterized by moderate LREE depletion(LREE/HREE=0.95-3.57,(La/Yb)N=0.08-2.84) and enrichment of Sr(146×10-6-596×10-6) and moderately positive Eu anomalies(δEu=1.10-1.34),which are similar to those of the ho... 相似文献
970.