铁锰结壳年代学方法及其应用     

方志浩  屠霄霞  乔志国  周怀阳 《海洋科学》2019,43(9):104-113

铁锰结壳记录了丰富的古海洋和古气候信息,要分析这些信息,必须先确定各壳层的生长年龄。目前主要使用的定年方法有:Be同位素定年、U系同位素定年、Os同位素定年、经验公式法、古地磁地层学方法和古生物地层学方法等。每种定年方法均各有利弊,其中10Be是年龄小于10 Ma结壳的最佳定年方法; U系同位素定年精度高,但定年范围小于0.5 Ma; Os同位素定年时间尺度长,且可以判断沉积间断,但需要有区域的海水Os同位素演化曲线; Co经验公式因为简单易行,是结壳估算年龄最为常用的方法,但该法无法判断沉积间断,在使用时需特别谨慎,应确保经验公式适用于所研究的样品;如果结壳厚度大、生长速率较快且不存在沉积间断,古地磁地层学方法可以快速地进行定年;此外,如果结壳中古生物化石较多,可考虑采用古生物地层学方法。在分析铁锰结壳年代学方法利弊基础上,本文利用U系定年法、古地磁地层学法和经验公式计算法分别对南海铁锰结壳进行定年,通过比较,认为目前铁锰结壳较优的定年方法为古地磁地层学方法。  相似文献   

荒漠区踩踏生物土壤结皮对土壤微生物量的影响     

杨航宇  刘长仲  刘艳梅  杨昊天 《中国沙漠》2019,39(2):35-44

土壤微生物量可敏感指示土壤质量,是衡量荒漠地区生态恢复程度的重要生物学指标,而有关荒漠区人为踩踏生物土壤结皮与土壤微生物量关系的研究相对缺乏。以腾格里沙漠东南缘的人工植被固沙区和天然植被区人为踩踏生物土壤结皮下的沙丘土壤为研究对象,分别采集未踩踏、中度踩踏和重度踩踏结皮下0～5 cm和5～15 cm土样并测定土壤微生物量碳和氮。结果表明:人为踩踏藻-地衣结皮和藓类结皮可减少生物土壤结皮下土壤微生物量碳和氮,且土壤微生物量碳和氮随踩踏程度的增加而减少,重度踩踏显著减少土壤微生物量碳和氮(P<0.05),土壤速效磷、速效氮、全磷和全氮的损失是导致土壤微生物量碳和氮减少的重要因子。除踩踏程度外,土壤微生物量碳和氮也受结皮演替阶段的影响。人为踩踏的藓类结皮下土壤微生物量碳和氮显著高于藻-地衣结皮(P<0.05),表明演替晚期的藓类结皮比演替早期的藻-地衣结皮抗干扰能力更强;无论季节如何更替,土壤微生物量碳和氮均表现为未踩踏>中度踩踏>重度踩踏;人为踩踏结皮下土壤微生物量碳和氮均表现明显的季节变化,夏季>秋季>春季>冬季。腾格里沙漠人工植被固沙区和天然植被区人为踩踏生物土壤结皮可减少土壤微生物量,表明人为踩踏生物土壤结皮可引起土壤质量下降,导致荒漠生态系统的退化。因此,保护荒漠区生物土壤结皮有利于荒漠生态系统的修复。  相似文献   

中太平洋和中国南海富钴结壳稀土元素地球化学   总被引：10，自引：0，他引：10  

陈守余  张海生  赵鹏大 《海洋地质与第四纪地质》2006,26(4):45-50

对中太平洋海山和中国南沙海盆富钴结壳中稀土元素的含量、分布特征、配分模式分析结果表明:富钴结壳中稀土元素含量非常高,总量为1 380×10-6~2 360×10-6,约为正常深海沉积物和海水中稀土元素含量的10~100倍,与大陆地壳丰度相比Ce最为富集;中太平洋海山区和中国南沙海盆富钴结壳中的稀土元素配分模式与其他海域基本相同,属轻稀土元素富集、重稀土元素亏损型;Ce元素含量和轻重稀土元素的比值沿生长方向逐渐降低,底层比顶层高出近一倍;不同海域富钴结壳中稀土元素的含量变化较大,夏威夷群岛富钴结壳中的稀土元素总量最高,中太平洋海山区中等,中国南沙海盆偏低。  相似文献   

The effect of biological soil crusts on soil moisture dynamics under different rainfall conditions in the Tengger Desert,China          下载免费PDF全文

Wei Shi  Xin‐ping Wang  Ya‐feng Zhang  Yan‐xia Pan  Rui Hu  Yan‐xia Jin 《水文研究》2018,32(10):1363-1374

Rainfall is considered as the dominant water replenishment in desert ecosystems, and the conversion of rainfall into soil water availability plays a central role in sustaining the ecosystem function. In this study, the role of biological soil crusts (BSCs), typically formed in the revegetated desert ecosystem in the Tengger Desert of China, in converting rainfall into soil water, especially for the underlying soil moisture dynamics, was clarified by taking into account the synthetic effects of BSCs, rainfall characteristics, and antecedent soil water content on natural rainfall conditions at point scale. Our results showed that BSCs retard the infiltration process due to its higher water holding capacity during the initial stage of infiltration, such negative effect could be offset by the initial wet condition of BSCs. The influence of BSCs on infiltration amount was dependent on rainfall regime and soil depth. BSCs promoted a higher infiltration through the way of prolonged water containing duration in the ground surface and exhibited a lower infiltration at deep soil layer, which were much more obvious under small and medium rainfall events for the BSCs area compared with the sand area. Generally, the higher infiltration at top soil layer only increased soil moisture at 0.03 m depth; in consequence, there was no water recharge for the deep soil, and thus, BSCs had a negative effect on soil water effectiveness, which may be a potential challenge for the sustainability of the local deep‐rooted vegetation under the site specific rainfall conditions in northwestern China.  相似文献   

高寒沙区生物土壤结皮覆盖区凝结水组分分析     

成龙  贾晓红  吴波  李元寿  赵雪彬  周虹 《高原气象》2019,(2):439-447

凝结水作为干旱半干旱地区重要的组分,对生物土壤结皮具有重要的生态学作用。为阐明高寒沙区青海共和盆地生物土壤结皮表层5 cm凝结水水汽来源,利用2017年5—9月自制微渗仪对土壤表层5 cm不同类型生物土壤结皮(苔藓结皮、藻类结皮、物理结皮)和流沙凝结水进行了观测。结果表明:高寒沙区凝结水量随结皮发育程度变化呈增加趋势,表现为:苔藓结皮>藻类结皮>物理结皮>流沙;生物土壤结皮覆盖区凝结水量显著大于流沙凝结水量,即生物土壤结皮有利于凝结水的产生;凝结水主要由吸湿水和大气水汽凝结水与土壤凝结水两部分组成;观测期间,不同类型结皮日土壤凝结水量无显著性差异;吸湿水量和大气水汽凝结水总量显著高于土壤凝结水量(P<0. 05);随时间的变化,吸湿水和大气水汽凝结水与土壤凝结水对凝结水的贡献率呈波动性变化;吸湿水和大气水汽凝结水贡献率主要集中在65%～80%,土壤凝结水贡献率主要集中在20%～35%。  相似文献   

太平洋多金属结核和富钴结壳稀土元素地球化学对比及其地质意义   总被引：4，自引：1，他引：3       下载免费PDF全文

何高文孙晓明  杨胜雄朱克超宋成兵 《中国地质》2011,38(2):462-472

多金属结核和富钴结壳是大洋两类典型的铁锰产物。为探讨不同海区多金属结核和富钴结壳之间稀土元素特点及其揭示的地质意义,利用近年中国在太平洋获取的样品进行对比,采用ICP-AES对稀土元素测试。结果表明,结壳具有正Ce异常明显、LREE富集、∑REE高的特点,而结核表现为HREE相对富集、∑REE相对较低,因成因类型不同,Ce异常或表现为正异常、负异常或异常不明显。结核形成后受到成岩作用的影响,而结壳则为水成作用形成;结核和结壳中REE的存在形式比较复杂,不同海区各不相同,中太平洋东部产出的结壳和位于东太平洋的结核中REE可能主要赋存于铁矿物相,而西太平洋结壳REE可能主要赋存于锰矿物相;结核和结壳REE可能分别来自海水和海山蚀变玄武岩,热液作用影响有限。  相似文献   

基于声学深拖调查的海山微地形地貌研究——以马尔库斯-威克海岭一带的海山为例   总被引：1，自引：0，他引：1  

徐建  郑玉龙  包更生  吴学文  张恺  金肖兵 《海洋学研究》2011,29(1):17-24

利用"大洋一号"科学考察船DY115-21航次第1航段采集于西太平洋马尔库斯-威克海岭一带海山的声学深拖数据资料,借助GeoDas和PDS 2000等软件,对获取的侧扫声呐、浅剖以及多波束数据资料进行了后处理,获得了该海区高分辨率的地形地貌特征,并结合深海摄像资料,探讨了其海底特征地貌的成因.结果表明:根据水深及其所处...  相似文献   

Distribution characteristics of seamount cobalt-rich ferromanganese crusts and the determination of the size of areas for exploration and exploitation   总被引：1，自引：1，他引：0  

HE Gaowen  MA Weilin  SONG Chengbing  YANG Shengxiong  ZHU Benduo  YAO Huiqiang  JIANG Xunxiong  CHENG Yongshou 《海洋学报(英文版)》2011,30(3):63-75

In 2001, the International Seabed Authority (ISBA) initiated the consideration relating to the Regulations for Prospecting and Exploration for Hydrothermal Polymetallic Sulphides and Cobalt-rich Ferromanganese Crusts in the Area at its 7th session. Since then, the consideration of the Regulations has been mainly focused on the size of areas to be allocated for exploration and exploitation of the crusts. This paper, based on the investigation data and the analysis of the distribution characteristics of the crusts, suggests a model for determining the size of areas for exploration and exploitation of the crusts, taking into account various factors such as production scale, crust thickness and grade, mineable area proportion, recovery efficiency, exploration venture, and so on. Through the modeling, the paper suggests that the exploration area (the area covered by each application for approval of a plan of work for exploration of cobalt-rich crusts) shall be 4 856 km² and the exploitation area (the mine site area) shall be 1 214 km², for 20 years of 1 million wet tonnes annual production.  相似文献   

中太平洋海山富钴结壳主要成壳元素特征     

于赫楠  孙国胜  初凤友  马维林  孙珍军  李超 《世界地质》2013,32(1):63-68

通过大洋一号船DY105--12 /14 航次采集的结壳样品,对中太平洋CL、CM2、CM3、CX、CQ、 CA、CB 海山结壳的主要成壳元素Mn、Fe、Co、Ni、Cu 的含量进行了测试统计,并与邻区的麦哲伦海山、马绍尔群岛、夏威夷群岛和莱恩群岛进行了对比,中太平洋各海山以及不同区域海山结壳的主成分之间存在一些差异,这主要与各海山结壳的物质来源、成壳环境和成壳时代的差异有关。不同形态类型的结壳主成分具有一定的差别,其主要原因可能是生长机制和形成环境不同造成的。  相似文献   

Geochemical features and genesis of continental cobalt-rich ferromanganese crusts   总被引：1，自引：0，他引：1  

S.O. Maksimov  P.P. Safronov 《Russian Geology and Geophysics》2018,59(7):745-762

Mass cobalt-rich ferromanganese microcrusts and nodules similar in morphology and chemical composition to cobalt-rich ferromanganese deep-ocean crusts were found in Cenozoic volcanic rocks in southern Primorye. Research has shown that ore genesis of this type is genetically related to argillization and destruction of siliceous rocks by CO₂-rich fluids, which is confirmed by experimental data on carbon erosion of iron-containing materials. Two types of this fluid ore genesis are recognized: (1) relatively high-temperature (vapor-condensate), related to late volcanic processes and fracture gas infiltration, and (2) low-temperature (vapor-liquid-condensate), controlled by degassing followed by carbon mobilization (gasification). Primarily colloidal ferromanganese segregations have high contents of Co, Ni, Pb, Cu, and Ce, typical of oceanic ore genesis. Regardless of the concentrations of these metals in the protoliths, their contents in microcrusts are similar (n-10n wt.%). This indicates the same ore genesis mechanism and similar sorption properties of the colloidal ferromanganese material formed. Barium- and cerium-rich ferromanganese microcrusts and nodules are abundant. Condensed drops of iron-containing platinum were found in apobasaltic nickel-rich ferromanganese segregations. There is a cerium paradox expressed as a minimum or a total lack of cerium among rare-earth phosphates associated with ferromanganese microcrusts. Fluid destruction and oxide metallization of ocean-floor basalts are assumed to be the main source of metals for oceanic ferromanganese crusts and nodules.  相似文献