太平洋海山成矿系统与成矿作用过程   总被引：2，自引：0，他引：2       下载免费PDF全文

石学法  任向文  刘季花 《地学前缘》2009,16(6):55

文中初步探讨了太平洋海山富钴结壳成矿系统的结构与成矿作用过程。海山成矿系统的控矿要素主要包括地质要素和海洋要素,地质要素主要包括海山的形成、迁移、沉降和水道的开合等,海洋要素主要包括大洋温盐环流、最低含氧带(OMZ)、文石溶跃面、碳酸盐补偿深度和海山周围海水的动力情况等。重点分析了海山漂移和沉降、水道开合、最低含氧带变化、大洋环流以及气候变化等要素对富钴结壳成矿的控制作用。海山为富钴结壳成矿提供了一个容矿空间,稳定的基岩,即长期稳定的容矿空间,是富钴结壳成矿的基本条件;海山的形成年龄、海山的迁移和水道的开合决定并改变了富钴结壳的成矿背景条件,促使海山成矿系统发生演化。最低含氧带作为富钴结壳成矿的地球化学障,是直接的矿源层;而海山周边的地形旋涡沟通了最低含氧带与富氧、富铁的深层和底层水,使得最低含氧带中的成矿金属离子得到氧化,进而发生胶体凝聚沉淀,形成富钴结壳。以西太平洋海山成矿系统为例,将该区白垩纪以来富钴结壳成矿作用过程划分为5个阶段:(1)白垩纪—始新世,(2)始新世末—晚渐新世,(3)晚渐新世—中中新世早期,(4)中中新世早期—晚中新世早期,(5)晚中新世早期—现代,其中(2)、(3)阶段有利于发育富钴结壳。  相似文献   

The genesis of late Quaternary caliche nodules in Mission Bay, Texas: stable isotopic compositions and palaeoenvironmental interpretation   总被引：1，自引：0，他引：1  

JIE ZHOU  HENRY S. CHAFETZ 《Sedimentology》2009,56(5):1392-1410

Caliche is a fairly widespread pedogenic carbonate that commonly has been used to reconstruct palaeoclimatological conditions. Stable isotopic analyses of three types of caliche nodules from Mission Bay, Texas, provide insights into the values and limitations in palaeoenvironmental interpretations. Soft incipient nodules (type I) and partially lithified chalky nodules (type II), composed of low Mg‐calcite, are in situ pedogenic products in the late Quaternary soils; they represent young to intermediate caliche nodules with no obvious diagenesis and, with constraints, can be used to investigate palaeoenvironmental conditions. The well‐lithified hard nodules (type III) dispersed on the beach and shallow bay exhibit complex shapes, fabrics, mineralogy and geochemical compositions. They are mature nodules that have undergone substantial diagenesis and, therefore, are believed to have lost their initial environmental signatures. The incipient nodules in the presently active grey soil and the older subjacent brown soil display significantly different δ¹³C values, ?8·4 and ?4·4‰, respectively, which indicates a change in palaeovegetation from C₃/C₄ mixed to C₃‐dominated flora. The δ¹³C values probably reflect a marked climate shift from warm and dry to cool and wet conditions in the middle Holocene. However, in the same grey soil, there is a sub‐set of incipient caliche nodules with δ¹³C values around 0·1‰, which is probably due to the input of localized carbon sources in the soil (e.g. shell fragments). The occurrence of essentially identical nodules appearing from the same modern soil horizon with significantly different δ¹³C values questions the universal reliability of this type of data for palaeoenvironmental interpretation. This study demonstrates that, whereas the stable isotopic compositions of caliche nodules can be used for palaeoenvironmental reconstruction, diagenesis and the influence of localized carbonate sources in the soils could lead to erroneous interpretations.  相似文献   

世界大洋地质与矿产标准物质评介   总被引：2，自引：0，他引：2       下载免费PDF全文

王毅民王晓红  高玉淑张学华 樊兴涛 《中国地质》2010,37(1):229-243

自20世纪80年代中以来,中国相继研制了4批共11个大洋地质与矿产标准物质,形成了多金属结核(GSPN-1～3)、海山富钴结壳(GSMC-1～3)、富钴结壳的铂族元素(MCPt-1,2)和深海沉积物(GSMS-1～3)4个标准物质系列。笔者简介了这些标准物质的研制背景,评介了中国和世界其他国家(美国、俄罗斯、印度和日本等)研制的大洋地质与矿产各标准物质系列,对比了其定值数据、特点及应用。虽然中国的研制工作起步较晚,但由于采用了更先进的分析测试技术和国内外多实验室合作定值方式,使这些标准物质定值组分多、系列性好,也有较大国际影响。  相似文献   

Nd同位素方法应用于示踪古洋流的研究进展   总被引：1，自引：0，他引：1  

吴琼  刘志飞 《地球科学进展》2010,25(2):220-229

大洋环流在调节全球水热分配方面起着举足轻重的作用,对全球气候变化有着重要影响。为了更好地了解未来的气候变化模式,掌握古洋流变化与气候冷暖交替耦合关系的机理成为当务之急。目前,海水Nd同位素是追踪洋流演化方式的有效指标,获得了越来越多的关注。通过从海洋环境Nd同位素的相关特性以及研究材料与方法方面来阐述Nd同位素应用于示踪古洋流研究的可行性以及最新的进展,并配合实例进行说明。  相似文献   

大洋多金属结核中几种常见锰矿相的特征及其相关性     

钱江初  初凤友  冯旭文 《矿物学报》2006,26(2):152-158

大洋多金属结核中的1 nm锰矿相常以陆上钡镁锰矿命名,但两者在晶体结构等方面有很大的差别,并不属同一种矿物,1 nm锰矿相与人工合成的布塞尔矿却有更多的相似性。1 nm锰矿相会因干燥失水而相变成0.7 nm锰矿相,因此结核中的大多数0.7 nm锰矿相很可能不是原生矿物,而仅仅是1 nm锰矿相的相变产物。水羟锰矿和1 nm锰矿相是多金属结核中最主要的两种锰矿物,它们两者均有0.24 nm和0.14 nm这两条特征X射线衍射峰,因此在对结核进行锰矿物相的鉴定中要注意把它们区分开。  相似文献   

Paleoceanographic Setting and Preservation of Buried Manganese Deposits in DSDP/ODP Cores     

Takashi Ito  Kosei Komuro 《Resource Geology》2006,56(4):457-470

Abstract. The occurrence, lithology, and stratigraphic setting of buried manganese deposits and associated host sediments in cores obtained on Legs 123–210 of the Ocean Drilling Program (ODP) are examined in order to establish the formative environment and conditions of preservation. Fossil manganese nodule and crusts are found to have formed or deposited throughout the period from 100 Ma to the present, with an additional example of formation near 137 Ma, suggesting that the deep-sea environment has been oxic and suitable for the formation of manganese nodules and crusts since the Cretaceous. Many manganese nodules and crusts occur on horizons corresponding to hiatuses in sedimentation or periods of slow sedimentation, consistent with the environment in which modern nodules form (sedimentation rate less than 10 m/m.y.). Sediments overlying the fossil nodules and crusts are oozes or biogenic sediments with sedimentation rates of 1–18 m/m.y. Low total organic carbon (<0.1 wt%) in the overlying sediments and high sulfate content (>25 mM) in interstitial water around the manganese horizon suggest that no strong reduction occurred within the overlying sediments. Coverage by biogenic sediments containing only small amounts of organic matter is therefore considered important for the preservation of manganese nodules and crusts. Manganese carbonate occurs sporadically as nodules, concretions or thin layers in various host sediments, including clay, calcareous ooze and siliceous ooze with sedimentation rates of 6–125 m/m.y. Hiatuses are rare around the host sediments of manganese carbonate. Higher total organic carbon (0.2–1.8 wt%) in the host sediments and lower sulfate content (0–25 mM) in interstitial water around the manganese carbonate horizon suggest that reduction in association with decomposition of organic matter would have proceeded in the host sediments.  相似文献   

Growth Rate Estimates of Supergene Manganese Nodule by^40Ar／^39Ar Isotopic Dating     

Vasconcelos P M 《中国地质大学学报(英文版)》2004,15(3):312-323

INTRODUCTIONModern4 0 Ar/ 39Arlaserstep heatinganalysishasbeensuccessfullyappliedtodateverysmallmineralgrainsfromdiversegeologicalenvironments .Thefineresolutionofthismethodhasgreatlyhelpovercomeproblemsintrinsicintradi tionalK Armethod ,inducedbyexcessargon ,argonlossbythermalresetting ,39Arrecoilduringirradiation ,andinter growthsand/orcontaminationofdifferentgenerationminer als ,withintheanalyzedmineral (Smithetal.,1998;Vas concelosetal.,1994 ) .Supergenemanganeseoredepositsareeconom…  相似文献   

薄层CT对肺内结节性病变的诊断价值     

王廷昱  古晓泉  荣振华  赵昶 《CT理论与应用研究》1993,(3)

本文利用薄层CT扫描技术,对支气管微细结构和改变,对肺内结节性病变大小、边缘、钙化、CT值及定位进行观察,分析了炎性纵隔淋已结肿大的特点。对肺内不肯定结节行CT 导引下活检,可明确诊断。切凹征、胸膜牵拉征、小泡征、小蜘蛛状改变、血管聚集等对肺癌的定性诊断具有重要价值。  相似文献   

安徽安庆石灰岩地区次生异常的强化方法     

李方林  颜少枝 《地球科学》1992,17(5):594-598

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世界大洋锰结核及沉积物标准物质评介     

王毅民  高玉淑  王晓红 《岩矿测试》1997,(3)

简介了世界大洋锰结核及深海沉积物标准物质概况，评述了它们的特点，同时也汇集了这些样品已确定的特性值。  相似文献