金属矿床中铀的来源

在目前开釆的許多矿床中,鈾的来源并不清楚,因而在成因上尚存在着許多不一致的假說。最流行的两种假说是:鈾是通过普通地下水从碎屑岩或火成岩中淋滤而来;鈾在晚期残余流体中从花崗岩浆或鹼性岩浆析出。經过慎重考証后发現,即使有属于对普通碎屑岩或火成岩的淋滤形成的矿床,也只是极少数,而許多矿床則是金属矿床中鈾的再分佈結果或是早先由上升溶液所形成的富集物。最近工作表明,上升溶液在花崗岩形成以前很早就由岩浆开始析出,可能一直断断續續到分离結晶結束为止。含鈾溶液从岩浆的析出和輝綠岩与煌斑岩脈的侵入似乎在同时一期。从較酸性的岩浆分異体中析出的鈾似乎比重不大。后生鈾矿床和各种类型火成岩侵入体以及主要构造单元之間的空間关系有力地說明了在大多数地区鈾都产于相当深的地方,这些矿床中的金属組合只能用这种假設才可得到解释。地表水只能淋滤和再分佈某些类型矿床中的內生鈾及其伴生金属,例如,在科罗拉多高原的那些矿床或气候干燥地区矿脈的上部。     

用于地质研究的质谱计

由于高精度质谱计的使用范围日益扩大及其可靠性的不断增长,使一些地质问题的研究方法有了新的重大发展。这些方法的重要性日益增加,目前已为质谱计的应用提供了主耍的场所。在地球化学中有三个经常碰到的问题,即放射性测定年龄、研究非放射成因的同位素丰度变异及分析微量元素,它们都需要相当专门性质的质谱技术。例如,在地质年代学研究中使用的仪器,要求在小质量范围内,重复测量结果的偏差不大于千分之几;而许多丰度变异的研究,要求偏差要在万分之一左右。本文从较为专门     

PROGRAM FOR PROCESSING OF HISTORICAL LABORATORY DATA BASED ON FUZZY SET THEORY AS A TOOL FOR DECISION SUPPORT

A computer program(FEA)is presented for processing historical laboratory data.It performs on a list ofsample entries stored in a laboratory information management system.Using an algorithm which is basedon fuzzy set theory,FEA classifies the entries into a limited number of clusters called sample types.Theclassification is fully user-defined.The program transforms the historical data into a representation whichis more suitable for studying the performance of the laboratory or which can be used as preparation for asimulation project.     

Gonadal histology and serum vitellogenin levels of bigeye tuna Thunnus obesus from the Northern Pacific Ocean--absence of endocrine disruption bio-indicators

Endocrine disrupting chemicals such as organochlorines have been detected in a large number of marine fish. Histological observation of the gonads, measurement of serum vitellogenin (VTG) level and of liver polychlorinated biphenyl (PCB) content were performed to evaluate the reproductive health and the contamination with endocrine disruptors in bigeye tuna Thunnus obesus, collected in the northern Pacific Ocean in 1999 and 2000. Abnormalities commonly found in species affected by endocrine disruptors such as the presence of oocytes in the testis or elevated serum VTG levels were not found in any of males examined. Both males and females had only small amounts of liver PCB content. The results suggest that currently there is little if any risk of organochlorine contamination or endocrine disruption of gonadal function in bigeye tuna from the northern Pacific Ocean. However, further studies are necessary to evaluate the health status of the open sea fishery resources.     

The status of the ecological environment and a proposed protection strategy in Sanya Bay,Hainan Island,China

Sanya Bay encompasses a high diversity of natural habitats, ranging from coral reefs, rocky and sandy shores and mudflats to mangroves. Seasonal physicochemical and biological investigations were conducted from 1998 to 1999 and again in April 2000. Water-related environmental quality in Sanya Bay is in good condition. The levels of dissolved oxygen, nitrogen, phosphorus and heavy metals are within the first class of National Seawater Quality Standards for China. Annual mean values of chlorophyll a of 0.93 mg m(-3) and phytoplankton primary productivity of 440.8 mgC m(-2)d(-1), respectively, were found in the waters, both of which show a significant correlation with inorganic nitrogen. A mean new productivity of 144.6 mgC m(-2) d(-1) was recorded in summer. Sanya Bay is rich in natural resources and biodiversity with 235 species of phytoplankton and 129 species of zooplankton identified in the survey. The annual mean abundance of phytoplankton and zooplankton were 1564 x 10 cells m(-3) and 121 individuals m(-3), respectively, with an annual mean zooplankton biomass of 129 mg m(-3). A total of 243 species of fish were sampled in the survey including many of high economic value. Three hundred and eighty-four species of benthos in 121 families were found by mud sampling and trawling. The average biomass of benthic organisms was 11.55 gm(-2), with a density of 31 individuals m(-2). Molluscs were the dominant group, followed by crustaceans; coelenterates exhibited the lowest biomass. One hundred and twenty-six species from 48 families of intertidal organisms were collected by frame sampling, with a mean annual biomass of 644.7 gm(-2) and average density of 816 individuals m(-2). The highest biomass of 1673.5 gm(-2) was collected in a coral reef region, while the highest density of 1219 individuals m(-2) occurred in a mangrove region. The coastline is characterized by coral reefs that accounts for 30% of the total coastline length in the bay, so coral reefs are a key ecosystem that are important for maintaining the regional marine resources and biodiversity. We need to pay much more attention to such diverse marine resources to maintain the integrity and function of these coastal ecosystems.     

黑龙江嘉荫地区白垩纪-第三纪界线初步观察

本文报道了黑龙江嘉荫白山头地区一条新的地层剖面及其K／T界线的初步研究。新命名的“白山头段”代表乌云组下部的早古新世地层,含以Tiliaephyllum tsagajanicum等为代表的达宁早期植物化石。在白山头剖面上,作者发现可能为白垩纪末期的凝灰岩。结合与俄罗斯布列亚盆地含K／T界线的查加扬群标准剖面的对比,推测嘉荫地区的K／T界线可能位于白山头段底部与上述凝灰岩之上的一层炭质泥岩之间。