FEATURES OF Pb ISOTOPIC COMPOSITION OF ORES AND EVOLUTION OF CONTINENTAL CRUST OF CHINA

Based on the Pb isotopic features, the ore leads in the continent of China can be dividedinto four types: (i) single-stage lead of low μ value derived from mantle, (ii) homogeneouslead of crustal source with high μ value, (iii) modern mixing lead between mantle andcrust, and (iv) residual lead of crustal source. As the leads from mantle had possessed single-stage features (μ = 7.8) before the Proterozoic, the ages of continental crust can be calculatedbased on the mixing Pb of type (iii). The results hidicate that the continental crust of Chinawas mainly generated during the Archaean, and the growth rates of crust reached the max-ima by the ages of 3.3-3.4, 2.6 and 1.6-1.7 b.y. The occurrences of residual crust Pbwith high ~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb anomalies were associated with the remelting andreconstruction of crust since 1.6 b.y. ago. The lead sources in the continent of China showhigher Th/U ratios (3.3-6.5) and ~(207)Pb anomalies than those in other continents, indicationthe conti     

万洋山-诸广山加里东期花岗岩的物质来源——Ⅱ.同位素多维空间的拓扑分析

Sr-Nd-O-Pb~3六维同位素空间的拓扑分析结果表明,万洋山-诸广山加里东期花岗岩的源岩主要由三端元物质组成,混合模式判别证明花岗岩是由三端元组分不同比例混合的产物,多元同位素体系和元素地球化学综合示踪研究表明,这三端元地壳成分为陆源沉积物、地槽沉积物和蚀变的基性火山岩。     

THREE-COMPONENT MIXING AND FOUR-SYSTEM RECYCLING MODELS FOR EXPLAINING Nd-Sr-Pb ISOTOPIC CORRELATIONS OF SUBOCEANIC AND SUBCONTINENTAL MANTLES

The Pb-Sr-Nd isotopic data of Cenozoic volcanic rocks from the continent of China show that there exist three main end members of the mantle, which are the enriched mantle of Wudalianchi in Northeast China, the depleted mantle in South China and the recycling mantle of Yunnan in southwestern China. A11 the data can well fit a curved surface of three-component mixing in Pb-Sr-Nd isotopic space. Seven major end members in the global mantle can be identified. Based on the intersection line between two curved surfaces of three-component mixing in the continent of China and the ocean, the Pb-Sr-Nd isotopic ratios in the primatire mantle can be calculated. In order to explain the genesis of seven end members of the mantle, four-and three-system recycling models were used. The theoretical results are well comparative with the isotopic distribution observed in global Cenozoic volcahics, and can provide useful constraints on the process of the geochemical evolution in the crust-mantle system.     

Source Rocks of the Caledonian-Age Granitoid Rocks in Wanyanshan-Zhuguangshan, Southeast China (Ⅱ)——Topological Analysis in Isotopic Multispace

Topological analysis in Sr-Nd-O-Pb_3 six-dimensional isotopic space suggests that the source rocks of the Caledonian-age granitoid rocks in Wanyangshan-Zhuguangshan, southeast China, comprise three end-member components. Isotopic mixing model discrimination indicates that the granitoid rocks were produced through mixing of the three componentsin varying proportions. Comprehensive study of multiple isotopic systems and geochemistry of the granitoid rocks suggests that the three end-member components were crustal rocks which are continent-derived sediments, geosycline sediments and altered basic volcanic rocks.     

矿石铅同位素组成特征与中国大陆地壳的演化

本文根据壳幔混合铅的二阶段模式计算,表明大陆地壳主要派生于太古代,地壳增加速率在33—34,26和16—17亿年出现极大值.晚元古代后,中国大陆出现广泛的重熔再造,导致了高Pb~(207)/Pb~(204)与Pb~(208)/Pb~(204)异常铅的出现,表明其改造程度要比其他大陆强烈.中国大陆铅源普遍具有高Th/U比特征也可能反映原始地球的区域不均一性。     

新石器晚期祭祀彩石的多种谱学方法研究

作为“中国古代文明探源工程”在淮河流域确定的唯一一处重要的龙山文化时期遗址,安徽省蚌埠市禹会遗址出土了大量彩石,引起考古学界广泛关注。本文利用同步辐射X射线荧光(SR-XRF)、X射线衍射(XRD)、激光拉曼光谱(LRS)、热释光光谱(TL)等多种光谱分析手段,并结合电子探针(EPMA)分析结果,对禹会遗址出土“红-黄”彩石不同颜色区域的元素、物相组成及经热历史进行了测定。结果表明,该矿石主体为褐铁矿,有大量石英夹杂,表层黄色物质主要为针铁矿(α-FeOOH),红色物质主要为赭石(α-Fe₂O₃+粘土+硅土);内部主要是隐晶质针铁矿,并含有一定数量铬铁矿、二氧化锰,及少量重晶石和金属铋。该类彩石并无人工热历史,应属于一种性质独特、地质起源复杂的多金属天然矿石,大量出现在新石器时代晚期遗址之中,可能与某种原始信仰和特殊祭祀活动有关。     

华北麻粒岩相带铅同位素组成特征及其与全球对比

本文通过对华北麻粒岩相岩石的Pb同位素组成特征的研究表明,华北太古宙地幔μ值在7.81±0.03。其下地壳μ值在2—4左右,Th/U在1.6—13.6,与全球范围内下地壳深变质作用引起的U和Th的亏损程度相似。通过对全球麻粒岩相岩石Pb同位素组成的对比研究表明,全球太古宙地幔的μ值存在明显的区域性的差异,南半球的μ值高于北半球,表明地球存在初始不均一性。     

上海市力学学会第2届工业流体力学交流会(1992年12月7日)

<正> 会议在中国纺织大学召开,上海市各有关高等院校,研究所和工矿企业的65名代表参加了会议。中国力学学会副理事长、上海市力学学会理事长何友声到会祝贺并讲话。他强调指出,工业与环境流体力学虽然近些年才发展起来,却是力学中最有生命力的学科之一。在谈到科技人员“下海”时,他指出,这包含了两层意思,即既要突破原来的专业范围,又要投身到生产实际中去。中国力学学会环境与工业流体力学专业组组长朱之墀在重庆主持了第2届      

上海市力学会工业流体力学协作组成立暨第1届应用推广交流会

<正> 会议在上海市科学会堂隆重举行。来自12所高等院校和研究所的60名流体力学工作者与6家工矿企业的7名代表参加了会议。会议由上海市力学会理事、流体力学专业组组长陈月林主持。上海市力学会副理事长,上海机械学院院长赵学端代表学会对协作组的成立表示热烈祝贺。工业流体力学协作组组长杨文熊介绍了国内外在工业流体力学领域中的发展概况和      

大陆与大洋地幔Nd-Sr-Pb同位素特征与三组份混合-四体系再循环模式

中国大陆新生代火山岩Pb-Sr-Nd同位素研究表明大陆地幔存在3个主要端元,即五大莲池富集端元、雷琼-南海亏损端元与云南西部再循环端元。在Nd-Sr-Pb同位素空间数据可拟合于三元混合曲面,并与大洋地幔三元混合曲面相交。根据交线求得了原始地幔的同位素组成。全球地幔可大体分成7个主要端元。根据上、下地幔与上、下地壳四体系再循环理论可以较好解释Nd-Sr-Pb同位素分布规律与7个端元的形成机制。