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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 相似文献
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THREE-COMPONENT MIXING AND FOUR-SYSTEM RECYCLING MODELS FOR EXPLAINING Nd-Sr-Pb ISOTOPIC CORRELATIONS OF SUBOCEANIC AND SUBCONTINENTAL MANTLES 总被引:1,自引:0,他引:1
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. 相似文献
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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. 相似文献
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矿石铅同位素组成特征与中国大陆地壳的演化 总被引:8,自引:0,他引:8
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。 相似文献
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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。 相似文献
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<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 相似文献
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<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 相似文献
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