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61.
本文根据Sm-Nd同位素工作结果,给出五台群的顶界年龄为2470Ma,属太古代地层。华北地台基底的太古代地层中几处出现世界上同时代的其它构造单元中尚未发现过的高∈~Nd(T)值,表明当时地幔的局部不均匀性已很可观。岩石的既往亏损史与Nd相对富集的情况相矛盾,可能是由于深部地幔去气流体的补入或形成时间不长的地壳物质的混染。 相似文献
62.
试论月龄历谱的数理结构及编排规则 总被引:7,自引:1,他引:6
运用数理统计方法,借鉴天文历算及历谱编排的有关知识,试图提供一种被称为月龄历谱的数理结构模型(数表),以作为对具有某些月龄特征的词语的研究工具。其用途:(1)由这些月龄词语的干支差直接得出它们可能的年代间隔;(2)可用于编排相应的月龄历谱(如金文历谱、某些甲骨文历谱等);(3)能对月龄历谱(如“夏商周断代工程”给出的西周金文历谱)方案中月龄词语的月龄范围及年代间隔进行误差分析。 相似文献
63.
《夏商周断代工程》得到的年代结果中,有些与天文学方法有关.本文介绍4个这样的问题:对宾组卜辞的5次月食记录的天文学认证与武丁王年,与武王伐纣有关的诸多天象历日记录的分析,竹书纪年中"懿王元年天在旦于郑"的日食说研究以及由西周铜器铭文中的诸多历日月相记录排出整个西周王年. 相似文献
64.
65.
Scheelite Sm-Nd dating and quartz Ar-Ar dating for Woxi Au-Sb-W deposit,western Hunan 总被引:14,自引:0,他引:14
PENG Jiantang HU Ruizhong ZHAO Junhong FU Yazhou & LIN Yuanxian . Institute of Geochemistry Chinese Academy of Sciences Guiyang China . Tianjin Institute of Geology & Mineral Resources Chinese Ministry of Land Resources Tianjin China Correspondence should be addressed to Peng Jiantang 《科学通报(英文版)》2003,48(23):2640-2646
SinceFryeretal.[1](1984)firstdatedthehydrother-maldepositusingtheSm-Ndisotopemethod,thisisotopesystematicshasbeenwidelyappliedinthegeochro-nologicalstudyforhydrothermalmineralization.Inrecentyears,manyhydrothermalmineralssuchasfluorite[2—7],tourmaline[8,9],wolframite[5,10,11]andcalcite[12,13]havebeensuccessfullydatedusingtheSm-Ndgeochronometer.ScheeliteisoneofCa-bearingminerals,andrareearthelements(REE)areincorporatedinscheelitebysubstitu-tionatCa2+structuralstiesinminerallattices;moreove… 相似文献
66.
Nd isotopic characteristics of post-Archean sediments from the Eastern Nanling Range: Evidence for crustal evolution 总被引:4,自引:0,他引:4
SHENWeizhou YUJinhai ZHAOLei CHENZelin LINHengcai 《科学通报(英文版)》2003,48(16):1679-1685
A systematic Sm-Nd isotopic study was carried out for sediments and metasediments of different ages from Mesoproterozoic to early Mesozoic era in southwestern Fujian, Eastern Nanling Range. The results show that Nd model age (tDM) and εNd(t) value of most sediments are closely similar to those of Paleoproterozoic Mayuan Group, indicating that they may mainly be the recycling product of Paleoproterozoic crustal materials. However, the Nd model age significantly decreases with a corresponding increase in the εNd(t) value at Neoproterozoic (ca. 0.8-0.7 Ga) and Late Paleozoic (ca. 0.25 Ga), respectively. This is manifested by prominent vales and apexes on the diagrams of tDM VS. tStr. (stratum age) and εNd(t) VS. tstr. The decrease in tDM and the increase in εNd(t) are explained as a result of the significant incorporation of juvenile crustal materials that originated from depleted mantle due to strong lithospheric extension during both periods. It appears that tectonic magmatism in the Neoproterozoic and the Late Paleozoic is of prominent importance in affecting the geochemical nature of sediments in South China. 相似文献
67.
Climate change over southern Qinghai Plateau in the past 500 years recorded in Sabina tibetica tree rings 总被引:4,自引:0,他引:4
QINNingsheng SHAOXuemei JINLiya WANGQingchun ZHUXide WANGZhenyu 《科学通报(英文版)》2003,48(22):2483-2487
Two tree ring-width chronologies of Sabina tibetica were developed based on cores sampled in Qumalal and Zhiduo, southern Qinghai Plateau. The response function analysis showed that the chronologies were sensitive to temperature and precipitation from April to June in the plateau. Moisture index (MI) was defined, reconstructed and extended back to AD 1550. The cross-validation method was used to check the stability of the calibration equation, and the result indicated that the equation was stable. Six severe dry periods were found in this region in the past 453-year reconstruction, which were 1592 to 1610, 1649 to 1665, 1687 to 1697, 1740 to 1750, 1818 to 1829 and 1918 to 1933. Five severe wetting periods were 1669 to 1682, 1700 to 1709, 1800 to 1814, 1898 to 1909 and 1935 to 1950. Spectrum analysis indicated that there existed long-term cycles of 60.4 and 53.4 a, solar cycle of 11 a and short-term cycles of 8, 6 and 4 a in the reconstructed series. 相似文献
68.
The field investigations of geomorphology and Quaternary sediment sequences show that the sediment stratigraphic profile containing
the skull of the Homo sapiens Daliensis (Dali Man) at Tianshuigou trench, Jiefang Village (109° 44′E, 34°52′N), Dali County, Shaanxi Province, is composed of the
loess-paleosol sequence, 17.3 m thick, in the upper part, and the alluvial silts, fine sands and sandy gravels interbedded,
15.4 m thick, in the lower part. There are the well developed layers L1, S1, L2 and S2 in the loess-paleosol sequence of the profile, which are comparable; to those of the Luochuan loess section on the basis
of magnetic succeptibility measurements and IRSL dating of the loess samples. An alluvial gravel layer, where the skull of
the Dali Man was discovered, is in 13 m beneath the bottom of paleosol S2, implying that, the age of the Dali Man must be older than about 247 kaBP when the paleosol S2 began to be developed. The samples of mammal animal tooth and shell fossils from the gravel layer containing the skull of
the Dali Man have been dated by uranium series and ESR methods respectively. Based on the multiple dating results and the
stratigraphic chronology, the age of the Dali Man, therefore, would be estimated as older than 250 kaBP and younger than 350
kaBP, and reasonably estimated as 260–300 kaBP. 相似文献
69.
海南岛海西-印支期花岗岩和暗色包体的Sm-Nd同位素特征 总被引:5,自引:0,他引:5
海南岛花岗岩以海西-印支期巨型花岗岩岩基为主体,面积7000km2以上。花岗岩的εNd(t)为-17.2至-5.1,Isr为0.7087,δ18O平均值10.66,属壳源型岩基。但各别岩体的εNd(t)值和tDM值均不同,反映其原岩成分的差异。花岗岩中,最大tDM为1.8Ga和1.7Ga,与该区最古老变质岩中的变质火山岩Sm-Nd全岩等时线年龄1.7Ga几乎一致,代表了该岛早期一次重要的地壳生长时期。花岗岩中暗色包体系残留体,具有低的εNd(t)值-12.8至-10.15;εSr(t)值-86至6;以及高的Sm/Nd值0.38至0.59,表明在花岗岩形成过程中熔体和残留体之间发生了较强的Sm-Nd分馏作用。 相似文献
70.
Discovery of the Early Proterozoic Basement in the Middle-Lower Reaches of Yangtze River and Its Significance 总被引:3,自引:0,他引:3
《科学通报(英文版)》1994,39(2):135-135