排序方式: 共有65条查询结果,搜索用时 280 毫秒
21.
内蒙古银都银铅锌多金属矿床成矿流体特征及成矿年代学研究 总被引:6,自引:0,他引:6
内蒙古银都银铅锌多金属矿床属于特大型银矿床, 经研究, 确定成矿过程经历了早、中、晚 3 个阶段, 分别形成以闪锌矿-磁黄铁矿-黄铜矿、方铅矿-磁黄铁矿、萤石- 白云母-碳酸盐为代表的矿物组合。其中, 早阶段为锌、铜的主成矿阶段, 中阶段则是银铅锌的成矿阶段, 晚阶段矿化较弱。激光拉曼显微探针分析表明成矿流体为 H2O-CO2-CH4-NaCl 体系。包裹体研究显示成矿流体具有低盐度( 2%~5% ) 、低密度( 0. 72 ~0. 88 g/ cm3 ) 的特点, 成矿温度随着成矿流体的演变, 逐渐降低, 早、中、晚阶段分别为 340. 5℃, 282. 4℃及260. 3℃, 成矿压力为37 ~74 MPa, 成矿深度为 3. 7 ~7. 0 km。经对萤石- 白云母-碳酸盐阶段白云母的激光探针 40Ar-39Ar年代学测定, 确定成矿年代为 135±3 Ma, 为白垩纪早期。 相似文献
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An Sm-Nd isotopic dating study of the Archean Kongling Complex in the Huangling area of the Yangtze Craton 总被引:2,自引:0,他引:2
Sm Nd isotopic compositions of associated amphibolites, TTG gneisses and granitic gneisses from the Archean Kongling Complex of the Yangtze Craton, South China are systematically analyzed. The results show that the amphibolites and TTG gneisses have a similar age of ca. 2 700 Ma, which well agrees with zircon U Pb dating of previous studies. However, their ε Nd ( t ) are different, suggestive of possible dissimilarity in source composition. 相似文献
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Hans W. LINDERHOLM 《科学通报(英文版)》2011,(Z2)
A tree-ring-width chronology of Pinus tabulaeformis from Kalaqin, Inner Mongolia was developed using modern dendroc hronological techniques. Based on the results of correlation function analysis, the total precipitation from the previous August to current July was reconstructed for 1771-2008 AD with an explained variance of 49.3%. The reconstruction correlated well with the dryness/wetness series derived from historical documents, as well as the precipitation reconstruction of the Chifeng-Weichang region. T... 相似文献
24.
相对年代与绝对年代之间的区别,并不在于时间精确度的高低而在于所选参照点的不同。绝对年代必须以已知时间点或时间段为参照点,而相对年代的参照点则可能是未知时间点或时间段。 相似文献
25.
汤军 《邵阳高等专科学校学报》2010,(5):119-123
永州以其独特的地理位置,承接了一批又一批的流寓之人,而两宋时期尤为突出,此间贬于永者达47人之多。这一现象反映了两宋"以文治特著"的社会政治状况,同时也造就了永州独特的地方文化。 相似文献
26.
刘仁江 《湘潭师范学院学报(自然科学版)》2000,21(2):78-81
古今字和通假字,一直是传统语言文字学两个界限不清的术语。历代语言学家对两者的含义及区别曾作过一些有益探索,但至今尚未形成一个圆满而统一的答案。通过从字形、意义、时间三个角度来正确区分两者,澄清人们对两者的错误认识,从而使两个术语趋向科学化、标准化。 相似文献
27.
商王征伐人方在十祀(10年),联系3件其铜,证明帝辛(即商纣)十祀在公元前1154年或1092年。构建帝辛历谱的初步框架。 相似文献
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tmRNA,a combination of a tRNA-related fragment and a small mRNA fragment,was confirmed as the integration site of genomic islands(GIs).Using sequence alignment and comparative genomics,68 GIs associated with tmRNA genes were identified among 13 genera of Enterobacteriaceae.Among them,53 GIs were found in Escherichia coli and Salmonella enterica.Among these 53 GIs,tandem GIs were verified in eight S.enterica and two E.coli chromosomes.The downstream regions of the tmRNA genes in most of the E.coli and S.enterica chromosomes include one GI or tandem GIs region and a remnant variable region distal to the tmRNA.The chronology of integration of tandem GIs into the genome indicated that GIs farther from the tmRNA were incorporated into the genome earlier than those nearer from the tmRNA.The integrases of the tmRNA gene-associated GIs can be further categorized into three subtypes:HP1 integrases,PhiCTX integrases,and P4 integrases,which are the most predominant.The GIs were first integrated into the chromosome by the P4 integrase,subsequently by the PhiCTX integrase,and finally by the HP1 integrase.Thus,the tmRNA gene is an important site for investigating the genetics and evolution of tandem GIs. 相似文献
30.
相对年代与绝对年代之间的区别,并不在于时间精确度的高低而在于所选参照点的不同.绝对年代必须以已知时间点或时间段为参照点,而相对年代的参照点则可能是未知时间点或时间段. 相似文献