Chondritic osmium isotopic composition of late Archean convecting upper mantle:Evidence from Zunhua

来源 :科学通报(英文版) | 被引量 : 0次 | 上传用户:johndovl1
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
Podiform chromite deposits are a characteristic feature of the mantle sequences of harzburgitic ophiolites. The chromites usually have very low Re and high Os contents, which makes it the most resistant phase remaining from the primary magmatic history of the ultramafic sections of ophiolites. The podiform chromite is one of the robust indicators of initial Os isotopic compositions of the ophiolites where podiform chromites were derived from, which provides strong evidence for the origin and evolution of oceanic lithosphere. The Re and Os contents and the Os isotopic compositions of seven podiform chromitites from Zunhua ophiolitic mélange belt, North China are reported in this study. The Re contents range from 0.019 to 0.128 ng/g, Os from 8.828 to 354.0 ng/g, and the 187Os/188Os ratio from 0.11003 to 0.11145. Three massive chromitites among the sample set have very high Os contents (>300 ng/g), and their 187Os/188Os ratios range from 0.11021 to 0.11030, averaging 0.11026 ± 0.00005 (σ), equivalent to a γOs = -0.12 ± 0.06 at 2.6 Ga, which means that the Os isotopic composition of convecting upper mantle is chondritic in late Archean. It is the Os isotopic composition of podiform chromitites that are derived from the oldest ophiolite in the world till now.
其他文献
In the context of historical climate records of China and early meteorological measurements of Beijing discovered recently in Europe, a study is undertaken on t
Grain size analysis was undertaken for the 2-cm interval sub-samples of eight short cores collected along the Zhoushan-Jinshanwei transect in Hangzhou Bay, usin
In Yuka-Luofengpo area of the north Qaidam Mountains, eclogitic metapelites are recognized. The metapelites enclosed lenses of eclogites, and locally intercalat
Paleomagnetic study on the Cenozoic volcanic rocks from the Tuoyun Basin of the southwest Tien Shan indicates that most samples could isolate a stable character
权力等级作为中国古代重要的等级秩序,在中国古代建筑中多有体现,这主要表现在建筑的空间布局,"数"的限定和装饰的颜色等方面.对于这些的研究可为现代建筑功能的拓展提供一定
Under the impact of climatic warming, the glaciers in the High Asia in China have been retreating continuously with negative glacial mass balance in recent seve
不论是国际国内,新闻官司屡见不鲜。从国情实际看,一些新闻官司的产生有多种原因,包括我们新闻工作者原因在内。对此,我们必须采取相应对策,本文提出一些建议。 Both domest
简述了政务窗口工作的特点,提出了提高窗口服务水平的措施,以期为政务窗口建设提供依据.
The southern and northern parts of the eastern margin of the Jiangnan Upheaval, located in the northeast of Jiangxi Province (Gandongbei) and the south of Anhui