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Rare-earth element (REE) abundances and major chemical compositionsof six late Palaeozoic geosynclinal basalts at Nakaoku, theKii peninsula, southwest Japan are discussed from the generalviewpoint of geosynclinal basalt magma. The REE patterns ofbasalt samples are smoothly and progressively enriched relativeto Leedey chondrite. The lighter REE are considerably fractionated,whereas concentrations of heaviest REE remain approximatelyconstant. Each fractionation pattern probably corresponds toresidual liquid at different stages during the solidificationof magma in depth. The partition coefficients of REE betweenmagma (i.e. liquid) and crystallizing solid can be calculated,assuming that the partition coefficient of Lu is nearly unity,because the Lu contents show little change among samples. Byusing the REE contents and partition coefficients, solidifiedpercentages for various stages of the magmatic process werecalculated; the percentage shows a good correlation with thesolidification index calculated from major chemical compositions.Some major compositions are also correlative with the solidifiedpercentage calculated from REE data. The Nakaoku basalts when plotted on a silica-alkali diagramshow a change of type from tholeiitic to alkali basalt duringthe solidifying process in depth. These petrochemical aspectsof the Nakaoku basaltic body are compatible with the resultsof experimental melting study at moderate pressures of about10 kb carried out by Green & Ringwood (1967). The spatialcoexistence of tholeiitic and alkali basalt in the Japaneselate Palaeozoic geosyncline found by Sugisaki & Tanaka (1971b)and disclosed here in the Nakaoku basalts, is not uncommon phenomenon. 相似文献
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Kohei TANAKA Lü Junchang Yoshitsugu KOBAYASHI Darla K. ZELENITSKY XU Li JIA Songhai QIN Shuang TANG Min’an 《《地质学报》英文版》2011,85(1):66-74
Here, we examine 145 dinosaur eggshells from a new fossil locality in the Qiupa Formation (Upper Cretaceous) of the Luanchuan area in western Henan Province, China. The eggshells display elongatoolithid macro- and microstructures, including ridges and nodes on the outer surface, two ultrastructural layers, and an undulatory boundary between the mammillary and continuous layers. A phylogenic analysis shows that the Luanchuan eggshells belong to the ooclade Elongatoolithidae. Within Elongatoolithidae, the thickness ratio of the mammillary layer to the entire eggshell, and the porosity of the Luanchuan eggshells are comparable to the oogenera Macroolithus and Elongatoolithus. There is no direct evidence for the taxonomic identity of the Luanchuan eggshells; however, they were likely laid by oviraptorids based on their phylogenetic position and their similarities with known oviraptorid eggs. 相似文献
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RUILIN WEN JULE XIAO ZHIGANG CHANG DAYOU ZHAI QINGHAI XU YUECONG LI SHIGERU ITOH 《Boreas: An International Journal of Quaternary Research》2010,39(2):262-272
Wen, R. L., Xiao, J. L., Chang, Z. G., Zhai, D. Y., Xu, Q. H., Li, Y. C. & Itoh, S. 2009: Holocene precipitation and temperature variations in the East Asian monsoonal margin from pollen data from Hulun Lake in northeastern Inner Mongolia, China. Boreas, 10.1111/j.1502‐3885.2009.00125.x. ISSN 0300‐9483. Quantitative palaeoclimatic reconstruction with the weighted averaging partial least squares method was applied to the pollen profile from Hulun Lake in northeastern Inner Mongolia. The data provide a detailed history of variations in precipitation and temperature over the northeastern margin of the East Asian summer monsoon during the Holocene. A warm and dry climate prevailed over the lake region until c. 8000 cal. BP. During the period c. 8000–4400 cal. BP, precipitation increased markedly and temperature gradually declined. The interval between c. 4400 and 3350 cal. BP was marked by extremely dry and relatively cold conditions. Precipitation recovered from c. 3350 to 1000 cal. BP, with temperatures rising c. 3350–2050 cal. BP and dropping c. 2050–1000 cal. BP. During the last 500 years, the climate of the lake region displayed a general trend of warming and wetting. While Holocene temperature variations in the mid‐high latitude monsoonal margin were controlled by changes in summer solar radiation in the Northern Hemisphere, they could also be related to the strength of the East Asian summer monsoon. The lack of precipitation during the early Holocene could be attributed to the weakened summer monsoon resulting from the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoonal precipitation during the middle to late Holocene would have been associated with the ocean–atmosphere interacting processes occurring in the western tropical Pacific. 相似文献
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Shigeru TERASHIMA Shiro ITOH Masumi UJIIE Hikari KAMIOKA Tsuyoshi TANAKA Hitoshi HATTORI 《Geostandards and Geoanalytical Research》1993,17(1):1-4
Three new rock reference samples, Rhyolite JR-3, Gabbro JGb-2 and Hornblendite JH-1 have been prepared by the Geological Survey of Japan for collaborative studies on their chemical composition. Twenty-eight major, minor and trace elements were determined and presented. The results of homogeneity tests showed that all elements are considered to be distributed homogeneously in each reference sample. Geological and mineralogical characteristics are also described. 相似文献
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