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Geochemistry of Picritic and Associated Basalt Flows of the Western Emeishan Flood Basalt Province, China 总被引：21，自引：1，他引：20
ZHANG ZHAOCHONG; MAHONEY JOHN J.; MAO JINGWEN; WANG FUSHENG 《Journal of Petrology》2006,47(10):1997-2019
Picritic lava flows near Lijiang in the late Permian Emeishanflood basalt province are associated with augite-phyric basalt,aphyric basalt, and basaltic pyroclastic units. The dominantphenocryst in the picritic flows is Mg-rich olivine (up to 91·6%forsterite component) with high CaO contents (to 0·42wt %) and glass inclusions, indicating that the olivine crystallizedfrom a melt. Associated chromite has a high Cr-number (73–75).The estimated MgO content of the primitive picritic liquidsis about 22 wt %, and initial melt temperature may have beenas high as 1630–1690°C. The basaltic lavas appearto be related to the picritic ones principally by olivine andclinopyroxene fractionation. Age-corrected Nd–Sr–Pbisotope ratios of the picritic and basaltic lavas are indistinguishableand cover a relatively small range [e.g. Nd(t) = –1·3to +4·0]. The higher Nd(t) lavas are isotopically similarto those of several modern oceanic hotspots, and have ocean-island-likepatterns of alteration-resistant incompatible elements. Heavyrare earth element characteristics indicate an important rolefor garnet during melting and that the lavas were formed byfairly small degrees of partial melting. Rough correlationsof isotope ratios with ratios of alteration-resistant highlyincompatible elements (e.g. Nb/La) suggest modest amounts ofcontamination involving continental material or a relativelylow-Nd component in the source. Overall, our results are consistentwith other evidence suggesting some type of plume-head originfor the Emeishan province. KEY WORDS: Emeishan; flood basalts; picrites; mantle plumes; late Permian 相似文献
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For the identification of Milleporidae in this paper four designs are given as follows:(1) According to the morphological characters of the studied materials, the computer can present a rapid way to help in identifying specimens and to answer the tpecies name at well at its synonyms.(2) The user can take the second design, if asking for synonyms, numbers and a check of the synonyms are shown on the Video Display of the micromputer.(3) If you want to know the morphological characters of a certain specics, you can take the third design, that is, input a valid species name and its morphological characters will be output automatically.(4) When asking for a valid or an invalid species of Millepora, you caa sclect the fourth design, i.e. input its Latin name and the computer will answer "it is a valid species" or "it is an invalid species and the synonym of a certain valid species". 相似文献
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