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大兴安岭中生代两类流纹岩与玄武岩的成因联系 总被引：2，自引：0，他引：2
根据地质产状和地球化学特征大兴安岭中生代流纹岩类可划分为高Ti流纹岩和低Ti流纹岩。高Ti流纹岩类与亚碱性系列玄武岩类紧密伴生 ,两者在地球化学上构成连续变异系列。低Ti流纹岩类则与碱性系列玄武岩类构成地球化学双峰态。岩相学和地球化学研究表明 ,这两类流纹岩与该区同期玄武岩类有着密切的成因联系 :起源于地幔柱亏损成分的亚碱性系列玄武岩浆经过单斜辉石、斜长石、磷灰石、锆石的分离结晶 ,形成亚碱性系列低钾玄武岩→高钾玄武岩→高Ti流纹岩演化系列 ;起源于地幔柱富集成分的碱性系列玄武岩浆侵入下地壳 ,使下地壳岩石发生部分熔融 ,形成碱性系列玄武岩 -低Ti流纹岩双峰态组合 相似文献
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A factor analysis was applied to soil geochemical data to define anomalies related to buried Pb-Zn mineralization. A favorable main factor with a strong association of the elements Zn, Cu and Pb, related to mineralization, was selected for interpretation. The median + 2MAD (median absolute deviation) method of exploratory data analysis (EDA) and C-A (concentration-area) fractal modeling were then applied to the Mahalanobis distance, as defined by Zn, Cu and Pb from the factor analysis to set the thresholds for defining multi-element anomalies. As a result, the median + 2MAD method more successfully identified the Pb-Zn mineralization than the C-A fractal model. The soil anomaly identified by the median + 2MAD method on the Mahalanobis distances defined by three principal elements (Zn, Cu and Pb) rather than thirteen elements (Co, Zn, Cu, V, Mo, Ni, Cr, Mn, Pb, Ba, Sr, Zr and Ti) was the more favorable reflection of the ore body. The identified soil geochemical anomalies were compared with the in situ economic Pb-Zn ore bodies for validation. The results showed that the median + 2MAD approach is capable of mapping both strong and weak geochemical anomalies related to buried Pb-Zn mineralization, which is therefore useful at the reconnaissance drilling stage. 相似文献
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The Sinuiju Formation in Paekto-dong, Sinuiju City in the Democratic People's Republic of Korea has yielded Mesozoic nonmarine bivalve fossils, which is the first occurrence of such in the DPRK. Based on these fossil specimens, a new Cretaceous bivalve assemblage, the Arguniella yanshanensis-Sphaerium anderssoni Assemblage is erected. This assemblage includes Arguniella yanshanensis, A. lingyuanensis and Sphaerium anderssoni and can be compared with the Jehol Biota. The age of the Sinuiju Formation is also clarified and on the basis of the bivalves and the presence of a Eosestheria–Ephemeropsis–Lycoptera(E–E–L) assemblage, the formation is not Upper Jurassic, but Lower Cretaceous in age. 相似文献
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The Petrology and Geochemistry of Volcanic Rocks on Jeju Island: Plume Magmatism along the Asian Continental Margin 总被引：2，自引：0，他引：2
TATSUMI YOSHIYUKI; SHUKUNO HIROSHI; YOSHIKAWA MASAKO; CHANG QING; SATO KEIKO; LEE MOON WON 《Journal of Petrology》2005,46(3):523-553
The incompatible element signatures of volcanic rocks formingJeju Island, located at the eastern margin of the Asian continent,are identical to those of typical intraplate magmas. The sourceof these volcanic rocks may be a mantle plume, located immediatelybehind the SW Japan arc. Jeju plume magmas can be divided intothree series, based on major and trace element abundances: high-aluminaalkalic, low-alumina alkalic, and sub-alkalic. Mass-balancecalculations indicate that the compositional variations withineach magma series are largely governed by fractional crystallizationof three chemically distinct parental magmas. The compositionsof primary magmas for these series, using inferred residualmantle olivine compositions, suggest that the low-alumina alkalicand sub-alkalic magmas are generated at the deepest and shallowestdepths by lowest and highest degrees of melting, respectively.These estimates, together with systematic differences in traceelement and isotopic compositions, indicate that the upper mantlebeneath Jeju Island is characterized by an increased degreeof metasomatism and a change in major metasomatic hydrous mineralsfrom amphibole to phlogopite with decreasing depth. The originalplume material, having rather depleted geochemical characteristics,entrained shallower metasomatized uppermost mantle material,and segregated least-enriched low-alumina alkalic, moderatelyenriched high-alumina alkalic, and highly enriched sub-alkalicmagmas, with decreasing depth. KEY WORDS: Jeju Island; magma genesis; mantle plume; subcontinental mantle 相似文献
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