共查询到20条相似文献，搜索用时 328 毫秒
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Peter J. Webster 《Quaternary Research》1981,16(1):123
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F.L. Staplin 《Earth》1979,14(4):364-366
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Robert L. Cullers Subramanian Ramakrishnan Pieter Berendsen Tom Griffin 《Geochimica et cosmochimica acta》1985,49(6):1383-1402
Lamproite sills and their associated sedimentary and contact metamorphic rocks from Woodson County, Kansas have been analyzed for major elements, selected trace elements, and strontium isotopic composition. These lamproites, like lamproites elsewhere, are alkalic (molecular ), are ultrapotassic , are enriched in incompatible elements (LREE or light rare-earth elements, Ba, Th, Hf, Ta, Sr, Rb), and have moderate to high initial strontium isotopic compositions (0.7042 and 0.7102). The silica-saturated magma (olivine-hypersthene normative) of the Silver City lamproite could have formed by about 2 percent melting of a phlogopite-garnet lherzolite under high ratios in which the Iherzolite was enriched before melting in the incompatible elements by metasomatism. The Rose Dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain. Significant fractional crystallization of phases that occur as phenocrysts (diopside, olivine, K-richterite, and phlogopite) in the Silver City magma and that concentrate Co, Cr, and Sc are precluded as the magma moved from the source toward the surface due to the high abundances of Co, Cr, and Sc in the magma similar to that predicted by direct melting of the metasomatized Iherzolite.Ba and, to a lesser extent, K and Rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone. The Silver City lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected. 相似文献
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Benjamin N. Powell 《Tectonophysics》1975,27(3):295-297
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Petrogenesis and Experimental Petrology of Granitic Rocks, by Wilhelm Johannes and Francois Holtz. Minerals and Rocks, Vol. 22 (Editors P. J. Wyllie, A. El Goresy, W. von Engelhardt and T. Hahn). Springer-Verlag, Berlin, 1996. 335 pp. DM 168. 
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下载免费PDF全文 Granite petrology has achieved significant progress during thelast four decades. More and more components have been addedto the pure system Ab–Or–Qz–H2O to ensurethat the results obtained from the experiments reflect naturalprocesses to a higher degree. The significance of water forthe formation, intrusion, and crystallization of granitic magmasforms an 相似文献
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Ultrapotassic basaltic lavas erupted 3.4–3.6 m.y. ago(K/Ar) in the central Sierra Nevada and originated by partialmelting of a phlogopite-enriched, garnet-bearing upper mantlesource. Ultrapotassic basanites (K2O: 5–9 per cent), whichare spatially related to contemporaneous potassic olivine basalts(K2O: 3–5 per cent) and alkali olivine basalts (K2O: 1–3per cent), contain the K2O-bearing minerals phlogopite, sanidine,and leucite as well as olivine, diopside, apatite, magnetite,and pseudobrookite. The presence and modal abundance of theK2O-bearing minerals closely reflects the east to west increasein K2O throughout the basaltic suite. Many lines of evidence support the derivation of the ultrapotassicbasanites and the related basalts from an upper mantle source:TiO2 in phlogopite phenocrysts and groundmass crystals, 2–3and 7–9 per cent respectively, support phlogopite phenocrystcrystallization at high pressure, whole rock Mg values (100Mg/Mg + 0.85 Fe) range from 66–78, phlogopite-rich pyroxeniticand periodotitic nodules are included in some flows, and geobarometriccalculations indicate depths of generation at 100–125km. Also, model calculations show that the major, rare earth,and trace elements, except for Ba, Rb, and Sr, can be accuratelygenerated by 1.0–2.5 per cent melting of a phiogopite-and garnet-bearing clinopyroxene-rich upper mantle source. Partialmelting occurred after a general upper mantle enrichment beneaththe Sierra Nevada, the phlogopite- and clinopyroxene-rich sourceof the ultrapotassic lavas being the extreme result of the enrichmentprocess. Clinopyroxene enrichment of the upper mantle probablyoccurred by introduction of a partial melting fraction intothe upper mantle source areas. Enrichment of the upper mantlein the alkali and alkali-earth elements was not accomplishedby a partial melt, but resulted from influx of a fluid phaserich in Ba, K, Rb, Sr, and, probably, H2O The continuous rangein K2O of the erupted lavas implies that the upper mantle enrichmentis a cumulative process. The inverse relationship in the SierraNevada between uplift and the K2O content of the erupted basaltsimplies that a critical relationship may exist between upliftand upper mantle enrichment. 相似文献
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《Quaternary Science Reviews》2007,26(11-12):1690-1691
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