fic magmas: evidence from a neral phases are olivine, clinopyroxene, Fe–Ti oxides, amphibole, plagioclase and alkali feldspar. Quartz occurs in some samples as a late magmatic phase. Liquidus temperatures of olivine-bearinga relative enrichment of LIL elements with Ba peaks andNb troughs. Clinopyrox...
| Main Authors: | , , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2003
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.548.6756 http://homepages.uni-tuebingen.de/wolfgang.siebel/pdffiles/halama_2004.pdf |
| Summary: | fic magmas: evidence from a neral phases are olivine, clinopyroxene, Fe–Ti oxides, amphibole, plagioclase and alkali feldspar. Quartz occurs in some samples as a late magmatic phase. Liquidus temperatures of olivine-bearinga relative enrichment of LIL elements with Ba peaks andNb troughs. Clinopyroxenes show a general enrichment in REE relative to chondritic values with variable slightly positive to prominent negative Eu anomalies. Two of the dikes were dated with Sm–Nd three-point isochrons at 1190F 44 and 1187F 87 Ma, respectively. Initial 87Sr/86Sr ratios of mafic mineral separates range from 0.70289 to 0.70432 and initial eNd values vary from + 0.3 to 10.7. Whole-rock initial 187Os/188Os ratios are highly variable including very radiogenic values of up to 7.967. d18Ov-smow values of separated clinopyroxene and amphibole range from + 5.2x to + 6.2xand fall within the range of typical mantle-derived rocks, although mixing with a lower crustal component is permitted by the data. Using energy-constrained assimilation-fractional crystallization (EC-AFC) modeling equations, the Sr–Nd isotope data of the more radiogenic samples can successfully be modeled by addition of up to 10 % lower crustal granulite-facies Archean gneisses as contaminants. The Os isotopic data also suggest the involvement of old radiogenic crust. In accordance with seismic data, we conclude that a wedge of Archean crust extends fromWest Greenland further to the south below the present erosion level. D 2004 Elsevier B.V. All rights reserved.The rocks haveMgO contents < 6wt.%withMg # between 5samples range between 1120 and 1145 jC and solidus temperatures are 850–930 jC. Calculated silica activities are highly variable between 0.53 and unity. Oxygen fugacities vary from 3 to + 1 log units relative to the fayalite–magnetite–quartz buffer. 3 and 17. Primitivemantle-normalized trace element patterns showfrom gabbroic to syenitic in composition. Major magmatic mipetrological, geochemical and Sr–Nd–Os–O isotopic study of the |
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