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  • 1980-1984  (11)
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Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Uranium in peridotite inclusions in basalts from Hoggar (Southern Algeria) (1984)
    Springer
    Bulletin of volcanology 47 (1984), S. 627-634 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Abundances of U have been determined in minerals of the spinel peridotite xenoliths in basaltic rocks from Hoggar (Southern Algeria) by the fission-track method. Olivine and spinel have the lowest U abundances (∼ 0.10–0.13 ppm) followed by orthopyroxene (∼ 0.22–0.24 ppm). The clinopyroxene has a large variation of U (0.23–0.74 ppm). The contents of U in amphibole are within the range of those of clinopyroxene (∼ 0.30–0.37 ppm). Although most of the U in the xenoliths is homogeneously distributed in the major rock-forming minerals, the whole-rock U abundances are at least twice as high as estimates of the upper mantle. The high contents of U even in rocks without amphibole is probably due to metasomatism by a fractionated fluid phase which took place before or during the recrystallization. The host basaltic rocks are not genetically related to the spinel peridotite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01961231
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  • 2
    Electronic Resource
    Electronic Resource
    Geochemistry and petrogenesis of late proterozoic volcanic rocks from north-western Africa (1980)
    Springer
    Contributions to mineralogy and petrology 73 (1980), S. 375-388 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Upper Proterozoic volcanism of northwestern Africa is characterized by the predominance of calc-alkaline rocks. Volcanics with tholeiitic affinities and alkali basalts are rare. The geochemistry and the relative proportions of calc-alkaline rocktypes in the Silet zone (Algeria) and the Ouarzazate formation (Morocco) are similar to those of recent island arc suites where basalts are most abundant while in the Tassendjanet and Gara Akofo zones (Algeria) they resemble contintal margin volcanic suites with a predominance of andesites. The volcanic rocks have undergone low-grade metamorphism which strongly affected alkali and alkali-earth elements and also to a smaller degree, the less mobile elements such as REE, Zr, Hf, Nb, and P. The geochemistry of the calc-alkaline rocks point to a complex origin involving low-pressure fractional crystallization, crustal contamination and derivation from a source already enriched in LILE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376630
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  • 3
    Electronic Resource
    Electronic Resource
    Geochemistry of an ophiolitic complex from New Caledonia (1981)
    Springer
    Contributions to mineralogy and petrology 76 (1981), S. 77-83 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ophiolites of New Caledonia are composed of ultramafics overlain by mafic rocks, all of which were affected by low P metamorphism. The mafic rocks studied (gabbroic cumulates, and basaltic flows and dikes) from Montagne des Sources are similar to recent mid-ocean ridge rocks. They are olivine-normative with Mg/Mg+Fe2+ ratios ranging from 0.69 in lavas to 0.90 in gabbroic cumulates and show tholeiitic fractionation trends such as a negative correlation of Ti and V with the Mg/Fe ratio. The lavas have a flat REE pattern with a slight depletion of light REE and a La/Yb ratio 〈2. The dikes have three different types of REE patterns. The first type is nearly parallel to that of lavas, the second one is enriched in LREE (La/Yb∼4) and the third type with the lowest REE contents and a distinct LREE depletion is similar to that of cumulitic pyroxene gabbro. The variations in chemical compositions of the mafic rocks can be accounted for by the dynamic partial melting process of Langmuir et al. (1977). In agreement with structural and tectonic observations, the geochemical data suggests that the ophiolites were formed during the spreading of a mid-ocean ridge with a spreading half-rate of about 1 cm/ year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373686
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamic melting of proterozoic upper mantle: Evidence from rare earth elements in oceanic crust of Eastern Newfoundland (1980)
    Springer
    Contributions to mineralogy and petrology 72 (1980), S. 165-173 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Rare Earth Element (REE) data confirm earlier suggestions from major and trace elements that the Proterozoic Burin Group in the southwestern Avalon Zone is similar to modern oceanic tholeiites, and also exhibit a systematic evolution through the sequence. The Group forms a 60-km long belt consisting of four formations of pillowed basalt, two of subaqueous volcaniclastic and minor stromatolitic sediments and pyroclastics, and a thick gabbro-quartz diorite sill, with a total thickness of about 5000 m. Basalts of the oldest formation are enriched in light (LREE) with a chondrite-normalized pattern similar to alkali basalts. REE patterns through the rest of the sequence can be matched by those of modern ocean basins, with a steady decrease in total REE and a distinct depletion in LREE at the top of the sequence. REE patterns of the gabbroic sill are similar to those of oceanic gabbros, with LREE depletion and a small positive Eu anomaly. This evolutionary pattern can be interpreted as the result of progressive ‘dynamic’ partial melting and depletion of a single mantle source region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399476
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  • 5
    Electronic Resource
    Electronic Resource
    Geochemistry of the Adamello massif (northern Italy) (1982)
    Springer
    Contributions to mineralogy and petrology 80 (1982), S. 41-48 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Tertiary Adamello massif, outcropping over an area of more than 550 km2 in the southern Alps (northern Italy) is composed mainly of granitoid rocks (granodiorite, tonalite, quartz diorite) with minor amounts of diorite and gabbro. The major and trace element composition of these rocks is comparable to calc-alkaline volcanic rocks of continental margins. The granitoid rocks display spatial and temporal variations in their composition, particularly in Na, P, Sr, La, Nb and Y contents and 87Sr/86Sr ratios. The variations were probably produced by concurrent contamination/wall-rock assimilation and fractional crystallization of high-alumina basaltic magma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376733
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  • 6
    Electronic Resource
    Electronic Resource
    Geochemistry of Precambrian ophiolites from Bou Azzer, Morocco (1984)
    Springer
    Contributions to mineralogy and petrology 87 (1984), S. 43-50 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Upper Proterozoic ophiolite complex of Bou Azzer, Morocco, includes ultramafic rocks, cumulate gabbros, sheeted dykes, pillow lavas and diorite-quartz diorite intrusions and an overlying volcano-sedimentary sequence. The gabbroic cumulates, basaltic flows and dykes have compositions similar to recent ocean-floor rocks (N- and/or T-type). Among other features, they have comparable light REE-depleted patterns and relations of Ti-Zr and La-Nb. Although fractional crystallization played an important role in the evolution of these rocks, the large variations in their chemical compositions require generation from a heterogeneous upper mantle source and/or by a dynamic partial melting process. Diorites, quartz diorites and the volcanic rocks of the overlying sequence are calc-alkaline, genetically unrelated to the tholeiitic suite and indicative of an island arc setting. A possible tectonic model for the ophiolite complex is a marginal basin just behind a still active island arc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371401
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  • 7
    Electronic Resource
    Electronic Resource
    Petrology and geochemistry of granulite xenoliths from Central Hoggar (Algeria) — Implications for the lower crust (1982)
    Springer
    Contributions to mineralogy and petrology 79 (1982), S. 68-75 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Granulitic xenoliths, enclosed in Neogene alkali basalts from the Atakor and Adrar N'Addjer volcanic massifs in Central Hoggar, southern Algeria, include mafic metaigneous and felsic metasedimentary rocks. The main mineral phases of metaigneous xenoliths are plagioclase and pyroxenes whereas quartz, feldspars, sillimanite, garnet and sapphirine occur in metasedimentary granulites. The metaigneous xenoliths represent a magmatic sequence of cumulitic and non-cumulitic rocks which resembles gabbroic bodies associated with anorthosites and has calc-alkaline affinities. Similar types and distributions of granulitic xenoliths are widespread and are probably characteristic of the lower crust in general, suggesting its homogeneity on a large scale but heterogencity on a local scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376962
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  • 8
    Electronic Resource
    Electronic Resource
    Geochemistry of ophiolites from the Chamrousse complex (Belledonne Massif, Alps) (1982)
    Springer
    Contributions to mineralogy and petrology 78 (1982), S. 379-388 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ophiolite complex of Chamrousse (Belledonne Massif, Alps), consists of mafic to ultramafic cumulates and non-cumulates metamorphosed to amphibolite facies grade. The non-cumulitic rocks are similar in chemical composition to recent ocean-floor olivine tholeiites (both N-type and enriched P-type). The distribution of lithophile elements shows that the non-cumulitic rocks represent several magmas of different parentage. The character of the magmas varies according to the time of emplacement. Geological and geochemical data suggest that the Chamrousse complex was formed at a spreading oceanic ridge. The dynamic partial melting of an upper mantle diapir generated tholeiitic melt which decreased in amount and in REE contents. The first melt, enriched in light REE, was generated along the axis of the ridge while the second batch of melt, of lesser quantity and slightly depleted in light REE, was emplaced on the flank of the ridge. The third melt formed cross-cutting dikes with REE abundances typical of N-type (strongly light REE depleted) mid-ocean ridge basalts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375200
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  • 9
    Electronic Resource
    Electronic Resource
    The geochemistry and petrogenesis of an ophiolitic sequence from Pindos, Greece (1980)
    Springer
    Contributions to mineralogy and petrology 74 (1980), S. 189-200 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ophiolites of Northern Pindos have been studied in a section close to the village of Perivoli (Grevena District). The section comprises cumulus rocks ranging from ultramafics to gabbros, overlain by dolerites (non-cumulus microgabbro) capped by thick frequently pillowed lava flows. The sequence is cut by basaltic dykes. While the cumulus rocks and the dolerites are mostly fresh, the lavas and dykes are strongly transformed. Major and trace element (Ni, Cr, Sc, Y, Zr, Nb, Sr, Ba, Zn, Cu, V, Li) data are presented for selected samples from the sequence. For some elements, the volcanic/subvolcanic rocks (flows, dykes, dolerites) exhibit wide chemical characteristics which are considered to mainly reflect variations within the parent magmas. Some lavas appear to be closely comparable with the present-day ocean-floor basalts, while other flows and most of the dykes are strongly depleted in some “incompatible” elements and are similar to some rocks from immature island arcs. The dolerites have transitional chemical features. The Pindos lavas differ from Western Mediterranean ophiolites in that the former have lower Ti,P,Zr,Y, higher Fe tot. and normally higher Ti/Zr ratio. The volcanic/subvolcanic rocks from Pindos have been derived from separate magmas. Some lavas were possibly produced by variable partial melting of an already depleted mantle source, while the lavas exhibiting ocean-floor affinity were probably generated by partial melting of a less depleted source. The wide chemical variations of the Pindos lavas cannot be easily explained by an ocean-ridge system. An “island arc-marginal basin system” could better account for the observed chemical features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01132004
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  • 10
    Electronic Resource
    Electronic Resource
    Geochemistry and petrogenesis of ophiolites from Northern Pindos (Greece) (1984)
    Springer
    Bulletin of volcanology 47 (1984), S. 39-46 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ophiolitic complex of Northern Pindos (Greece) contains ocean-floor basalts and low-Ti mafic rocks. The former rocks are similar to recent mid-ocean ridge basalts with a light REE depletion and a La/Yb ratio 〈 2. The low-Ti rocks resemble boninites in their high Mg and very low Ti and Zr contents and in their REE patterns which have convex-downwards shape with a slight light REE enrichment. However, their Zr/Ti, Ti/V and Zr/Y ratios are lower than in boninites. Both rock-types could be generated by dynamic partial melting of a rising upper mantle diapir. Slight enrichment in light REE, Sr, Rb and Ba in low-Ti rocks could be the result of either metasomatic or alteration processes. Although a subduction zone origin of the sequence is possible, the geochemical data do not necessarily imply such a setting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01960539
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