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  • 1
    Electronic Resource
    Electronic Resource
    Orthogneisses of the Spessart crystalline complex, Northwest Bavaria: Indicators of the geotectonic environment? (1986)
    Springer
    International journal of earth sciences 75 (1986), S. 555-568 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The orthogneisses of the Spessart crystalline complex are derived from a granitic to granodioritic magma of S-type character which must have formed by anatexis of continental crust. It intruded into a relatively shallow crustal level, 410–420 Ma ago, at the Silurian. Trace element characteristics are consistent with a post-collision geotectonic environment testifying to extensional tectonics at the end of the Caledonian era.
    Abstract: Résumé Les orthogneiss du Spessart sont dérivés d'un magma granitique à granodioritique de type S qui doit s'Être formé par anatexie de la croûte continentale. Ce magma a été intrudé dans un niveau peu profond de la croûte il y a 410–420 Ma c'est-à-dire au Silurien. La distribution des éléments en traces est en accord avec celle des granitoÏdes formés dans un contexte géodynamique de post-collision. Cette observation est en faveur d'une phase d'extension tectonique à la fin du cycle calédonien.
    Notes: Zusammenfassung Die Orthogneise des Spessartkristallins lassen sich von einem granitischen bis granodioritischen Magma von S-Typ-Charakter ableiten, das durch Anatexis kontinentaler Kruste entstanden sein mu\ und in ein relativ oberflächennahes Krustenniveau intrudierte. Die Platznahme erfolgte vor 410–420 Ma, d. h. im Silur. Die Spurenelement-Muster der Orthogneise entsprechen denen von Post-Kollisions-Granitoiden, was als Hinweis auf eine Phase der Dehnungstektonik am Ende der kaledonischen ära bewertet werden kann.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01820631
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  • 2
    Electronic Resource
    Electronic Resource
    High-pressure relics in meta-sediments intercalated with the Weissenstein eclogite, Münchberg gneiss complex, Bavaria (1991)
    Springer
    Contributions to mineralogy and petrology 107 (1991), S. 328-342 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The mineral assemblages in the eclogites and meta-sediments of the Münchberg gneiss complex suggest minimum pressures of about 15 kbar, and temperatures of 600±30° C for the eclogite-facies metamorphism. Both rock types underwent a subsequent amphibolite-facies metamorphism at almost the same temperature range. In the Weissenstein borehole the eclogites and meta-sediments show an intimate interlayering on a centimetre scale. Contacts between the two rock types are often sharp and untectonized suggesting in-situ metamorphism of the eclogites. The following features indicate that the gneisses were subjected to eclogite-facies metamorphism: 1. Phengite relics and phengite inclusions in garnet contain up to 3.45 Si per formula unit while amphibolite facies phengites have considerably lower Si-contents (3.0–3.25 p.f.u.). 2. Omphacite relics occur in the form of Na-augite (6–9 mol% jadeite)-oligoclase symplectites. 3. Garnets with up to 40 mol% of the pyrope component occur. The geological and mineral-chemical data indicate that large volumes of crustal material have been buried to depths possibly exceeding 70 km. The preservation of primary eclogitic textures as well as symplectitic textures in the presence of a fluid phase, are indicative of a rapid decompression. This would suggest a tectonic uplift (e.g. underthrusting) as is also indicated by the virtually constant temperature range during the uplift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325102
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  • 3
    Electronic Resource
    Electronic Resource
    Chloritoid-bearing metapelites associated with glaucophane rocks in western Crete, Greece (1975)
    Springer
    Contributions to mineralogy and petrology 49 (1975), S. 105-115 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In western Crete, Greece, a widespread occurrence of chloritoid-bearing metapelites with the main mineral assemblage chloritoid-phengitic white mica-Fe-rich chlorite-quartz was recorded to form the country rock of glaucophane-bearing metabasalts. Six bulk rock analyses of the metapelites conform to the compositional restrictions evaluated by Hoschek (1967) for the formation of chloritoid. Three microprobe analyses revealed chloritoid compositions low in Mg and Mn, and, consequently, high in Fe. The metamorphic grade documented in the metapelites is obviously related to a subsequent prograde metamorphism by which, in the adjacent meta-basalts, epidote is formed at the expense of lawsonite. No relict of a high-P, low-T assemblage, in part well preserved in the meta-basalts, was recognized in the chloritoid schists. The significance of the metamorphic history is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373854
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  • 4
    Electronic Resource
    Electronic Resource
    Eclogite facies relics and a multistage breakdown in metabasites of the KTB pilot hole, NE Bavaria: implications for the Variscan tectonometamorphic evolution of the NW Bohemian Massif (1992)
    Springer
    Contributions to mineralogy and petrology 112 (1992), S. 261-278 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Complex reaction textures in coronitic metagabbros and retrograded eclogites of the KTB pilot and an adjacent drilling provide evidence for a multistage metamorphic history in the Variscan basement of the NW Bohemian Massif. The eclogites show complete metamorphic recrystallization leaving no textural or mineral relics of their igneous precursors. In contrast, textural relics of the igneous protolith are still preserved in the metagabbros where the metamorphic overprint under high pressure conditions achieved only partial replacement of the initial assemblage plagioclase + augite + amphibole (+olivine or orthopyroxene?) + ilmenite to form the eclogite facies assemblage garnet + omphacite + kyanite + zoisite + quartz+rutile. The garnets in the metagabbros occur in the typical ‘necklace’ fashion at the borders between the original plagioclase and mafic phase domains. In the same rocks, omphacite formed by a topotactic reaction mechanism replacing igneous augite as well as in smaller grains at the margins of the texturally igneous clinopyroxene where it occurs without fixed orientation with respect to the relict phase. Both eclogites and metagabbros show a partial breakdown under high pressure granulite (transitional to high pressure amphibolite) facies conditions during which omphacite broke down to vermicular symplectites of diopside + plagioclase. A later pervasive medium pressure metamorphism under amphibolite facies conditions led to the development of assemblages dominated by hornblende + plagioclase+titanite: phases prevailing in the overwhelming majority of the surrounding metabasites. Subsequent vein-associated retrogression produced minerals typical of the greenschist to zeolite facies. All metamorphic stages may be represented in a single thin section but although the overall reaction sequence is apparent, the obvious disequilibrium in the rocks makes the use of conventional geothermobarometry difficult. However, calculations made by assuming an approach to domainal equilibrium show that both the eclogite facies and early breakdown occurred above 10 kb. As the metamorphic unit hosting these particular metabasites is generally characterized by pressures below 10 kb these results have important implications for understanding the tectonometamorphic evolution of the region. The relationship between the studied rocks and other units in the NW Bohemian Massif exhibiting a multistage metamorphic evolution is discussed and possible tectonic models evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310460
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  • 5
    Electronic Resource
    Electronic Resource
    Phase relations in the greenschist-blueschist-amphibolite-eclogite facies in the system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH), with application to metamorphic rocks from Samos, Greece (1998)
    Springer
    Contributions to mineralogy and petrology 132 (1998), S. 85-102 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Calculated phase equilibria among the minerals sodic amphibole, calcic amphibole, garnet, chloritoid, talc, chlorite, paragonite, margarite, omphacite, plagioclase, carpholite, zoisite/clinozoisite, lawsonite, pyrophyllite, kyanite, sillimanite, quartz and H2O are presented for the model system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH), which is relevant for many greenschist, blueschist, amphibolite and eclogite facies rocks. Using the activity-composition relationships for multicomponent amphiboles constrained by Will and Powell (1992), equilibria containing coexisting calcic and sodic amphiboles could be determined. The blueschist–greenschist transition reaction in the NCFMASH system, for example, is defined by the univariant reaction sodic amphibole + zoisite = calcic amphibole + chlorite + paragonite + plagioclase (+ quartz + H2O) occurring between approximately 420 and 450 °C at 9.5 to 10 kbar. The calculated petrogenetic grid is a valuable tool for reconstructing the PT-evolution of metabasic rocks. This is shown for rocks from the island of Samos, Greece. On the basis of mineral and whole rock analyses, PT-pseudosections were calculated and, together with the observed mineral assemblages and reaction textures, are used to reconstruct PT-paths. For rocks from northern Samos, pseudomorphs after lawsonite preserved in garnet, the assemblage sodic amphibole-garnet-paragonite-chlorite-zoisite-quartz and the retrograde appearance of albitic plagioclase and the formation of calcic amphibole around sodic amphibole constrain a clockwise PT-path that reaches its thermal maximum at some 520 °C and 19 kbar. The derived PT-trajectory indicates cooling during exhumation of the rocks and is similar to paths for rocks from the western part of the Attic-Cycladic crystalline complex. Rocks from eastern Samos indicate lower pressures and are probably related to high-pressure rocks from the Menderes Massif in western Turkey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050406
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  • 6
    Electronic Resource
    Electronic Resource
    Steady state geotherm, thermal disturbances, and tectonic development of the lower lithosphere underneath the Gibeon Kimberlite Province, Namibia (1996)
    Springer
    Contributions to mineralogy and petrology 126 (1996), S. 181-198 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Gibeon Kimberlite Province of southern Namibia comprises more than 75 group 1 kimberlite pipes and dykes. From the Gibeon Townsland 1 pipe, 38 upper mantle xenoliths (23 garnet lherzolites and 15 garnet harzburgites) were collected and minerals were analysed by electron microprobe for major elements. Pressures and temperatures of crystallisation for xenoliths with either coarse equant, porphyroclastic and mosaic-porphyroclastic textures were estimated by a number of combinations of geothermometers and geobarometers judged to be reliable and accurate for peridotites by Brey and Köhler (1990): The P-T estimates for equilibrated xenoliths agree within the errors of the methods and plot within the stability field of graphite. The P-T values for coarse equant xenoliths fall close to a geothermal gradient of about 44 mW/m2 within a very restricted pressure range. The porphyroclastic xenoliths yield similar and higher temperatures at similar depths. In these xenoliths Ca in orthopyroxene and Ca in olivine increase towards the rims and are high in the neoblasts indicating a stage of transient heating at depth. The mosaic-porphyroclastic xenolith minerals yield the highest temperatures, are unzoned and indicate internal mineral equilibrium. The depth of origin for the xenoliths from Gibeon Townsland 1 ranges from 100 to 140 km. The “cold”, coarse equant peridotites are relatively enriched garnet lherzolites with comparatively (to the “hot” peridotites) low modal orthopyroxene contents, whereas the “hot”, mosaic-porphyroclastic peridotites are depleted garnet harzburgites with high modal amounts of orthopyroxene. This is opposite to the findings for peridotites from the Kaapvaal craton where the cold peridotites are depleted harzburgites with high modal orthopyroxene and many of the hot peridotites are fertile lherzolites with low modal abundance of orthopyroxene. We present a model in which the high temperature, depleted garnet harzburgites are equated to the cold, coarse equant peridotites from the Kaapvaal craton. It is envisaged that this material was detached and transported laterally by an upwelling, deflected plume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050243
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  • 7
    Electronic Resource
    Electronic Resource
    Garnet-cordierite-biotite equilibria in the Steinach aureole, Bavaria (1971)
    Springer
    Contributions to mineralogy and petrology 32 (1971), S. 1-23 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Three garnet-biotite pairs and eleven garnet-cordierite-biotite triplets from the Steinach aureole (Oberpfalz, North-East Bavaria) were analyzed using an electron probe microanalyzer. The regional metamorphic muscovite-biotite schists contain garnets strongly zoned with Mn-Ca-rich centers and Fe-rich edges, the average composition being almandine 67 — spessartine 4 — pyrope 4 — grossular (+andradite) 25. The first contact garnet that is formed in mica schists of the outermost part of the aureole is small, virtually unzoned, and has an average composition of almandine 52 — spessartine 37 — pyrope 8 — grossular (+andradite) 3. With increasing metamorphic grade, there is a consistent trend to form garnets richer in Fe ending up with a composition almandine 84.5 — spessartine 5.5 — pyrope 7.5 — grossular (+andradite) 2.5. This trend is accompanied by a general increase in grain size and modal amount of garnet. Associated cordierites and biotites also become richer in Fe with increasing grade. While the garnets in the highest grade sillimanite hornfelses are poorly zoned, the transitional andalusite-sillimanite hornfelses contain garnets with distinct but variable zonation profiles. These facts can possibly be explained by the time-temperature relationships in the thermal aureole. In a phase diagram such as the Al′-Fe-Mg-Mn tetrahedron, the limiting mineral compositions of a four-phase volume or a three-phase triangle are fixed by T and P (the latter remaining effectively constant within a thermal aureole). Thus, in garnet-cordierite-biotite assemblages, garnet zonation should be controlled by temperature variation rather than by a non-equilibrium depletion process. Taking into account the experimental data of Dahl (1968), a zoned garnet from a transitional andalusite-sillimanite hornfels would reflect a temperature increase of about 40° C during its growth. A hypothetical P-X diagram is proposed to show semi-quantitatively the compositional variation of garnet-cordierite pairs with varying pressures (T constant).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372230
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  • 8
    Electronic Resource
    Electronic Resource
    Intrusive rocks in the ophiolitic mélange of Crete – Witnesses to a Late Cretaceous thermal event of enigmatic geological position (2000)
    Springer
    Contributions to mineralogy and petrology 139 (2000), S. 339-355 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The ophiolitic mélange in the uppermost tectonic unit of the Cretan nappe pile contains crystalline slices which consist of a low-pressure/high-temperature metamorphic sequence and synmetamorphic intrusions, ranging in composition from diorite to granite. The plutonic rocks conform to two different igneous suites, dominated by diorites in eastern, and granites in central Crete, displaying I-type and A-type characters, respectively. Some of the granites from central Crete are classified as transitional I/S-type. They are closely associated with migmatitic paragneisses. Based on major and trace element, REE, Sr- and Nd-isotope geochemistry, the mafic members of both suites are derived from a depleted mantle source. The higher concentrations of P and Ti in the mafic members of the igneous suite in central Crete and the deviant trend of the whole suite may be explained by a different mantle source or a lower degree of partial melting. In both suites, magmatic evolution was governed by fractional crystallization of amphibole/clinopyroxene, plagioclase and minor phases. In addition, mixing or mingling of compositionally different magmas is indicated for the intrusive suite of eastern Crete whereas in central Crete the magma composition was at least partially modified through assimilation of (meta)pelites. The geochemical results suggest that the plutonic rocks formed in a supra-subduction zone setting. However, a formation during continental lithospheric extension cannot be ruled out. Published and new Rb–Sr and K–Ar dates on amphiboles and biotites from intrusive rocks and their metamorphic country rocks show that the peak of the low-P/high-T metamorphism and the intrusion of the two igneous suites testify to the same thermal event of Late Cretaceous age. A similar Late Cretaceous association of metamorphic and plutonic rocks has been described from the uppermost tectonic unit in the Attic–Cycladic Crystalline Complex. Together with the Cretan occurrences, they form a small sector radiating SSW along a distance of 300 km, across the general trend of the tectonic zones in the Hellenic orogen. This N–S alignment is regarded as a primary feature which may delineate the frontier zone between the Hellenides and the Taurides. The real paleogeographic position and geodynamic significance of the Late Cretaceous low-pressure/high-temperature belt, however, remains enigmatic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100000136
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  • 9
    Electronic Resource
    Electronic Resource
    Eo-alpine metamorphism in the uppermost unit of the Cretan nappe system — Petrology and geochronology (1981)
    Springer
    Contributions to mineralogy and petrology 76 (1981), S. 351-361 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The uppermost unit of the Cretan nappe system consists of ophiolites on the top, and an ophiolitic mélange at the base. Among the various constituents of the mélange, there are slices of low-P/high-T metamorphics. They form a variegated series consisting of tholeiitic ortho-amphibolites, para-amphibolites, andalusite and sillimanite-cordierite-garnet bearing mica schists, calcsilicate rocks, and marbles. The metamorphic sequence is locally intruded by early tectonic magmatites of gabbroic, dioritic and granitic composition. Critical mineral assemblages lead to a maximum temperature of about 700° C reached during metamorphism, at a total pressure of 4–5 kilobars. K — Ar dating on 6 hornblendes, 7 biotites and 1 muscovite yielded cooling ages of 75–66 m.y. and confirmed earlier results according to which the metamorphism and related magmatism took place in Late Cretaceous times. In order to evaluate the age relationships between the hightemperature metamorphics within the ophiolitic mélange and the ophiolites, hornblendes from ultramafic and mafic rocks of the ophiolite complex were dated by the K — Ar method. Hornblende from one schistose hornblendite forming a constituent of the ophiolites proper yielded 156 m.y. and thus provides a middle Jurassic minimum age for the formation of this piece of oceanic lithosphere. Four hornblendes of calc-alkaline gabbrodiorite dikes within the ophiolite complex gave distinctly lower K — Ar dates of about 140 m.y.. The dikes probably intruded after the detachment of the ophiolites in an island-arc or continental-margin environment. As a consequence, the high-temperature metamorphics and related intrusives in the ophiolitic mélange of Crete are genetically unrelated to the overlying ophiolites. The paleogeographic position of the crystalline terrane, slices of which are now incorporated into the ophiolitic mélange is still open to discussion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375462
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  • 10
    Electronic Resource
    Electronic Resource
    Genesis of acid/basic rock associations: a case study The Kallithea intrusive complex, Samos, Greece (1985)
    Springer
    Contributions to mineralogy and petrology 90 (1985), S. 353-366 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Kallithea intrusive complex on Samos forms part of the Miocene granitoid province of the central Aegean. The complex consists of numerous composite dikes consisting of different I-type diorites, monzodiorites, (quartz) monzonites, granodiorites, and granites, as well as rare pegmatites. Within individual dikes the different rock types display various structural relationships to each other, most of which indicate that multiple intrusion was the main process responsible for the association of different rock types. Petrographical, geochemical, and Sr isotope data prove that at least some of the different magma pulses were genetically unrelated. For others, a comagmatic relationship cannot be excluded. The most spectacular feature of the composite dikes are net-veined parts in which spherical (pillow-like) to angular bodies of microdiorite are surrounded by a network of more felsic rocks of varying compositions (monzonites, granodiorites, and monzogranites). — For the microdiorite/monzogranite pairs, a formation by unmixing due to liquid immiscibility is suggested by the following facts: (a) the presence of monzogranite ocelli within the microdiorite bodies, (b) similar compositions of those minerals present in both the basic and felsic parts, (c) the enrichment of HFS elements in the basic parts and the depletion of these elements in the acid parts, (d) similar Sr isotope initial ratios. Such an origin, however, is excluded for the other net-veined parts having felsic veins of either monzonitic or granodioritic compositions. In these pairs, the HFS elements are enriched in the acid parts, common minerals may have different compositions, and Sr isotope initial ratios are different. These net-veined parts can only be explained by the model of multiple injections whereby a felsic melt intruded into a basic magma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384714
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