A sherd found at the Iron Age settlement of Kristineberg in Malmo, Scania, Sweden, carried remnan... more A sherd found at the Iron Age settlement of Kristineberg in Malmo, Scania, Sweden, carried remnants of an unusual silvery layer on the outer surface. It was suggested that this consisted of graphite, because of its macroscopic appearance and the existence of contemporary parallels on the continent. SEM analysis confirmed that the layer was pure carbon. Although organic carbon cannot be completely excluded, there were no other traces of use on the vessel and nothing to indicate coating or sealing of the vessel with materials such as tar or resin.
TEKTITES. A. Ocampo, J. Gómez, J. A. García, A. Lindh, A. Scherstén, A. Pitzsch, L. Page, A. Ishi... more TEKTITES. A. Ocampo, J. Gómez, J. A. García, A. Lindh, A. Scherstén, A. Pitzsch, L. Page, A. Ishikawa, K. Suzuki, R. S. Hori, Margarita Buitrago and José Abel Flores, D. Barrero, V. Vajda; NASA HQ, Science Mission Directorate, US (aco@nasa.gov), Colombian Geological Survey, Bogotá, Colombia; Universidad Libre, Sociedad astronomica ANTARES, Cali, Colombia; Department of Geology, Lund University, Sweden; MAX–lab, Lund University, Sweden/ Helmholtz Zentrum Berlin, Institute Methods and Instrumentation for Synchrotron Radiation Research, Berlin, Germany; Department of Earth Science & Astronomy, The University of Tokyo, Japan; IFREE/SRRP, Japan Agency for Marine–Earth Science and Technology, Yokosuka, Japan; Department of Earth Science, Ehime University, Japan; Department of Geology, University of Salamanca, Spain. Consultant geologist, Bogotá, Colombia; Department of Palaeobiology, Swedish Museum of Natural History, Sweden
Abstract The Mueilha granite pluton is one of the rare-metals bearing peraluminous granitic pluto... more Abstract The Mueilha granite pluton is one of the rare-metals bearing peraluminous granitic plutons in the Arabian-Nubian Shield. It represents the apical part of a highly evolved magma chamber emplaced at a shallow level subsequent to the post Pan-African orogeny. The pluton can be seen as a highly leucocratic medium-grained albite/oligoclase framework infilled with quartz, K-feldspar and muscovite that are variably overgrown by K-feldspar, muscovite, quartz and topaz megacrysts. The increasing number and size of the K-feldspar megacrysts at the expense of the whitened albite/oligoclase framework imparts variably red color to the Mueilha granite. Contacts between the milky white and red granites are usually gradational, but may be locally sharp or may form narrow transition zones resulting from abrupt variations in texture and lithology. Textural relations indicate an initial stage of hydrothermal albitization of magmatic plagioclase and crystallization of topaz megacrysts resulting from infiltration of Na-rich fluorine bearing fluids. A subsequent stage of metasomatic enrichment is characterized by extensive growth of large K-feldspar, quartz and muscovite megacrysts at the expense of the albite/oligoclase crystals as a result of infiltration of K-Si rich hydrous fluids. Post-magmatic infiltration of hydrous fluids along the fault planes is shown by the intense replacement of alkali feldspar megacrysts by quartz, development of myrmekitic intergrowth pockets along the K-feldspar megacrysts and sealing of the micro-fractures by cryptocrystalline mixtures of clay minerals, iron oxides, sericite and chlorite. Compositionally, the red granitic rocks have higher SiO 2 , Fe 2 O 3total , K 2 O/Na 2 O, Σ REE, Y, Th, U, Zr and Zn and lower Al 2 O 3 , Ga, Ta, Nb and Mo compared to the milky white granites. LILE and Sn do not show clear variation trends throughout the Mueilha granite pluton, suggesting their immobility during hydrothermal alteration. Microthermometric measurements indicate that the interactions with the hydrothermal fluids started at a minimum temperature > 400°C, most likely during the late-stage crystallization of the Mueilha granite and continued after their complete solidification (i.e. subsolidus conditions) at a temperature as low as 120 °C. The high fertility of Mueilha granite is most plausibly the result of partial melting within the undepleted juvenile crust of the Arabian–Nubian Shield that has formed during the Pan-African orogeny.
This contribution presents complimentary mineralogical and whole-rock chemical data for the Mulln... more This contribution presents complimentary mineralogical and whole-rock chemical data for the Mullnäset rapakivi massif. Three rock types occur: gabbro, syenite with associated granite and “normal” rapakivi granite, here denoted rapakivi-textured granite. In the syenite-associated granite, extremely Mg-poor clinopyroxene and fayalite are the most important mafic minerals, whereas ferrohornblende and strongly chloritized biotite are most important in the rapakivi-textured granite. All mafic minerals are Fe-extreme. The two rapakivi granites are metaluminous straddling the boundary between calc-alkaline and alkaline granite, whereas the neighbouring, older Sörvik granite is peraluminous and typically calc-alkaline. The Mullnäset rapakivi granite is A-type. It is lower in incompatible trace elements than the Sörvik granite. The HFSE patterns differ between the two granites. In both the rapakivi and Sörvik granites, Archaean rocks form part of the source rocks. The Archaean input seems to be more important in the Mullnäset (and other rapakivi granites from the same general area) granite than in the Sörvik granite. No data contradict the suggested formation of rapakivi granite magma: upwelling mantle melts under a thickened continental crust triggering melting of the continental crust.
The orbicular rock at Slättemossa, southeastern Sweden, has a quartz monzodioritic composition. T... more The orbicular rock at Slättemossa, southeastern Sweden, has a quartz monzodioritic composition. The cores of the orbicules crystallized directly from the orbicule-forming magma; cores made up of xenoliths have not been observed. Outside the core follow first an inner mafic, a felsic and then an outer mafic shell. The orbicules occur in a matrix, which is similar to the core. They grew simultaneously and show an almost perfect parallelism in evolution. After initial ‘normal’ crystall-ization of the magma, superheating probably triggered by a sudden addition of volatiles destroyed earlier formed nuclei and also affected the already crystallized part of the rock. Cooling caused heterogeneous nucleation and rapid crystallization, which formed the inner mafic shell. This is enriched in mafic minerals, especially biotite, compared to the core. At the same time the grain size becomes significantly smaller. Depletion in mafic components, possibly intensified by a sudden change in physical conditions, destabilized biotite and amphibole crystallization, causing oversaturation in plagioclase components, forming a felsic shell having a sharp boundary with the mafic shell. Plagioclase is extremely altered. Mafic minerals were then stabilized, probably due to depletion of plagioclase components, and an outer mafic shell formed. With the return to homogeneous nucleation, matrix formation concluded the crystallization. Orbicules might have moved in the magma causing some squeezing of magma surrounding the orbicules, but major movements involved the settling of the whole package of orbicules and matrix in the surrounding non-orbicular magma.
... Sweden, this orogen is divided into the Western, Median and Eastern seg-ments, which are sepa... more ... Sweden, this orogen is divided into the Western, Median and Eastern seg-ments, which are separated by major ductile deformation zones (Berthelsen 1980; Gaal & ... retrograde zoning about 50 Jim in width occurs within the outer-most part of the rim (Wang & Lindh 1996). ...
Granites, among them three generations of microline-rich granites, intruded repeatedly between 16... more Granites, among them three generations of microline-rich granites, intruded repeatedly between 1600 and 900 Ma in the South-western Swedish Gneiss Complex. The deformed and metamorphosed Gösta and Sundsta granites are medium-grained, pale greyish red rocks belonging to the oldest generation of microclinerich granites.Biotite dominates over hornblende. Allanite, titanite, apatite and zircon are important accessory minerals. The granites are metaluminous and
A sherd found at the Iron Age settlement of Kristineberg in Malmo, Scania, Sweden, carried remnan... more A sherd found at the Iron Age settlement of Kristineberg in Malmo, Scania, Sweden, carried remnants of an unusual silvery layer on the outer surface. It was suggested that this consisted of graphite, because of its macroscopic appearance and the existence of contemporary parallels on the continent. SEM analysis confirmed that the layer was pure carbon. Although organic carbon cannot be completely excluded, there were no other traces of use on the vessel and nothing to indicate coating or sealing of the vessel with materials such as tar or resin.
TEKTITES. A. Ocampo, J. Gómez, J. A. García, A. Lindh, A. Scherstén, A. Pitzsch, L. Page, A. Ishi... more TEKTITES. A. Ocampo, J. Gómez, J. A. García, A. Lindh, A. Scherstén, A. Pitzsch, L. Page, A. Ishikawa, K. Suzuki, R. S. Hori, Margarita Buitrago and José Abel Flores, D. Barrero, V. Vajda; NASA HQ, Science Mission Directorate, US (aco@nasa.gov), Colombian Geological Survey, Bogotá, Colombia; Universidad Libre, Sociedad astronomica ANTARES, Cali, Colombia; Department of Geology, Lund University, Sweden; MAX–lab, Lund University, Sweden/ Helmholtz Zentrum Berlin, Institute Methods and Instrumentation for Synchrotron Radiation Research, Berlin, Germany; Department of Earth Science & Astronomy, The University of Tokyo, Japan; IFREE/SRRP, Japan Agency for Marine–Earth Science and Technology, Yokosuka, Japan; Department of Earth Science, Ehime University, Japan; Department of Geology, University of Salamanca, Spain. Consultant geologist, Bogotá, Colombia; Department of Palaeobiology, Swedish Museum of Natural History, Sweden
Abstract The Mueilha granite pluton is one of the rare-metals bearing peraluminous granitic pluto... more Abstract The Mueilha granite pluton is one of the rare-metals bearing peraluminous granitic plutons in the Arabian-Nubian Shield. It represents the apical part of a highly evolved magma chamber emplaced at a shallow level subsequent to the post Pan-African orogeny. The pluton can be seen as a highly leucocratic medium-grained albite/oligoclase framework infilled with quartz, K-feldspar and muscovite that are variably overgrown by K-feldspar, muscovite, quartz and topaz megacrysts. The increasing number and size of the K-feldspar megacrysts at the expense of the whitened albite/oligoclase framework imparts variably red color to the Mueilha granite. Contacts between the milky white and red granites are usually gradational, but may be locally sharp or may form narrow transition zones resulting from abrupt variations in texture and lithology. Textural relations indicate an initial stage of hydrothermal albitization of magmatic plagioclase and crystallization of topaz megacrysts resulting from infiltration of Na-rich fluorine bearing fluids. A subsequent stage of metasomatic enrichment is characterized by extensive growth of large K-feldspar, quartz and muscovite megacrysts at the expense of the albite/oligoclase crystals as a result of infiltration of K-Si rich hydrous fluids. Post-magmatic infiltration of hydrous fluids along the fault planes is shown by the intense replacement of alkali feldspar megacrysts by quartz, development of myrmekitic intergrowth pockets along the K-feldspar megacrysts and sealing of the micro-fractures by cryptocrystalline mixtures of clay minerals, iron oxides, sericite and chlorite. Compositionally, the red granitic rocks have higher SiO 2 , Fe 2 O 3total , K 2 O/Na 2 O, Σ REE, Y, Th, U, Zr and Zn and lower Al 2 O 3 , Ga, Ta, Nb and Mo compared to the milky white granites. LILE and Sn do not show clear variation trends throughout the Mueilha granite pluton, suggesting their immobility during hydrothermal alteration. Microthermometric measurements indicate that the interactions with the hydrothermal fluids started at a minimum temperature > 400°C, most likely during the late-stage crystallization of the Mueilha granite and continued after their complete solidification (i.e. subsolidus conditions) at a temperature as low as 120 °C. The high fertility of Mueilha granite is most plausibly the result of partial melting within the undepleted juvenile crust of the Arabian–Nubian Shield that has formed during the Pan-African orogeny.
This contribution presents complimentary mineralogical and whole-rock chemical data for the Mulln... more This contribution presents complimentary mineralogical and whole-rock chemical data for the Mullnäset rapakivi massif. Three rock types occur: gabbro, syenite with associated granite and “normal” rapakivi granite, here denoted rapakivi-textured granite. In the syenite-associated granite, extremely Mg-poor clinopyroxene and fayalite are the most important mafic minerals, whereas ferrohornblende and strongly chloritized biotite are most important in the rapakivi-textured granite. All mafic minerals are Fe-extreme. The two rapakivi granites are metaluminous straddling the boundary between calc-alkaline and alkaline granite, whereas the neighbouring, older Sörvik granite is peraluminous and typically calc-alkaline. The Mullnäset rapakivi granite is A-type. It is lower in incompatible trace elements than the Sörvik granite. The HFSE patterns differ between the two granites. In both the rapakivi and Sörvik granites, Archaean rocks form part of the source rocks. The Archaean input seems to be more important in the Mullnäset (and other rapakivi granites from the same general area) granite than in the Sörvik granite. No data contradict the suggested formation of rapakivi granite magma: upwelling mantle melts under a thickened continental crust triggering melting of the continental crust.
The orbicular rock at Slättemossa, southeastern Sweden, has a quartz monzodioritic composition. T... more The orbicular rock at Slättemossa, southeastern Sweden, has a quartz monzodioritic composition. The cores of the orbicules crystallized directly from the orbicule-forming magma; cores made up of xenoliths have not been observed. Outside the core follow first an inner mafic, a felsic and then an outer mafic shell. The orbicules occur in a matrix, which is similar to the core. They grew simultaneously and show an almost perfect parallelism in evolution. After initial ‘normal’ crystall-ization of the magma, superheating probably triggered by a sudden addition of volatiles destroyed earlier formed nuclei and also affected the already crystallized part of the rock. Cooling caused heterogeneous nucleation and rapid crystallization, which formed the inner mafic shell. This is enriched in mafic minerals, especially biotite, compared to the core. At the same time the grain size becomes significantly smaller. Depletion in mafic components, possibly intensified by a sudden change in physical conditions, destabilized biotite and amphibole crystallization, causing oversaturation in plagioclase components, forming a felsic shell having a sharp boundary with the mafic shell. Plagioclase is extremely altered. Mafic minerals were then stabilized, probably due to depletion of plagioclase components, and an outer mafic shell formed. With the return to homogeneous nucleation, matrix formation concluded the crystallization. Orbicules might have moved in the magma causing some squeezing of magma surrounding the orbicules, but major movements involved the settling of the whole package of orbicules and matrix in the surrounding non-orbicular magma.
... Sweden, this orogen is divided into the Western, Median and Eastern seg-ments, which are sepa... more ... Sweden, this orogen is divided into the Western, Median and Eastern seg-ments, which are separated by major ductile deformation zones (Berthelsen 1980; Gaal & ... retrograde zoning about 50 Jim in width occurs within the outer-most part of the rim (Wang & Lindh 1996). ...
Granites, among them three generations of microline-rich granites, intruded repeatedly between 16... more Granites, among them three generations of microline-rich granites, intruded repeatedly between 1600 and 900 Ma in the South-western Swedish Gneiss Complex. The deformed and metamorphosed Gösta and Sundsta granites are medium-grained, pale greyish red rocks belonging to the oldest generation of microclinerich granites.Biotite dominates over hornblende. Allanite, titanite, apatite and zircon are important accessory minerals. The granites are metaluminous and
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