Metamorphic evolution of aluminous granulites from Labwor Hills, Uganda

Sandiford, Mike; Neall, F. B.; Powell, Roger

doi:10.1007/bf00381271

Cited by 89 publications

(52 citation statements)

References 31 publications

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“…The order of mineral textural relationships in South Harris are closely similar to those observed in isobaric cooling (IBC) UHT terrane in the world, such as Spr stable at an early stage, and then replaced by Opx or Sil (e.g. Sandiford et al, 1987). The Opx and Sil are commonly identified as "reaction rim" on the Spr margin in the most of other IBC terranes.…”

Section: Uht Metamorphism In the South Harris Complexsupporting

confidence: 62%

“…Sandiford et al, 1987). In the case of South Harris, it is obvious that magmatic arc model is favorable for causing UHT conditions, because the South Harris igneous complex has calc alkaline magmatic affinities (Fettes et al, 1992) and precursory rocks for Leverburgh belt is considered to be subduction related materials.…”

Section: Uht Metamorphism In the South Harris Complexmentioning

confidence: 99%

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Palaeoproterozoic UHT metamorphism in the Lewisian complex and North Atlantic region

Baba

2004

Journal of Mineralogical and Petrological Sciences

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Palaeoproterozoic ultra high temperature (UHT) metamorphism of the Lewisian complex in South Harris and the North Atlantic regions were examined. The characteristic features of the UHT metamorphism in the South Harris can be summarized as a) mineral textures and constituent mineral associations are concordant with anti clockwise metamorphic history, b) presence of subduction related various precursory rocks lead to formation of various types of sapphirine bearing rocks, and c) heat source that established UHT metamorpism in South Harris is the emplacement of igneous suite in the magmatic arc at c. 2.18 1.87 Ga. In the North Atlantic region, possible UHT metamorphism were reported from the Boothia Somerset granulite terrane, Taltson Thelon orogen and Kolvista Umba zone during 1.9 2.0 Ga. Precise correlation between UHT in South Harris and these terranes are not clear, although magmatic arc or island arc are considered to be reasonable tectonic setting for the UHT metamorphism in the Palaeoproterozoic North Atlantic region.

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Section: Uht Metamorphism In the South Harris Complexsupporting

confidence: 62%

Section: Uht Metamorphism In the South Harris Complexmentioning

confidence: 99%

Palaeoproterozoic UHT metamorphism in the Lewisian complex and North Atlantic region

Baba

2004

Journal of Mineralogical and Petrological Sciences

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“…18a) that abundant large garnets (20-25 vol %) are surrounded by reaction corona of cordierite + quartz symplectite, sillimanite (likely as pseudomorphs after kyanite), and cordierite + hercynite + corundum symplectite. Coexisting hercynite + quartz are preserved as small inclusions within the garnets and represent the peak metamorphic assemblage -a characteristically high-temperature assemblage that has been reported from several UHT (> 900 • C) localities (Lal et al, 1987;Sandiford et al, 1987;Waters, 1991;Dasgupta et al, 1995;Ouzegane and Boumaza, 1996;Morimoto et al, 2004;Tsunogae and Santosh, 2006). Reaction structures within the garnet corona are indicative of near-isothermal decompression, and so record the exhumation history of the Kobipoto Complex in the Kobipoto Mountains.…”

Section: Wai Tuhmentioning

confidence: 78%

Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

2013

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Abstract. The island of Seram, which lies in the northern part of the 180 • -curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic sole. However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent and rapid N-S extension that has caused the hightemperature exhumation of lherzolites beneath low-angle lithospheric detachment faults that induced high-temperature metamorphism and melting in overlying crustal rocks. These "Kobipoto Complex" migmatites include highly residual AlMg-rich garnet + cordierite + sillimanite + spinel + corundum granulites (exposed in the Kobipoto Mountains) which contain coexisting spinel + quartz, indicating that peak metamorphic temperatures likely approached 900 • C. Associated with these residual granulites are voluminous MioPliocene granitic diatexites, or "cordierite granites", which crop out on Ambon, western Seram, and in the Kobipoto Mountains and incorporate abundant schlieren of spineland sillimanite-bearing residuum. Quaternary "ambonites" (cordierite + garnet dacites) emplaced on Ambon were also evidently sourced from the Kobipoto Complex migmatites as demonstrated by granulite-inherited xenoliths. Exhumation of the hot peridotites and granulite-facies Kobipoto Complex migmatites to shallower structural levels caused greenschistto lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation to be overprinted by sillimanite-grade metamorphism, migmatisation, and limited localised anatexis to form the Taunusa Complex. The extreme extension required to have driven Kobipoto Complex exhumation evidently occurred throughout Seram and along much of the northern Banda Arc. The lherzolites must have been juxtaposed against the crust at typical lithospheric mantle temperatures in order to account for such high-temperature metamorphism and therefore could not have been part of a cooled ophiolite. In central Seram, lenses of peridotites are incorporated with a major left-lateral strike-slip shear zone (the "Kawa Shear Zone"), demonstrating that strike-slip motions likely initiated shortly after the mantle had been partly exhumed by detachment faulting and that the main strike-slip faults may themselves be reactivated and steepened lowangle detachments. The geodynamic driver for mantle exhumation along the detachment faults and strike-slip faulting in central Seram is very likely the same; we interpret the extreme extension to be the result of eastward slab rollback into the Banda Embayment as outlined by the latest plate reconstructions for Banda Arc evolution.

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“…Other than these, osumilite or its psudomorphs have also been reported from a few localities from some other parts of the world. Osumilite was reported from Paderu (Lal et al, 1987) and Chimakurthy (Dasgupta et al, 1997) in the Eastern Ghats Belt, India, Ouzzal block in Algeria (Audibert et al, 1993), Eastern Labrador, Canada (Arima and Gower, 1991); Labwor Hills, Uganda (Sandiford et al, 1987); Namaqualand, South Africa (Nowicki et al, 1995) and Rogaland, Norway (Tobi et al, 1985). In most of the cases (except East Antarctica, Algeria and South Africa) the osumilite bearing rocks do not contain garnet.…”

Section: Discussionmentioning

confidence: 99%

Osumilite and spinel+quartz from Sri Lanka: Implications for UHT conditions and retrograde P-T path

Sajeev

Osanai²

2004

Journal of Mineralogical and Petrological Sciences

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We report here the occurrence of osumilite as fine isolated inclusions in garnet porphyroblasts from a granulite facies rock in the southwestern part of the Highland Complex in Sri Lanka. Garnet porphyroblasts in the matrix are partly rimmed by sillimanite biotite K feldspar assemblage as well as cordierite K feldspar quartz assemblage. Spinel coexisting with quartz is also observed in the same sample. The pressure temperature condition must be above 950°C at around 7 kbar pressure, on the basis of osumilite stability in KFMASH system. The cooling and decompression continued down to 850°C, into the biotite sillimanite K feldspar quartz stability field. During decompression f o2 must have increased leading to the stability of Zn rich spinel with quartz after cordierite. Our findings provide direct evidence for ultrahigh temperature (UHT) metamorphic conditions in southwestern Highland Complex, and also suggest the existence of a possible UHT zone within the high grade terrane of Sri Lanka.

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Metamorphic evolution of aluminous granulites from Labwor Hills, Uganda

Cited by 89 publications

References 31 publications

Palaeoproterozoic UHT metamorphism in the Lewisian complex and North Atlantic region

Palaeoproterozoic UHT metamorphism in the Lewisian complex and North Atlantic region

Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

Osumilite and spinel+quartz from Sri Lanka: Implications for UHT conditions and retrograde P-T path

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