Eclogitic amphibolites from the Grampian Moines

Baker, A. J.

doi:10.1180/minmag.1986.050.356.04

Cited by 16 publications

(14 citation statements)

References 8 publications

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“…Of particular interest are the symplectitic aggregates replacing the high-P mineral assemblages. Symplectites are well known in the metamorphic literature (Mysen & Griffin, 1973;Boland & Van Roermund, 1983;Baker, 1986) as textures occurring during the retrogression of high-P and/or high-grade terranes, but they have never been used in the Western Alps as a key to provide important constraints on the P-T paths.…”

Section: General Approach To Microstructural Problemsmentioning

confidence: 99%

Retrograde P‐T‐t path for the Voltri Massif eclogites (Ligurian Alps, Italy): some tectonic implications

Messiga¹,

Scambelluri²

1991

Journal Metamorphic Geology

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The retrograde P-T trajectory of the eclogitic Fe-Ti-gabbros from the Ligurian Alps is constrained by the appearance of mineral parageneses post-dating the Na-clinopyroxene + garnet eclogitic assemblage and indicating the following sequence of metamorphic events: (1) amphibolitic stageedenite/katophorite + plagioclase (An33-43) + oxides in symplectitic aggregates; (2) glaucophanic stagea porphyrohlastic glaucophanic amphibole has overgrown the symplectite, winchite also occurs as thin rims around glaucophane and both amphiboles are, sometimes, armoured by atoll garnets; (3) albite-amphibolite stage-barroisite/katophorite + albite + epidote + oxides f chlorite overprint the glaucophanic stage minerals; (4) greenschist stage-represented by actinolite + albite + epidote + oxide paragenesis.The metamorphic evolution is complex and the decompression path, on a P-T diagram, is significantly different from those defined in the literature for the Voltri eclogites. The main features inferred from the P-T path are the following: (1) the pressure climax does not match the thermal climax, the maximum temperature conditions are in fact achieved during the early stage of uplift; (2) a decrease in temperature, suggested by the appearance of glaucophane after the amphibolitic symplectite; (3) successive uplift, probably accompanied by an increase in temperature.The complexity of the P-T path drawn for the Voltri eclogites can be explained with a mechanism of successive underthrusts propagating from the innermost to the outermost sector of the Ligurian Alps. List of abbreviationsC =homogenization temperature C,ol = total homogenization temperature tr = tremolite V =vapour Vol. % = volume per cent of vapour/gas bubble in the fluid inclusion

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Section: General Approach To Microstructural Problemsmentioning

confidence: 99%

Retrograde P‐T‐t path for the Voltri Massif eclogites (Ligurian Alps, Italy): some tectonic implications

Messiga¹,

Scambelluri²

1991

Journal Metamorphic Geology

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“…In northern exposures of the Moine Supergroup mafic rocks, high-pressure granulite parageneses are interpreted to have formed at c. 467 Ma (Friend et al 2000) during an earlier Taconic phase of the Caledonian orogeny. As yet undated eclogites also occur within the Dava Succession (Baker 1986), a sub-Grampian Group sequence of partially migmatized metasediments tentatively correlated with the Moine Supergroup (Kirkland et al 2008). Therefore, further younger high-pressure metamorphic events are present farther east than the GlenelgAttadale Inlier Grenvillian high-pressure remnants, which have also been translated westward during later compression.…”

Section: Tectonothermal History and Correlation With The Lewisian Gnementioning

confidence: 85%

Multiple high-pressure metamorphic events and crustal telescoping in the NW Highlands of Scotland

Storey

Brewer

Anczkiewicz

et al. 2010

JGS

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The Glenelg–Attadale Inlier is the largest basement inlier within the Caledonian orogen in NW Scotland. A Western Unit consists of trondhjemite–tonalite–granodiorite (TTG) gneisses and subordinate mafic intrusions with locally preserved mafic high-pressure granulite and eclogite assemblages. An Eastern Unit comprises TTG gneisses, Grenville-age ( c . 1.1 Ga) eclogite and metasediments. U–Pb zircon ages from the Western Unit TTG gneisses are highly disturbed with Neoarchaean upper intercepts and Palaeo- to Mesoproterozoic lower intercepts, suggesting strong reworking at these times. U–Pb zircon, Sm–Nd and Lu–Hf garnet–clinopyroxene dates from the Western Unit high-pressure granulite and eclogite yield Neoarchaean ( c . 2.6–2.8 Ga) and Palaeoproterozoic ( c . 1.75 Ga) ages, respectively. These ages correspond to the ages of partial resetting of the TTG gneisses. The eclogite in the Western Unit may represent the high-pressure convergent margin to the lower-pressure Laxfordian events within the Lewisian Gneiss Complex, whereas the Mesoproterozoic eclogites in the Eastern Unit may represent a farther eastward Grenville-age margin. Further east, Ordovician high-pressure granulites within the Moine Supergroup may represent another, later, Grampian convergent margin. These high-pressure belts were developed sequentially towards the east and telescoped westwards from Palaeoproterozoic to Early Palaeozoic times. Supplementary material: U–Pb analytical data and LA-ICP-MS trace element data are available at http://www.geolsoc.org.uk/SUP18389 .

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“…Omphacite is commonly replaced by a fine-grained vermicular intergrowth of clinopyroxene (Jd 14) and plagioclase (An 8±11), similar to that observed in other eclogites (Fig. 5a;e.g., De Wit and Strong 1975;Okay et al 1985;Baker 1986). In the advanced stages, hornblende crystals have replaced the clinopyroxene in the symplectite.…”

Section: Decompression Texturesmentioning

confidence: 94%

“…Minor hornblende also occurs as vermicular intergrowths oriented radially to the garnet boundary. The resorption of garnet is interpreted to reflect a decrease in pressure during the retrogression of the eclogites (Baker 1986;Wilkerson et al 1988). Plagioclase collars between relic igneous and high-pressure phases, which are regarded to be related to de-jadeitization of adjacent clinopyroxene during decompression of high-pressure rocks (Indares 1993), are extensively developed in the coronites and eclogitic metagabbros.…”

Section: Decompression Texturesmentioning

confidence: 98%

Pan-African high-pressure metamorphism in the Precambrian basement of the Menderes Massif, western Anatolia, Turkey

Candan

Dora

Oberhänsli

et al. 2001

International Journal of Earth Sciences

132

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The Menderes Massif is made up of Pan-African basement and a Paleozoic to Early Tertiary cover sequence imbricated by Late Alpine deformation. The Precambrian basement comprises primarily medium-to high-grade schists, paragneisses, migmatites, orthogneisses, metagranites, charnockites, and metagabbros. High-pressure relics in the Pan-African basement are divided into two groups: eclogites and eclogitic metagabbros. The mineral assemblage in the eclogites is omphacite (Jd 44)±garnet±clinozoisite± rutile. The eclogites occur as pods and boudinaged layers in the basement schists and paragneisses. Inclusions found in the cores of the garnets indicate a medium-pressure protolith. The eclogitic metagabbros are closely related to Precambrian gabbroic stocks. The igneous texture and relic magmatic phases are preserved in these high-pressure rocks, which are characterized by the mineral assemblage omphacite (Jd 25)±garnet±rutilekyanite. The P±T conditions of the Pan-African high-pressure metamorphism in the eclogites are estimated to be 644 C with a minimum pressure of approximately 15 kbar. The eclogites are partly to completely retrograded to garnet amphibolites by a Barrovian-type overprint which developed under isothermal decompression conditions. For this post-eclogitic event, the P±T estimates are 7 kbar and 623 C. The eclogite relics provide strong support for a correlation of the Menderes Massif with the Bitlis Massif in terms of common Pan-African high-pressure evolution.

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Eclogitic amphibolites from the Grampian Moines

Cited by 16 publications

References 8 publications

Retrograde P‐T‐t path for the Voltri Massif eclogites (Ligurian Alps, Italy): some tectonic implications

Retrograde P‐T‐t path for the Voltri Massif eclogites (Ligurian Alps, Italy): some tectonic implications

Multiple high-pressure metamorphic events and crustal telescoping in the NW Highlands of Scotland

Pan-African high-pressure metamorphism in the Precambrian basement of the Menderes Massif, western Anatolia, Turkey

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