Development of the Fe-Ti-oxides in the Koster dyke swarm during amphibolite facies metamorphism

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1990-38-11 ◽

1990 ◽

Vol 38 ◽

pp. 109-118

Author(s):

Aage Jensen

Keyword(s):

Electron Microprobe ◽

Amphibolite Facies ◽

Dyke Swarm ◽

Late Proterozoic ◽

Ti Oxides ◽

Facies Metamorphism

The 1421 Ma old Koster dyke swarrn is part of the late Proterozoic Kattsund-Koster dyke swann running from Bohus Lan in Sweden into Oslofjord in Norway. On the basis of the degree of amphibolite facies deformation and recrystallisation, Hageskov (1984) has divided the dyke swann into three sectors, where sector I is the southemmost part of the dyke swann consisting of undefonned tholeiitic dolerites, sector III dykes are transformed to amphibolites, and sector II is transitional. From a number of miroscopically investigated dykes 5 dykes from sector I, 5 dykes from sector II and 4 dykes from sector III have been selected for electron microprobe analyses of the Fe-Ti-oxides. No significant differences could be found between the titanomagnetite groundmass in sector I and sector II, but in sector III the titanomagnetite groundmass is completely altered to turbid titanite. Some of the dykes in sector II have an ilmenite composition similar to the sector I dykes, but other dykes from sector II have clearly lost Fe203 and are correspondingly richer in Ti; in sector III the ilmenite no longer contains Fe203• Based on the composition of coexisting ilmenite and titanomagnetite, temperature and f02 have been deterrnined for sector I and sector II dykes, but they cannot be deterrnined for sector III dykes as no titanomagnetite is left here. The dykes of sector I give temperatures between 1100° and 1280°, and f02 between 10-10 and 10-•. The least altered dykes of sector II give similar values of temperature and f02 as sector I dykes, whereas the more altered dykes of sector II show considerably lower values of temperature and f02• These values, however, are not meaningful as they neither indicate temperature and f02 of interoxide reequilibration nor temperature and f02 of metamorphism; they are the result of ilmenite loosing Fe203 during metamorphism.

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Thermochronological evidence for late Proterozoic (Vendian) cooling in southwest Wedel Jarlsberg Land, Spitsbergen

Geological Magazine ◽

10.1017/s0016756897008297 ◽

1998 ◽

Vol 135 (1) ◽

pp. 63-69 ◽

Cited By ~ 19

Author(s):

M. MANECKI ◽

D. K. HOLM ◽

J. CZERNY ◽

D. LUX

Keyword(s):

Geological Mapping ◽

Greenschist Facies ◽

Amphibolite Facies ◽

Variable Intensity ◽

Late Proterozoic ◽

Facies Metamorphism ◽

History Of ◽

Greenschist Facies Metamorphism

Two Proterozoic terranes with different metamorphic histories are distinguished from geological mapping in southwestern Wedel Jarlsberg Land: a northern greenschist facies terrane and a southern amphibolite facies terrane which has been overprinted by greenschist facies metamorphism. To better characterize the tectonothermal history of these terranes we have obtained new 40Ar/39Ar mineral dates from this area. A muscovite separate from the northern terrane yielded a Caledonian plateau age of 432±7 Ma. The southern terrane yielded significantly older 40Ar/39Ar ages with three muscovite plateau dates of 584±14 Ma, 575±15 Ma, and 459±9 Ma, a 484±5 Ma biotite plateau date, and a 616±17 Ma hornblende plateau date. The oldest thermochronological dates are over 300 Ma younger than the age of amphibolite facies metamorphism and therefore probably do not represent uplift-related cooling. Instead, the Vendian dates correlate well with a regionally widespread magmatic and metamorphic/thermal resetting event recognized within Caledonian complexes of northwestern Spitsbergen and Nordaustlandet. The apparent Ordovician dates are interpreted to represent partial resetting, suggesting that late Caledonian greenschist facies overprinting of the southern terrane was of variable intensity.

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An unusual titanomagnetite replacing spinel

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-1993-40-14 ◽

1993 ◽

Vol 40 ◽

pp. 300-313

Author(s):

Aage Jensen

Keyword(s):

Core Temperature ◽

Electron Microprobe ◽

The Other ◽

Dyke Swarm ◽

The Core ◽

Ti Oxides ◽

Small Content ◽

Good Agreement

n a recent investigation of the Fe-Ti-oxides in the Koster dyke swarm, SW Sweden, one of the dykes from sector I (41197) was omitted because the cubic Fe-Ti-oxides in this dyke were found to deviate from those in all the other dykes. The Fe-Ti-oxides in 41197 consist partly of ilmenite as free grains, and partly of titanomagnetite with sandwich as well as trellis oxyexsolution lamellae of ilmenite. Some of the titanomagnetite grains have a core of grey spine!, and there are also grains consisting mainly of spine!, but with the spine! clearly being replaced by titanomagnetite. Electron microprobe analyses of these Fe-Ti-oxides have revealed that the ilmenite as free grains has a composition quite similar to that in the other Koster dykes from sector I. Apart from a small content of Cr, the ilmenite lamellae in the titanomagnetite grains also show good agreement with the other Koster dykes from sector I, but there are small but significant differences between the ilmenite lamellae from grain to grain within the sample. The titanomagnetite groundmass also shows small but significant differences between different grains. The composition of the titanomagnetite varies from ferroferrites to ferrochromferrites. The grey spine! varies from ferrospinel over ferrochromspinel to ferroferrichromspinel. Except for the spine! grain with only incipient replacement by titanomagnetite, the spinels have a rim which is richer in Mg, Al and Zn and poorer in Cr and Fe+++ than the core. Temperature and fO2 of coexisting pairs of ilmenite and titanomagnetite varies from 991°C, fO2 10-12-9, to 1104°C, fO2 10-11-2.

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Neoproterozoic pegmatite from Skoddefjellet, Wedel Jarlsberg Land, Spitsbergen: Additional evidence for c. 640 Ma tectonothermal event in the Caledonides of Svalbard

Polish Polar Research ◽

10.2478/v10183-012-0003-6 ◽

2012 ◽

Vol 33 (1) ◽

pp. 1-17 ◽

Cited By ~ 13

Author(s):

Jarosław Majka ◽

Alexander Larionov ◽

David Gee ◽

Jerzy Czerny ◽

Jaroslav Pršek

Keyword(s):

Electron Microprobe ◽

Regional Metamorphism ◽

Amphibolite Facies ◽

The Other ◽

Clear Distinction ◽

Metasedimentary Rocks ◽

Facies Metamorphism ◽

Shrimp Zircon ◽

Tectonothermal Event

Neoproterozoic pegmatite from Skoddefjellet, Wedel Jarlsberg Land, Spitsbergen: Additional evidence forc. 640 Ma tectonothermal event in the Caledonides of SvalbardNeoproterozoic (c. 640 Ma) amphibolite facies metamorphism and deformation have been shown recently to have affected the Isbjørnhamna and Eimfjellet Complex of Wedel Jarlsberg Land in southwestern Spitsbergen. New SHRIMP zircon U-Pb andin situelectron microprobe monazite and uraninite U-Th-total Pb ages are presented here on a pegmatite occurring within the Isbjørnhamna metasedimentary rocks. Although the dated zircons are full of inclusions, have high-U contents and are metamict and hence have experienced notable Pb-loss, the new Cryogenian ages are consistent with the age of regional metamorphism of the host metasediments, providing additional evidence for a clear distinction of the Southwestern Province from the other parts of the Svalbard Caledonides.

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The Nagssugtoqidian boundary and the deformation of the Kângamiut dyke swarm in the Søndre Strømfjord area

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v28.7226 ◽

1970 ◽

Vol 28 ◽

pp. 21-23

Author(s):

A Escher ◽

J.C Escher ◽

J Watterson

Keyword(s):

Granulite Facies ◽

Amphibolite Facies ◽

Dyke Swarm ◽

Southern Limit ◽

Ice Cap ◽

Facies Metamorphism ◽

Inland Ice ◽

Comprehensive Study

The season's objective was the reconnaissance mapping of a c. 7000 km2 area lying between Søndre Strømfjord, the Inland Ice and the Sukkertoppen ice capo. An important feature of this region was known to be the progressive northward deformation of the Kangamiut dyke swarm and an associated amphibolite facies metamorphism of both the dykes and their granulite facies country rocks (Noe-Nygaard & Ramberg, 1961). These changes have been regarded as marking the southern limit of Nagssugtoqidian orogenic activity. In order to make a more comprehensive study of this boundary, the reconnaissance was extended to include the c. 3000 km2 area southwest of the Sukkertoppen ice cap, bounded by Søndre Strømfjord and Evigheds Fjord.

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DIVING DEEPER INTO THE PICURIS OROGEN: UPPER AMPHIBOLITE FACIES METAMORPHISM AND BRITTLE DEFORMATION ALONG THE PLOMO SHEAR ZONE

10.1130/abs/2020am-354334 ◽

2020 ◽

Author(s):

Adrian E. Castro ◽

◽

Chloe Bonamici ◽

Christopher G. Daniel ◽

Danielle Shannon Sulthaus

Keyword(s):

Shear Zone ◽

Amphibolite Facies ◽

Brittle Deformation ◽

Facies Metamorphism

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REGIONAL LOW-PRESSURE AMPHIBOLITE-FACIES METAMORPHISM AT THE PIPE II MINE, THOMPSON NICKEL BELT, MANITOBA, AND COMPARISON OF METAMORPHIC ISOGRADS IN METAPELITES AND META-IRON FORMATIONS

The Canadian Mineralogist ◽

10.3749/canmin.49.3.721 ◽

2011 ◽

Vol 49 (3) ◽

pp. 721-747 ◽

Cited By ~ 5

Author(s):

C. G. Coueslan ◽

D. R. M. Pattison ◽

D. K. Tinkham

Keyword(s):

Low Pressure ◽

Amphibolite Facies ◽

Facies Metamorphism ◽

Iron Formations

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Metamorphic evolution and U-Pb zircon SHRIMP geochronology of the Belizário ultramafic amphibolite, Encantadas Complex, southernmost Brazil

Anais da Academia Brasileira de Ciências ◽

10.1590/s0001-37652003000300010 ◽

2003 ◽

Vol 75 (3) ◽

pp. 393-403 ◽

Cited By ~ 20

Author(s):

Léo A. Hartmann ◽

João O.S. Santos ◽

Jayme A.D. Leite ◽

Carla C. Porcher ◽

Neal J. Mcnaughton

Keyword(s):

Ultramafic Rock ◽

Greenschist Facies ◽

Amphibolite Facies ◽

Rio De La Plata ◽

Metamorphic Evolution ◽

Río De La Plata ◽

La Plata ◽

Shrimp Geochronology ◽

Facies Metamorphism ◽

Magnesian Basalt

The integrated investigation of metamorphism and zircon U-Pb SHRIMP geochronology of the Belizário ultramafic amphibolite from southernmost Brazil leads to a better understanding of the processes involved in the generation of the Encantadas Complex. Magmatic evidence of the magnesian basalt or pyroxenite protolith is only preserved in cores of zircon crystals, which are dated at 2257 ± 12 Ma. Amphibolite facies metamorphism M1 formed voluminous hornblende in the investigated rock possibly at 1989 ± 21 Ma. This ultramafic rock was re-metamorphosed at 702±21 Ma during a greenschist facies eventM2; the assemblage actinolite + oligoclase + microcline + epidote + titanite + monazite formed by alteration of hornblende. The metamorphic events are probably related to the Encantadas Orogeny (2257±12 Ma) and Camboriú Orogeny (~ 1989 Ma) of the Trans-Amazonian Cycle, followed by an orogenic event (702±21 Ma) of the Brasiliano Cycle. The intervening cratonic period (2000-700 Ma) corresponds to the existence of the Supercontinent Atlantica, known regionally as the Rio de la Plata Craton.

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Zircon U–Pb Dating and Lu-Hf Isotope of the Retrograded Eclogite from Chicheng, Northern Hebei Province, China

Shock and Vibration ◽

10.1155/2021/1445653 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Xu Kong ◽

Xueyuan Qi ◽

Wentian Mi ◽

Xiaoxin Dong

Keyword(s):

Regional Metamorphism ◽

Granulite Facies ◽

Amphibolite Facies ◽

Metamorphic Event ◽

Isotopic Data ◽

Metamorphic Condition ◽

Eu Anomaly ◽

Facies Metamorphism ◽

Eclogite Facies ◽

Plagioclase Gneiss

We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

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Mapping in the Fiskefjord area, southern West Greenland

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v110.7797 ◽

1982 ◽

Vol 110 ◽

pp. 55-57

Author(s):

A.A Garde ◽

V.R McGregor

Keyword(s):

Granulite Facies ◽

Amphibolite Facies ◽

Isotopic Age ◽

Supracrustal Rock ◽

Granulite Facies Metamorphism ◽

West Greenland ◽

Facies Metamorphism ◽

Geological Work ◽

Age Determinations

Previous geological work on the 1:100000 map sheet 64 V.l N (fig. 15) includes published maps of smaller areas by Berthelsen (1960, 1962) and Lauerma (1964), mapping by Kryolitselskabet Øresund A/S (Bridgwater et al., 1976) and mapping by GGU geologists for the 1:500000 map sheet Frederikshåb Isblink - Søndre Strømfjord (Allaart et al., 1977, 1978). The Amltsoq and Niik gneisses and Malene supracrustal rock units south and east of Godthåbsfjord have not so far been correlated with rocks in the Fiskefjord area. Godthåbsfjord separates the granulite facies gneisses in Nordlandet from amphibolite facies Nûk gneisses on Sadelø and Bjørneøen; the granulite facies metamorphism occurred at about 2850 m.y. (Black et al., 1973), while no published isotopic age determinations from the Fiskefjord area itself are available.

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