35 Ma old ultrahigh-pressure metamorphism and evidence for very rapid exhumation in the Dora Maira Massif, Western Alps

Gebauer, D.; Schertl, Hans‐Peter; Brix, M.; Schreyer, Werner

doi:10.1016/s0024-4937(97)82002-6

Cited by 406 publications

(270 citation statements)

References 33 publications

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“…This large contrast in peak metamorphic conditions (≈2.5 GPa) suggests a significant structural decoupling at the base of the coesitebearing unit. Fission track dates on Unit I indicates that they were already at shallow crustal levels by $29.9 Ma [Gebauer et al, 1997]. This implies a very rapid exhumation rate, a feature common to most UHP massifs [e.g., Ernst et al, 1997].…”

Section: Geology Of the Sampling Localitiesmentioning

confidence: 99%

Magnetic properties of fault pseudotachylytes in granites

Ferré¹,

Geissman²,

Zechmeister³

2012

J. Geophys. Res.

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[1] We investigate the petrographic, geochemical and magnetic properties of fault pseudotachylytes formed by frictional melting in granitic rocks from Southern California, the Italian Alps and Kyushyu, Japan. The main magnetic remanence carriers are mixtures of grain sizes of fine grained magnetite. These ferrimagnetic grains record a stable, multicomponent magnetization that consists of one or more of the following: coseismic thermal remanent magnetization, coseismic lightning isothermal remanent magnetization and post-seismic chemical remanent magnetization. Fault pseudotachylytes from the three localities display contrasting magnetic properties, which suggests that oxygen fugacity and host rock composition ultimately control the magnetic assemblage.

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Section: Geology Of the Sampling Localitiesmentioning

confidence: 99%

Magnetic properties of fault pseudotachylytes in granites

Ferré¹,

Geissman²,

Zechmeister³

2012

J. Geophys. Res.

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“…It presents external and internal features useful for its characterization [3][4][5]. It can incorporate fluid/melt (e.g., vapor bubbles, and glass) [6,7] and other minerals (e.g., biotite, quartz, feldspar, magnesian calcite, uraninite, apatite, galena, garnet, diamond, monazite, coesite, and omphacite) in their structure during crystal growth [5,[8][9][10]. Zircon is the most widely used mineral for the extraction of information on the pre-history and genesis of magmatic, metamorphic, and sedimentary rocks [5,11].…”

Section: Introductionmentioning

confidence: 99%

U-Pb Zircon Age: Preliminary Data Evaluating the Earth History Recorded by Two Basement Rocks (Granitic Pegmatite and Mica-Schist) in Mamfe Basin (Sw Cameroon, Central Africa)

Kanouo¹

2017

J Geol Geophys

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Zircon crystals from two basement rocks (granitic pegmatite and mica-schist) in the Mamfe Basin were studied to provide petrogenetic and geochronologic constraints, therefore were characterized and dated by LA-Q-ICP-MS analytical techniques, after their internal textural features were determined.Zircon crystals with oscillatory zoning from the granitic pegmatite exceed 200 µm are mainly euhedral to prismatic. The U (≤169 ppm), Th (≤240 ppm), and Th/U (0.6-1.7) are within the range of zircon crystallized in crustal magmatic environment. Zircon crystals from the mica-schist are ˂100 to ˃200 µm in size, have magmatic (e.g., euhedral prismatic with oscillatory zone) and metamorphic (e.g., form round soccer ball, sub-hedral with overgrowth) features. The U (23-687 ppm), Th

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“…Such cor ol lary is en tirely in com pat i ble with the lo cal ge ol ogy and other re sults of iso to pic stud ies. Con versely, all these fea tures can also de velop dur ing var i ous stages of crystallisation from a lo cally de rived melt (migmatitic) or hot super criti cal flu ids (in this case U-rich) in ter act ing with the rock at the peak or high-grade meta mor phic con di tions, usu ally in the pres ence of an ac tive aque ous phase (see Gebauer et al, 1997;Corfu et al, 2003;Geisler et al, 2007). In very fluid-rich sys tems, newly formed com po nents will crys tal lise with usual char ac ter is tics of mag matic zir con; i.e.…”

Section: Discussion Zircon Morphologymentioning

confidence: 99%

An insight into a gneiss core of the Orlica-Śnieżnik Dome, NE Bohemian Massif: new structural and U–Pb zircon data

Redlińska-Marczyńska

Żelaźniewicz

Fanning

2016

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The Orlica-OEnie¿nik Dome in the Sudetes, the NE Bo he mian Mas sif, em braces two for ma tions of fel sic gneiss es of con trover sial or i gin and evo lu tion. Our study shows that de spite sim i lar geo chem i cal sig na tures, they carry sys tem atic mi nor dif ferences in min eral, iso tope, zir con and geothermobarometric char ac ter is tics. Four vari ants of the Giera³tów gneiss es in clude migmatites and have a lon ger struc tural his tory than the OEnie¿nik augen orthogneisses. U-Pb SHRIMP anal y ses yielded U-Pb ages of ~500 Ma for cores and ~498 Ma for wide outer parts of zir con grains in the twice-folded Giera³tów gneiss es, and an age of ~500 Ma for a dis cor dant neosome vein. Neoproterozoic meta sedi ments were among pre cur sors of the lithologically di ver si fied Giera³tów Gneiss For ma tion. First de for ma tion, meta mor phism, and migmatisation of these rocks oc curred at 515-475 Ma and over lapped with the de vel op ment and em place ment of a por phy ritic S-type gran ite pre cur sor to the OEnie¿nik Gneiss For ma tion. The metagranite (= OEnie¿nik augen orthogneiss) em braced migmatitic xe no liths. Zir con grains from such xe no liths re vealed dis torted and re placed cores which yielded U-Pb ages that dis persed around 507-487 Ma, whilst wide darker poorly zoned out growths yielded ages from ~343 Ma to ~325 Ma (mean ~340 Ma). These out growths were in ter preted as a re cord of Car bon if er ous meta mor phism as sisted by rich Zr-and U-car ry ing flu ids. The Variscan meta mor phic over print was het er o ge neous, and var i ously af fected rocks of the two gneiss for ma tions.

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35 Ma old ultrahigh-pressure metamorphism and evidence for very rapid exhumation in the Dora Maira Massif, Western Alps

Cited by 406 publications

References 33 publications

Magnetic properties of fault pseudotachylytes in granites

Magnetic properties of fault pseudotachylytes in granites

U-Pb Zircon Age: Preliminary Data Evaluating the Earth History Recorded by Two Basement Rocks (Granitic Pegmatite and Mica-Schist) in Mamfe Basin (Sw Cameroon, Central Africa)

An insight into a gneiss core of the Orlica-Śnieżnik Dome, NE Bohemian Massif: new structural and U–Pb zircon data

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