Burial rates during prograde metamorphism of an ultra-high-pressure terrane: an example from Lago di Cignana, western Alps, Italy

Lapen, T. J.; Johnson, Clark M.; Baumgartner, Lukas P.; Mahlen, Nancy J.; Beard, Brian L.; Amato, Jeffrey M.

doi:10.1016/s0012-821x(03)00455-2

Cited by 293 publications

(253 citation statements)

References 62 publications

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“…44-45 Ma (zircon SHRIMP-data by Rubatto et al 1998 andHermann 2003) or between 48.8±2.1 and 40.6±2.6 Ma. The latter age range (not fully consistent with the SHRIMP-data) was interpreted by Lapen et al (2003) to reflect the duration of the prograde PT path, based on their Lu-Hf data, as well as on SmNd data by Amato et al (1999).…”

Section: Geodynamic Implications and Discussionmentioning

confidence: 90%

Jurassic ophiolites within the Valais domain of the Western and Central Alps: geochronological evidence for re-rifting of oceanic crust

Liati

Froitzheim

Fanning

2005

Contrib Mineral Petrol

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Metabasic rocks from different parts of the Antrona ophiolites, Western Alps, as well as from the Misox zone, Central Alps, were dated using ion microprobe (SHRIMP) U-Pb analyses of zircon, in association with cathodoluminescence (CL) imaging. HP metamorphism must have affected at least the major part of the Antrona ophiolites, although HP relics are rarely preserved, probably due to the Lepontine metamorphic overprint. HP metamorphism has affected also the area of the Misox zone. The origin of the Antrona ophiolites is arguable. They were interpreted as part of both the Piemont-Ligurian (PL) and the Valais ocean, the two main oceans in the area of the Alps before Alpine convergence. SHRIMP-analyses of co-magmatic zircon domains from the Antrona ophiolites (Guggilihorn, Passo del Mottone and Quarata areas) yielded identical (within uncertainty) weighted mean 206 Pb/ 238 U ages of 155.2±1.6 Ma, 158±17 Ma (or 163.1±2.4 Ma: one analysis; 1r error) and 155.6±2.1 Ma, respectively, interpreted as the time of crystallization of the magmatic protoliths. These Late Jurassic ages fit well to the time span considered for the formation of Piemont-Ligurian oceanic crust. The metagabbro of the Misox zone (Hinterrhein area), for which a Valaisan origin is generally accepted, gave also a Late Jurassic, PL protolith age of 161.0±3.9 Ma. The metamorphic zircon domains from the amphibolitized eclogite of Mottone yielded an age of 38.5±0.7 Ma, interpreted as the time of HP metamorphism. This age is in good agreement with the time of metamorphism reported from previous zircon SHRIMP-data for eclogites and amphibolites of other parts in the Valais domain. In order to bring in line the PL protolith ages with the Valaisan metamorphic ages, we suggest a scenario involving emplacement of part of the PL oceanic crust to the north of the newly formed Brianc¸onnais peninsula, inside the Valais geotectonic domain. This paleotectonic configuration was probably established when younger Valaisan oceanic crust formed by spreading and re-rifting, partly within PL oceanic crust.

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Section: Geodynamic Implications and Discussionmentioning

confidence: 90%

Jurassic ophiolites within the Valais domain of the Western and Central Alps: geochronological evidence for re-rifting of oceanic crust

Liati

Froitzheim

Fanning

2005

Contrib Mineral Petrol

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“…reinecke 1998). A Lu-Hf garnet metamorphic age of 48.8 ± 2.1 Ma was obtained by Lapen et al (2003). the authors proposed that their Lu-Hf age is skewed towards the onset of garnet growth because Lu is partitioned in the early-formed core of garnets.…”

Section: Review Of Metamorphic Agesmentioning

confidence: 99%

“…101 (2008) their high grade rocks this is likely due to a higher t c for the Lu-Hf, compared to the sm-Nd system. Lapen et al (2003) interpreted a similar age difference in lower temperature rocks to reflect prograde zoning, based on the fact that Lu, in contrast to sm, will be strongly partitioned into garnet and hence, will be concentrated in the early grown core region. the knowledge whether prograde Lu-Hf zoning is preserved in a sample or not can be used to distinguish the two interpretations.…”

Section: Introductionmentioning

confidence: 99%

“…the stability relations of garnet are generally well understood, hence constraints can be placed on the age(s) of specific P-t conditions at which the mineral grew (e.g. Lapen et al 2003;Whitehouse & Platt 2003) provided garnet has not been heated beyond its t c . Most t c studies so far concern sm-Nd garnet geochronology because diffusion experiments exist for sm and/or Nd in garnet (Harrison & Wood 1980;coghlan 1990;Ganguly et al 1998;Van Orman et al 2002;tirone et al 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Eclogite facies metamorphism of the northern ZsF zone was reached in tertiary times (~52-40 Ma: bowtell et al 1994;rubatto et al 1998;Amato et al 1999;Mayer et al 1999;Dal Piaz et al 2001;Lapen et al 2003;Mahlen et al 2005Mahlen et al , 2006Gouzu et al 2006). these ages are partially in conflict with each other, and the interpretation of each of those ages is variable in the above cited literature (discussed below).…”

Section: Introductionmentioning

confidence: 99%

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Estimation of a maximum Lu diffusion rate in a natural eclogite garnet

et al. 2008

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Lutetium zoning in garnet within eclogites from the Zermatt-saas Fee zone, Western Alps, reveal sharp, exponentially decreasing central peaks. they can be used to constrain maximum Lu volume diffusion in garnets. A prograde garnet growth temperature interval of ~450-600 °c has been estimated based on pseudosection calculations and garnet-clinopyroxene thermometry. the maximum pre-exponential diffusion coefficient which fits the measured central peak is in the order of D 0 = 5.7*10 -6 m 2 /s, taking an estimated activation energy of 270 kJ/mol based on diffusion experiments for other rare earth elements in garnet. this corresponds to a maximum diffusion rate of D (~600 °c) = 4.0 Introduction the closure temperature, t c , has been defined by Dodson (1973) to be "the temperature at the time corresponding to its apparent age". It is dependant on the diffusion rate, the cooling rate, grain size, and grain shape. Following Dodson (1973) for spherical minerals one obtains:(1) (Q = activation energy; r = universal gas constant, A = numerical geometry factor, D 0 = diffusion coefficient at infinitely high temperatures, r = radius, dt/dt = cooling rate). In terms of geochronology, the mineral specific t c determines, among other factors, whether its age represents the timing of mineral crystallization or whether it corresponds to an age where a particular isotope geochronometer was closed.Garnet geochronology is particularly useful for systems such as sm-Nd and Lu-Hf because this mineral has high 147 sm/ 144 Nd and 176 Lu/ 177 Hf ratios (e.g. Mezger et al. 1992;Duchêne et al. 1997). the stability relations of garnet are generally well understood, hence constraints can be placed on the age(s) of specific P-t conditions at which the mineral grew (e.g. Lapen et al. 2003;Whitehouse & Platt 2003) provided garnet has not been heated beyond its t c . Most t c studies so far concern sm-Nd garnet geochronology because diffusion experiments exist for sm and/or Nd in garnet (Harrison & Wood 1980;coghlan 1990;Ganguly et al. 1998; Van Orman et al. 2002;tirone et al. 2005). However, published estimates for sm-Nd t c ' span a large range in temperature from around 500 °c (e.g. Mezger et al. 1992) to around 800 °c (e.g. Jagoutz 1988). Not much is known about the t c of the Lu-Hf system, and, to our knowledge, no Lu and Hf diffusion data in garnet have been determined. In general, Lu-Hf ages have been found to give older ages when compared to sm-Nd ages. scherer et al. (2000) Geosci. 101 (2008) their high grade rocks this is likely due to a higher t c for the Lu-Hf, compared to the sm-Nd system. Lapen et al. (2003) interpreted a similar age difference in lower temperature rocks to reflect prograde zoning, based on the fact that Lu, in contrast to sm, will be strongly partitioned into garnet and hence, will be concentrated in the early grown core region. the knowledge whether prograde Lu-Hf zoning is preserved in a sample or not can be used to distinguish the two interpretations.1661-8726/08/030637-14 DOI 10.1007/s00015-008-...

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Constraints on Lu‐Hf and Nb‐Ta systematics in globally subducted oceanic crust from a survey of orogenic eclogites and amphibolites

Zirakparvar

2016

Geochem Geophys Geosyst

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To further understand Lu‐Hf and Nb‐Ta systematics in globally subducted oceanic crust, this paper evaluates all available Lu‐Hf garnet isochron ages and initial ɛHf values in conjunction with present‐day bulk‐rock Lu‐Hf isotope and trace element (K, Nb, Ta, Zr, and Ti in addition to Lu‐Hf) data from the world's orogenic eclogites and amphibolites (OEAs). Approximately half of OEAs exhibit Lu‐Hf and Nb‐Ta systematics mimicking those of unsubducted oceanic crust whereas the rest exhibit variability in one or both systems. For the Lu‐Hf system, mixing calculations demonstrate that subduction‐related phase transformations, in conjunction with open system behavior, can shift subducted oceanic crust toward higher Lu/Hf, or toward lower Lu/Hf that can also be associated with unradiogenic ɛHf values. However, evaluation of potential mechanisms for fractionating Nb from Ta is more complicated because many of the OEAs have Nb‐Ta systematics that are decoupled from Lu‐Hf and the behavior of K, Zr, and Ti. Nonetheless, the global data set demonstrates that the association between unradiogenic ɛHf and elevated Nb/Ta observed in some kimberlitic eclogite xenoliths can be inherited from processes that occurred during subduction of their oceanic crustal protoliths. This allows for a geologically based estimate of the Nb concentration in a reservoir composed of deeply subducted oceanic crust. However, mass balance calculations confirm that such a reservoir, when considered as a whole, likely has a Nb concentration similar to unsubducted oceanic crust and is therefore not the solution to the problem of the Earth's “missing” Nb.

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Burial rates during prograde metamorphism of an ultra-high-pressure terrane: an example from Lago di Cignana, western Alps, Italy

Cited by 293 publications

References 62 publications

Jurassic ophiolites within the Valais domain of the Western and Central Alps: geochronological evidence for re-rifting of oceanic crust

Jurassic ophiolites within the Valais domain of the Western and Central Alps: geochronological evidence for re-rifting of oceanic crust

Estimation of a maximum Lu diffusion rate in a natural eclogite garnet

Constraints on Lu‐Hf and Nb‐Ta systematics in globally subducted oceanic crust from a survey of orogenic eclogites and amphibolites

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