Non‐silicate inclusions in garnet from an ultra‐deep orogenic peridotite

Roermund, H.L.M. van; Drury, M. R.; Barnhoorn, Auke; Ronde, A. de

doi:10.1002/gj.858

Cited by 50 publications

(31 citation statements)

References 48 publications

(81 reference statements)

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“…The model a completely continental upper mantle. This prevents lateral heat transport form the sub-continen-( p, T, F, t)-paths show similarities with recent peridotite samples found in mantle xenoliths tal mantle, which would enhance the secular cooling (Nyblade and Pollack, 1993;Pollack, (Bernstein et al, 1998) and peridotite massifs (Roermund and Drury, 1998). The analysis of the 1997).…”

Section: Discussionsupporting

confidence: 59%

See 1 more Smart Citation

Early formation and long-term stability of continents resulting from decompression melting in a convecting mantle

2000

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The origin of stable old continental cratonic roots is still debated. We present numerical modelling results which show rapid initial formation during the Archaean of continental roots of ca. 200 km thick. These results have been obtained from an upper mantle thermal convection model including differentiation by pressure release partial melting of mantle peridotite. The upper mantle model includes time-dependent radiogenic heat production and thermal coupling with a heat reservoir representing the Earth's lower mantle and core. This allows for model experiments including secular cooling on a time-scale comparable to the age of the Earth. The model results show an initial phase of rapid continental root growth of ca. 0.1 billion year, followed by a more gradual increase of continental volume by addition of depleted material produced through hot diapiric, convective upwellings which penetrate the continental root from below. Within ca. 0.6 Ga after the start of the experiment, secular cooling of the mantle brings the average geotherm below the peridotite solidus thereby switching off further continental growth. At this time the thickness of the continental root has grown to ca. 200 km. After 1 Ga of secular cooling small scale thermal instabilities develop at the bottom of the continental root causing continental delamination without breaking up the large scale layering. This delaminated material remixes with the deeper layers. Two more periods, each with a duration of ca. 0.5 Ga and separated by quiescent periods were observed when melting and continental growth was reactivated. Melting ends at 3 Ga. Thereafter secular cooling proceeds and the compositionally buoyant continental root is stabilized further through the increase in mechanical strength induced by the increase of the temperature dependent mantle viscosity. Fluctuating convective velocity amplitudes decrease to below 10 mma−1 and the volume average temperature of the sub-continental convecting mantle has decreased ca. 340 K after 4 Ga. Surface heatflow values decrease from 120 to 40 mW m−2 during the 4 Ga model evolution. The surface heatflow contribution from an almost constant secular cooling rate was estimated to be 6 mW m−2, in line with recent observational evidence. The modelling results show that the combined effects of compositional buoyancy and strong temperature dependent rheology result in continents which overall remain stable for a duration longer than the age of the Earth. Tracer particles have been used for studying the patterns of mantle differentiation in greater detail. The observed ( p, T, F, t)-paths are consistent with proposed stratification and thermo-mechanical history of the depleted continental root, which have been inferred from mantle xenoliths and other upper mantle samples. In addition, the particle tracers have been used to derive the thermal age of the modelled continental root, defined by a hypothetical closing temperature.

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Section: Discussionsupporting

confidence: 59%

“…This is consistent with the ( p, T, t)-parameters for the theoretical geotherm computapaths derived for upper mantle samples described tion as given by Chapman (1986). Note that the by Roermund and Drury (1998).…”

Section: Time Conventionmentioning

confidence: 99%

Early formation and long-term stability of continents resulting from decompression melting in a convecting mantle

2000

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“…The assumption is consistent with XANES data (Waychunas, 1987;Locock et al, 1995). The possible components of TiO 2 -bearing garnet were postulated by many authors (e.g., Ito and Frondel, 1967;Henmi et al, 1995;Van Roermund et al, 2000;Yang and Liu, 2004;Smith, 2006;Proyer et al, 2013). The components of Ti VI -garnet are tabulated in Table S1 (Ito and Frondel, 1967) (Yang and Liu, 2004), and majoritic garnet such as M 3 [SiM]Si 3 O 12 (Akaogi and Akimoto, 1977) Motoyoshi, 1995;Kawasaki and Motoyoshi, 2000;Kawasaki et al, 2002) to constrain the equilibrium or near-equilibrium TiO 2 content of garnet.…”

Section: +supporting

confidence: 87%

“…Armbruster et al (1998) considered Ti occupies at tetrahedral position as well as octahedral. Van Roermund et al (2000) proposed the model that Ti occupies both tetrahedral and octahedral sites from the petrological study of the ultrahigh-pressure garnet containing exsolution lamellae of rutile and ilmenite in peridotite from Otrøy, Western Gneiss Region, Norway. They derived the general formula of Ti-garnet:…”

Section: Previous Studiesmentioning

confidence: 99%

Ti–in–garnet thermometer for ultrahigh–temperature granulites

Kawasaki

Motoyoshi

2016

Journal of Mineralogical and Petrological Sciences

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We propose a Ti-in-garnet thermometer for ultrahigh-temperature granulites calibrated from experimentally reversed data of the TiO 2 solubility in garnet coexisting with orthopyroxene, rutile and quartz at pressures 7-23 kbar and temperatures 850-1300°C. We confirm that the combined substitution Ti where N is the number of cation per formula unit based on a 12-oxygen atom normalisation. Temperature T and pressure P are given in Kelvin and kbar, respectively. The present thermometer is useful to estimate metamorphic conditions. This new thermometer is applied to natural garnet in geologically and petrologically well-characterised Antarctic ultrahigh-temperature granulites. The resultant pressure and temperature estimates are consistent with those reported from granulites of these areas.

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“…Since Si : O ratios in garnet and pyroxene are 1 : 4 and 1 : 3, respectively, some Si 4+ may substitute for Al 3+ , Cr 3+ , Fe 3+ and enter the octahedral sites to form super-silicic garnet (Si (pfu) > 3.0) when pyroxene dissolves into garnet. The super-silicic garnet stably exists at more than 5 GPa and is a typical ultra-high pressure mineral.Van Roermund et al [10] found garnets with ilmenite and rutile exsolutions, in addition to super-silicic garnet, in garnet-peridotite of Norway Caledonian orogenic belt. They proposed that the original mineral of the garnet with ilmenite and rutile exsolutions is a typical ultra-high pressure mineral and similar to super-silicic garnet, named super-titanic garnet.…”

mentioning

confidence: 98%