Factors in the preservation of coesite: The importance of fluid infiltration

Mosenfelder, J. L.; Schertl, Hans‐Peter; Smyth, Joseph R.; Liou, J. G.

doi:10.2138/am.2005.1687

Cited by 82 publications

(60 citation statements)

References 74 publications

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“…Related factors include the relative size of the inclusion and host, and the hardness and fracturing intensity of the latter. For Tianshan UHP rocks, petrographic studies show the resetting of schistosity during uplift, which tends to crack garnet, thereby enabling fluid ingress into the garnet and deleting most pristine coesite inclusions [22]. Even though coarse-grained garnet is strongly fractured, some segments remain large enough.…”

Section: Discussionmentioning

confidence: 99%

Coesite in the eclogite and schist of the Atantayi Valley, southwestern Tianshan, China

Lü

Zhang

2012

Chin. Sci. Bull.

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Coesite is an indicator mineral of ultra-high-pressure metamorphism. Since coesite was reported in the Habutengsu Valley, we have also found it in eclogite and schist from the Atantayi Valley in the southwestern Tianshan, China. Petrographic and micro-Raman analyses were carried out for the Atantayi metamorphic rocks and coesite was recognized in the predominant rock types, i.e. schist and eclogite, from three sections. The coesite-bearing schist consists mainly of garnet, Na-Ca amphibole, quartz, white mica and albite; the coesite-bearing eclogite is mainly composed of omphacite, garnet, glaucophane and zoisite. The coesite occurs as various mineral inclusions within porphyroblastic garnet. Findings of coesite in eclogite and associated schist indicate not only the regional in situ formation of the Atantayi ultra-high-pressure eclogite, but also the large areal extent of ultra-high-pressure metamorphism in southwestern Tianshan, extending up to 10 km north-south and 60-80 km east-west. Coesite is an indicator mineral of ultra-high-pressure (UHP) metamorphism [1]. In well-established UHP belts worldwide, coesite is usually preserved in relatively refractory minerals, such as garnet and zircon. An increasing number of studies show that garnet can preserve abundant information on the pressure-temperature (P-T) evolution of a metamorphic garnetiferous rock, as evidenced by the applicability and reliability of garnet isopleth geothermobarometry [2]. In the UHP field, the occurrence of coesite inclusions in garnet is of significance because it identifies the possible episodic growth of garnet, which may, combined with garnet isopleth thermobarometry, decipher the P-T trajectory of a specific UHP rock. The first reports of UHP metamorphism in the southwestern Tianshan instigated debate that has continued until the recent discovery of coeiste in the Habutengsu Valley of this orogenic belt [3][4][5][6][7][8]. However, until now, coesite had not been optically identified in the rocks of the Atantayi Valley, where the eclogites involved in the "UHP versus HP" controversy were sampled [5,9]. Detailed investigations of UHP minerals such as coesite are critical for elaborating on the spatial distribution and evolutionary characteristics of the UHP belt in the southwestern Tianshan. Recently, we collected a number of samples of different rock types along the Atantayi Valley and conducted detailed petrographic analyses on them. In order to find any evidence of ultra-high pressures in these rocks, we carefully examined tiny inclusions in garnets found in these samples employing Raman spectroscopy. This has provided fundamental information on the metamorphic evolution of the HP-UHP belt of the southwestern Tianshan.

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Section: Discussionmentioning

confidence: 99%

Coesite in the eclogite and schist of the Atantayi Valley, southwestern Tianshan, China

Lü

Zhang

2012

Chin. Sci. Bull.

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“…Slabs denser than the surrounding mantle are destined to sink to greater depths, while ductile rocks might be preferentially exhumed (Hermann et al 2013), where inclusions of coesite into stiff minerals (e.g., garnet) are preserved from the back reaction to quartz (Gillet et al 1984). Indeed, during the past decades, natural coesite was repeatedly found in continental orogens (Chopin 1984;Liou et al 2004), however, mostly depleted in water (Rossman and Smyth 1990;Mosenfelder 2000;Mosenfelder et al 2005), probably because OH-rich crystals transform much faster back to quartz (Lathe et al 2005). By now, natural hydrous coesite have been found only as mineral inclusions in diamonds from Venezuela (Koch- Müller et al 2003).…”

Section: Petrological and Geodynamical Applicationsmentioning

confidence: 99%

OH defects in coesite and stishovite during ultrahigh-pressure metamorphism of continental crust

2018

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The high-pressure silica polymorphs coesite and stishovite were synthesized under water-saturated conditions from a natural granitic composition doped with Li and B. Experiments were performed in a Multi-Anvil apparatus between 4 and 9.1 GPa and 900 and 950 °C, based on the conditions of a subducting continental crust as realistic for the ultrahigh-pressure metamorphic units Dora Maira and Kochetav massifs. Run products consisted of coesite/stishovite + kyanite ± phengite ± omphacite, and quench material. The synthesized silica polymorphs were successively analyzed by infrared spectroscopy, electron microprobe, and Secondary-Ion Mass Spectrometry (SIMS). No hydrous defects were observed in coesite synthesized at 4 GPa and 900 °C, whereas coesite grown at higher pressures revealed a triplet of infrared absorptions bands at 3575, 3523, and 3459 cm − 1 , two minor bands at 3535 and 3502 cm − 1 , and a small band at 3300 cm − 1 that was only visible at 7.7 GPa. The total amount of Al was charge-balanced by H and the other monovalent cations. However, the band triplet could not be associated with AlOH defects, while the band doublet was inferred to BOH defects and the small band probably corresponded to interstitial H. Stishovite displayed one dominant band at 3116 cm − 1 with a shoulder at 3170 cm − 1 , and a minor band at 2665 cm − 1 , probably all associated with AlOH defects. BOH defects were not observed in stishovite, and LiOH defects were neither observed in coesite nor stishovite, probably because of preferentially partition of Li in other phases such as omphacite. The total amount of defect protons increased with pressure and with metal impurity concentrations. The general increase in OH defects in silica polymorphs with increasing pressure (this study) contrasted the negative pressure trend of OH in quartz observed previously from the same starting material, and revealed an incorporation minimum of OH in silica polymorphs around the quartz/coesite phase transition.

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“…However, the coesite subsequently transformed into quartz following eruption and long-term cooling at low pressure, as the diamond was entrained in the host kimberlite. However, fluids are well known to have a catalytic effect on reactions; the coesite fi quartz growth rates determined by Perrillat et al (2003) are an order of magnitude faster than those of Mosenfelder and Bohen (1997), this difference is attributed to the possible presence of fluids in the experimental system of Perrillat et al (2003) by Mosenfelder et al (2005) and Lathe et al (2005). Lathe et al (2005) show that the rate of coesite-to-quartz transformation is 10· faster in the presence of water.…”

Section: Inclusion-forming Processes Along the Isochorementioning

confidence: 97%

Quartz-bearing C–O–H fluid inclusions diamond: Retracing the pressure–temperature path in the mantle using calibrated high temperature IR spectroscopy

Tomlinson

McMillan

Zhang

et al. 2007

Geochimica et Cosmochimica Acta

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Infrared spectra of C-O-H micro-inclusions were collected from a micro-inclusion bearing diamond during step-heating and freezing experiments to examine fluid speciation as a function of pressure and temperature. The inclusions contain H 2 O, CO 2 , carbonate, apatite, quartz and mica, which together represent the oxidising remnant mantle fluid composition after diamond crystallisation. The internal pressure of the inclusions, measured from calibrated shifts of the quartz peaks, increases from 1.3 GPa at ambient temperature, to approximately 4-5 GPa at 737°C, close to the conditions of crystallisation of the host diamond in the mantle.

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Factors in the preservation of coesite: The importance of fluid infiltration

Cited by 82 publications

References 74 publications

Coesite in the eclogite and schist of the Atantayi Valley, southwestern Tianshan, China

Coesite in the eclogite and schist of the Atantayi Valley, southwestern Tianshan, China

OH defects in coesite and stishovite during ultrahigh-pressure metamorphism of continental crust

Quartz-bearing C–O–H fluid inclusions diamond: Retracing the pressure–temperature path in the mantle using calibrated high temperature IR spectroscopy

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