Petrography, Mineralogy, and Metamorphic Evolution of an Eclogite from the Island of Margarita, Venezuela

Maresch, Walter V.; Abraham, K.

doi:10.1093/petrology/22.3.337

Cited by 42 publications

(36 citation statements)

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“…A large number of geothermometric studies exist for Group C eclogites, generally utilizing the Ellis and Green (1979) calibration of the garnet -clinopyroxene Fe -Mg exchange equilibrium. Group C eclogites from California (e.g., Moore, 1984;Oh and Liou, 1990), Alaska (Patrick and Evans, 1989), Venezuela (Maresch and Abraham, 1981), Western Alps (e.g., Ernst and Dal Piaz, 1978), Cyclades (e.g., Schliestedt, 1986), Turkey (Okay, 1989b;Okay and Satır, 2000) and Oman (e.g., El-Shazly et al, 1990) give consistent temperature estimates of 500 F 50 jC at 10 -15 kbar pressure range. These temperature estimates are similar to those from omphacite -garnet contacts in the eclogite sample, and a temperature of 500 F 50 jC at 10-15 kbar pressure range can be assumed for the Muttalip eclogite.…”

Section: P -T Evolution Of the Eclogite Blueschist And Epidote-amphimentioning

confidence: 85%

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

Okay

Monod

Monié

2002

Lithos

152

100

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Triassic eclogite and blueschist facies rocks occur as a thrust sheet, 25-km long and over 2-km thick, in an Eocene fold-andthrust belt in northwest Turkey along the İzmir -Ankara suture. The thrust sheet consists mainly of metabasites with minor marble, phyllite and metachert, and rare lenses of serpentinite. The common blueschist facies mineral assemblage in the metabasites is sodic amphibole + epidote + albite + chlorite + phengite F garnet. Sodic amphibole commonly shows replacement by barroisite, and there is continuous petrographic transition from blueschist -metabasites to barroisite-bearing epidoteamphibolites. Eclogite with the mineral assemblage of garnet + sodic pyroxene + sodic -calcic amphibole + epidote is found only in one locality. P -T conditions of the epidote -blueschist facies metamorphism are estimated as 450 F 50 jC and 11 F 2 kbar. The blueschist formation was followed by a decrease in pressure and increase in temperature, leading to the development of barroisite-bearing epidote -amphibolites. Phengite, sodic amphibole and barroisite Ar/Ar ages from three metabasic rocks range between 215 and 205 Ma, and indicate Late Triassic high-pressure metamorphism. The Triassic blueschists in northwest Turkey constitute part of a much larger allochthonous tectonic unit of Triassic mafic volcanic rocks. They probably represent the upper layers of a Triassic oceanic plateau, which was accreted to the Laurasian margin during the latest Triassic. The close spatial association of the Triassic and Cretaceous blueschists along the İzmir -Ankara suture suggests that the suture represents a long-lived plate boundary of Late Palaeozoic to early Tertiary age. D

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Section: P -T Evolution Of the Eclogite Blueschist And Epidote-amphimentioning

confidence: 85%

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

Okay

Monod

Monié

2002

Lithos

152

100

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“…The co-existence of kyanite and glaucophane in pelitic schists adjacent to the eclogite blocks at Puerto Cabello suggests that the entire mélange experienced high-pressure metamorphism at N630°C and N2.2 GPa, however, garnet-muscovite-biotite-plagioclase thermobarometry on pelitic schists returned lower P-T conditions of~450-520°C and~1.8 GPa (Sisson et al, 1997). Thermobarometry shows that the eclogites of Isla Margarita experienced high-pressure/low-temperature (HP/LT) metamorphism at conditions of~525-650°C and 1.3-1.9 GPa (Blackburn and Navarro, 1977;Maresch and Abraham, 1981;Bocchio et al, 1996). Knowledge on the timing of metamorphism of the Cordillera de la Costa is limited to c. 76 Ma and 43-28 Ma K-Ar/Ar-Ar amphibole and mica dates, and 49-42 Ma and 24-14 Ma fission-track apatite and zircon dates (Table 1).…”

Section: Conditions and Timing Of Metamorphismmentioning

confidence: 95%

“…1), where eclogite and amphibolite blocks are also hosted within a mélange of continentally derived metasediments (Blackburn and Navarro, 1977;Maresch and Abraham, 1981;Bocchio et al, 1996). The origins of the Isla Margarita and Puerto Cabello eclogites are often linked (Bellizia and Dengo, 1990;, however, the peak P-T conditions (Sisson et al, 1997), fluid histories (Sorensen et al, 2005) and cooling histories are different.…”

Section: Cordillera De La Costamentioning

confidence: 99%

“…The c. 33.0 Ma age for amphibolite-facies metamorphism at Puerto Cabello is at least 20 Myr younger than cooling ages from Isla Margarita and Villa de Cura (Table 1). This finding suggests that, despite mineralogical and petrological similarities (Morgan, 1970;Blackburn and Navarro, 1977;Maresch and Abraham, 1981;Bocchio et al, 1996;Sisson et al, 1997), the exhumation-related overprints on HP/LT assemblages at Isla Margarita and Puerto Cabello were fundamentally different in terms of timing and thus tectonic context (see Sorensen et al, 2005).…”

Section: Igneous and Metamorphic Ages For The Cordillera De La Costamentioning

confidence: 99%

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Single-shot laser ablation split stream (SS-LASS) petrochronology deciphers multiple, short-duration metamorphic events

2015

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“…Peak metamorphic conditions for the magnesite hostrocks have been estimated at 450-525 ~ and 11.5-13.5 kbars (Maresch and Abraham 1981). However, serpentinization probably has occurred at lower T and P. Wenner and Taylor (1974) conclude that lizarditechrysotile serpentinization generally occurs at T < 200 ~ and P < 4 kbar.…”

Section: Depths Of Serpentinization and Magnesite Precipitationmentioning

confidence: 99%

Origin of ultramafic-hosted magnesite on Margarita Island, Venezuela

Abu-Jaber

Kimberley

1992

Mineral. Deposita

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Abstract. Ultramafic-hosted deposits of magnesite (MgCO3) have been studied on Margarita Island, Venezuela, to elucidate the source of carbon and conditions of formation for this type of ore. Petrographic, mineralogic, and 6~sO data indicate that magnesite precipitated on Margarita in near-surface environments at low P and T. ~13C ranges from -9 to -16%o PDB within the magnesite and -8 to -10%o PDB within some calcite and dolomite elsewhere on the island. The isotopically light dolomite fills karst and the calcite occurs as stockwork veins which resemble the magnesite deposits. These carbon isotopic ratios are consistent with a deep-seated source rather than an overlying source from a zone of surficial weathering. However, there is not much enrichment of precious metals and no enrichment of heavy rareearth elements, as would be expected if the carbon had migrated upward as aqueous carbonate ions. The carbon probably has risen as a gaseous mixture of CO2 and CH4 which partially dissolved in near-surface water before leaching cations and precipitating as magnesite and other carbonates. The process probably is ongoing, given regional exhalation of carbonaceous gases.

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Petrography, Mineralogy, and Metamorphic Evolution of an Eclogite from the Island of Margarita, Venezuela

Cited by 42 publications

References 0 publications

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

Triassic blueschists and eclogites from northwest Turkey: vestiges of the Paleo-Tethyan subduction

Single-shot laser ablation split stream (SS-LASS) petrochronology deciphers multiple, short-duration metamorphic events

Origin of ultramafic-hosted magnesite on Margarita Island, Venezuela

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