Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile
Triassic-Jurassic volcano-sedimentary sequences in the Coastal Range of central Chile (34° 45/35°20'S) from the Vichuquén-Tilicura and Hualañé-Gualleco basins display metamorphic assemblages indicative of very low-grade conditions. Triassic and Lower Jurassic metapelites achieved anchizonal con...
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2005
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oai:scielo:S0716-020820050002000022005-08-30Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central ChileBelmar,MauricioMorata,Diego Very low-grade metamorphism Metabasites Triassic-Jurassic basins Coastal Range Central Chile Triassic-Jurassic volcano-sedimentary sequences in the Coastal Range of central Chile (34° 45/35°20'S) from the Vichuquén-Tilicura and Hualañé-Gualleco basins display metamorphic assemblages indicative of very low-grade conditions. Triassic and Lower Jurassic metapelites achieved anchizonal conditions (IC, b o, coal-rank and fluid inclusions data: P »1.3, T»190) at 181-184 Ma, under geothermal gradient of »35°Ckm-1 during extensional geodynamic conditions. Nevertheless, in stratigraphically higher mafic volcanic sequences, of Middle to Late Jurassic age, the presence of chlorite (Xc =0.98-0.99), three types of epidote (XFe3+ = 41.14±0.90, 30.08±1.53 and 18.05±1.75), titanite, Fe-rich and Fe-poor pumpellyite and hydrogarnet (+albite and quartz) are indicative of re-equilibration under prehnite-pumpellyite facies conditions (P »3 kbar, T »300°C) and variable oxygen fugacity. A change from an extensional setting (with maximum basin subsidence and development of burial very low-grade metamorphism in the Triassic-Lower Jurassic metapelitic sequences) to a compressional setting (with local overthrusting of Triassic and Lower Jurassic sequences over Middle to Late Jurassic volcano-sedimentary sequences) is proposed to explain the contrasting metamorphic conditions between Triassic-Lower Jurassic metapelites and Middle-Late Jurassic metabasitesinfo:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Revista geológica de Chile v.32 n.2 20052005-07-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082005000200002en10.4067/S0716-02082005000200002 |
| institution |
Scielo Chile |
| collection |
Scielo Chile |
| language |
English |
| topic |
Very low-grade metamorphism Metabasites Triassic-Jurassic basins Coastal Range Central Chile |
| spellingShingle |
Very low-grade metamorphism Metabasites Triassic-Jurassic basins Coastal Range Central Chile Belmar,Mauricio Morata,Diego Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile |
| description |
Triassic-Jurassic volcano-sedimentary sequences in the Coastal Range of central Chile (34° 45/35°20'S) from the Vichuquén-Tilicura and Hualañé-Gualleco basins display metamorphic assemblages indicative of very low-grade conditions. Triassic and Lower Jurassic metapelites achieved anchizonal conditions (IC, b o, coal-rank and fluid inclusions data: P »1.3, T»190) at 181-184 Ma, under geothermal gradient of »35°Ckm-1 during extensional geodynamic conditions. Nevertheless, in stratigraphically higher mafic volcanic sequences, of Middle to Late Jurassic age, the presence of chlorite (Xc =0.98-0.99), three types of epidote (XFe3+ = 41.14±0.90, 30.08±1.53 and 18.05±1.75), titanite, Fe-rich and Fe-poor pumpellyite and hydrogarnet (+albite and quartz) are indicative of re-equilibration under prehnite-pumpellyite facies conditions (P »3 kbar, T »300°C) and variable oxygen fugacity. A change from an extensional setting (with maximum basin subsidence and development of burial very low-grade metamorphism in the Triassic-Lower Jurassic metapelitic sequences) to a compressional setting (with local overthrusting of Triassic and Lower Jurassic sequences over Middle to Late Jurassic volcano-sedimentary sequences) is proposed to explain the contrasting metamorphic conditions between Triassic-Lower Jurassic metapelites and Middle-Late Jurassic metabasites |
| author |
Belmar,Mauricio Morata,Diego |
| author_facet |
Belmar,Mauricio Morata,Diego |
| author_sort |
Belmar,Mauricio |
| title |
Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile |
| title_short |
Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile |
| title_full |
Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile |
| title_fullStr |
Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile |
| title_full_unstemmed |
Nature and P-T-t constraints of very low-grade metamorphism in the Triassic-Jurassic basins, Coastal Range, central Chile |
| title_sort |
nature and p-t-t constraints of very low-grade metamorphism in the triassic-jurassic basins, coastal range, central chile |
| publisher |
Servicio Nacional de Geología y Minería (SERNAGEOMIN) |
| publishDate |
2005 |
| url |
http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082005000200002 |
| work_keys_str_mv |
AT belmarmauricio natureandpttconstraintsofverylowgrademetamorphisminthetriassicjurassicbasinscoastalrangecentralchile AT moratadiego natureandpttconstraintsofverylowgrademetamorphisminthetriassicjurassicbasinscoastalrangecentralchile |
| _version_ |
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