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2. PETROGENESIS OF THE METACARBONATE AND RELATED ROCKS OF THE SILGARÁ FORMATION, CENTRAL SANTANDER MASSIF, COLOMBIAN ANDES: AN OVERVIEW OF A "REACTION CALCIC EXOSCARN.".
- Author
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Ríos, C. A., Castellanos, O. M., Gómez, S. I., and Ávila, G. A.
- Subjects
- *
PETROGENESIS , *ROCKS , *SEDIMENTARY rocks , *METAMORPHISM (Geology) , *SKARN , *MINERALOGY - Abstract
Metacarbonate rocks (pure and impure marbles, carbonate-silicate rocks, calc-silicate rocks and carbonate-bearing silicate rocks) form a very complex group within the metamorphic sequence of the Silgará Formation at the central Santander Massif(CSM). These rocks are interpreted as derived from a sedimentary sequence (including limestones and dolostones, carbonate-bearing mudstones, sandstones, tuffaceous and evaporitic sediments and marlstones) overprinted by near-isochemical regional metamorphism. They usually appear as scarce intercalations from millimeter up to meter scale, within the high-grade pelitic rocks, in the lower part of the metamorphic section, although the proportion of metacarbonate rocks can be higher and different marble layers are exploited. We report for the first time the occurrence of a "reaction calcic exoskarn", which corresponds to such metacarbonate rocks, taking into account that a skarn can be developed during regional metamorphism and by different metasomatic processes, adjacent to intrusive bodies, along faults and shear zones, and what defines these rocks as a skarn is its mineralogy, which includes a variety of calc-silicate and associated minerals, usually dominated by garnet and pyroxene. Therefore, this paper focus attention to the occurrence of metacarbonate and related rocks, which occurs as small scale reactions zones that show a gradational contact from garnet-bearing pelitic rocks to marbles or carbonate-silicate rocks, giving particular interest to the calc-silicate rocks, which are characterized by the presence of elongated grains of banded clinopyroxene (diopside) and scapolite and massive or scattered garnet. Several reaction-zones occur in the contact between impure calcite marble and garnet-bearing metapelite and the sequence of mineral assemblages in these reaction zones is: biotite + plagioclase ± K-feldspar ± garnet (Zone I), biotite + plagioclase ± K-feldspar ± garnet ± staurolite ± epidote (Zone II), plagioclase + amphibole ± garnet + epidote (Zone III), amphibole + diopside + garnet + plagioclase (Zone IV), plagioclase + diopside ± scapolite (Zone V). epidote ± calcite (Zone VI), and calcite ± dolomite (Zone VII). [ABSTRACT FROM AUTHOR]
- Published
- 2008
3. Occurrence of chloritoid-bearing metapelitic rocks and their significance in the metamorphism of the Silgará Formation at the Central Santander Massif.
- Author
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Castellanos-Alarcón, Oscar Mauricio, Ríos-Reyes, Carlos Alberto, and García-Ramírez, Carlos Alberto
- Subjects
METAMORPHISM (Geology) ,AMPHIBOLITES - Abstract
Copyright of Boletín de Ciencias de la Tierra is the property of Universidad Nacional de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2016
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4. A NEW APPROACH ON THE TECTONOMETAMORPHIC MECHANISMS ASSOCIATED WITH P-T PATHS OF THE BARROVIAN-TYPE SILGARÁ FORMATION AT THE CENTRAL SANTANDER MASSIF, COLOMBIAN ANDES
- Author
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Castellanos A., Óscar M., Ríos R, Carlos A, and Takasu, Akira
- Subjects
Metamorfismo tipo Barroviense ,Barrovian type metamorphism ,petrologic analysis ,lcsh:QE1-996.5 ,Silgará Formation ,rocas pelíticas ,geotermobarometry ,central Santander Massif ,geotermobarometría ,lcsh:Geology ,región central del Macizo de Santander ,Análisis petrológico ,Formación Silgará ,pelitic rocks - Abstract
Metamorphic pressure and temperature trajectories are generally used as tools to interpret the tectonic history of deformed belts of rocks that record past activity along active plate margins. The pre-Devonian metamorphic sequence of the Silgará Formation forms part of the ancient basement of the central Santander Massif, including pelitic schists, siliceous schists and intercalation of amphibolites accompanied by marble. This metasedimentary unit has been affected by Barrovian type metamorphism under middle-pressure/high-temperature conditions. This paper presents on the relationship of tectonic processes to pressure-temperature paths development. Detailed petrologic analysis of pelites and related rocks has been used to constrain the P-T history of this region in the eastern colombian cordillera. Mineral assemblages and Geothermobarometric calculations indicate metamorphic temperatures and pressures of 400-600 °C and 4.0-6.5 kbar, respectively. Las trayectorias de presión y temperatura de metamorfismo generalmente son usadas como herramientas para interpretar la historia tectónica de cinturones de rocas deformadas que registran antigua actividad a lo largo de bordes de placa activos. La secuencia pre-Devónica de la Formación Silgará forma parte del antiguo basamento que aflora en la región central del Macizo de Santander, incluyendo esquistos pelíticos, esquistos silíceos con intercalación de anfibolitas acompañadas por mármol. Esta secuencia metasedimentaria ha sido afectada por un metamorfismo tipo Barroviense en condiciones de presión intermedia / temperatura alta. Este artículo especula sobre la relación entre los procesos tectónicos y el desarrollo de trayectorias de P-T. Un análisis petrológico detallado de las pelitas y rocas relacionadas ha sido usado para deducir la historia de P-T de esta región. Las paragénesis minerales y los cálculos geotermobarométricos indican temperaturas y presiones metamórficas de 400-600 °C y 4.0-6.5 kbar, respectivamente.
- Published
- 2008
5. Petrogenesis of the metacarbonate and related rocks of the silgará formation, central santander massif, colombian andes: an overview of a 'reaction calcic exoscarn'
- Author
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Ríos, C.A., Castellanos, O.M, Gómez, S.I., and Ávila, G.A.
- Subjects
lcsh:Geology ,Metacarbonatadas ,diópsido ,lcsh:QE1-996.5 ,exoskarn ,Silgará Formation ,Formación Silgará ,granate ,garnet ,diopside ,Metacarbonate - Abstract
Metacarbonate rocks (pure and impure marbles, carbonate-silicate rocks, calc-silicate rocks and carbonate- bearing silicate rocks) form a very complex group within the metamorphic sequence of the Silgará Formation at the central Santander Massif (CSM). These rocks are interpreted as derived from a sedimentary sequence (including limestones and dolostones, carbonate-bearing mudstones, sandstones, tuffaceous and evaporitic sediments and marlstones) overprinted by near-isochemical regional metamorphism. They usually appear as scarce intercalations from millimeter up to meter scale, within the high-grade pelitic rocks, in the lower part of the metamorphic section, although the proportion of metacarbonate rocks can be higher and different marble layers are exploited. We report for the first time the occurrence of a "reaction calcic exoskarn", which corresponds to such metacarbonate rocks, taking into account that a skarn can be developed during regional metamorphism and by different metasomatic processes, adjacent to intrusive bodies, along faults and shear zones, and what defines these rocks as a skarn is its mineralogy, which includes a variety of calc-silicate and associated minerals, usually dominated by garnet and pyroxene. Therefore, this paper focus attention to the occurrence of metacarbonate and related rocks, which occurs as small scale reactions zones that show a gradational contact from garnet-bearing pelitic rocks to marbles or carbonate-silicate rocks, giving particular interest to the calc-silicate rocks, which are characterized by the presence of elongated grains of banded clinopyroxene (diopside) and scapolite and massive or scattered garnet. Several reaction-zones occur in the contact between impure calcite marble and garnet-bearing metapelite and the sequence of mineral assemblages in these reaction zones is: biotite + plagioclase ± K-feldspar ± garnet (Zone I), biotite + plagioclase ± K-feldspar ± garnet ± staurolite ± epidote (Zone II), plagioclase + amphibole ± garnet ± epidote (Zone III), amphibole + diopside + garnet + plagioclase (Zone IV), plagioclase + diopside ± scapolite (Zone V), epidote ± calcite (Zone VI), and calcite ± dolomite (Zone VII). Las rocas metacarbonatadas (mármoles puros o impuros, rocas carbonatosilicatadas, rocas calcosilicatadas y rocas silicatadas con presencia de carbonato) forman un grupo muy complejo dentro de la secuencia metamórfica de la Formación Silgará en la región central del Macizo de Santander. Estas rocas son interpretadas como derivadas de una secuencia sedimentaria (incluyendo calizas y dolomías, lodositas con presencia de carbonato, areniscas, sedimentos tobáceos y evaporíticos y margas) afectada por metamorfismo regional casi isoquímico. Ellas usualmente ocurren como esazas intercalaciones a escala milimétrica a métrica, dentro de las rocas pelíticas de alto grado, en la parte inferior de la sección metamórfica, aunque la proporción de rocas metacarbonatadas puede se mas alta y diferentes niveles de mármol son explotados en esta región. Aquí reportamos por primera vez la ocurrencia de un "exoskarn cálcico de reacción", el cual corresponde a tales rocas metacarbonatadas, tomando en cuenta que un skarn puede desarrollarse como consecuencia del metamorfismo regional y por diferentes procesos metasomáticos, adyacente a cuerpos intrusivos, a lo largo de fallas y zonas de12:52 p.m. 11/12/2008 cizallamiento, y lo que define estas rocas como un skarn es su mineralogía, la cual incluye una variedad de minerales calcosilicatados y asociados, usualmente dominados por granate y piroxeno. Por lo tanto, este articulo esta enfocado a la presencia de rocas metacarbonatadas y asociadas, las cuales ocurren como zonas de reacción a pequeña escala que muestran un contacto gradacional desde rocas pelíticas con presencia de granate hasta mármoles o rocas carbonatosilicatadas, dando particular interés a las rocas calcosilicatadas, las cuales se caracterizan por la presencia de cristales alargados de clinopiroxeno (diópsido) y escapolita bandeados y granate masivo o disperso. Varias zonas de reacción ocurren en la interfase entre mármol y metapelita con granate y la secuencia de paragenesis minerales en estas zonas de reacción is: biotita + plagioclasa ± feldespato potasico ± granate (Zona I), biotita + plagioclasa ± feldespato potasico ± granate ± estaurolita ± epidota (Zona II), plagioclasa + anfíbol ± granate ± epidota (Zona III), anfíbol + diopsido + granate + plagioclasa (Zona IV), plagioclasa + diopsido ± escapolita (Zona V), epidota ± calcita (Zona VI), y calcita ± dolomita (Zona VII).
- Published
- 2008
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