Mineralogical investigations of agates from Cordon de Lila, Chile
In the present study a first found of agates in Chile is reported from the Cordón de Lila region in northern Chile. The agates occur as veins and lenses in altered Permian volcanic rocks. The rock composition is rhyodacitic/dacitic consisting of a fi ne-grained K-feldspar-quartz groundmass with phen...
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Servicio Nacional de Geología y Minería (SERNAGEOMIN)
2015
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oai:scielo:S0718-710620150003000062015-10-20Mineralogical investigations of agates from Cordon de Lila, ChileRichter,StefanGötze,JensNiemeyer,HansMöckel,Robert Cordón de Lila Volcanic rocks Mineralogy Geochemistry Agate In the present study a first found of agates in Chile is reported from the Cordón de Lila region in northern Chile. The agates occur as veins and lenses in altered Permian volcanic rocks. The rock composition is rhyodacitic/dacitic consisting of a fi ne-grained K-feldspar-quartz groundmass with phenocrysts of plagioclase (An50-60) and pyroxene (augite). The volcanic host rocks show strong features of alteration and brecciation. Results of XRD, polarizing microscopy and cathodoluminescence (CL) microscopy and spectroscopy point to a late- to postvolcanic formation of the agates by hydrothermal fluids and SiO2 which was released during the alteration of unstable minerals and volcanic glass. Strongly varying agate micro-textures and the appearance of euhedral quartz crystals with pm-sized growth lamellae (so called Bambauer quartz) indicate fluctuations in the physico-chemical conditions (SiO2 concentration, pH) during alteration and agate formation. Another indication for the alteration processes is the occurrence of secondary calcite in the agate-bearing rocks.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.42 n.3 20152015-09-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000300006en10.5027/andgeoV42n3-a06 |
| institution |
Scielo Chile |
| collection |
Scielo Chile |
| language |
English |
| topic |
Cordón de Lila Volcanic rocks Mineralogy Geochemistry Agate |
| spellingShingle |
Cordón de Lila Volcanic rocks Mineralogy Geochemistry Agate Richter,Stefan Götze,Jens Niemeyer,Hans Möckel,Robert Mineralogical investigations of agates from Cordon de Lila, Chile |
| description |
In the present study a first found of agates in Chile is reported from the Cordón de Lila region in northern Chile. The agates occur as veins and lenses in altered Permian volcanic rocks. The rock composition is rhyodacitic/dacitic consisting of a fi ne-grained K-feldspar-quartz groundmass with phenocrysts of plagioclase (An50-60) and pyroxene (augite). The volcanic host rocks show strong features of alteration and brecciation. Results of XRD, polarizing microscopy and cathodoluminescence (CL) microscopy and spectroscopy point to a late- to postvolcanic formation of the agates by hydrothermal fluids and SiO2 which was released during the alteration of unstable minerals and volcanic glass. Strongly varying agate micro-textures and the appearance of euhedral quartz crystals with pm-sized growth lamellae (so called Bambauer quartz) indicate fluctuations in the physico-chemical conditions (SiO2 concentration, pH) during alteration and agate formation. Another indication for the alteration processes is the occurrence of secondary calcite in the agate-bearing rocks. |
| author |
Richter,Stefan Götze,Jens Niemeyer,Hans Möckel,Robert |
| author_facet |
Richter,Stefan Götze,Jens Niemeyer,Hans Möckel,Robert |
| author_sort |
Richter,Stefan |
| title |
Mineralogical investigations of agates from Cordon de Lila, Chile |
| title_short |
Mineralogical investigations of agates from Cordon de Lila, Chile |
| title_full |
Mineralogical investigations of agates from Cordon de Lila, Chile |
| title_fullStr |
Mineralogical investigations of agates from Cordon de Lila, Chile |
| title_full_unstemmed |
Mineralogical investigations of agates from Cordon de Lila, Chile |
| title_sort |
mineralogical investigations of agates from cordon de lila, chile |
| publisher |
Servicio Nacional de Geología y Minería (SERNAGEOMIN) |
| publishDate |
2015 |
| url |
http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000300006 |
| work_keys_str_mv |
AT richterstefan mineralogicalinvestigationsofagatesfromcordondelilachile AT gotzejens mineralogicalinvestigationsofagatesfromcordondelilachile AT niemeyerhans mineralogicalinvestigationsofagatesfromcordondelilachile AT mockelrobert mineralogicalinvestigationsofagatesfromcordondelilachile |
| _version_ |
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