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Vad kan inneslutningar i zirkon berätta om Varbergscharnockiten, SV Sverige

Engström, Simon LU (2013) In Examensarbeten i geologi vid Lunds universitet GEOX01 20112
Department of Geology
Abstract (Swedish)
Charnockit (hypersten granit), förekommer över hela världen och har beskrivits som en magma-tiskt eller metamorft bildad bergart, ursprunget till charnockiter och definitionen är därför omdiskuterad. Det finns två ytterligheter bland förklaringsmodeller för charnockitbildning, antingen bildas de genom (1) kristallisation av torra magmor eller (2) i metamorfa miljöer vid lågt PH2O. Denna studie omfattar undersökning av mineralinklusion-er i zirkoner från Varbergscharnockiten i svepelektronmikroskop (SEM), zirkonmättnadstermometri och en analys av zirkonernas texturella förekomst i charnockiten. Resultaten gav att Varbergscharnockiten var zirkoniummättad mellan 766 - 844°C, zirkonerna förekommer huvudsakligen i korn-gränserna utan någon... (More)
Charnockit (hypersten granit), förekommer över hela världen och har beskrivits som en magma-tiskt eller metamorft bildad bergart, ursprunget till charnockiter och definitionen är därför omdiskuterad. Det finns två ytterligheter bland förklaringsmodeller för charnockitbildning, antingen bildas de genom (1) kristallisation av torra magmor eller (2) i metamorfa miljöer vid lågt PH2O. Denna studie omfattar undersökning av mineralinklusion-er i zirkoner från Varbergscharnockiten i svepelektronmikroskop (SEM), zirkonmättnadstermometri och en analys av zirkonernas texturella förekomst i charnockiten. Resultaten gav att Varbergscharnockiten var zirkoniummättad mellan 766 - 844°C, zirkonerna förekommer huvudsakligen i korn-gränserna utan någon särskild mineralassociat-ion men ibland i associerade med Fe-oxider och Fe-sulfider. Inklusionsstudien visar att apatit och K-fältspat är de vanligaste mineralinklusionerna i zirkon från Varbergscharnockiten och att klinopyroxen och omvandlingsmineral av ortopyroxen förekommer som inneslutningar. Resultaten tyder klart på att Varbergscharnockiten bildades genom kristallisation från en torr magma där klino- och ortopyroxen var primära mineral. (Less)
Abstract
Charnockite (hypersthene granite), occurs worldwide and has been described as an igneous or meta-morphic rock. The origin of charnockites and the definition of the concept has been widely debated. There are two hypotheses concerning possible formation models for charnockite: (1) crystallization from dry magmas, and (2) low PH2O during metamorphism. This study investigated mineral inclusions, saturation thermometry, and microtextures in zircons from the Varberg charnockite, using a scanning electron microscopy (SEM). The results suggest that the Varberg charnockite is zircon saturated between 766-844 °C, and the zircons are generally found along the grain boundaries of minerals; infrequently as inclusions. Although there was no apparent... (More)
Charnockite (hypersthene granite), occurs worldwide and has been described as an igneous or meta-morphic rock. The origin of charnockites and the definition of the concept has been widely debated. There are two hypotheses concerning possible formation models for charnockite: (1) crystallization from dry magmas, and (2) low PH2O during metamorphism. This study investigated mineral inclusions, saturation thermometry, and microtextures in zircons from the Varberg charnockite, using a scanning electron microscopy (SEM). The results suggest that the Varberg charnockite is zircon saturated between 766-844 °C, and the zircons are generally found along the grain boundaries of minerals; infrequently as inclusions. Although there was no apparent mineral association preference, zircons were frequently associated with Fe-oxides and Fe-sulfides. Apatite and K-feldspar are the most common occuring mineral inclusions in zircon; less frequent inclusions are clinopyroxene and alteration products of ort-hopyroxene. The results indicate that the Varberg charnockite was formed by crystallization from dry magma in which clino- and orthopyroxene were primary minerals. (Less)
Please use this url to cite or link to this publication:
author
Engström, Simon LU
supervisor
organization
alternative title
What do inclusions in zircon tell about the Varberg charnockite, SW Sweden
course
GEOX01 20112
year
type
M2 - Bachelor Degree
subject
keywords
charnockit, Varberg, zirkon, mineralinneslutning, zirkoniummättnad, charnockite, zircon, inclusion, zircon saturation thermometry
publication/series
Examensarbeten i geologi vid Lunds universitet
report number
362
language
Swedish
id
3966682
date added to LUP
2013-08-12 15:29:56
date last changed
2013-08-12 15:29:56
@misc{3966682,
  abstract     = {Charnockite (hypersthene granite), occurs worldwide and has been described as an igneous or meta-morphic rock. The origin of charnockites and the definition of the concept has been widely debated. There are two hypotheses concerning possible formation models for charnockite: (1) crystallization from dry magmas, and (2) low PH2O during metamorphism. This study investigated mineral inclusions, saturation thermometry, and microtextures in zircons from the Varberg charnockite, using a scanning electron microscopy (SEM). The results suggest that the Varberg charnockite is zircon saturated between 766-844 °C, and the zircons are generally found along the grain boundaries of minerals; infrequently as inclusions. Although there was no apparent mineral association preference, zircons were frequently associated with Fe-oxides and Fe-sulfides. Apatite and K-feldspar are the most common occuring mineral inclusions in zircon; less frequent inclusions are clinopyroxene and alteration products of ort-hopyroxene. The results indicate that the Varberg charnockite was formed by crystallization from dry magma in which clino- and orthopyroxene were primary minerals.},
  author       = {Engström, Simon},
  keyword      = {charnockit,Varberg,zirkon,mineralinneslutning,zirkoniummättnad,charnockite,zircon,inclusion,zircon saturation thermometry},
  language     = {swe},
  note         = {Student Paper},
  series       = {Examensarbeten i geologi vid Lunds universitet},
  title        = {Vad kan inneslutningar i zirkon berätta om Varbergscharnockiten, SV Sverige},
  year         = {2013},
}