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A study of shock-metamorphic features in zircon from the Siljan impact structure, Sweden

Martell, Josefin LU (2016) In Dissertations in Geology at Lund University GEOL01 20161
Department of Geology
Abstract
Shock-metamorphic features such as planar deformation features (PDFs) and in some cases planar fractures (PFs) are widely used as impact-indicators when to confirm a suspected impact structure. These features only develop when exposed to a sudden and immense pressure and temperature increase in association with meteorite impacts. In previous studies, quartz and k-feldspar containing PDFs have been found at the Siljan impact structure, and the quartz samples enabled an approximation of different shock-zones and the craters original size. In this study, the potential shock-metamorphic effects in the mineral zircon are investigated through scanning electron microscopy (SEM). The samples originate from the Siljan impact structure and are of... (More)
Shock-metamorphic features such as planar deformation features (PDFs) and in some cases planar fractures (PFs) are widely used as impact-indicators when to confirm a suspected impact structure. These features only develop when exposed to a sudden and immense pressure and temperature increase in association with meteorite impacts. In previous studies, quartz and k-feldspar containing PDFs have been found at the Siljan impact structure, and the quartz samples enabled an approximation of different shock-zones and the craters original size. In this study, the potential shock-metamorphic effects in the mineral zircon are investigated through scanning electron microscopy (SEM). The samples originate from the Siljan impact structure and are of Järna-granite type. All samples contained planar microstructures, and some of these are assumed to be PDFs based on observations of so called decorations in the lamellae. The nomenclature on shock-features in zircon is not well established and needs further discussion. However, the findings in this study are in most cases comparable to findings of microstructures in zircon from other impact structures. (Less)
Abstract (Swedish)
För att kunna fastställa om en misstänkt nedslagsstruktur verkligen bildats genom ett meteoritnedslag så används så kallade chockstrukturer som planar deformation features (PDFs) och i vissa fall planar fractures (PFs) som indikatorer. Tidigare studier har visat att kvarts och kalifältspat från nedslagsstrukturen Siljansringen innehåller bland annat PDFs. I denna studie har zirkon från samma lokal undersökts genom svepelektronmikroskopering (SEM).
Resultatet visade att samtliga prover innehöll zirkon med planar microstructures, och några av dessa kan möjligtvis klassificeras som PDFs. Nomenklaturen för chockstrukturer i zirkon inte lika väletablerad som för kvarts vilket försvårar klassificering av de funna strukturerna. Jämförelser med... (More)
För att kunna fastställa om en misstänkt nedslagsstruktur verkligen bildats genom ett meteoritnedslag så används så kallade chockstrukturer som planar deformation features (PDFs) och i vissa fall planar fractures (PFs) som indikatorer. Tidigare studier har visat att kvarts och kalifältspat från nedslagsstrukturen Siljansringen innehåller bland annat PDFs. I denna studie har zirkon från samma lokal undersökts genom svepelektronmikroskopering (SEM).
Resultatet visade att samtliga prover innehöll zirkon med planar microstructures, och några av dessa kan möjligtvis klassificeras som PDFs. Nomenklaturen för chockstrukturer i zirkon inte lika väletablerad som för kvarts vilket försvårar klassificering av de funna strukturerna. Jämförelser med mikrostrukturer i zirkon från andra nedslagskratrar visar dock att dessa är jämförbara med de från Siljansringen. (Less)
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author
Martell, Josefin LU
supervisor
organization
course
GEOL01 20161
year
type
M2 - Bachelor Degree
subject
keywords
Zircon, impacts, shock metamorphism, shock metamorphic features, planar deformation features, Siljan impact structure
publication/series
Dissertations in Geology at Lund University
report number
482
language
English
id
8878794
date added to LUP
2016-06-09 14:34:51
date last changed
2016-06-09 14:34:51
@misc{8878794,
  abstract     = {Shock-metamorphic features such as planar deformation features (PDFs) and in some cases planar fractures (PFs) are widely used as impact-indicators when to confirm a suspected impact structure. These features only develop when exposed to a sudden and immense pressure and temperature increase in association with meteorite impacts. In previous studies, quartz and k-feldspar containing PDFs have been found at the Siljan impact structure, and the quartz samples enabled an approximation of different shock-zones and the craters original size. In this study, the potential shock-metamorphic effects in the mineral zircon are investigated through scanning electron microscopy (SEM). The samples originate from the Siljan impact structure and are of Järna-granite type. All samples contained planar microstructures, and some of these are assumed to be PDFs based on observations of so called decorations in the lamellae. The nomenclature on shock-features in zircon is not well established and needs further discussion. However, the findings in this study are in most cases comparable to findings of microstructures in zircon from other impact structures.},
  author       = {Martell, Josefin},
  keyword      = {Zircon,impacts,shock metamorphism,shock metamorphic features,planar deformation features,Siljan impact structure},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {A study of shock-metamorphic features in zircon from the Siljan impact structure, Sweden},
  year         = {2016},
}