ICATE   21876
INSTITUTO DE CIENCIAS ASTRONOMICAS, DE LA TIERRA Y DEL ESPACIO
Unidad Ejecutora - UE
artículos
Título:
Glasses in coarse-grained micrometeorites
Autor/es:
VARELA, M.E.; KURAT G,
Revista:
EARTH AND PLANETARY SCIENCE LETTERS
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Año: 2009 vol. 284 p. 208 - 218
ISSN:
0012-821X
Resumen:
Micrometeorites (MMs, interplanetary dust particles with 25 500 ìm diameters) carry the main mass of
extraterrestrial matter that is captured by Earth. The coarse-grained MMs mainly consist of olivine
aggregates, which - as their counterparts in CC chondrites - also contain pyroxenes and glass. We studied
clear glasses in four coarse-grained crystalline MMs (10M12, M92-6b, AM9, and Mc7-10), which were
collected from the ice at Cap Prudhomme, Antarctica. Previous studies of glasses (e.g., glass inclusions
trapped in olivine and clear mesostasis glass) in carbonaceous and ordinary chondrites showed that these
phases could keep memory of the physical-chemical conditions to which extraterrestrial matter was exposed.
Here we compare the chemical compositions of MM glasses and glasses from CM chondrites with that in
experimentally heated objects from the Allende CV chondrite and with glasses from cometary particles. Our
results show that MMs were heated to variable degrees (during entry through the terrestrial atmosphere),
which caused a range from very little chemical modification of the glass to total melting of the precursor
object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of
volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not
primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical
modification, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs
heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild
2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents
samples from comets 500 ìm diameters) carry the main mass of
extraterrestrial matter that is captured by Earth. The coarse-grained MMs mainly consist of olivine
aggregates, which - as their counterparts in CC chondrites - also contain pyroxenes and glass. We studied
clear glasses in four coarse-grained crystalline MMs (10M12, M92-6b, AM9, and Mc7-10), which were
collected from the ice at Cap Prudhomme, Antarctica. Previous studies of glasses (e.g., glass inclusions
trapped in olivine and clear mesostasis glass) in carbonaceous and ordinary chondrites showed that these
phases could keep memory of the physical-chemical conditions to which extraterrestrial matter was exposed.
Here we compare the chemical compositions of MM glasses and glasses from CM chondrites with that in
experimentally heated objects from the Allende CV chondrite and with glasses from cometary particles. Our
results show that MMs were heated to variable degrees (during entry through the terrestrial atmosphere),
which caused a range from very little chemical modification of the glass to total melting of the precursor
object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of
volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not
primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical
modification, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs
heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild
2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents
samples from cometsfication of the glass to total melting of the precursor
object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of
volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not
primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical
modification, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs
heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild
2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents
samples from cometsfications include dissolution of minerals in the melted glass precursor and some loss of
volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not
primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical
modification, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs
heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild
2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents
samples from cometsfication, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs
heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild
2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents
samples from comets